YUP still working on it.

[Watterbug]

Last test reveled I needed more work...

So I moved the motor( 300 pounds ish) back seven Inches and plan to tip the prop/drive UP 2" from level on the floor.
I'm also moving the fuel tank to about the center of the boat, 15 gal.
I was driving the nose of the bot in to the water the harder I pushed the deeper it would go.
I also did some drive work and changed the reduction to 1.6 to 1 so at 4000rpm on the bug motor the prop will be 2500.
I'm hopping for a little more go.
1600cc 34carb the prop is wood and marked 64x 32.

You think it will be enough?
This time I made it so I can move it back another foot and up what ever I need.



:?: :scratch:

 

[Watterbug]

HUMM no response ? Dang really looking for advice and opinions.

First post link
https://southernairboat.com/phpBB3/viewtopic.php?f=57&t=72271

All the info ext. there.
Thanks for the insight guys :fishing

 

[SWAMPHUNTER45]

If the boat is riding on it's nose under full power and are shifting weight rearward and changing engine angle you are moving in the right direction. Another modification that can help is a pair of hull jacks pushing down slightly making a round "BALL" amidship. You apply slight pressure downward with the jacks to achieve this round bottom effect which tends to lift the nose under power.

Now if your boat is grossly out of balance it will not be a remedy but if your close it will get you where you want to be.

 

[Watterbug]

Thanks

I did not want to move TOO much back AND re point the prop,
7" of 300 pound and the 15 gal tank, 2" up on the prop. But this time I made it adjustable I can go a foot more on the weight and as much s I need on the prop.
I'll get the cage back on and try it in the water as hunting season allows.

 

[SWAMPHUNTER45]

Ok, generally speaking the shifting of weight will yield a significant effect.

We on occasion alter engine angle but I am suspecting that you are doing it to a more radical degree.

We typically will add a thin stainless fender washer at a rate of one or two on top of our mounting bushings and test. If more is needed additional washers may be added but this is not over used. We do it slow to see if a desired result occurs. On airboats "IN GENERAL" you want the engine and prop level. Yours may be a special case but typically we are close to level and tune weight and hull shape with minimal engine alteration. We don't move them around like an outboard engine uses a trim and tilt, our use is much more subtle.

In testing you can try adding a few 50 pound bags of sand or carry a person rearward in a safe fashion to help get a feel for how shifting a known amount of weight may react.

Best of luck and always think safety and what your modification will do to stability!

An airboat that at high speed rides on its nose hard will lift it's rear end and this will cause instability and the boat is prone to "swap ends." It happens in an instant and is an extremely dangerous event. I have survived this personally on two occasions both which were in deep water at high speed. A cross wind will destabilize a boat running nose down flat at speed and spin you 180 degrees in an instant. A ride where the bow is slightly up but as not to "buck or hop" or what power boaters call "porpoise" is the most desirable ride tune in my experience.

 

[Watterbug]

Sounds scary.
I'm thinking my little 1600cc at 60 hp Hi speed will not be a big factor .
The twin hulls I'm thinking will not let it slid sideways .
The shifts I have done I hope to put the prop Parallel with the water at least.
My prop is not up hi and the weight is all low, with us sitting IN the cats , tipping should not huge factor. I hope.
Make any sense ??? :scratch:

 

[SWAMPHUNTER45]

I had a hard time looking at the pics on a small screen and thought it was a mono hull with float pods.

The issue may be the 2 sponson design! Twin sponson is traditional viewed as a displacement rather than planing hull in the pontoon boat world. Take a 2 sponson vs 3 sponson hull with equal power the 3 sponson will run like a sports car and the twin will run like a school bus.

Maybe your experience or design is different but there are strong parallels. The 2 sponson pontoon as power is added tends to go to it's nose as it lacks lift where the 3 sponson will lift and ride more level or bow slightly elevated.

 

[Watterbug]

That's what I'm thinking too.
I'm going to make this thin worn one way or another.
Thanks.
Any new thoughts to make it little better will be appreciated