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Old 05 June 2011, 17:47   #11
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Can it really make that much of a difference?..

I thought the prop may have been tilted too much down in the water as the stern wave behind seemed pretty high...the bow didn't lift right up either though...?
Typically you trim down for takeoff. Meaning the prop is closer to the boat, and deeper in the water. This keeps the bow down, and helps push the boat out of the water. Trimming up raises the prop and is used when you want to fly the boat at higher speeds lifting the bow and allowing the boat to only contact the rear pad. Of course that would be for a boat with adjustable trim.

Try having your son sit in the bow to help get it on plane.

Proper air pressure could make a big difference. Make sure you can't fold the ends of the cones over or even better use a pressure gauge.
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Old 05 June 2011, 18:00   #12
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Proper air pressure could make a big difference. Make sure you can't fold the ends of the cones over or even better use a pressure gauge.
I'd forgotten to harp on about this - thanks Peter!

The QS airdeck will have pressures marked at each valve. These MUST be correct, or the boat will fail to act as it should. The airdeck will need something silly like 11psi in it. You can't judge this by hand and will require a gauge to do the job properly.
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Old 06 June 2011, 12:48   #13
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I only checked air pressure by hand - until the tubes showed decent firm resistance (... the double hand pump I used to finish off had a guage that didn't show a steady pressure reading). Once in the sea the tubes did feel softer than I expected..probably temperature?

How much difference would higher tube pressure make guys?.. (Hoping you say "a lot"!)
I think I'll try to find a pump with a guague to ensure I blow up to max...

I'll also play with the trim...

Fingers crossed!
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Old 06 June 2011, 13:54   #14
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you would be better of with a seperate gauge in my opinion.

I think the ones that are on pumps arent that accurate. (i may be wrong!)

I have one of these but obviously your valves may be different.

INFLATABLE BOAT PRESSURE GAUGE, Europa Sport, ** NEW ** | eBay UK
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Old 06 June 2011, 14:37   #15
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How much difference would higher tube pressure make guys?.. (Hoping you say "a lot"!)
A lot. Are you using a pump like this to finish the floor and keel? It must be the cheapest one about and if you have the Quicksilver clip-in valves, will show a constant pressure when you pause pumping. The airdeck should be like a plank when it's done,
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Old 06 June 2011, 15:09   #16
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My old SIB was a 3.2 with an 8hp on the back and this planed very easily with two adults in, 1, 10st and the other 15st, plus fuel, kit etc etc.

3 adults and we started to struggle , so with a 15 you should be flying

My air deck as has been said was like a "plank", to the point when i thought it couldnt take any more, but when i put the pressure gauge in it still needed a bit more puff.

I would certainly get the tuubes up to their recommended pressure, but you wont know what level your at until you get a gauge.

good luck.
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Old 08 June 2011, 05:18   #17
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Feryden, How are you getting along? I have to agree about the pressure comments. If you are woefully underpressure, it WILL affect the boat alot. If you are in the right ballpark though, t should be much less noticeable. The hard as a plank school of thought definitely applies for the floor. Using the two way pump that comes with the boat, i can tell you that you will be pumping almost to the point where it seems pointless (seems no air is going into the floor), at THIS point if you pause between strokes you should find the pressure is just right. 11 PSI is a lot more than you think in this situation. To convince myself, in the early days of my sibbing career, I inflated just the airdeck on the living room floor and walked on it. At pretty much anything under the correct pressure lots of deflection. It doesn't really start to behave like a stiff board until anything after 9 PSI. I also tend to fill my tubes to 3.5 to start and then check again after wetting them (this usually works out for me). Last silly thought but I don't recall anyone asking, what length is your motor leg (and you thought I would say shaft, didn't you). I only ask because very infrequently someone is found to be using a motor off their old sailboat or such and it has a very long shaft. This would absolutely KILL performance with all the extra drag. You must use a short shaft for that boat. Some folks even raise the motor a bit but I found that makes mine cavitate something awful. Just a thought.
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Old 09 June 2011, 15:04   #18
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Thanks for asking bud - I'm sure that I can improve my trim as had my prop set right under into the transom - but I also think I need a different pump and am looking at alternatives... I think I was too nervous of blowing the tubes up too hard on first voyage so know I can 'pump it up'!
Unfortunately I'm gonna be travelling around with work over the next few weeks despite being champing at the bit to go and see what difference these adjustments might make..
But the Doubting Thomas side of me still says the engine should still be firing this boat forward under semi pressure, rather than chugging along...
Hmmmnnn

Thanks again for asking ... the people on this forum are brilliant!..Thanks to you all!
:-)
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Old 09 June 2011, 15:10   #19
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A lot. Are you using a pump like this to finish the floor and keel? It must be the cheapest one about and if you have the Quicksilver clip-in valves, will show a constant pressure when you pause pumping. The airdeck should be like a plank when it's done,
Thanks mate...mine looks identical, but not Quicksilver logo. As the needle was firing around as I pumped I didn't trust the guage...think I need to pause and wait on a stable reading.... To be honest the airdeck rose in the middle a bit when I inflated the keel, so maybe the deck wasn't hard enough on that basis..

The keel inflated quickly and I was nervous it was going to burst as it went up so fast... I need to Get Some Nuts!! and pump her a bit harder ...
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Old 09 June 2011, 16:32   #20
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The keel inflated quickly and I was nervous it was going to burst as it went up so fast... I need to Get Some Nuts!! and pump her a bit harder ...
That's because it has a small volume. Do watch it, it would be easy to overfill it.
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