4X8 Wood boat build.

Airboats with smaller powerplants.
papajack
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Re: 4X8 Wood boat build.

Postby papajack » Thu Oct 03, 2013 12:26 pm

Gg Kustomz wrote:Thanks guy's. I found a really good deal on a 4a032 new still in the crate. The military are getting rid of them after sitting unopened in a crate for 30 yrs. I have read that they are capable of 30hp with a couple of small mods. Has anybody used one of these motors for a mini? If so can you please let me know how it performed. Thanks

Try a search in miniairboat forum for 4a032. You should find some info there.

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Wild Bill
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Re: 4X8 Wood boat build.

Postby Wild Bill » Thu Oct 03, 2013 6:14 pm

So are those 2X12 stringers. Very impressive how it runs. Do you think you will reduce performance much with real rudders. :D

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Re: 4X8 Wood boat build.

Postby Gg Kustomz » Mon Oct 07, 2013 8:57 pm

Just a little update on the build. I picked up the 4A032 today brand new in the crate for $340. It also came with exhaust and a 1'' shaft for the fly wheel. We started it up on the second pull and I was all smiles :cheers:. This little motor sounds bad ass and I think it's going to be perfect for the mini. I have read about Papa jacks boat and it seems he had decent results on a boat twice the size as mine. If I can get in 20's for hp that would be awesome. Going to run a wood prop from RnD prob dd 42x26. I will post pic's as soon as I can. OH yeah stringers are 2x6 and I hope the rudders help.lol

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Re: 4X8 Wood boat build.

Postby Gg Kustomz » Tue Oct 15, 2013 11:52 am

Got the cage completely welded and rudder made just have the throttle and bell crank to make.
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Re: 4X8 Wood boat build.

Postby Gg Kustomz » Tue Oct 15, 2013 11:59 am

Just another pic!
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Re: 4X8 Wood boat build.

Postby Gg Kustomz » Sun Nov 03, 2013 8:41 pm

Well got her out on the water! The canal was deep and the wind was blowing, but she got up on plane and did her thing!


http://youtu.be/GWAH4DaFGLQ

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:)
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Re: 4X8 Wood boat build.

Postby :) » Sun Nov 03, 2013 9:50 pm

Man thats very cool... couole curiositys though.. did u stop to turn around or did u slide her on around? How did it do? Were u wide open on those passes? U gonna change anything?
14 ft Combee. 4 seater, BPE 383 sb chevy, 2.09 stinger, 3 blade ww stump puller.
"When the people fear their government, there is tyranny; when the government fears the people, there is liberty." Thomas Jefferson

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Re: 4X8 Wood boat build.

Postby :) » Sun Nov 03, 2013 9:51 pm

Btw it looked like it was riding really good to me.. awesome job
14 ft Combee. 4 seater, BPE 383 sb chevy, 2.09 stinger, 3 blade ww stump puller.
"When the people fear their government, there is tyranny; when the government fears the people, there is liberty." Thomas Jefferson

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Wild Bill
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Re: 4X8 Wood boat build.

Postby Wild Bill » Mon Nov 04, 2013 1:02 am

I'm impressed!

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Re: 4X8 Wood boat build.

Postby Gg Kustomz » Mon Nov 04, 2013 8:30 am

:) wrote:Man thats very cool... couole curiositys though.. did u stop to turn around or did u slide her on around? How did it do? Were u wide open on those passes? U gonna change anything?




It did not want to get on plane in the deep water but once in got on plane in the shallow she did fine. I slowed down to almost an idol when turning because I have zero experience running an airboat and did not want to sink her on the first time out.lol I was about 3/4 throttle and in the deep and felt like I was cruising pretty good. I think the next time out we will find a better spot and check top speed and how good she slides. But all n all I was pretty pleased with the results being that it is what it is. I will post another vid as soon as I can with more details.


Thanks

Les

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Re: 4X8 Wood boat build.

Postby bentonquick » Mon Nov 04, 2013 8:50 am

Looks good might consider decking it in. :old_glory: :florida:

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Re: 4X8 Wood boat build.

Postby Salty Techsan » Mon Nov 04, 2013 7:10 pm

dude.... well done!!! You should be proud.. I got inspired by your posts and decided to tackle my mini build as well... all praise the internet! Thanks for taking the time to post photos and a play by play... Very exciting to see that your rig runs that well... good stuff!!! Did you abandon the idea of switching to the 4a032?

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Re: 4X8 Wood boat build.

Postby :) » Mon Nov 04, 2013 8:22 pm

Definately be careful in the deep when turning.. in a few inches of water she should be a blast..
Last edited by :) on Mon Nov 04, 2013 9:13 pm, edited 1 time in total.
14 ft Combee. 4 seater, BPE 383 sb chevy, 2.09 stinger, 3 blade ww stump puller.
"When the people fear their government, there is tyranny; when the government fears the people, there is liberty." Thomas Jefferson

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Re: 4X8 Wood boat build.

Postby Gg Kustomz » Mon Nov 04, 2013 8:43 pm

Salty Techsan wrote:dude.... well done!!! You should be proud.. I got inspired by your posts and decided to tackle my mini build as well... all praise the internet! Thanks for taking the time to post photos and a play by play... Very exciting to see that your rig runs that well... good stuff!!! Did you abandon the idea of switching to the 4a032?



Thanks guy's for the kind remarks. You guy's no how it is to build your own stuff you take pride in what you do and when somebody gives a thumbs up or good job it goes a long ways. Anyways I like that 4a032 and I am going to make sure it gets a good home on another hull. I think when I am completely done I am going to build another mini out of aluminum and use the 4a032. That motor is to cool not to use! Make sure u post pic's of your build so we can all enjoy the build!

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Re: 4X8 Wood boat build.

Postby Olf Art » Mon Nov 04, 2013 9:07 pm

Gg, look in my photo gallery for a picture of what's possible with one of those little 4aO32's. I didn't build any of that one,
but you can get a good look at the re-drive and the improved intake manifold the guy fabricated for it.

One thing to keep in mind with them ...... the crankshaft is pressure lubricated, but the rods are splash fed. You could bump the
compression a little if you wanted, but don't get carried away with it. They're very cool little engines.
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Member: KRVSA, FAA, TAA, and life member NRA and VFW

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Re: 4X8 Wood boat build.

Postby :) » Mon Nov 04, 2013 9:15 pm

So that the 13hp motor ur running?
14 ft Combee. 4 seater, BPE 383 sb chevy, 2.09 stinger, 3 blade ww stump puller.
"When the people fear their government, there is tyranny; when the government fears the people, there is liberty." Thomas Jefferson

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Re: 4X8 Wood boat build.

Postby Gg Kustomz » Tue Nov 05, 2013 5:59 pm

:) wrote:So that the 13hp motor ur running?



The motor I am running now is a Predator 420cc from Harbor Freight. It's a Honda GX 390 clone motor. They say it's about 15hp stock. But I just got a bigger jet,K&N filter and am making a small header very cheap too. Jet=$6 K&N=$16 and the header is free. Supposed to make between 18 and 20hp. Also will be testing a 42x24 instead of the 42x14.

Thanks for the reply on the 4a032 thats good info! I feel like 4A032 could easily reach in the low to mid 20's for HP and would have more torque than a single cylinder engine as well. Only way to know is to do the damn thing.lol

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Re: 4X8 Wood boat build.

Postby :) » Tue Nov 05, 2013 9:58 pm

So i been thinking..... and now my head hurts but do u think using a 5x10 sheet of plywood would have helped.. i know they say with the bigger boats that like a 8 ft wide boat will plane before a 7 ft or 7'-6" wide boat. And i wanna say ive seen 5x10 sheets b4
14 ft Combee. 4 seater, BPE 383 sb chevy, 2.09 stinger, 3 blade ww stump puller.
"When the people fear their government, there is tyranny; when the government fears the people, there is liberty." Thomas Jefferson

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Re: 4X8 Wood boat build.

Postby :) » Tue Nov 05, 2013 10:00 pm

Or are u just under/over proped or under powered?
14 ft Combee. 4 seater, BPE 383 sb chevy, 2.09 stinger, 3 blade ww stump puller.
"When the people fear their government, there is tyranny; when the government fears the people, there is liberty." Thomas Jefferson

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Re: 4X8 Wood boat build.

Postby DDSBC » Wed Nov 06, 2013 7:01 am

Gg Kustomz you make building one of these look really fun. I've been research a lot on small engines and from what I read the 13hp Harbor Freight Tools motor shows it makes 18.4 ft. lbs. peak torque at 2500rpm and has a max rpm of 3600 rpm. If you do the math, in order for it to have 13hp at 3600rpm it would have to be making 18.97 ft. lbs. of torque but that's more then the max torque it's supposed to make so I'm kinda doubting Harbor Freight Tools listed specs on this motor. Anyways I might being going crazy with the numbers here but I also noticed you stated that you thought the prop you are running is holding the engine back to 2800-3000rpm. If that's true and lets assume that the motor has a completely flat torque curve and is making the same peak torque they claim it makes of 18.4 ft. lbs. at 2500rpm even up between 2800-3000rpm then your only making between 9.8-10.5 hp in that rpm range. Please someone correct my math if I'm wrong but man is that video of it running impressive if all my math is correct. Also wondering if it would be safe to spin a small wood prop up to the max 3600rpm that most of these small motors can go. I know it won't be spinning the tips over .6 mach so I'd think it would be safe and then you'd be making use of the engines full potential right?
Micah Smith

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Re: 4X8 Wood boat build.

Postby Gg Kustomz » Wed Nov 06, 2013 8:14 am

DDSBC wrote:Gg Kustomz you make building one of these look really fun. I've been research a lot on small engines and from what I read the 13hp Harbor Freight Tools motor shows it makes 18.4 ft. lbs. peak torque at 2500rpm and has a max rpm of 3600 rpm. If you do the math, in order for it to have 13hp at 3600rpm it would have to be making 18.97 ft. lbs. of torque but that's more then the max torque it's supposed to make so I'm kinda doubting Harbor Freight Tools listed specs on this motor. Anyways I might being going crazy with the numbers here but I also noticed you stated that you thought the prop you are running is holding the engine back to 2800-3000rpm. If that's true and lets assume that the motor has a completely flat torque curve and is making the same peak torque they claim it makes of 18.4 ft. lbs. at 2500rpm even up between 2800-3000rpm then your only making between 9.8-10.5 hp in that rpm range. Please someone correct my math if I'm wrong but man is that video of it running impressive if all my math is correct. Also wondering if it would be safe to spin a small wood prop up to the max 3600rpm that most of these small motors can go. I know it won't be spinning the tips over .6 mach so I'd think it would be safe and then you'd be making use of the engines full potential right?



Man that sounds like to much thinking!lol I honestly can't say 100% of how much HP the motor is putting out at what RPM I am just going by what I have read. But I can tell you that a 42x14 and a 42x18 prop on a 13-15hp motor on a light 4x8 boat will push you around pretty good. If you look at the Lake buggy on You tube Im running basically the same set up, just a 4 degrees less pitch on the prop. As far as the lugging down to 2,800 to 3,000 rpm thats just a an uneducated guess. I am very new to the air boating world and am being schooled by all of you guy's. But what I can do is buy a small tachometer for a cylinder motor and and check both RPM's,one with the prop and without the prop and see exactly how much it lugs the motor. My new prop came yesterday from Robin at RnD great guy by the way! It's a 42X24 so my plan is to test both props with a tach on the stock motor then test after I put on the bigger jet,intake and header and check the differences. Also I guess it would make since to run a pulley reduction if you wanted all the HP possible at the 3,600 rpm range? But so far the DD has proven worthy for this application.

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Re: 4X8 Wood boat build.

Postby Gg Kustomz » Wed Nov 06, 2013 8:15 am

:) wrote:Or are u just under/over proped or under powered?

I am going to try and find out for you!

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Re: 4X8 Wood boat build.

Postby Gg Kustomz » Wed Nov 06, 2013 8:35 am

:) wrote:So i been thinking..... and now my head hurts but do u think using a 5x10 sheet of plywood would have helped.. i know they say with the bigger boats that like a 8 ft wide boat will plane before a 7 ft or 7'-6" wide boat. And i wanna say ive seen 5x10 sheets b4



From what I have read so far the more displacement you have on the water the faster you will plane. So if I had built this lil boat 5x10 rather then 4x8 would it have planed in the deep water? Not sure but but it makes sense that it's a good possibility due to the extra width making it sit hire in the water. The only thing negative I think would be is the extra weight. But I seriously doubt that the extra weight would be so minor it would not make a difference. But thats just my opinion. To be honest if I could start over I would go 5x10 rather than 4x8. Maybe the next person to build a Lake buggy will go 5x10 and then we will really find out.lol

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Re: 4X8 Wood boat build.

Postby DDSBC » Wed Nov 06, 2013 2:43 pm

I need a new project like a hole in my head but man I can't help but think a 8x5 mini with a 23hp Vanguard set up DD wouldn't be an awesome little project to build and teach my kids to drive on. Don't know how bad the mini airboat bug has bit you but I saw you got another prop to test as well as another motor. If you could hook up a tach while testing I know I as well as probably others would eat up the technical numbers on your various engine and prop combo tests. Even cooler would be if you could figure out a way to measure the lbs of thust each prop and engine combo makes at various rpm. Sorry if I'm taking the joy out of a simple airboat build by asking all these questions lol
Micah Smith

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12x7 Diamondback w/ rivited on poly, double rear driver double front passenger, full cage, 285 hp IO-520 swingin a 74" Whirl Wind Whisper Tip.

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Re: 4X8 Wood boat build.

Postby Salty Techsan » Wed Nov 06, 2013 7:43 pm

I might have a useful case study in the works... After getting inspired by GGK's build posts and pics, I jumped into a mini project that is intended for my two boys and their buds (or dad on solo missions).. Its "Lake Buggyish".. but pulls a little more inspiration from traditionally stringered hulls.. for better or worse.. Its a 5' x 9'6" size, with a tapered non trip chine, and will ultimately be a deck over. Stringers are 1x Pine (wanted to use cedar or doug fir for weight, but SYP all I could get my hands on), skinned in 7/32" BC Plywood.. will glass the sides and bottom a with a single course of fabric and epoxy resin.. and probably just paint or gel-cote the top. It seems to be about 20lbs heavier than I had hoped, but the motor (4a032) is a bit lighter than the original Honda I had planned on using.. so hopefully it will all come out in the wash. After seeing Papee's posts about the ultra prop on his 4a032, I went that route.. I'm spinning a 44", 12" pitch 3 blade Ultra Prop on an Arrow hub that they make for the goofy tapered shafts which is common on the generator engines. Static rpm test only has her spinning at about 2400RPM or so at WOT according to the "Tiny Tach" I installed... engine sounds awesome and seems to be generating good thrust.... but RPMS coming up short, which is dissapointing... but.. thats exactly why I spent the extra couple hundred bucks for the adjustable prop.. Stay tuned for a water test.... a few photos below.
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