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  1. #1
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    questions about thickness, shape and materials choice

    I am wanting to plan for some structural work on my boat. I know most everyone doing this usually does it on a Hydrostream or some other sought after performance hull but i am going to be doing this on my old bass boat, a 1979 Cobra Phantom. I know it isn't a fancy, sought after hull but it is what i have and unless i win the lottery the best i am gonna be able to do.

    So, is there a common thickness for the transom?
    What about stringers and knee braces?
    I think i should make the knees as tall on the transom side as room will allow, how far forward should i take them when I tie them into the floor and stringers?

    Is there a site i could read some sort of tutorial or guide to doing this type of work?

    Now for the argument starting question:
    what materials are preferred for best performance while saving as much weight as i can?

    All these questions while keeping in mind that this is a bass boat and i do use it to fish quite often.
    Hire the handicapped, we're fun to watch

  2. #2
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    Slimm buddy dont matter whether u got a $100,000 Fountain or a $100 Cajun its all about what the individual wants. Ive restored or put back together several boats and none of them where actually referred to as high performance but the end result ended up being much better performance.
    Anyways as far as transom thickness I have always shot for 1 1/2" at least. Sealed up and done with the correct materials you could hang any motor you wanted to off it.
    As far as knee braces I always run them as high as space permits and if just adding them to a good boat again run them as far forward as possible. Of course composits are the best choice but if working with a limited budget (which I do all the time) wood will suffice and outlive you and the boat. The whole trick is do it RIGHT. Take time and care to seal everything and it will be better....WAY BETTER than factory.
    As as resin is concerned epoxy is the best but expensive. Poly works just fine
    Laser 1550 ...under construction with a serious weight loss
    Motor 2.4....undecided on hp yet

  3. #3
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    Lots of pics on my thread of the knees I built for my boat

    http://www.screamandfly.com/showthre...restore-thread

  4. #4
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    Quote Originally Posted by roadkill636 View Post
    Lots of pics on my thread of the knees I built for my boat

    http://www.screamandfly.com/showthre...restore-thread

    Thanks buddy, headed to check it out now.

    Slimm
    Hire the handicapped, we're fun to watch

  5. #5
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    Slimm, congrats on fixing your old boat up. Fastlaser gave excellent advice. Check out my Shadow build. I added two more knees. 4 total.

    Good luck and post pics.

    http://www.bbcboards.net/rare-boat-b...bass-boat.html
    1990 Shadow bass boat w/ 2.4 200 Merc. Totally resto'd boat and love it!

  6. #6
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    When you dig into the boat you may find the original transom was built with either two plys or three " plys. Either one of these cores is good but during rebuilds it looks like the ply is more common.
    For adding knees, the size of them is really dictated by the confines of the hull. The deck or splashwell is only so high and so far forward before the tanks or cockpit define the space.
    Depending on configuration of the splashwell and if the exterior surface presuming it is metalflake needs rework you might eliminate the splashwell?
    This allows the structure to tie in as high as possible.
    If you are working with an existing splashwell that will dictate the thickness of your transom.

    When I rebuilt my Glastron I added a third ply to the upper half of the transom, actually I had not cut the bottom of the inner ply to fit the hull perfectly so I added a full ply of CDX which is laminated between the two marine plys.
    As can be seen on this hull the transom is not full width. With this in mind I narrowed the inner plys so the knees are bonded and screwed to the outside to increase sheer strength.
    In my application all wood to wood bonds are done with MAS epoxy with Vinylester used for the 1800 and 1708 glass work. I also use a peel ply on my structures allowing for ease of future bonding.


    This boat had a full splashwell which I eliminated allowing for the added thickness and height of the knees.
    Regards,
    Charlie North
    If it ain't broke, modify it.
    87 Glastron CVX20 with Yamaha ProV 150 power
    80 21' Superboat to be powered with a turbocharged 4 stroke OB

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