Hey, I thought I would post some of my pictures and descriptions instead of littering other threads with my stuff. This is my first airboat build, it's 13' long over all, 5'6"at the bottom of the transom and 80" at the top. Soft chines built to a 6" radius. The hull tapers to 60"wide at the bow.1813
.125" floor plating, the rear 4' of the side are .125 as well with the forward sections .080". Transom is also .125" and 24" tall with a 4" center dip for prop clearance.1812
I Choose a 2010 Yamaha Nytro snow-machine engine for power, it is a three cylinder, four stroke, 1049cc's and dry weight is around 150lbs. This engine is from Yamaha's Genesis platform and was origionally designed as a four cylinder motorcycle engine but has found it's way into all powersports. This model is fuel injected with an aftermarket turbo set-up and produces around 200hp at 9000 rpm. Engine red-line is somewhere north of 12000 rpm.1814
I used the factory exhaust but had to massage it heavily due to the new turbo location, full stainless on the header. I had the pieces of the prop shaft custom machined to use 2- 1/2" pillow block bearings with a spherical roller element for axial thrust loading. Theses bearings spec out at about 1200lbs each for axial loading. The belt drive is a 36mm wide, 8mm pitch Gates timing belt.

My rigging is made from 1" by 1" by .125 wall square tubing (aluminium) with 1/8" and 1/4" gusseting. Bow deck structure is 1" by 2" by .125" tubing with the obligatory 2" aluminium pipe at the leading edge.1815 18161817
I've been at it for almost a year now. Holidays, kids sports and paying side jobs getting in the way of my free build time at home. This past weekend I have skinned the rudders and started on the steering linkages and my level of excitement on the project is at a new high. I've had it running twice with power to the prop, and on the dollies it pushes hard enough a man can't hold it back at about 800 prop RPM.

TO do list as of Mar 8
- complete steering linkage
-build accelerator linkage
-complete bow deck
-install UHMW to bottom of hull
-install lighting
-install bilge pump
....install the 1000 little things I haven't thought of yet....

That boat is awesome !! You're up on the next level with that build..;thumb;....With that kind of HP and RPM you HAVE to make sure all the components are up to the task and it looks like you're accomplishing it...I can't wait to hear and see your boat in action....

After viewing your build Corky, I really appreciate your words. Thank you. I've got a few more pictures to post but I'm having trouble uploading them from my phone.

That boat is awesome !! You're up on the next level with that build..;thumb;....With that kind of HP and RPM you HAVE to make sure all the components are up to the task and it looks like you're accomplishing it...I can't wait to hear and see your boat in action....
Unfortunately the forum software will flip the photo to its widest size sometimes placing them sideways. My only suggestion for that is to take photos landscape or sideways when taking them on your phone.

Thanks for the hint. I thought it was something I was doing.

I got a little more done with the rudder linkage but ran into a snag with the steering handle. I measured the right amount of travel calculated from the steering arm pivot but failed to realize where in the arc of travel that distance was. I ended up with full left rudder and 0% right. Papee, I'm sure you've seen something like this before! I had a good laugh at myself, opened a beer and went back to the house. I'll build another steering lever and primary link-arm tonight. 18201821

P.S. it was me doing something wrong, my camera has the auto rotate feature off!! LOL

So I've been finalizing some mechanical linkages and have got my "go pedal" finished. Last night, I asked a friend to stop in and we stripped the hull and flipped it for the poly install. There's my son in the cage "flying" it. LOL1838 and the rigging,
1839 and the hull. I'll finish a little welding touch ups, as I did the external seam overhead and then on with the UHMW, 1/4" thick.1840

Nice to see the boy getting involved with your project...;thumb;...

The local boat builder around here adds the poly to all his bottoms no matter how small the engine or hull is...His argument is the poly floats and ends up with a neutral balance between the added weight and bouyancy to the hull... As papee has pointed out it still adds mass to the overall build and could create problems for some low horsepower builds...But you're not in that category with your engine...:cool:....Now he does use stainless hardware and has a custom stop on the countersink for the perfect hole everytime...And uses a marine grade sealer with the stainless screws...

Thanks again for the tips. I do have a countersink tool and stainless fasteners but they are self tapping. ...do you think sealant would still be required? ? I have been scratching my head on this one, and any input is valued.

Self tappers are fine....I'd use the sealant...There's just too many factors not to do it...The aluminum will expand and contract at a different rate than the stainless fasteners...You run the risk of the fasteners getting jarred if they take a hit and even a little movement leads to a leak...This is the stuff I'd use.. it's an adhesive/sealant and supposedly you'll ruin the fastener before it comes back out...Check out the 3m line of marine sealants there's semi-permanent and permanent sealers....

I don't have much experience with poly but I do know it has to be warm to put it on. It should be laid out flat in the heat to warm up then warm when putting it on.

I think you are going to be running that engine hard to move that boat along. It's a toss up for me and the poly on a lower horsepower setup. The poly does add protection but also more weight. As far as flotation it's a wash, the poly will float its own weight but there still is that weight you are adding, like hauling around an extra person all the time.

Id rather cut the bottom off and put a new one on than put poly on. That's just me though, most folks know I march to the beat of a different drummer. The key to this whole low horsepower deal is weight, you're already heavy with that hull, not that it's a bad thing,I just think running that oil burner(2 stroke) will be running hard to push that barge around.

I may be way way off on my thinking, my wife can tell you Ive been wrong a lot. I'm very interested in seeing the results of your build. It reminds me of a guy I saw at the river last year or the year before. He had a beautiful hull made by a local guy. He put fancy food up instrument panel on it, a big junction box to house all his wiring and fuses, and a few other weight hogs. He powered it with a really nice looking VW engine. The thing won't get on plane. I've never seen him on the river since, I don't know what became of his build.

Id rather cut the bottom off and put a new one on than put poly on. That's just me though, most folks know I march to the beat of a different drummer. The key to this whole low horsepower deal is weight, you're already heavy with that hull, not that it's a bad thing,I just think running that oil burner(2 stroke) will be running hard to push that barge around.

I guess we shall see. I'm defiantly impressed with your posted weight, very light! I'm very excited as well to try my creation out, although the ice will be on our lakes for a few more weeks. HA! It's the first day of spring and I woke up to 3" of snow on the ground!! The rivers are starting to flow a bit as we have been above average for temps lately. Day time highs around 8*C...not sure what that is in *F. I thought I mentioned that my engine is a four stroke.... it is a snowmobile engine, made by Yamaha in 2010, fuel-injected four stroke

...I'd use the sealant...There's just too many factors not to do it...The aluminum will expand and contract at a different rate than the stainless fasteners...You run the risk of the fasteners getting jarred if they take a hit and even a little movement leads to a leak...This is the stuff I'd use.. .

Very good point on the different coefficients of expansion! Thank you Corky. I'll be looking for this stuff shortly. I guess it's better to be safe than burn out a bilge pump!!

That is one bad motor right there. 200 hp at only 150lb. Thats insane considering the 084 weighs around 130 and puts out a conservative 40 hp. That is shocking though that the rig ended up weighing over 1000 pounds. Would have shot for around 750 at the most. But hey itll still move provided all your reduction drive parts can hold together at those high rpms. I see your spinning a sensenich prop. Very good choice there...well know and have been around forever and a day. Good luck on the build I look forward to the results. Word of caution though, go easy at first maybe just some idle om the trailer testing to make sure none of your bearings move of shift on you from all that thrust that prop is guna do.

best of luck and great looking boat.
Steve

Here's a few more pictures of my progress. Haven't been around the forum for a while. I finished a tear down of my rigging and finalized the welding on all the tacked bits, added some black paint and began reassembly. I finished the UHMW install and ended up using this for sealant. Corky, I couldn't find that 5200 product from 3M locally, and after talking to a marine mechanic he suggested this.
1883

I've almost finished the front deck with only a little cleanup to do and also have the floor installed. Also the fuel tank is finalized, painted and installed.
18841885

I did end up modifying an auto belt tensioner. I bought one from a scrap yard for $20 and then had an aluminium sleeve machined to increase the pulley width for my belt.
1886
I'll remove it for a little cleaning but I wanted to get a pic for you guys. We had a decent discussion on another thread around this.
Anyway the weekend is here and with any luck I'll have the wire on the cage by the end of it and then.....trials

i'm glad you've found a sealant that worked for you....;thumb;....The idler looks great with the added advantage you can just order another from the auto parts store if it wears out....I was wondering how your build was coming along ...It's tough working on the fun stuff and still getting the chores done....

I hear you there On finding spare time Corky. Thanks for the encouragement. I got the rigging and motor remounted in the hull this morning. Locking all the fasteners with either cotter pins, stainless tie wire or blue locktite. Very tedious but I certainly don't want some thing vibrating loose.

After I finish the mesh on that cage, I'll mount some brackets for lighting and reinstall the assembly. Then final wiring, a couple guards......The list isn't getting any shorter is it???lol

So a couple of days ago I drug the airboat out of the shop with the intent of an actual test. WELL! It surprised the heck out of me as I hit about 2100 prop RPM and it push itself off the wet gravel in my driveway and on to the snow in my yard. My wife heard the racket and grabbed a phone to video the carnage to ensue.... Again I've never even sat in an airboat before building this one and had no idea how it would handle. In the snow it was down right scary as there was so little friction slowing me down, I have a fairly steep hill in the yard and after scooting down I spun it around and climbed right back up with out a problem and slid into the wood pile beside the fire pit! HA HA. No damage, after buzzing around for about 5 minutes in the snow, I pointed it back to the shop and headed across the concrete apron and right back into my work space. And then I took a breath. Wow

I've spent a few days going over little things I've noticed after the shakedown. I'm planning to head to the lake tomorrow where I can pay attention to things like RPM when it breaks free to max rpm on the trailer to verify the prop pitch is correct. I saw 7400 engine rpm which equals 2466 prop rpm but that wasn't constant.... and I only glanced down without really relaizing what I was doing as well.... time to pay attention. Wish me luck, at least the ice is still on and I shouldn't sink

Be careful on that ice! Especially since you've never driven an airboat ...(reference my crash video if you are curious). The boat will probably turn quickly with rudder input but that's not to say the boat will go in that direction, especially if you're moving at any rate of speed (remember - the bottom is FLAT). Sounds like you're definitely in the "FUN" phase of your build:-D

I made it back without major incident! Words of wisdom from you Kirk, I saw your video and that looked sketchy to say the least. Statistic report- breaks loose on dry ground(packed and loose gravel, wet and dry) at about 7400 rpm. Max engine rpm 8500. The sensenich salesman said it was a bit big for the power i'm making but i'm only about 170 rpm short of max prop so I think I will leave it as is. That's making 8 psi of boost. I can close the by-pass valve to the turbo cutting it back to 7800 engine RPM and 5 psi boost=2600 prop rpm. About a 4" draft.
After a few minutes buzzing around the broken ice at the ramp I had my confidance up and I drove up the ramp and my son climbed aboard. We cruised around the lake in the open water along the shore for about 40 minutes with out issue. It gets on step quickly and maintains plane at 4800-5200 rpm(1660 prop). We buzzed across the outlet(blocked by a bridge) and headed to the inlet where we could travel up stream to the first beaver dam. It was there I tagged the shore for the first time in the tight narrow stream in about 10 inches of water, with the rear of the boat in a turn I didn't initiate early enough, no damage though. We left the inlet and climbed back up on the heavier main ice and buzzed across the lake. This was a little scary as it didn't seem to want to hold a straight line until we were travelling faster than I was comfortable with. A change of direction seemed almost impossible at speed with the boat twisting but still maintaining coarse. Once along the opposite shore back in the reeds and open water where I felt better about control is where I peeled the leading edge of my side UHMW off on a log.

Finding the weak spots. I'll add a few more fasteners to that.

I am really struggling again to add pictures. The "pic add" button doesn't seem to want to work.....

Go higher up with the poly on the bottom. Higher as in further forward if you can though you prob can because its been cut and all. Soooo driving and airboat aint like nothin else out there huh lol. Glad you made it back safe and sound.

I am really struggling again to add pictures. The "pic add" button doesn't seem to want to work.....
What sort of problem are you having?

looks like you've got a runner! How much more weight will you be adding? Try to get a video of it on water so we can have a look at how it is running on the water.

It maybe a couple weeks before I can get a good video of it on the water as the ice is still hanging on.

I can choose the file I want but the uploader never seem to start. I've been able to do it before....

I've got picturns and a short video of today on my facebook Page. Search "Shop76 Onoway" and you'll find all sorts of things I do there.

Just went and checked you out on facebook. You make some pretty cool stuff my man. I like that fire sphere thing. Real cool

Oh and the video looks nice too. Yall got some nasty waters up there. Looks like it sits ok in the water though so thats good.

Ya the waters a little hard still Lol. At the end of the video the bow was resting on a big rock. It actually sits a lot more level when not moving. Me and my boy are gonna head to a different lake about 20 miles upstream from here where we can get a better run on the river today. Wish me more luck. Oh and I'll bring my GPS for more performance reports.

Ok cool best wishes be safe. Let us know how she moves.

I just thought I'd try to upload from work and here we go. When the water opens up a bit more I'll have some more pictures. These are from Saturday. Had a blast on Sunday am as well. With GPS i see it planes at about 7 mph not as fast as I'd thought before. Not really enough room to have really opened it up but that will be soon enough. Handles like nothing I've ever drove before, lots of fun. I did get to about 25 mph on the ice but with the limited control I was defiantly nervous, lots of throttle left at that speed. A bad cross wind too on Sunday which adds more to learn.
1915191619171918

Even in water a cross breeze will push you sideways when you up on plain. Ive actually had my boat going straight down a shallow trail but at an angle with my boat so kind of like dog tailing with an out of aligned trailer. And did you say 7mph to plane out???? That dont sound right. Maybe 17mph?? Lol

Yeah the wind was playing havoc with my nerves. I finally figured out to "tack" like sail boats do. Drive more into the wind for a while, turn 90* and go more with the wind for a while. That made things way more comfortable even if less direct. I'll have to check my GPS next time I'm out, I'll confirm that 7. my big ski boat planes out at about 15 mph (on the factory speedo) if I trim it right and it's obviously a deep V hull compared to this flat one. You got me second guessing myself now LOL!!

It might be 7 but I dont know I know ill plain out at about 15 or so. Then again I usually just hit the gas and hop up on plane then back it down so not reall sure about speed. I know when I frog at night I found I can hold at about 2000 rpm and stay on plain maybe a little less rpm but too much more and it drops back into the water. Thats with my yellow boat which has a 65" bottom in the back and tapers smaller towards the front. And my boat is a lot lighter then yours. My bare hull weighed in at 220 lb. Though you do produce a substantial amount more thrust then I do so its possible I suppose lol.

Like I said, I don't mind confirming, with all the action going on in my mind it's very possible i'm mistaken. My boat is about 66" across the bottom of the transom, then the soft chine rolls up on a 6"radius. At 99" forward, the hull is 60" wide and the soft chine has tapered away to a sharp angle. This is the same point where the hull bottom starts it's upward curve to the bow. The amount of "lift" we get to put us on plane is only dependent on the surface area, the speed, where the CofG is, and maybe a hundred other things. LOL Should be easy to figure out right? Anyways when the ice is gone around here and I've got a nice straight run to spend some time looking at the GPS and not at what is coming at me I'll check again.

How much effect does anyone think the actual thrust you make has on what speed you plane at?? I suppose it would need to look at the prop center-line distance from the bottom of the boat as well. I'll measure all day if an engineer wants to spend some brain power at analysis.

You sound like your boat is a bit wider then mine and your right about the surface area as to how it acts differently. It would take much more speed I would think to get a skinny boat to plane out and most importantly to stay on plane. A wideer hull will certainly plane out much faster and with less effort. I have the privilege to have both types of hulls with the same power plant. My dads boat is 7' wide at the transom and requires far less effort to get up on plane and stay on plane.
Thrust I feel has atleast a small part to do with planeing out as it requires less effort to achieve this. With your wide blades I would think that with a slight pedal movement you can hop up on plane with a wider boat in quite a short order. Like if/when you get the chance with open water id be very curious as to how low in the rpms you can go to stay up on plane. A wider blade captures more air. And a few hundred rpms can make a big difference in speed were a narrower blade like I have may spin up faster but would require more rpms to keep up the same speed as a wider blade.

Just some rambling put into text lol. Hope you get some open water soon. I would venture to say that you will see speeds in the mid to uper 40's mph range. If not more. Be safe and remember there arent any brakes on these things....unless you make one that is lol
Steve

When I first put the green boat on the water before adding any of the accessories the boat planed fast. Just a bit of throttle and it was on top the water. There most likely is a point as he is saying that it gets on top of the water and that speed may very well be 7 mph. You are at that speed a short time so it would be hard to measure.

Now holding plane at 7mph is a different story.

A wider hull will displace more water and be easier to get on plane. With that said, once on plane giving you have a hull that is wide enough but not too wide a more narrow hull will be faster because there is less surface area or "wetted surface" contacting the water causing drag.

The more wetted surface you have the more drag. This is why I make the small step in my hulls and set the boat up to ride on that area. There is less surface area there. There is a flip side to this also, if you have to tilt your engine too much to raise the front to run on this small area you may be putting downward force on the back of the boat causing more drag.

This is what is referred to when we say a boat is running "free".

I'll have to watch the gps some time when I am gliding after I get off the gas to what mph the boat falls off plane. I'm sure it will be a low number between 7-10 mph.


To add to this, with the Ultra Prop on my boat it will get on plane in less than the length of the boat. It jumps right up there. The engine is able to spin that short narrow prop very quick which produces maximum thrust very quick but on the other end it is not a very good prop for top end or cruise speeds.

I can run about 1500-1600 rpm and stay on plane, I'm direct drive so that is both engine and prop speed.

Earlier this week I met a rock in the cattails, it might have been a log or a frozen muskrat house,(yes frozen still in northern Alberta). Any way, the point I wanted to make from the lesson I learned is that whole "for every action there is an equal and opposite reaction" thing. There is a considerable amount of upward force at the rear hold down point of the engine rigging. This is created by the high centerline of forward thrust from the prop shaft. I know this because i was very concerned of a "hair-cut" and built my rigging very strong to resist the forward thrust, but did not take into account the reacting "pivot" force, which tries to raise the rear of the boat. All of this, when mixed with said "rock", equals two broken rear motor mounts which then failed to hold down the rigging, which then allowed my prop to come into contact with protective cage.(as they are separate assemblies) I should have recognized the potential here as when on dry ground the boat actually rocks forward a bit before breaking free and sliding.

Soooo.... New prop blades on order, boat stripped down to hull again for structural reinforcement and lost the time to enjoy my new hobby. Everyone was safe and sound and no damage to the cage.(impressed my self with that one) and overall thankful for the positives. I think my pride took the biggest hit followed by my wallet.

I guess I'm trying to say that if you figure one should be good put in a second just in case. LOL I will add at least two more mounting points to the rear and possibly two more in the center of the rigging. Also I'm trying to devise a way to tie the prop cage to the rigging. I will post a couple pictures of the carnage as I think that any fails are better talked about for others to learn from rather than hiding them and letting others find out for themselves.

Wow! Sounds like a real impact. Glad that you're all OK ... as I was told after my crash "you built it so you'll certainly know how to fix it" ... not real comforting but certainly true. Tying in the cage to the rest of the rigging is a good idea because it makes everything much more ridgid. Along with the forces of thrust, there is also a gyroscopic inertia applied by the spinning propellor when it is forced to change direction quickly. If you've ever tried to quickly change the direction of a toy gyroscope as a kid you know what I mean. Aerobatic aircraft need very strong engine mounts for this reason.

Glad your ok...lesson learned I guess huh. Always a learning experience...

1925This was all the cage damage. I may just leave it as a reminder....
1926Here is the hull damage, not too bad, I've already began to tap it back to where it belongs, no damage to the bottom. I guess that's heavy enough!
1927 Ahh, the story makes sense with this one. The tabs bent on the rigging but the hull tabs pulled straight off. Ended up breaking one center mount tab off the rigging legs, same side as the impact.
1928 And the expensive parts trimmed down to about 62" diameter from 72". Replacements on order....

All in all a disheartening morning, but I'm very thankful no injuries and the damage is limited to what you see here. I've started on repairs and will have pictures to follow of the improvements. And my son and I have a story to share. They say life is about the stories you have when you're done, I intend to have more good ones with this boat than bad ones.

Wow thats some good investigating..looks like maybe a redesign of where the engine mounts to the hull is really the only real change?? Shame about the blades though :/ atleast nobody was hurt so thats a big plus.

My blunder is on here also. Two weeks after a new prop I lost the edge going around a corner going from deep to shallow water. The boat slid out into some low trees and when I looked up I was headed straight for a tree. I put a huge dent in the bow, broke the rear engine mounts, bent the front, and made toothpicks out of a new prop.

Well much like the drag racing world, if you aren't breaking things once in a while you aren't learning. At least my wife is used to that part! Thank you all for your words of support.

Thanks for sharing your mishap. I'm glad to hear everyone's ok.
I'll have to make sure I really build strong mounts when I finally do my boat because I just know I'll be hitting frozen things.

Cheers ;beer;

Yup. That is one of the reasons I really like the airboat idea. When winter lasts 5 or 6 months you can still get them out to play

Finally got my new prop blades last night!!. While the boat's been down I've mounted lights on the cage and bow, added grip tape to the top of the gunnels and fore deck and built a guard for the prop shaft, on top of the repairs needed on the rigging. I've also bought a second seat which I still need to mount and am contemplating how to do it so it doesn't look like an add-on(which it is)...I'm pushing to get it finished for the Victoria Day long weekend which signals the unofficial beginning of Summer in these parts. I should be close but it is only 3 days away.

I hope you get it done in time for the weekend...Post pics when you get a chance...;thumb;

1962Here's a shot of what I ended up with at the rear. I doubled the tie-down points and added a partial cross joist instead of stand-alone mounting points.
1963This is what I came up with for the prop shaft guard and header/wiring harness cover. They are individual pieces made from .060" aluminium. I'd guess the prop shaft cover weighs a pound and a 1/2 and the header cover maybe 2 lbs. I tig welded this light stuff together and remember why I don't tig so much any more...man is it slow!!
1964Here's a front view of the grip tape and the lights, looks kinda like a bug, LOL

Tomorrow night I'll build a frame for the second seat...either that or take it to the river... A guys gotta play some time but I am starting to have a couple jobs stack up around here. Either way I should have some more pictures by the end of the week.

outstanding work! my rig would rock a little as well when i would hammer on it. i went back and added more braceing to the engine stand and that helped a lot.

i have a few questions on your lights.

1. do you have an onboard charging system?

2. are lights ran off of cranking battery?


i will be adding lights soon myself. most texas air boats must deal with trees more than anything else. here the lights that are mounted on the cage are actually mounted inside of the cage safe from tree limbs. just a thought i wanted to pass on, i have no idea what type of terrain you will be dealing with but may save you some trouble.

Good job on getting the repairs done in time for the long weekend. Now go have some fun and take lots of pics to show us please,
And Be Safe.

It does look like a bug lol. A fast bug hahahaha. I think I remember somebody saying that the lights on I think the cage just shine on the deck and dont really help see but rather do the opposite. It might be a different position and/or light so id be interested to know if each one helps or not. Oh and great job on the repairs they look great. Oh and might be talking to you about perhaps tigging me up a gas tank for my boat.

On the lights, the Yamaha engine has an internally built alternator so the I ran the lights right off the cranking battery. There is a huge difference in light output when the engine is running even at an idle so I know there is enough charging amps. I guess we shall see how much reflection we get, I totally see what you mean especially with all the bare aluminium.
I ended up putting a double front seat in. I had bought the seats so I figure I may as well use them both.
thanks for all the compliments.
Doozit- I'd love to help you on your tank but I think the shipping would kill you. I ended up paying $135 just on shipping for my new blades. Ugh!! Also just putting it out there for any one building, I have a CNC plasma table that I use for my side job. If you need multiple parts from plate and are interested in shipping stuff across the boarder I would be willing to work with any one. Even if it's just one or two complex layouts that would be difficult to cut its really quite easy on the computer.

Off to the lake for mee tomorrow afternoon, I will be sure to take a few pics hopefully with some pike in them as well!

Very nice craftsmanship !! Those guards are top notch...;thumb;...It's amazing how every step of the build adds to the appeal of your boat...Have a great weekend...;beer;

Very nice craftsmanship !! Those guards are top notch...;thumb;...It's amazing how every step of the build adds to the appeal of your boat...Have a great weekend...;beer;

Thanks alot Corky, I did have a great weekend as well. We went to a little puddle sized lake not far from home with some good friends. Maybe only a mile across the long way. I did get the boat out and immediately drew a crowd. :shock: Now I had some pressure. Things went fairly well launching from the beach but I did have to ask some people to move back before I swung the boat 180* and headed for the water.

Being the first time I had it in big open water it was another learning experience. It handles totally different in 1' water than 5' water and I have to say I'd take 1' any day. It seems alot tighter in the corners and tends to slide way better. Any way, my good buddy and I caught a half dozen pike and I think I gave him a surprise on how stable the boat was. He's got a few spots on the Athabasca river he'd like to get to now but never could due to the shallows in between.

Stupid me though in all the action the only picture that was took was of the fish!! There will be a next time soon.....:-D
:-D

Good!!!!

Water depth makes a huge difference. You should try going from 10' of water to 6" of water in a flooded field while on plane. That scared the crud out of me! It was like hitting the nitrous bottle after cutting the brake lines. Lots to learn!!!


Sent from my iPhone using Tapatalk

1988Here's a pic after my first ride on the river. Had a blast and no issues! I was on the river about 5 1/2 hours, driving time around 2-1/2 hours and burnt about 5 gals of fuel. All in all a gorgeous afternoon. Found that i can comfortably cruise on plane at about 5500 rpm with only me in the boat. 1989 No problems in the shallows (less than a foot) but i do notice that in deep water the boat tips to the right. I'm thinking it's to do with prop torque because if I lift the throttle it gets better and in a turn to the left it doesn't happen at all if i enter the turn on an even keel. Any thoughts on what this migh be or how to fix it if I've properly diagnosed???

Glad you are having some success! With every build there are always a few bugs that need worked out. With that motor and prop setup you shouldn't have any torque twist. Are you sure the prop is in alignment with the hull? If it's off to one side or another it will give you that symptom. Does your motor move in the mounts to one side when you gas it?

Glad you are having some success! With every build there are always a few bugs that need worked out. With that motor and prop setup you shouldn't have any torque twist. Are you sure the prop is in alignment with the hull? If it's off to one side or another it will give you that symptom. Does your motor move in the mounts to one side when you gas it?


I'm fairly confidant the prop is centered in the hull, but how much out of center do you think would make a difference? Are we talking 1/16" or would it be more like an inch?? The lean or tip is fairly pronounced at times but always when under throttle. When there is a bit of ripple in the water and I can get some air under the hull the lean goes away completely. I'm not sure if that is related but the more info the better i guess.

Also can you give me more of an explanation on how the torque twist effect works? I've read the term and i think i understand it in case with airplanes but am unsure if it's even relevant in these boats.

Thanks for any guidance you can give on this.

It really has more to do with weight and rotating mass. That motor is not really heavy enough to have the inertia to twist that amount of weight. There is also the rpm deal, you are already turning a good amount of rpms at speed and the change in rpms is not enough added with the rotating mass to cause much twist.

I suppose the next steps would include some more measurements and a good inspection of the bottom side. Any other possibilities come to mind?

Nothing I can think of right now without seeing the boat run. When you start from a dead stop and punch it to get on plane does it go over the top even? By over the top I mean right at the point it starts to plane.

Yes, it is level right to left as i plane out. Its after i go over the top and start to accelerate more, does the lean start.

It's most likely something with the hull then. I just went back and reread about your crash. I'd drop a string line from the center of the prop then somewhere on the front where you can find that same center and see if it's straight with the bottom. Looks like your engine stand took quite a hit. Set the boat on a level floor and see if it's twisted. Also, do you have a slight arch to the bottom at the transom?

i see also that you have welds where you joined the bottom to your soft chines. It could be that one of the welds on a side is larger than the other causing it to pull. Could be any number of things. One thing that would have helped is the arch in the back.

on second thought, I think you put poly on that. Check that also

In all the boats I looked at i never saw an arch across the bottom of the transom until i joined your site. Whether I just didn't see it or it wasn't there on the bigger boats i don't know, but as soon as I saw Corky's pictures I thought that is something I should have done. But by that point it was too late.;bawl; I would imagine they track way better with the arch as well. Anyway, I will focus my attention to the hull, what you are saying makes sense to me, there is possibly a flaw of some sort in the poly, damage, something that is different from the other side perhaps a dent under the inner floor I cant see, time to put on my investigator hat....again.

I realize I've defiantly overbuilt the hull and being the first one I guess it's better than under building. It does handle better with 1/2 tank of gas in it and therefore there is another point of reduction for the future. I've yet to burn more than 5 gals an outing. Good judgement is gained by experience and experience is gained by poor judgement. Thanks for your help.

Just a few quick questions and thoughts...dr.peck76 Is this something that you consider critical or just a fine tune of the boat ???

Papee,in general how much hull warpage/inconsistancy does it take for the hull to lean or wander ??? Is any areas more critical than others as far as "bad spots" that would affect the hull more than others ???? I realize that's a tough question but I've looked at the pics many times and from what I can see it looks pretty good...

I'm looking at the build in general and the fuel tank is centered{and relatively big for the size of the boat} but I have to wonder if by chance the fuel itself is rushing back and possibly biased to one side as you accelerate on plane....I've been around enough to know any objects in the boat have the potential to put a lean on the plane and may need moved around to even everything out...

I guess as Papee has suggested start with the level and stringline and do some checking...Keep us posted...

Dr peck most boats have the arch but it's pretty much unnoticeable in a photo. The arch is so slight that it's hard to see. You may not even see it in person if you're not looking for it.

Corky, it all depends where the dent is at. If you get one back at the transom a softball size one would be noticeable if you're paying attention. I have a few narrow long ones where I skipped over a rock ledge. I'm sure those ones make a difference but not as much as a cup around the transom. One of these winters I'm going to have to tear my boat down and fix some of the dents. I have 3-4 pretty long gashes. I use to be able to hit 34 mph in the right conditions but now I can only get 29 mph tops. Part of that may be the damage to my prop.

Here is a dumb idea, do you lean at all in the seat while driving? I have 3 little boys who always want to hang over the side if the boat and put their hands in the water. I can notice this in the trim of the boat while running. This is in my flat bottom river boat with an outboard. Thinking about it now I do tend to lean on the arm rest of my airboat. A little weight can go a long way in a small boat.


Sent from my iPhone using Tapatalk

All very good discussion.


Corky; What is happening is not just fine tuning unfortunately, the boat seems to suck down to the right, to the point where water sprays above the gunnel and sloshes into the boat. I seem to need to be constantly veering to the right while riding unless i can get some air to "break the seal" under the hull. Then it rides very flat. Also it seems the faster I go the worse it gets. If I load the left front seat with someone heavier, then the lean is not nearly as bad. Also to note, it is almost un-noticable in water less than 1'. But I think that has to do with the pressure wave we create in shallow water.

the fuel tank has two baffles splitting it into 3 compartments lengthwise and is only 12" wide from left to right, it is centred as well to the hull. I don't think that would be it but I've made mistakes before, that's for sure!

Froghunter, this lean makes me nervous enough I lean the other way! LOL When fishing from it, two men can stand on the front deck and it seem quite safe and stable. It is about 66" on the flat and the rolls up on a 6" radius on either side for another few inches on each side . It's about 72" wide about 1" above the poly at the transom.

Unfortunately i'm gonna have to wait for a couple days to do this research as I'm bogged down with another customer project! Ugh, paying jobs getting in the way of important fun again.

All very good discussion.


Corky; What is happening is not just fine tuning unfortunately, the boat seems to suck down to the right, to the point where water sprays above the gunnel and sloshes into the boat. I seem to need to be constantly veering to the right while riding unless i can get some air to "break the seal" under the hull. Then it rides very flat. Also it seems the faster I go the worse it gets. If I load the left front seat with someone heavier, then the lean is not nearly as bad. Also to note, it is almost un-noticable in water less than 1'. But I think that has to do with the pressure wave we create in shallow water.

the fuel tank has two baffles splitting it into 3 compartments lengthwise and is only 12" wide from left to right, it is centred as well to the hull. I don't think that would be it but I've made mistakes before, that's for sure!

Froghunter, this lean makes me nervous enough I lean the other way! LOL When fishing from it, two men can stand on the front deck and it seem quite safe and stable. It is about 66" on the flat and the rolls up on a 6" radius on either side for another few inches on each side . It's about 72" wide about 1" above the poly at the transom.

Unfortunately i'm gonna have to wait for a couple days to do this research as I'm bogged down with another customer project! Ugh, paying jobs getting in the way of important fun again.

Thats interesting about the low water comment and also the spray. Where do the sides of you poly end in reference to your hull?

Looked back again. Is your poly white? If that is the white poly I see coming up the side in the one photo I can see how/ why this is happening. Depending on how your boat rides on the water of course. If the spray is coming out the front about where the bow arch is you may be able to remedy it by lowering the front of your motor. This will raise the bow and maybe not catch on the front of the poly. In low water your boat may be riding higher in the water so it's not doing it there.

Yes Papee, the poly is white. On the sides it ends right at the transom, and starts right at the base of the bow curve, on the bottom it wraps up almost to the bow eye and ends again at the transom. When underway and planed out, when the lean is bad, the spray comes up about 1 foot behind the driver seat on the right. On the left, the spray pushes out flat on the water like you'd expect it should at about the driver seat. (I'm sure this is because the other side is so low)

I'm trying to give as much info as i can here . I hope I'm going overboard on it...

That spray is where you problem is. Check you poly good.

https://www.youtube.com/watch?v=2uuzRg0J5Wo

Check this one out I finally go my boy to get me on a fly by. This is in deep water on lake isle. So you can judge, the poly wraps up the sides 8" in height from the flat bottom. I examined the bottom and there doesn't seem to be any damage. the only thing that really stands out is a dent at the base of the bow curve, near the center line. It's only about 1/2" deep at the deepest and 6" across. Take a peek at the video and let me know what you think.

Is what you've posted a link ??? If so i cant get it to work...EDIT: Got it to work took the slashes off the beginning and did an internet search then it came up... I'm certainly no expert but I'm going to throw this out there...It looks like the back end of your boat is heavy...You're moving fast but it does'nt seem to level off as much as it should...I have a checkmate speedboat with a 250 yamaha outboard and if I'm right at the point of jumping up on the water and hold the throttle there I can get the boat to do exactly what your's is doing where the bow is up,it's moving at a good pace but the water wraps back around the boat to the point where it'll soak the rear passengers....Then if I get moving faster it jumps up on top of the water and "frees itself" from the drag...

Is what you've posted a link ??? If so i cant get it to work...EDIT: Got it to work took the slashes off the beginning and did an internet search then it came up...

I'll have to remember to edit it like that. Thanks

I edited your post to fix the link. it just looks like it is a symptom of the hull design and it running on one side heavier than the other, The boat really isn't running free. it looks fine though, just a bit heavy of a hull for that motor. If it would take more pitch to get it on top of the water it would probably run more free. That water has to come out somewhere and that point is where it comes out with the way the boat rides. Maybe moving around some weight would help.

All good suggestions. If I were to adjust prop angle, maybe raise the rear 1/8", do you think that would help? Also I've read of guys sliding a strip of poly between the hull and the main sheet of poly to act like a trim tab. Any opinions on that. The boat does porpoise if I pick up a little more speed and I was on the understanding that if it was porpoising it was definitely running free. Any more thoughts?

If a boat is running free you will see almost no wake behind the boat. My opinion is that the hull being flat and maybe a little heavy for the power is causing these symptoms. I don't think a trim tab is the answer, if it's porpoising you need to put more downforce on the nose.

I don't think a trim tab is the answer, if it's porpoising you need to put more downforce on the nose.

Can that be achieved by adjusting the prop shaft angle? I'm thinking I'd raise the rear.... I can shim the whole rigging without having to mess with my motor to shaft alignment. Would there be suggestion of how much?

I'm not sure what you are calling the rear. raising the rear to me means raising the prop end which would raise the front. you want the prop pointed more at the water. I'd start with two washers. I'll try to get some video of my boat running in the next couple days. My boat really runs free with almost no wake and very little splash out the sides.

You're not going to get it to run perfect on the water because it's just too heavy as I think I mentioned in the first post when I saw your build. Things like the weight and the hull design will hold you back some from getting it to run well on the water. You're kinda stuck because you just need a little more power than you have for that weight but it's too narrow to put on a bigger engine. The missing arch in the hull and weight is what is hurting the performance. If you get it tweaked it should be a half decent runner though.I would have also not gone with the poly.

EDIT: Forgive me if I'm confusing your hull with another build, I get a lot of calls and emails each week and my memory is getting older than I.

LOL, you've mentioned a couple time that it's too heavy... yeah I get it. No hard feelings. The poly works great for protection as this boat will push on dry ground, the wet sand seems to stop me but gravel bars and my own driveway I seem to do fine on.

Anyway, here's very technical question that I'm obviously confused on, and keeping in mind that I have a prop shaft over top of my engine (parallel to the floor of the boat). As I'm understanding it after your last post, If i adjust the stern end of the prop shaft down, the effect would be when running, that the front of the boat would push more down as well. (Kind of like the whole boat assembly acting like a rocker) Do I have a grasp on this or am I completely bass ackwards???

I really appreciate your advice and certainly am not wanting to take up your whole day but the conversation has me fascinated. I would have thought that by pointing the forward line of thrust at the front floor of the boat it would have pushed the front down but i think now that i see that the there must be a point where the line of thrust wants to rotate around the center of mass of the boat. .......I have no idea if that makes sense to anyone but myself.

I will add two washers to the front rigging mounts, and one washer to the center rigging mount. This will effectively point the prop wash more in the direction of the water, unless you come back and tell me I've got it all backwards LOL!!!

Also as far as more power...there is always the possibility of asking this little bullet for more, add a few more pounds of boost, maybe another fuel injector..(insert evil laugh here) LOL

You Have it right. You did a good job on the boat, just a few things missed. I know I don't do things the same as others either but I do know what will make these things run the best they can with the power available.

Hey Dr Peck did you get a chance to do any tuning ???

I think he has his prop out being repaired.

EDIT: Guess we were posting at the same time.

Hi Corky, I wish I had. Before I started changing things about I noticed some of the leading edge protection on my prop was de-laminating.20412042 I sent some pictures to Sensenich and they explained it was very unusual, and set me up with a warranty claim. they were very good, no questions at all and covered the shipping costs both ways. You may remember I've mentioned that I always thought that this prop was a little big, after discussing my running conditions with Darren from Sensenich, he agreed and we decided to exchange on a slightly smaller design which will allow me to get it pitched into a more effective setting. Long story short, the new ones should be arriving on Tuesday next week... and I've missed two weeks of the hottest weather we've seen around here in recent history.....oh well not much I can do about it. I'll be sure to report as soon as I have some news.

Hey, I thought I would post some of my pictures and descriptions instead of littering other threads with my stuff. This is my first airboat build, it's 13' long over all, 5'6"at the bottom of the transom and 80" at the top. Soft chines built to a 6" radius. The hull tapers to 60"wide at the bow.1813
.125" floor plating, the rear 4' of the side are .125 as well with the forward sections .080". Transom is also .125" and 24" tall with a 4" center dip for prop clearance.1812
I Choose a 2010 Yamaha Nytro snow-machine engine for power, it is a three cylinder, four stroke, 1049cc's and dry weight is around 150lbs. This engine is from Yamaha's Genesis platform and was origionally designed as a four cylinder motorcycle engine but has found it's way into all powersports. This model is fuel injected with an aftermarket turbo set-up and produces around 200hp at 9000 rpm. Engine red-line is somewhere north of 12000 rpm.1814
I used the factory exhaust but had to massage it heavily due to the new turbo location, full stainless on the header. I had the pieces of the prop shaft custom machined to use 2- 1/2" pillow block bearings with a spherical roller element for axial thrust loading. Theses bearings spec out at about 1200lbs each for axial loading. The belt drive is a 36mm wide, 8mm pitch Gates timing belt.

My rigging is made from 1" by 1" by .125 wall square tubing (aluminium) with 1/8" and 1/4" gusseting. Bow deck structure is 1" by 2" by .125" tubing with the obligatory 2" aluminium pipe at the leading edge.1815 18161817
I've been at it for almost a year now. Holidays, kids sports and paying side jobs getting in the way of my free build time at home. This past weekend I have skinned the rudders and started on the steering linkages and my level of excitement on the project is at a new high. I've had it running twice with power to the prop, and on the dollies it pushes hard enough a man can't hold it back at about 800 prop RPM.

TO do list as of Mar 8
- complete steering linkage
-build accelerator linkage
-complete bow deck
-install UHMW to bottom of hull
-install lighting
-install bilge pump
....install the 1000 little things I haven't thought of yet....

This is sweet.

Corky, I'm happy to update on my tuning!!

I was able to put almost a full tank of fuel through the boat this weekend with about 4-1/2 hours of run-time on the river and another hour or so on Lake Isle. It was fairly windy and I spent about 1/2 my time pushing a fairly good headwind.UGH!

Anyway, after some measurements I ended up adding 1/4" to the front of my rigging to adjust the thrust angle from skyward to toward the water. Of coarse Papee was right in saying this would get rid of the porpoising. His guess that the mysterious spray and the boat lean when under power were connected was also correct. After this prop angle adjustment, the lean that had me so nervous and the climbing spray are all but gone under most conditions. The boat only porpoises at high speed and runs very level left to right now. Thanks so much for the advice and the lesson, Papee. I think I will add a little more shim to the front of the rigging just to see the result, but overall I'm very happy with the way it's running as compared with before.

Still haven't made a GPS speed measurement a priority...

I also have some good words to say on Sensenich. In dealing with my prop warranty issues, we decided instead of repairing my existing blades to trade for the next smaller model. I am now running a 70" dia. 10" wide as opposed to the 72" dia. 11-1/2" wide blade. This was a good decision as now the prop is set well into the useful pitch angle instead of running so flat. With the old one, it was set just below the first pitch mark. The 70" performs much better at all RPM's. I seem to have more push at the bottom and on river rock, the boat has no problem climbing the sloped bank. All in all a great weekend of riding.
2056

www.youtube.com/watch?v=yusd3GM43q8 Here's a 50 sec video of July 19. The water level rose about 2 feet over night( they may have opened the dam upstream) and the riding was awesome. I've got more videos if you follow my youtube account. Cheers

Thanks for the update I'm sure I'm not the only one following this thread and hoping you get the boat fine tuned the way you expected it to run...;thumb;...Sounds like the prop swap was a good move and has you shifted into your powerband...You've got more than enough HP and torque to get that boat moving it just needs some trial and error as most builds do..

It looks like you're having a blast running up that stream that's what it's all about !!! ;beer;

I'm glad you're happy with it that's all that is important. My boat is a pile compared to some of these new builds but I love it! I'd put more shim in it as you mentioned, you should be able to get rid of the porpoise.

OK! we were talking about steering linkages yesterday on Corky's build, and I mentioned I'd add some pics of mine. I have very steep ratio's but I've never thought the steering to be heavy in feel, and the pieces I've fabricated have been working without fault for the hours of operation so far. (about 25)209720982099 The first picture is my triangle plate pivot. From center of the fulcrum to the center of both linkage points is 4", this is the same distance from the fulcrum of my rudders to the linkage point point on my rudders. This keeps the math easy as far as figuring the length of stoke differences...isn't a difference here. The second pic is of the bottom of my control stick, I have a center pivot and the reaction link has adjustment. It is about 24" up to the top of the handle from the pivot and 5" to the hole I have it set to currently.

Very nice and excellent craftsmanship !!;thumb;...I like the builds where the steering stick sits high, the linkages are relatively on the same plane, and have a more direct route...In your case it got you out and around the engine and prop nicely...

I've seen the gas peddals that have the triangle pivot they're a great set-up...

[...] I Choose a 2010 Yamaha Nytro snow-machine engine for power, it is a three cylinder, four stroke, 1049cc's and dry weight is around 150lbs. This engine is from Yamaha's Genesis platform and was origionally designed as a four cylinder motorcycle engine but has found it's way into all powersports. This model is fuel injected with an aftermarket turbo set-up and produces around 200hp at 9000 rpm. Engine red-line is somewhere north of 12000 rpm. I used the factory exhaust but had to massage it heavily due to the new turbo location, full stainless on the header.

1814


Great build and thread dr.peck76.

Question. Do you have any other pictures of the Turbo setup/design layout? Which turbo is this - any idea? (Bender, Full Power - or an auto turbo modified?) I'm curious how your intercooler, blow-off valve, etc is set up and can't tell from your photos. I'm looking at adding Turbo Options to my airboat build (2004 RX1 4 cyl) but don't want to pay $4K for a stock system and so far have not found anything 'used'. If anything, pics will help me along the process as I work through my build - I've been considering building my own kit. Thanks!