Help: info needed for Avon Typhoon S4.00

russhenchman · 27 January 2012, 17:42

Hello everyone!

I could use some help. I recently bought an 1990 Avon S4.00 Typhoon. The boat is awesome except for a handling problem I am having. Once on plane, at certain speeds the boats wants to occasionally hop out of the water almost as if it hit a speed bump even on flat water. It almost feels as if the bottom fabric is stretched not letting the water flow smoothly underneath. Although it feels tight if I bounce my hand off of it. I have tried every combination of air pressure and weight distribution.

Questions:
1) Should this boat have a thrust board? I see that some models do and others do not.

2) If the bottom is stretched out, is there any way to tighten it?

3) Where could I find the optional side helm and inflatable seat? IBS does not carry them any longer.

4) Should the keel be glued down at the fore and aft ends?

Any other information or tips about this boat would be greatly appreciated!

Thanks guys!

Downhilldai · 27 January 2012, 21:55

Lovely SIB

Is the keel chamber inflated?

russhenchman · 27 January 2012, 22:23

Thank you Downhilldai!

Yes the keel is inflated. I have tried different pressures from 2-4 psi in the keel.

mister p · 27 January 2012, 22:37

Keel chamber should be fixed about the centre but free fore and aft. When inflated it's held in place by it's pressure against the underside of the floor and the hull.

mister p · 27 January 2012, 22:40

Engine might need trimming in a touch. Could be light porpoising.
Cool boat though. Try it without the fins.

Downhilldai · 27 January 2012, 22:48

Quote:

Originally Posted by mister p

Try it without the fins.

Was about to suggest this

mister p · 27 January 2012, 22:56

Yes, on that set-up from your pictures can't see that the fins would be first on my shopping list.
Trim in, ditch the fins. But do these one at a time as you won't see the benefits clearly.
Trim in first, then if no good, trim back to where you were and lose the fins. Then after that try the trim again.
But as I said, your rig looks cool so it shouldn't be an unfixable issue.
Nice one Dai.

great minds think alike

mister p · 27 January 2012, 23:06

Or at least yours does!

mister p · 27 January 2012, 23:10

Having had a closer look at your picture of the rear of the boat, I'd trim in one notch first.

russhenchman · 28 January 2012, 16:04

Thank you for your help Mister P. I have tried every pin position on engine bracket. The lower the position the worse it is. I will try without the fins next. They came with package but I don't know if I've ever seen another SIB with them!
When the problem happens, it feels like a bulge of water is being formed underneath and then the boat hops over it. The boat even jumps to the side a little.
Anyone know if this boat should have a thrust board?

sinner · 28 January 2012, 16:57

I agree with removing the hydrofoil. I have a bombard C3 3.8m with a 40hp and put smart tabs on it. It occasionally will do the same thing you are describing, and did not do it until I installed the tabs. I've changed the settings on the tabs and it decreased it greatly. I have a solid wood keel and the fabric feels tight. I'm sure mine is the tabs.

russhenchman · 28 January 2012, 17:08

Thanks sinner. Hydrofoil is coming off this spring!

mister p · 28 January 2012, 19:58

Ok then, next question. Are the floor stringers correctly fitted and tubes at sufficient pressure. When launched the water temp can drop the pressures considerably causing the boat to bend. Esp if stringers have been fitted upside down causing the keel to sit incorrectly.

russhenchman · 28 January 2012, 20:20

Yes I monitor the pressure while in the water...3 tube chambers and keel chamber kept at recommended PSI by Avon. (I have the original owners manual).
I took the whole boat apart and scrubbed every inch upon purchase. I'm positive that the stringers are proper side up /l_______l\.

One thing I might try is fully inflating the port/starboard chambers first followed by the bow chamber.

Downhilldai · 28 January 2012, 22:16

Don't do that - it may bugger up the baffles.

russhenchman · 29 January 2012, 00:12

Roger!...that's why I haven't tried it yet. I read about that being an issue.

m chappelow · 29 January 2012, 08:09

Quote:

Originally Posted by russhenchman

Roger!...that's why I haven't tried it yet. I read about that being an issue.

Silly question but looking at the pics do you run it with the fuel tanks at the stern it could be just a weight trim problem as much as anything else

russhenchman · 31 January 2012, 19:49

I have tried fuel tank fore and aft....as well as shifting gear around and 1..2..3 people and shifting them around.

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mister p · 31 January 2012, 20:06

Last attempt. Has the engine the correct length shaft? Don't know the correct length for your vessel......but you may be have cavitation problems, although unlikely.

russhenchman · 31 January 2012, 20:34

Yes. It is a standard shaft and I just checked the owners manual which matches up. I will take off the fins and cross my fingers!