Honda CBR 600cc 10x6 Aluminum Airboat Build

Airboats with smaller powerplants.
Muckduck
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Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Aug 20, 2017 6:49 pm

Hi everyone, I want to attempt to document this build for the benefit of the airboat community. Let me just share a little of the build up to this build. I moved to Florida in 2005 from Washington state and knew almost nothing about an airboat. A friend took me for my first ride on a Friday night and Saturday he let me drive, I was hooked. I have a few other friends with boats but I just had to have my own.

I briefly owned a small 11'6'' fiberglass boat with an 0290 and until it left my wife and I stranded in the marsh. My wife was a great sport about walking back through the marsh and it turned out to just be a fuel pump (running but not actually pumping). The boat needed stringers and burned a ton of oil among other things like a new prop, so after spending $500 on the mags to get it going in the first place I lost interest in the other work and decided to cut my losses. Some time passed and I a acquired a 28hp Kohler engine and I was bent on building a mini but I was concerned about performance. I decided to sell the engine and move on again.

Finally I came across this aluminum beauty! The boat was complete!

-10x6 Aluminum hull
-Rigging
-Rudder
-trailer
-3 blade adjustable pitch prop
-Single Cylinder Diesel Engine
-Rake
-Fuel Tank and pump

It was cheap and I bought it within 20 minutes of being posted in craigslist on a Sunday afternoon.

The bad:

The seam down the center of the hull was never welded among numerous other cracks and holes so water would just pour in if it were not for all the silicone sealing it. The rigging is designed for a 54'' or so jon boat. The engine was locked up but I wasn't going to use that anyhow and the 3 blade prop is really only a sun bleached 2 1/2 blade prop.

I was stoked with the possibilities!
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Aug 20, 2017 7:04 pm

The first order of business was to see how it floats! After taking all the loose stuff off the boat I dumped it in the pond and it is surprisingly stable. The hull is exactly 10' long and 6' wide at the bottom and about 8'' tall. I could stand at a rear corner and had about 2 inches to the waterline and I was fine standing in the center of the front but I could push it under on a front corner.

I knew I would have to deck it over to keep from sinking it.
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Aug 20, 2017 7:09 pm

First order of business was to remove the relatively well thought out bracing and supports to make room to strip some paint. Also during this time I picked up from a friend a 1993 Honda cbr 600cc bike that was laid down 10 years ago and then put in a storage shed. When we pulled the bike out of the shed a rat came running out of the air Box. After getting it home and hooking up a fresh battery and pouring some gas in the carbs I was able to get it to crank after about a pint of rusty rat piss came out of the exhaust. All I needed was to hear it run and I knew I had a wind maker in the works.
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Aug 20, 2017 7:13 pm

Making some serious progress. It took about a gallon of paint stripper, several late evenings and too much time on a flapper wheel to get to this point.
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Aug 20, 2017 7:30 pm

Boat is all cleaned up and I threw the rake on and dropped in the braces that came with the boat to get a feel for what it might look like. The transom on the boat was 2 separate pieces of metal screwed together and was never welded solid across the bottom.
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Aug 20, 2017 7:34 pm

This hull is a cut down something. I am not exactly sure what the person that cut it down was going for but I don't like it. It looks like its bent or has tail fins and I just was not into it.
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Aug 20, 2017 7:43 pm

All stripped and cleaned up. Terrible job. I had a few people through the processes tell me to not worry about stripping all the paint since it would be decked over but I knew and it just made me feel better knowing the paint was stripped completely. Also by this point I realized there was a substantial amount of welding that needed to be done and it would have to be clean.
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Aug 20, 2017 7:45 pm

I figured out real quick that I would need something a little different than my tractor supply Hobart handler 140 to weld all this aluminum. I have had limited success welding aluminum with that machine but I would say for every inch of weld I would throw away 20' of wire. If there is a an pressure at all on the feed rollers the aluminum wire will ball up. I thought about taking the boat to a friends shop and using his tig machines but I am an piddler and enjoy working at my leisure so I would much rather rent or own my own tig welder. Well this friend also happens to sell welding equipment. Their site is iwestore.com and they set me up with a tig 200 AC/DC machine. Their prices are hard to beat!

So this got me up to speed on a way to stick it all together.
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Aug 20, 2017 7:55 pm

I welded the center seam of the boat solid and warped the hull a fair bit but beat back flat with a rubber mallet :)

To solve the problem of the really ugly cut to the hull I removed the old aluminum 1/8'' angle and put a string across the length of the boat and my lowest point was about 2''. I picked up 2 8' sticks of 1/8'' angle and flat and welded them in place to fill in the gap make the boat flat across the top.
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Aug 20, 2017 7:57 pm

Removed the partial transom piece and tacked in the other transom piece that came with the boat. This piece of aluminum was a little thicker than what was cut out and had less holes and actually fit like a glove.
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Aug 20, 2017 8:05 pm

There she sits. This brings the build up to todays date and I will do my best to update as I go along and to add a little more written content to the posts since I was able to catch up to where I am. The transom is welded solid with just a couple screw holes to fill. There are a few bolt holes on the sides of the hull to fill but they are going to be used for alignment of braces since they were measured fairly accurately so they will be left open for now.

The next steps going forward are to cut and weld in a piece of 1''x1'' 1/8'' angle on the top of the transom level with the angle on the sides so that there is a place to rivet the .050 aluminum to the deck.
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THE NIGHT RIDER
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby THE NIGHT RIDER » Mon Aug 21, 2017 10:25 am

Bud u seem to be doing an excellent job cleaning cutting welding it up ,u hit the nail on the head most airboaters love to tinker with our boats tear down reconstruct them when needed ,so u gonna fit right in here ,keep up the great work up and well keep watching and waiting to check out the end project ,

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!!! IM THE REAL NIGHT RIDER B!TCH !!! !!! AND A PROUD TO BE IN THE DIAMONDBACK FAMILY !!!!

Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Mon Aug 21, 2017 8:34 pm

Hey thank you The Night Rider, I appreciate the encouragement!

I definitely have a few questions because with some pretty serious research attempts I have only been able to find 2 examples of airboats using crotch rocket engines. One was on ice in Canada with the engine way up high and the other was seen blasting around bs hill. I wish I could find that video of the later again and maybe some insight into the boat.

From what I can tell its just not done very often. Performance is definitely a concern. The engine I have is 100hp at the crank and 85hp at the rear wheel. I am going to try and keep it as light as I can and I think it could be a pretty rank boat... idk but that's what I'm hoping for.

I also found about a 10 year old post on this site of this boat sitting in someone's yard asking if it was a worthy project and i think the consensus was to pass on it :)

Any how i did a bunch more welding and added a 1/8'' 1x1 piece of angle over the transom and started welding it solid this evening. I am going to try and pick up some 1/2'' aluminum tubing tomorrow that i can use as drains in the hull. I'm thinking I'm going to drill a hole, weld the tube in place and tap it for a plug. Undecided on 1 or 2 drains since 1/2'' is a fairly small drain.

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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Oct 01, 2017 8:05 pm

A little update. I finished the "main structure" under the deck in 2" by 1/4 angle and 1 1/2" 1/8" angle. Added a few 1" angle support for the .050 aluminum decking. I still need to add a few more deck supports, weld in a bracket for a bilge pump and cut a hole and weld in a threaded drain in the transom. Then flip it over and prep for steel flex.
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Oct 01, 2017 8:09 pm

Making progress
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sun Oct 01, 2017 8:11 pm

Pretty sweet to come across the pre-threaded drain insert.
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SWAMPHUNTER45
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby SWAMPHUNTER45 » Sun Oct 01, 2017 11:11 pm

Real cool!

Only MC boat I have seen in person was the HD 88B engine that I think Chuck at Airboat Pro's had built. I would think your going to need a fabricated chain drive of sorts and may need to shift a gear to max out push. Probably a ratio of like 3.2 to 1 or more with an engine turning up around +9k rpm.

I applaud your effort so far and can't wait to see you get it out on the water.

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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Rick McC. » Fri Oct 06, 2017 10:49 pm

Nice work Sir, and good luck!
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Fri Oct 20, 2017 8:38 pm

Thank you all for the encouragement. Short update. I haven't been able to make as much progress as I would like but I have the threaded drain bushing welded in place, bracket for a bilge pump, added a few more cross supports to help support the decking and I just started tearing into the Honda CBR to free the engine.

This particular engine red lines at 13,500 rpm so I figure aiming for a 4:1 reduction would get me close to where a prop needs to be and the drag of the prop will bring it right about to 3,000rpms. I can get part of the reduction from the bikes transmission. I would have to look at the numbers I found again but I think 2nd gear was close to 2:1 so then I will likely go with a belt drive for the next 2:1. Ideally a nice 3" or so timing type belt or motorcycle belt if I can find one or like a 4 V belt set up. Also moving in that direction I'm on the look out for like a 3 blade warp drive that maybe has or needs to be cut down some. The hull is 72" so maybe some thing 68 to 64".
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OneBFC
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby OneBFC » Sat Oct 21, 2017 12:07 am

why not just use the factory chain and sprocket setup for your final reduction?

something like a 14 or 15 tooth on the transmission and a 28 or 30 on prop hub side?

pretty much that engine is designed to spin a chain those speeds.

would seem straight forward with a little fab work.

long prop nets more thrust per hp at the expense of forward speed potential.
-Russ
-----------------------------------
The only thing stopping you is FEAR
400+hp Ecotec, 12x7.6 DBDO, 80" 3B Maximus, 2.3 OX,85+mph, water = purely optional
Life begins at 2 BAR, Just a good ole boy

Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sat Oct 21, 2017 9:42 pm

Thank you for the excellent question and statement!

Initially I was thinking chain drive but then I started thinking about the chain breaking and going through the prop. I spent a fair bit of time with farm equipment and seen a lot of chains break. I thought maybe a belt wouldn’t be as bad. Never broke a chain on my dirt bike though now that I think about it.

This comes at a really good time because I just liberated the engine from the bike frame.

One issue I need to look a little closer at is the angle that the drive will be running off the engine there is a piece of cast around the sprocket which isn’t a huge deal to trim but I think the carbs and airbox will be on the way. May have to do a lovejoy connection or something to push the drive out away from the engine some.

The chain drive route may end up being more economical.

As for the prop length I learned something new as I have very minimal experience with airboats and prop sizing. The hull is 76” at its widest outside edge to outside edge so the cage is probably going to end up being about 72” inside to inside. So I know it needs to fit in between that with some clearance. The reason for going towards a shorter prop was more of a cost thing. The hope of picking up a short prop cheap. I have a 5 month old baby and a newer business so trying to be cost conscious and look for good opportunities.

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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sat Oct 21, 2017 9:44 pm

Pics
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sat Oct 21, 2017 9:45 pm

The engine isn’t sitting at quite the right angle. It’s laying further forward than it should.
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Muckduck
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby Muckduck » Sat Oct 21, 2017 10:17 pm

I think I will reconsider the chain drive.

Another thing I am trying to weigh out is if I do s steel engine stand vs. aluminum.

Any reason why I wouldn’t want to do the engine stand and seat stand out of aluminum? Undecided on conduit or aluminum for cage.

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OneBFC
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Re: Honda CBR 600cc 10x6 Aluminum Airboat Build

Postby OneBFC » Sun Oct 22, 2017 12:09 am

Aluminum has close to zero fatigue strength. Not jut "low", but nearly zero. So, if it starts bending (ie: flexing) it will break at some point due to material fatigue.

Steel on the other hand has a really good fatigue strength and can handle flexing for a considerable about of time and tends to fail gracefully as long as its not too severe and gets into the plastic deformation range of the material. This is known as the yield strength. Any stress beyond yield strength result in permanent deformation of the part and quickly leads to part failure.

Steel has very forgiving curves for these various stress points and is one of it's best qualities from an engineering stand point.

Stainless Steel on the other hand is not as good as regular old steel when it comes to dealing with flexing under stress. It has much better properties than Aluminum, but it tends to fail with less deformation before hand (ie: you'll find a cracked part suddenly). It has nice corrosion resistance though.

Overall, best material IMO is some type of steel alloy that you protect from corrosion via a coating like a good paint, powder coat, etc. It's just the most forgiving in day to day use.

Here's a good quote, "toughness is the ability of a material to absorb energy and plastically deform without fracturing". From here: https://en.wikipedia.org/wiki/Toughness

Steel is tough, stainless steel much less so and aluminum much less again. Think of a coat hanger that you had to bend back and forth to break. Steel you bend a bunch before it breaks, stainless less and aluminum just a few times (juts an example.)

This is very different than talking about a materials Ultimate Strength which is the stress where it fails. 7075 Alum actually has higher ultimate strength than some mild steel alloys. That said, 7075 is vastly less tough than those "weaker" mild steel alloys.

Perhaps you know this already, and I may have made some minor errors in conveying material properties here, but google around on it some and you'll see what I am talking about.
-Russ
-----------------------------------
The only thing stopping you is FEAR
400+hp Ecotec, 12x7.6 DBDO, 80" 3B Maximus, 2.3 OX,85+mph, water = purely optional
Life begins at 2 BAR, Just a good ole boy


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