I think i need some help/advice...

[mlynch]

Hi all! This is my first post and first rib! Sorry to say but i am getting myself extremely frusterated over this project.

A few months back i purchased an 89 HBI 14.7 ft RIB that looked to be in decent condition... for approx 2500 dollars. Seemed cheap enough. Boat was rated for 1400lbs motor gear and passengers. My goal was to make it a dive platform for 2-4 people. Manufacturer told me it was basically the same exact hull as they make today. My first mistake was it had PVC tubes under a canvas cover (the owner said he wasn't sure but he thought they must be hypalon). They dont stay hard and there are a few leaks but at this point it is moot because i dont think i would dump 6 grand into getting new tubes.

Over the months i have added a CNC trim tilt bracket ($500) to the 50 horse motor and a t-top ($1300). Along with a new gas tank ($400) that i didn't know was rotted out! I have redone all electrical and fuel systems as well as having the motor gone over and seals replaced.

Weight wise the boat is well within specs and is right at its upper limits for the motor rating however i am very disapointed with how low the stern sits in the water. The water level sits right at the scupper letting water into the boat if i dont plug it... 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. 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.

http://www.armstrongnautical.com/brackets.htm

My next biggest problem is power/speed... stripped the boat did 30 knots (was expecting more like 40). With the t top, furniture, and two people i am lucky to get 20 knots. This is hugely disapointing. I do not think the boat is propped wrong. But cant figure why such a small boat is having this kind of issue with 50 HP. Engine runs fine and has been gone over by a marine mechanic and has 130-140 compression.

So how am i suposed to dive off a boat that cant handle hardly any weight?!


Okay guys let me have it... what would you do? Would brand new tubes make it sit higher in the water/ less drag more speed? Pertinent suggestions would be great.

-Matt

[codprawn]

Pics will be a big help - where is your fuel tank? Could it be moved forward along with the battery?

And why do you need that bracket?

We really do need photos with the t top etc in place first - they are very easy to upload - even I can do it!!!

[codprawn]

Ahh that's better.

The bracket has moved the engine back so the c of g is very much to the rear. That T top - whilst very nice - would look far more at home on a Boston Whaler or a 9 metre(30') RIB!!!

[codprawn]

Also could there be water trapped in the hull???

[mlynch]

the bracket was needed for the tilt and trim function as i couldnt find an OEM version after searching for a few weeks and was eventually told there was not one made...

The gas tank is as far forward as the bulkhead will allow and sits in the middle of the boat... The batteries are under the console.

While the t top probably does add a good bit of wind resistance it suprisingly doesnt effect the boats stability or steering and is fairly light. (probably 100 lbs with the dry box at most) It also provides much needed overhead storage for life jackets and such. Also it is nice to grab onto to get into the boat or in rough water. This alone probably knocked 3 or 4 knots off the speed and i realize that.

as far as water in the hull... i had the floor off the boat when i replaced the gas tank and everything seemed nice and dry and the stringers/bulkheads and everything seemed nice and sealed. There is a plug to pull once the boat exits the water as well as a bildge system in case water does get inside while at sea.

ps one more picture from the rear

Oh and codprawn thankyou for the interest in my problems any and all advice is hugely appreciated!!

[codprawn]

It looks like the tubes may be twisting or rolling up - this could allow the boat to sit lower than it should - there are a few tube experts who could help more.

That T top may not add much weight but it looks like it could act like a big wing on a racing car - as the bow lifts it increase the lift even more at the bow - maybe you could rig up a lever and use it like a joystick on a plane..............

[mlynch]

Originally Posted by codprawn

It looks like the tubes may be twisting or rolling up - this could allow the boat to sit lower than it should - there are a few tube experts who could help more.

That T top may not add much weight but it looks like it could act like a big wing on a racing car - as the bow lifts it increase the lift even more at the bow - maybe you could rig up a lever and use it like a joystick on a plane..............

maybe i will try that :-) There was a little bit of forward thinking when i mounted the t-top... I added breakaways so it is easy to remove and put back on again and other than a little bit of speed loss i didnt notice much extra bow lift. The good news is next time out i will do a test with it on and off! Also the t top has vents in the canvas to minimize this kind of effect.

I am very curious as to this tube twisting issue!!! Maybe i can tell the girlfriend new tubes for the boat are more important than a new car for her!!! Other than that it would just be great having a difinitive answer to whats going on. Also the canvas on the bottom of the tubes seems like it would have a lot of drag in water unlike smooth rubber.

[mlynch]

Originally Posted by codprawn

it could act like a big wing on a racing car - as the bow lifts it increase the lift even more at the bow

One more thing to note... the stern level and boat are fine once it is on plane. i mainly have a problem with the waterline when at rest. this mostly eliminates the t top when it comes to stern level issues.

[Pete7]

Originally Posted by mlynch

My next biggest problem is power/speed... stripped the boat did 30 knots (was expecting more like 40). With the t top, furniture, and two people i am lucky to get 20 knots. This is hugely disapointing. I do not think the boat is propped wrong. But cant figure why such a small boat is having this kind of issue with 50 HP. -Matt

Matt, those figures are about right, but I think you're asking to much from a little rib and small engine. We used to dive off a Humber Alpha (4.9m) of similar size with a 55 hp mariner. Cruising speed with 4 divers and kit was 20 knots and about 26 knots empty. However other than the engine and two 5 gallon tanks of fuel there was very little furniture in the boat. Even the steering console was a simple stand up light weight affair.

If you want to use it for diving you are going to have to ditch the canopy frame and seats. 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. Bottom line is you need to strip the boat of anything that isn't essential including seats, canopy frame and large amounts of petrol. Then move the stand up steering console further forward to create deck space for diving and keep the weight forward. All this will save the weight and give room for the dive kit and getting kitted up.

Pete

[9D280]

Mylinch,

Welcome to ribnet. I have a smiliar size / engine to yourself, which is an increase from my old boat, which was a 4m / 25Hp. 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.

Also, don't underestimate the power of wind drag. (Try sticking your hand out the car window & you'll get the idea). Now, think of the length of your arm compared to the T- top........ There's dingies out there with less canvas on their masts! Half the day you'll be motoring against the wind. If you need it to stop your "surface buddy" getting sunstroke, dismantle it and assemble when you're in position, or at least remove the canvass bit.

Weight wise I'd ditch the power lift, and have a play with the tilt pin. You'll find that different pin settings will probably be needed for diving and you alone. As long as you remember to alter it before you go out, the worst that will happen is you have a bit of a wait to get on the plane. Then keep an eye on the local O/B dealers - someone will eventually blow up an engine with a compatible working OEM power trim. Rememebr also that you can look for a Johnson PTT unit. It sounds like your main problem is at rest, so if you can get it nicely trimmed when on the plane without the power lifter, then you will gain in freeboard at rest!

Also have you checked the transom max rated engine weight? I suspect the power lift + engine may be a touch OTT? I couldn't change to a 4- stroke because of that!

[jyasaki]

Originally Posted by mlynch

The water level sits right at the scupper letting water into the boat if i dont plug it...

Sounds normal.

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.

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.

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

[spartacus]

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.

[spartacus]

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.

[columbiachop]

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

[mlynch]

First i wanna say WOW this forum is great... Thanks everybody for the suggestions they are hugely appreciated! Now for a couple responses...

Originally Posted by Pete7

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

Originally Posted by 9D280

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...

[mlynch]

Originally Posted by jyasaki

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.

Originally Posted by spartacus

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!

[mlynch]

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.

[spartacus]

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.

[mlynch]

Originally Posted by spartacus

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!

[Richard B]

Yep... just stop spending money on it!