aerokirk's build

[aerokirk]

I purchased the motor mounts along with the Circle S reducer from Chuck at Airboat Pros in FL. His mounts are probably best because they're not too heavy and are made of stainless steel so they'll never rust. Just make sure that you take the urethane cones off of them before you do any welding so they don't melt. It's ok to tack weld with them on but don't apply too much heat before removing them. As for the cage wire, I used 1/8" stainless rod (20' long) and welded them individually after marking locations with a marker which worked out great. It takes time and is a real pain to weld each intersection but it came really good and I'm getting compliments from the people that see it up close.

Oh, and by the way, I made a "tee" out of 1 1/2" square steel tube to match the bolt pattern of the engine so you can use it in place of the heavy engine when you start to weld your structure ... look back on my build thread and you'll see what I mean. It will also help when you true up your mounts ... I used plumb bobs down to a hull centerline string so I knew that the motor would be square with the boat.

[krwsr]

Great info! I really like the stainless rod idea; it looks better than any thing I have seen and well worth the extra time. I see what you mean about the square tubing, another good idea. Thanks for the help!
Kenneth

[krwsr]

What made you decide on the three bolt engine mounting?
Kenneth

[aerokirk]

What made you decide on the three bolt engine mounting?
Kenneth

The three bolt design is probably the lightest and most appropriate for the 084 since it is designed for the three point mount. Try not to add any more weight than you absolutely need to on your rigging but don't under-design the engine mount as you want to keep safety in mind. Airboat Pros sells the tube mounts, cone bushings and bolts for this engine and I would recommend that you purchase them as it makes the build go easier. I used 1/2" stainless tube for the majority of my structure and 3/4" for the engine mount. This really helped keep the weight down as the stainless tube is smaller diameter and lighter than 1/2" conduit but on the down side, more expensive.

[aerokirk]

Installed a cylinder head temperature gauge yesterday that I picked up during the Oshkosh EAA convention. I thought it was a great deal at $52 for both the gauge and the 18mm ring thermocouple. I installed it on #1 cylinder and took the boat for a hard run today where I found that the maximum CHT was 450 deg F which is well below the 475 degree maximum according to the 084 manual. I purchased it from Wag Aero at the show and they had one on hand so I was able to take it with me sans sales tax

[Corky]

Sounds like you got a great deal on the gauge and hardware... Your last post reguarding the prop pitch said you dialed it back to 13*...How are the RPMs now ??? It will be interesting to hear how your prop pitch dial-in{if any from this point} will affect the CHT readings...

[aerokirk]

At 13 degrees I am showing 3200 rpm at WOT and getting 32 mph in no wind conditions. I am thinking of taking a little more pitch out so I can get 3600 rpm but before I do that I want to confirm my tach readings are accurate. I purchased a photo tach which I will use to double check. I'm hoping that I won't lose much top end speed and gain some push to get on plane quicker with two people. I have 10 hours on the boat now and everything is working great ... the steering is very responsive and I haven't encountered any problems. I'm in the process of installing an intercom so we can communicate through our headsets.

[krwsr]

I have been trying to locate this roll on the net, but all I have found is the dies? Can you give me some direction?
Kenneth

[aerokirk]

Today we took the airboat to a local wildlife flooding to see how it would perform in the reeds and brush. I was pleasently surprised with it even though I haven't applied a slick bottom yet. Here's my first video ...

http://youtu.be/2x-AlHaUmrw

[Corky]

Hi aerokirk...How's the boat running ??? I've looked through your thread{and other places on the site} and have a question...What does the circle S reduction weigh ????

[aerokirk]

Hey Corky,

The boat is running fantastic ! I've installed an intercom so we can talk to each other and I did my first oil change on it yesterday to get rid of the break-in oil & filter. I replaced it with Shell Rotella T after reading many articles on the proper oil for that engine. I also added a can of STP to aid the lifters.

The Circle-S drive is working very well but I've got to place a call to Chuck (Airboat Pros) regarding it's idler roller which has started to hammer on it's adjustment screw. I've tried setting it loose and tight with no luck. The drive is quite heavy at about 40-50 lbs but it allows the prop to turn slower so the noise level is quite tolerable. I plan on taking a "walk around" video of the boat as soon as I can since I've been getting a lot of questions about construction.

It has been getting quite a lot of attention wherever I take it and draws a crowd when parked. There's aren't many airboats (if any) up here in the U.P. of Michigan so most have never seen one up close

[aerokirk]

A warning to other builders using the Circle-S reduction drive ... I have been trying to figure out how much tension (if any) should be put on the idler roller as the drive belt begins stretching. I have found that the idler arm hammers on it's adjustment screw as the idler roller rides the back of the belt (which has small grooves). On a couple of occasions I have found the adjustment screw has come loose due to this idler arm hammering so I called Chuck & Bruce for some idea of how to adjust it. The adjustment screw is a fairly large 1/2" diameter bolt with a 3/4' diameter locknut.

Yesterday I took the boat for a ride after adjusting the tensioner and insuring the locknut was tight. As I reached WOT I could hear the idler arm hammering and then I heard a distinct "Ping" sound. I pulled the boat over to the river bank and shut it down. It was then that I realized that the vibrating idler arm had caused the locknut to come loose and the bolt & locknut had gone through the prop causing a nasty gash in the prop leading edge! Now I have an almost new prop that must be sent in for repair. If you are using this redrive make sure yours isn't doing the same.

Update: It appears that the reason for the bolt vibrating off was that there was supposed to be a flat washer AND a lock washer on the adjusting bolt. I learned this from a phone conversation with Bruce from Circle-S. The re-drive I purchased had only the flat washer and no lock washer. I confirmed this by looking back on the photos I took of the reducer at the time of purchase. Frustrating to say the least!

[Papee]

What is your RPMs with this setup at cruising speeds? Say about 18-20 MPH. With my direct drive and my hull design I can cruise at about 2000 rpm.

[aerokirk]

Still don't have detailed numbers as I've been spending my time exploring waterways with my wife and not always taking my GPS so not too sure on the speeds. I can tell you that with two adults wind direction is critical to performance and the boat will come off plane at anything under 18mph in deep water which is about all we have up here. I'm convinced that I'm not getting all the power that the engine is capable of producing, because of the stock carb. I took some pitch out of the prop recently in order to get the engine up to 3600 but it didn't seem to help with planing faster. With my recent prop strike mishap I'm taking it a little easier until I get my re-designed idler from Bruce at Circle-S. I peened out the gash in the prop's nickel leading edge and I'll continue to use it until this winter when I'll probably send it back to whirlwind for repair.

[Papee]

I am working on another carb deal now. The Tillotson carb is working well but I think the engine will take more gas. My idea is to use two of the carbs taking the float off the front one and run them back to back with a progressive linkage. The stock fuel pump will have to be removed and an electric fuel pump installed for this to work because the second carb would hit the pump but I think its a good setup. I'll just make a plate to put between the carbs to mate them. The linkage and fuel lines will be simple.

[Corky]

Glad to hear they're going to take care of you with the redesigned idler...I'm suprised this issue has'nt come up before you...You really don't have that many hours on the boat and you have to wonder how the other builders got by...

[aerokirk]

Finally got some time today to finish the spider modification so now I'm just waiting for the paint to dry and I can install it in on the engine. Since I had the down time on the boat I took the opportunity to paint the mufflers with 2000 deg paint. Now I'll have to re-engineer the throttle linkage and take it for a spin ... vrrrooommm!

[Papee]

Get that thing on and get it on the water, you're going to like that new carb setup. I ended up just using a hose clamp and clamping my cable onto the rigging. I'll have to revisit that at some point and figure out a better deal but it works fine the way it is.

[aerokirk]

Nothing more boring than watching paint dry It's supposed to get down to 33 degrees tonight so I'll be a little slow getting it on tomorrow. Papee, did you add an extension to the bottom of your throttle lever on your carb to give it more travel? It doesn't seem to me that there's enough compared to the longer travel of the gas pedal.

[Papee]

I didn't do anything and mine works fine. The throttle is not hard to push and works smooth. On my pedal there are two holes, one for a short throw and one for long. I have mine in the end one for the long throw.