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Need suggestions on hull size for mini airboat

Truck Camper

Truck Camper

Member
boat ride.jpg
Just built this boat last year 10' x 5' with a 22 hp Predator with 1.68:1 drive and a 59" 3 blade ultra prop, runs great in skinny water but chugs in deep water. I'm wanting to build another one with the same motor and prop set up, would 9' x 5' be a better setup? Not looking to run dry just be able to run across deeper water on plane. Thanks
 
Displacement is everything, you state it is 5' wide, now is this the measurement at the top or the bottom running surface?
I would suggest a bit wider at the rear, say 6'2" at bottom, a gradual kickup to the bend of the sides from about 3' center out, up to about 1.5" at transom, match bulkhead to that pattern. Keep the 10' length.
As pictured.
 

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John Fenner said:
Displacement is everything, you state it is 5' wide, now is this the measurement at the top or the bottom running surface?
I would suggest a bit wider at the rear, say 6'2" at bottom, a gradual kickup to the bend of the sides from about 3' center out, up to about 1.5" at transom, match bulkhead to that pattern. Keep the 10' length.
As pictured.
Click to expand...
Thanks for the response. Yes the bottom is 5' wide, and by total accident (it pulled while welding) it does have a gradual kick from center to each side. 5' x 10' sheets of aluminum are the biggest I can get around here. I was trying to avoid putting a seam down the middle, was why i was thinking 5' x 8' 6" or 9' long. Thanks again for the information. Thats a nice hull you have there!
 
I agree with John, the first thought I had was you need more hull width to work better in deep water. I would also suggest more engine, but that's not what you asked about.

Truck Camper said:
5' x 10' sheets of aluminum are the biggest I can get around here.
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This I don't get, where are you? You can certainly order wider and longer, what grade of aluminum are you finding locally?
 
Slidin Gator said:
I agree with John, the first thought I had was you need more hull width to work better in deep water. I would also suggest more engine, but that's not what you asked about.



This I don't get, where are you? You can certainly order wider and longer, what grade of aluminum are you finding locally?
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I'm in south Texas, All the metal supply places carry are 4' x 8'or 10' and 5' x 8' or 10' aluminum in any grade or thickness. I have found some bigger sheets from out of state but the shipping cost more than the sheet itself. that's why I went with a 5' bottom on the first hull. Thats why i was wondering if I went shorter on the length and kept the 5' bottom would be all right? Yes I do want to go bigger on the engine but the 22hp Predator was given to me so I thought I'd make do with it. Then sell both the boats and build a bigger and better boat. Thank you for the response.
 
Increasing hull width is the #1 way to decrease power to plane in deepwater and the #1 way to decrease dry ground capacity.

When focused on running dry, narrow and more power are the solutions.

When focused on deepwater, wider and more power are the solutions.

Skinny water is easy.
 
Slidin Gator said:
Increasing hull width is the #1 way to decrease power to plane in deepwater and the #1 way to decrease dry ground capacity.

When focused on running dry, narrow and more power are the solutions.

When focused on deepwater, wider and more power are the solutions.

Skinny water is easy.
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Well heck, looks like I will be putting a seam in it. Thank you for the simple explanation.
 
Truck Camper said:
Yes I do want to go bigger on the engine but the 22hp Predator was given to me so I thought I'd make do with it.
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That's the lamest excuse I have ever heard for saving $$$ on a big lawnmower engine. I would upsize to a 35 Hp twin Briggs on the present hull. Need to look at the details, but 150% the power should have you on plane in deep water and trying to hold back the accelerator in the slick mud. Those 35 Hp Vanguard engines are $3-3.5K. Way cheaper than a new rig.

Don't even start on me about fuel consumption.
 
Slidin Gator said:
That's the lamest excuse I have ever heard for saving $$$ on a big lawnmower engine. I would upsize to a 35 Hp twin Briggs on the present hull. Need to look at the details, but 150% the power should have you on plane in deep water and trying to hold back the accelerator in the slick mud. Those 35 Hp Vanguard engines are $3-3.5K. Way cheaper than a new rig.

Don't even start on me about fuel consumption.
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I totally agree with you there, I just don't like the first hull. It was my first try at building an airboat and I rushed through it. The boat was built in 3 days, learned a little since then and more now from you guys. and its build another boat or another camper. I will definitely set this new one up for a bigger engine.
 
P.S., I spent some time on those mud flats years ago. We would launch my Geenoe on the beach side of the laguna madre with my 1980 bronco. We used to mark our distance down the beach by # of hardhats and used CB to call for help. One morning I found the bronco with sand over the doors. I had sand 3" high on the dash. I went full 4x4 low and she broke out, which solved a whole lot of issues!

Gheenoe Manufacturing, Titusville, FL

Bronco.jpg
 
Truck Camper said:
I totally agree with you there, I just don't like the first hull. It was my first try at building an airboat and I rushed through it. The boat was built in 3 days, learned a little since then and more now from you guys. and its build another boat or another camper. I will definitely set this new one up for a bigger engine.
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I here yah. Use the present hull as a test bed for power and prop. Try more power on what you got, it's cheap and might modify your plans.
 
Slidin Gator said:
P.S., I spent some time on those mud flats years ago. We would launch my Geenoe on the beach side of the laguna madre with my 1980 bronco. We used to mark our distance down the beach by # of hardhats and used CB to call for help. One morning I found the bronco with sand over the doors. I had sand 3" high on the dash. I went full 4x4 low and she broke out, which solved a whole lot of issues!

Gheenoe Manufacturing, Titusville, FL

View attachment 98192
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Lmao! yep seen many a truck in the same situation. and still plenty of hard hats on the beach
 
Ok, so, I figured that I would elaborate a bit, the hull pictured "thank you for the compliment by the way!" Is a 6'8"×11' built from 7075-T6 aircraft aluminum, which only comes in 4' widths and 12' lengths, the sides are bent using a 14' press brake with a 3/4" round top die and a v block bottom die, the rear is bent at 8" and the front at 13", giving the hull 5" of taper per side.
That said, you can do this with 4' material with a seam up the center, order a length of 1.5x1.5x3/16 T-bar for center stringer, there has to be a place around locally that has a brake to bend the material, bend the sides 11" at rear, 16" at front to about 80° this will give you a 6'2" bottom at rear, cut T-bar to 9'10-1/2", bend it to match your rake pattern, leaving 1-1/2" from rear.
Take the remaining T-bar, cut an 8' piece, this will build your transom rail. Once sides are bent, center stringer welded in along with the rake up the front sides, I will walk you through bending transom T-bar after this.
 
John Fenner said:
Displacement is everything, you state it is 5' wide, now is this the measurement at the top or the bottom running surface?
I would suggest a bit wider at the rear, say 6'2" at bottom, a gradual kickup to the bend of the sides from about 3' center out, up to about 1.5" at transom, match bulkhead to that pattern. Keep the 10' length.
As pictured.
Click to expand...
Hey bud I like your hull you did a great job. I have a 9ft keith hancock hull with 2 ft grass rake and it's 6.5ft wide with 5in tate I belive. I build rotax UL motors for a living and built my motor from 65hp to 106hp it has a 70in 3 blade whirlwind prop
 

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