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Old 12 May 2008, 13:24   #11
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Quote:
Originally Posted by mlynch View Post
The water level sits right at the scupper letting water into the boat if i dont plug it...
Sounds normal.

Quote:
Also in rougher sees water can makes it inbetween the tubes and the transom or sometimes even over the transom when sitting still and rocking. The self bailing capability is shot because of how low the scupper sits.
Indicative of too much weight at the back. Or near the limit of too much but having it too far back.

The self bailing stuff works best when you're moving, not so much when you're sitting still. A lot of boats have scuppers at or near the waterline at rest. Some (poorly designed, I'd say) sit below.


Quote:
I have considered some ways to fix this problem instead of selling the boat as i will take a bath if i do because i have way more $$$ into it than it is probably worth. The best solution i have come up with is the addition of something like an armstrong positive buoyancy bracket.
Uhhh, throw more money at it?

For a 15' RIB, you're asking a lot. My buddy has a roughly equivalent Zodiac and, while power and weight handling is OK, he takes 2 other divers max (though granted, that's for cold water diving).

I would suggest investigating as much as you can in terms of weight: Add up motor, bracket, all the stuff other than the hull. Figure the weight of your divers and gear, and add 5-10% for wet stuff. Add in fuel at 6lbs/gal, etc.

I think you'll find you approach your limit pretty quickly, and you're putting most of that weight in the rear half of the boat.


Quote:
I do not think the boat is propped wrong.
Are you sure? You should prop for a "normal" load (as that's what you run most of the time); it sounds as if your normal load will be much greater than the previous owners.

Luck;

jky
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Old 12 May 2008, 15:23   #12
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The transom itself has quite a shallow draught, so I can imagine at rest in a following sea - your 100kg engine is sitting heavy.

I know why you've got the bimini top. I was in Florida in March and it was hot (pushing 30 degrees celcius). You've still got the summer still to get through! This sort of set-up wouldn't look out of place in the Mediterranean on a 18 footer with an engine rated to at least 100hp. Over-sized sponsons and a deeper transom would all help.

Not to be dispondent, do as suggested and strip back everything. Investing in new tubes may help to a degree, but your hull-shape will still remain.

Looking at the stern - have you considered bolting on an additional tapered section from marine ply that would add another 6" in height and fill in those awkward channels between the sponsons and the transom (rubber edged - so not to chaff the PVC tubes) . It would need to be precisely cut, but is possible with a little know-how.
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Old 12 May 2008, 15:24   #13
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The transom itself has quite a shallow draught, so I can imagine at rest in a following sea - your 100kg engine is sitting heavy.

I know why you've got the bimini top. I was in Florida in March and it was hot (pushing 30 degrees celcius). You've still got the summer still to get through! This sort of set-up wouldn't look out of place in the Mediterranean on a 18 footer with an engine rated to at least 100hp. Over-sized sponsons and a deeper transom would all help.

Not to be dispondent, do as suggested and strip back everything. Investing in new tubes may help to a degree, but your hull-shape will still remain.

Looking at the transom - have you considered bolting on an additional tapered section from marine ply that would add another 6" in height and fill in those awkward channels between the sponsons and the transom (rubber edged - so not to chaff the PVC tubes) . It would need to be precisely cut, but is possible with a little know-how.
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Old 12 May 2008, 15:55   #14
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mlynch, i have the same boat as you. it's been a huge hassle i'm afraid. those tubes you have are the same rubber used in above ground swimming pools. they are tubes (sausages) wrapped in a nylon cover. i patched the tubes over and over until i realized the rubber was rotten. then the nylon cover ripped and continued to rip as it was rotten as well.

i ditched the tubes and installed the tubes from my bombard c5. they fit! of course it cost me a nice sib to get usable tubes. hbi no longer has replacement sausages but do carry the replacement covers ($900) i believe. maybe someone could make you the inner sausage tubes out of stronger material.

i think you are getting water up through the tubes is because they aren't inflated enough and the nylon cover lets water just pass through.

as for the transom sitting low...not sure. mine is a jet/prototype from quicksilver and is a one of a kind. (that's a bad thing i'm finding)

talk about throwing money at it. i bought a new engine/pump/tubes/trailer and it's STILL sitting in my shop.

ok, enough doomsday stuff i hear the hulls are nice and ride quite well .
good luck and pm for more info,

andy
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Old 12 May 2008, 18:40   #15
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First i wanna say WOW this forum is great... Thanks everybody for the suggestions they are hugely appreciated! Now for a couple responses...


Quote:
Originally Posted by Pete7 View Post
That engine lift isn't doing anything for you either. Manual engines normally have a gas assist strut to help lift them up, why doesn't it work? I would have thought as a diver you could lift a 50 hp up no problem.
Pete

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I would basically second all the other posts - I would think the gain from the power lift bracket would be more than offset by the extra weight. On my old boat the difference between crew / no crew was astounding.

Weight wise I'd ditch the power lift, and have a play with the tilt pin.

I mainly added the cnc power tilt/trim for going through what we call skinny water... Sometimes i find myself by neccesity in water 2 ft deep and it is nice to be able to pull up the engine while still underway as not to ruin props or anything else. There was no OEM power option ever made apparently from what i was told...
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Old 12 May 2008, 18:46   #16
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Quote:
Originally Posted by jyasaki View Post
Sounds normal.

Indicative of too much weight at the back. Or near the limit of too much but having it too far back.

The self bailing stuff works best when you're moving, not so much when you're sitting still. A lot of boats have scuppers at or near the waterline at rest. Some (poorly designed, I'd say) sit below.

jky
Is that really normal for a scupper to let water in the boat... i can't imagine how that is desirable at all! The self bailing works great while underway though.



Quote:
Originally Posted by spartacus View Post
Looking at the stern - have you considered bolting on an additional tapered section from marine ply that would add another 6" in height and fill in those awkward channels between the sponsons and the transom (rubber edged - so not to chaff the PVC tubes) . It would need to be precisely cut, but is possible with a little know-how.
the biggest problem i see with this is that there would be no place for the engine to tilt up... But boy would i love a higher transom!
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Old 12 May 2008, 18:52   #17
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I am also curious as to some more opinions of the armstrong buoyancy bracket... It would in effect turn my 15 footer into a 17 or 18 footer and keep the engine well off the back of the boat so i could build up the transom. I wonder if the center of gravity would even change with the added buoyancy?

I have not priced this out and i fear it is probably easily over a thousand dollars... but if it made me feel the boat was safer and increased my weight holding capacity then maybe it is worth looking into.
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Old 13 May 2008, 09:49   #18
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Quote:
the biggest problem i see with this is that there would be no place for the engine to tilt up... But boy would i love a higher transom!
This is what I was thinking off - tapering transom, so it is deeper, which would help in a rolling sea. You wouldn't have to move the engine, as this in itself would cause a problem, due to shaft-ength, etc.
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Old 13 May 2008, 17:20   #19
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Quote:
Originally Posted by spartacus View Post
This is what I was thinking off - tapering transom, so it is deeper, which would help in a rolling sea. You wouldn't have to move the engine, as this in itself would cause a problem, due to shaft-ength, etc.
Nice photochop skills! I see what you are talking about now... i could probably work something like this out and glass over it for a more professional look.


On another subject I spoke with a company here in florida that can make some hypalon tubes for the boat for about $5000... he suggested adding an inch or so to the tube diameter for better stability and most likely making the boat sit higher @ the stern. He also suggested tapering/flaring the tubes upward towards the front of the boat like in newer designs. Then all i need to do is repower the boat with a nice light 220lb yamaha 70 two stroke (ditch the heavy bracket and outboard) and i will be $17000 into the boat and i could have just bought something bigger and nicer and not had all this headache to begin with! Live and learn!
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Old 13 May 2008, 17:24   #20
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Yep... just stop spending money on it!
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