Hello Everyone !

[txriverrat]

I run the Brazos river in TX big rocks, sand bars, gravel bars, and concrete and steel in places. I have been running this river a long time and fiberglass doesnt do well here ,my boat will have 125 bottom. 90 sides and be aluminuim
Here is my thinking about poly.
It isnt trouble free . first you build a hull then drill a quillion holes in it ,besides the bolts sticking up in the boat , every one is a potential leak. Poly works great as long as it doesnt get a tear or rip in it ,if it does it can wreck you quick.Plus the added weight
I am going to use some form of quick slick ,very little added weight ,to me it is also safer, and I can always add the poly later.
As far as holes dent and tears in my aluminum hull ,heck I built it I can dang sure repair it.
Just my 2 cents worth.
Ron

[Papee]

There is no mini that I know of running poly even on the glass hulls. Chuck never put any on his hulls, he used a painted on coating also. My hull was made in 1974 and is still going strong. I just pound out the dents every couple years.

[Corky]

Wow, must be nice to live on the water. Welcome Aboard! Where did you find your 084?
Kenneth

Hi Kenneth, yes it's beautiful living along the susquehanna river...Great view and I can go fishing anytime I choose.. Most of this river is rocky and relatively shallow..The airboat is a perfect fit...There's a couple dams along the river's path which makes a few areas for the more conventional powerboats but for the most part an airboat would be able to run more water than any other boat with the least amount of problems...And so the reason for my build...
The widest span across is in Millersburg Pa.{where I grew up}measuring close to a mile... That's where Papee and other airboaters put in most of the time...Beautiful town with a wonderful, waterfront park that's very accomodating to the boaters...I'm not sure who's the first to bring the airboat to this area of the river but my dad helped a guy make wooden hulls for them back in the 50s so they've been here for a while and the sound of the airboats cranking up are a common occurance...

I snagged my new 084 off Ebay...There seems to be new engines on there all the time...I made the guy an offer and he accepted it{had 2 still has one}... I've read everything I could get my hands on for that engine and will be an expert at least from the mechanical end before I even get the boat finished...

[Corky]

Hi Guys,

I've seen boats with the poly on them but as papee has pointed out none of the minis have that on them... It just would'nt be worth the effort considering the added weight and the fact that an aluminum boat seems to do just fine in this weight range without it...All I've ever done is pound the dents out if they were real bad on my old boat... I'm sure there has to be a point where a heavier boat would need it for damage control but I'm not sure what that point would be...Someone mentioned a local boat builder using a better grade tempered aluminum{?} for the bottom but those airboats run the big guns on them and still no poly....

[Doozit20]

Boat hulls down here in florida are either made of 6061 or 7075 grade aluminum. The later is expensive but is extremely strong and is considered aircraft grade. 6061 is very strong as well and I think it can be welded where the 7075 has to be riveted or screwed together in some fashion. 5052 is another aluminum that can be used though it doesnt have the tensile strength that the other two have. However the 5052 has more of a bending characteristic to it along with good corosion resistant properties which means that if/when you hit something rock,tree,stump.. the aluminum will bend easier rather then risk of it tearing. Just food for thought in selecting your material...oh and the grades might be a little different but I think those are the right numbers for you to do some searching.

Steve

[Corky]

Steve,
Thanks for the reply on the aluminum...I've read multiple charts and other info on the aluminum sheet tempering but none have given examples of where/when to use it just general info comparing the different types to one another....From what I'm gathering the higher the temper the more difficult it is to weld...I have'nt even touched the "T" and Tube type supports that are normally used for these builds...As you can tell I like to know {as much as possible} all aspects of this and not just jump in,make mistakes, and wish I'd have done something differently... But of course that could happen anyhow...

[Doozit20]

Corky,
Im not sure what makes one metal harder to weld then the other but I know 6061 t6 can be welded and yet the 7075 t6 is more difficult. It could be the grade of aluminum or more so it could be the properties that make up the aluminum. Dont quote me on that one lol. I know papee built his boat out of 6061 t6 I believe. My buddy says that the 7075 "t6" I think, again not sure of the "T" on that one, is very hard to bend. And that you have to preheat it in order for it to work better. Preheating as in leaving it in the sun for a while. This of course is to have a single seem down the middle of the boat and then riveted. If you build as a lot of people on here then you will be welding a single sheet onto two seperate sides which is usually done using 6061 as it has good temper and yet still easily weldable. And yes definitly learn all you can before doing you buying as it can get expensive rather quickly. I know a single sheet of 4'×12' x .100 of the 7075 I think cost aomething like 400-500 bucks. Im planning another build that will be a deckover design out of 6061 but ill be riveting and ill be shooting for the hull to be under 200 lb when done so it will be some thin stuff

[Corky]

Here's something I ran into this week...Met a fellow who builds his own mini airboat hulls...And the difference being he laid two sheets side-by-side and had the sides bent on a press...Then welded the seam down the middle...Also has the rear transom floor/side area bent in a series creating a rounded transition so it's not a straight angle in the back where the side meets the floor...Says it won't "bite" while sliding hard into a turn and flip on it's side...I've seen this on a few hulls having the "rounded" corners back there and wondered what the advantage was{if any}... He gave the last hull built a small "V" when welding the center seam{about 1/2 to 3/4 inch} back at the transom and says it's a big improvement on cornering over the first "flat" bottom hull he built...

It's amazing the different designs and theorys surrounding these boats...Seem there as many as the people building them...

[Papee]

Are you saying that the bottom of the transom is rounded? I can't really see that as and advantage. Many of us even make the bottom piece go past the transom about an inch. As far as the digging in, as long as you have the slight arch in the bottom at the stern they don't dig in. In fact I have to slow in a turn to let the boat settle so it doesn't slide out.


I don't care for the "v" in the middle it would take the slide out of the boat and would catch more than an edge would. I'd rather be able to "slide out" in an emergeny. I'm just not sure I'd want something like that.

I'm also not so sure about a seam length wise up the middle. It most certainly wouldn't be a structurally sound as no seam or even a two piece welded across like I do. It could be that he is not seeing the speeds we are.

[Papee]

Now that I've thought about it a little. He has the rounded sides and no chines so it would really slide out easy. He had to add something to keep it from sliding. The way my hull is designed, the back has the slight arch in it where the boat runs when on plane the front part of the boat is flat. When you slow down a bit to turn the boat settles down in the water allowing the edge to catch to turn.

[Corky]

Basically he radiused the transition between the side and the bottom{mabe 2 inches +or-}at the transom area but picked a point farther up the hull to start the bends...To be honest I could'nt tell the bottom was'nt flat until he pointed it out.... It was'nt a distinct "V" being only a fraction of an inch across a 5.5 ft bottom{13ft long}...But it was interesting to see being that it was'nt built the traditional way welding the sides to the bottom...His engine of choice was a rotax/gear reduction with a 3 blade prop...Claims he's in the mid 40 MPH range single rider...

[Papee]

I agree with what you're saying about a jon boat...I'm keeping the antique intact...This will be a completely new build{revolving around the 084} for some fun the river...

Basically he radiused the transition between the side and the bottom{mabe 2 inches +or-}at the transom area but picked a point farther up the hull to start the bends...To be honest I could'nt tell the bottom was'nt flat until he pointed it out.... It was'nt a distinct "V" being only a fraction of an inch across a 5.5 ft bottom{13ft long}...But it was interesting to see being that it was'nt built the traditional way welding the sides to the bottom...His engine of choice was a rotax/gear reduction with a 3 blade prop...Claims he's in the mid 40 MPH range single rider...

Is that the you get guy that built two boat pretty similar? The guy I'm thinking of and his dad have similar boats but running different Rotax setups.

[Corky]

Yes, two different rotax engines...Believe it or not the kid welds better than his dad!! His dad admits that too......I was impressed with the hull quality from a 20 year old {but his dad guided him through the project} And I was there purely to see the different hull fabrication approach he used ...That being said, I'm not fond of the 2 cycle engine but do respect the light weight,HP and torque the rotax puts out and see why some go that route{but hang on to your wallet... The money and the lining would be ripped out and the moths would be flying..He did say a thermostat just cost him over 100 bucks !!}.. Bottom line yes, it's comparing apples to oranges with the different powerplant for our purposes but as far as the hull is concerned it's still educational...I've been absorbing everything I can see {even the big v8 boats} on hull design and structural bracing and why the manufacturer did what he did...and it's very interesting to me at this point...

The great thing about the 084 is the overall cost and parts availability... And being able to modify/improve it with some add-ons...The challenge for me will be to build a light,reliable, and respectibly fast 084 mini...

[Papee]

Just a little FYI, you don't want a rounded corner at the rear of the boat. They are harder to get on plane. The water runs up the back of the boat. With a sharp edge the water doesn't wrap the transom but flows straight back. A little lip back the is even better. It's discussed some in Busters build thread I think.

[Corky]

I don't think I'm describing it correctly... I'm not sure of the correct terminology for this...Here's a picture I found of what I'm talking about...The side contour where the wall meets the bottom is rounded not the actual transom ...

[Corky]

And for comparison I'll use a pic of yours from the back corner...that's got a distinct,sharp corner where the floor meets the side... And the second pic is what looks to be a combination of the two , semi-rounded but with a sharp corner....Not saying one is right or wrong I'm just trying to figure out why/when to use each configuration...

[Papee]

Ok the top pic with the rounded side would be the worst handling of the three. With the rounded side there is no edge there to turn on. My boat or the hard chine type boats float better and a a faster hull than a chined boat like in the third photo. A chined boat is the best handling boat as far as turning but you do lose some wetted surface or flotation with the chines. Chined boats are the most popular but I think it all depends on the area and the use of the boat. If you look most boats designed for low water are hard chined boats like the jet boats. A hard chined boat is also the most stable of the three. If you check out the builders around here you'll find most that have been building for a while use a hard chine design.

[Corky]

OK thanks for the clarification... I've read numerous times in these threads about the chines but did'nt realize it pertained to the hull, bottom and side angles as a whole...And this is the first overall performance description for the hard and soft chined hulls I've read relative to airboats....

And now for two more theoretical questions on the next level of this...

A) Pic 1, Would the completely radiused chine benefit/need the bottom shaped like a "V" to aid in turning ????

B)Pic 2, On a hard chined,flat bottom hull is there a point where it could "dig in" and possibly flip the boat over under a hard,fast turn ???

C) What effect does the actual angles of the hull sides do for stability and cornering ? {for instance the sides "straight up" compared to a 45* angle}

Sorry for all the questions...Somebody that buys a hull had the thought process taken care of for them and you get what you get...Building one is another story...You either copy someone elses boat or ask all the questions like me.. Im sure there's alot more people out there with the same questions but did'nt ask...

[Papee]

The hull in the first photo with the curved sides just would not turn well at all putting a v in the middle would be like trying to use a corrugated John boat hull for an airboat hull. Just not a good design.

Any boat could catch an edge and tip over depending on conditions. The angle of the sides has nothing to do with steering, putting an angle in adds to the width of the boat and also helps with flotation or more precise, displacement.