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Old 03 October 2008, 07:25   #11
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Country: Other
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Boat name: depends how I feel..
Make: Honwave Air 3.2
Length: 3m +
Engine: Tohatsu 18 2 Stroke
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Another approach

Hello all
Well, I made a test....
AND, it works well..
Heres what I did, no piccies at present cos I stripped it out to make a marine ply version.
10mm Plywood floor section extending forward 1.3 metres from the transom with a stiffner down to the keel underneath to stop the flexing, weighs next to nothing and the floor area is fairly flat section in this area.
Results....
No flexing to speak of, 5 knots increase in top end speed !.. now get 24 knots on the gps and the boat doesnt SUCK down into the water as the floor flexes. previous top speed was around 19 knots and the last third of gas made it worse. (Using the tohatsu 18)
I now think it could take a 25 no worries lol...
Now need to remake the test ´floor´insert in marine ply with protected anti chafe edges and padded keel spacer.
The whole sib felt completely different, far more responsive and superb even at WOT with the 18. No digging into the water as the floor flexed upwards.
Will post piccies in the next month or two as I remake the insert and am aiming for a total weight of the mod at less than 3 Kg´s. A couple of Stainless steel bracing rods from the transom should be the icing on the cake. It will also provide a solid mount for the steering system, the whole thing easy to add, easy to remove, light and simple and still retaining a reasonable degree of flex for the whole SIB.

Happy camper now. still a light weight unit.. now, If I can just find a good 30 to 40 hp light outboard Mohahahaha!!!!

Ruds
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Old 03 October 2008, 09:20   #12
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Country: UK - England
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Make: Honwave T35AE
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I'd be interested in seeing some pics of this.

I have a Honda 3.8m with a 2 stroke 25hp and also find the 'wobbly floor' a bit disconcerting. I think I can picture what your describing and it sound feasable to me, I've had similar thoughts myself.

If it's an easy mod then I reckon I'd be up for giving it a go.

Post some pics when you can
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Old 03 October 2008, 16:21   #13
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Country: UK - England
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or you could sell the air floor and buy a hard floor version , the 4m alloy floor is the same price as the 3.8 .
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Old 04 October 2008, 06:05   #14
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Quote:
Originally Posted by ian parkes View Post
or you could sell the air floor and buy a hard floor version , the 4m alloy floor is the same price as the 3.8 .
But surely the air floor actually has a more rigid floor than the ali or wood floor models? With the ali/wood floor models you have an inflatable or solid keel stretching and keeping taughtish, a large expanse of 'flappy' fabric. No mattter how taught there will still be a fair degree of give/"flappyness"

With the air floors (as in Hondas anyway) - the floor is a lot more rigid over the entire surface (if at the right inflation pressure) - sure there is a little flexing - but that will only ever be overcome with a solid hull.

I have to say I am very pleased with my Honwave 3.8 air-floor - handles very well - was at sea last weekend with four large adults aboard I'm sure a combined weight of well over 50 stone and it had no problem planing.

Did a quick gps test with only me aboard and had no problem getting high 20's mph ( actually forgot to check if i set it to read mph or kts....
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Old 04 October 2008, 08:28   #15
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Country: UK - England
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or you could sell the air floor and buy a hard floor version , the 4m alloy floor is the same price as the 3.8 .
I considered the hard floor at the time or purchase but it was surprisingly heavier. The 3.5m ally floor weighs 78kg compared to 53kg for the air floor. As I have to carry the boat up a steep pebble beach the weight factor is crucial.

If the above mod only adds another 3kg then it might be worth considering.
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Old 04 October 2008, 13:56   #16
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Originally Posted by longjohn View Post
But surely the air floor actually has a more rigid floor than the ali or wood floor models? With the ali/wood floor models you have an inflatable or solid keel stretching and keeping taughtish, a large expanse of 'flappy' fabric. No mattter how taught there will still be a fair degree of give/"flappyness"

With the air floors (as in Hondas anyway) - the floor is a lot more rigid over the entire surface (if at the right inflation pressure) - sure there is a little flexing - but that will only ever be overcome with a solid hull.

I have to say I am very pleased with my Honwave 3.8 air-floor - handles very well - was at sea last weekend with four large adults aboard I'm sure a combined weight of well over 50 stone and it had no problem planing.

Did a quick gps test with only me aboard and had no problem getting high 20's mph ( actually forgot to check if i set it to read mph or kts....
Yes I think you are correct the air floor does give a more rigid hull than the air tube type .
Iam amazed at the speed you guys are getting , my honda 3.8 with a honda 20 would do about 18 flat out with a bit of a load , and my futura mk3 with 25hp did just over 20 with 3 people in .
My 4.1 rib with a 50 only does 30
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Old 04 October 2008, 14:30   #17
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Glad to see your idea has worked. My old air floor sib was always slower than the wooden floored sib I had before. Same engine, despite being lighter the floor wasn't as well stretched, and caused drag when planing.

24knots is JUST possible with the tohatsu 18, assuming you are running a 10inch pitched prop, and reaching top RPM. The prop calculator gives 0.07% slip which is unlikley, so I expect this speed was recorded running with the tide.

Specs from here: http://www.watertoyz.com.au/outboard...roke-18hp.html

Prop Calculator: http://www.rbbi.com/folders/prop/propcalc.htm


Ian, I got 32knots with the mariner 40 on my searider. So I would think if you tried a few different props you'd find a few more knots with your 50.
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Old 04 October 2008, 15:49   #18
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Ian, I got 32knots with the mariner 40 on my searider. So I would think if you tried a few different props you'd find a few more knots with your 50. [/QUOTE]

Iam not too bothered about top speed on such a small boat with tiller steer , i wouldn't be able to use more speed very often unless it was flat calm
its on the standard alloy prop but revs to about 5500 so its about right .

Best thing is still gets that speed with 5 people in the boat or towing a donut with 3 adults on it and still comes out the water instantly like a rocket
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