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!