ply over glass hull leaking...help! :S

Discussion in 'Boat Design' started by floydrob, Jul 18, 2008.

  1. Dane Allen
    Joined: Jul 2008
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    Dane Allen Junior Member

    Ah, I stand corrected. I wasn't aware this was a stitch and glue boat, I thought it was ply over frame based on the pictures. What I was reading was in regard to the belief some people have that fiberglass greatly increases the strength of the plywood panel itself. I see now the focus of the conversation was on the joints.
     
  2. kengrome
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    kengrome Senior Member

    It almost never saves money on construction costs to use epoxy and glass on thin plywood rather than just using thicker plywood and no epoxy/glass. Plywood costs a lot less than epoxy and glass, that's all there is to it.
     
  3. floydrob
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    floydrob Junior Member

    hi, i take ur comments onboard, its now alot further on and i cut off all the foam, it was kinda expoetimental, i bought a dremel with a cutting blade and cleaned up al the joints one by one, all the edges and replaces all the crap wood towards the bow and got a better transom. it is all fiberglassed on the joints, sanded down smooth and then painted with primer and antifoul on the bottom and exterior gloss on the side which is nece and thick so it soaks into the wee pinholes. the construction is chine logs which the ply is screwed to with brass screws and fiberglassed over. i think the problem came when i filled it with too much water, done my calculations and it holds 1.5tonnes of water, so maybe thats why it started bursting little leaks.lol.

    would it be worth flippin the thing upsied down, getting a load of filler and smoothing everything perfectly and then use it as a mould to make a double skinned fiberglass hull and then add the cabin afterwards? i was just offered 3 binbags of fiberglass from my best mate who got it from the boatyard.

    my phone is getting repaired soi cant post pics, soz, i took onboard all those comments, they dont piss me off, they make me think, read up on it and then i 99% of the time, i apply what has been sed, but wat dus piss me off are naysayers and ppl like tom lathrop who recon i dnt take anything onboard like a typical teenager :-
    "Floyd could benefit greatly by taking his advice seriously also but I doubt that will happen"
    tbh, if ppl tell me i cant it just makes me more determined to prove them wrong...if u can constructively criticise my work ant tell me of improvements i can make...dont be afraid to, but dont tell me that u doubt i will take them onboard cos i will if i have good reason and at the end of the day, its my boat, if it sinks, i'm responsible. :D
     
  4. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    Well done Floydrob. Bouncing back like that and getting stuck into the fixes is the only way to go.
    In my not so humble opinion, I think thoroughly waterproofing your existing hull, and having a bit of fun with it is the way to go.
    The full fibreglass version with all the spare leftovers should be reserved for your next big project, because (whack on the chin) the current hull design is ahem.... very experimental, and you will do a much better job next time, I am sure.
     
  5. kengrome
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    kengrome Senior Member

    No, don't do this yet. If the boat turns out to be good enough to be molded you'll learn that AFTER you've had it on the water for a while.
     
  6. floydrob
    Joined: Jul 2008
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    floydrob Junior Member

    ok, thanks. the actual plans were adapted to make them easier for me to build from the "firefly" plans which can be found on svensons.com, i didnt have the tools to cut a curved bow frame, so i made it sharper, which i like better for looks, and i just put a flat deck on the bow and added a water tight compartment to the bow too, i want to have a watertight compartment in the stern and one midships too, so if she flips or anything happens, i can take her out the water and adjust it and repair it. i wanna put it in the water with some weight in it at the transom to replicate the engine (still have no clue what size) and some weight on the seat in the cabin, then i can see if it floats and how it sits in the water....one problem=my dad sed it aint goin near the water till i can prove there is no leaks, but he doesnt understand that putting that weight of water inside the hull will just create leaks and push the sides apart. any other methods i can use? i dont want it to float from the inside, preferably the outside. spur of the moment....i'll build a lake in my garden...lol, ko.
    thanks for ur help again :D
     
  7. the1much
    Joined: Jul 2007
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    the1much hippie dreams

    build a small cradle to put your boat in, if he's stuck on that method,,,,,make him help ya since its his test,,,hehe :D
     
  8. GTO
    Joined: Jul 2007
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    GTO Senior Member

    I built my boat from plans at http://www.instantboats.com.
    Dynamite Payson has a couple of books out that describe in good detail how to build simple, relatively inexpensive boats using plywood, nails, and glue, along with the stitch and glue method for some designs. The books contain small copies of some of his plans. Maybe you could find the books at a library or bookstore and review it for some help.

    He also has this powerboat that might be a fun build for the future.
    http://www.instantboats.com/skimmer.htm

    To test the hull, just drop it in the water with a few sandbags/weights equaling your hoped for payload and let it sit for a while. If it doesn't leak, start off with slow and easy trips near shore where its easy to beach if a leak does occur. You should be able to use a paddle or oars (you can make those if you don't have any) to test the boat out, before worrying about an outboard or electric motor.

    Good luck and just be safe!
     
  9. floydrob
    Joined: Jul 2008
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    floydrob Junior Member

    not tryin to be a smart arse or anything, but that power boat is a peice of pish...i dont want to take a step back, i have built many boats in the past using simple techniques, herb mcleods one sheet skiff(now how simple can u get), then i moved onto a jonboat, still relativesly simple, and now i'm making this...its a good leap, but i want a challenge, at first i wanted it in the water quick, but now i have slowed down, fixed most problems, trimmed verything nicely and am now working on the inside as i am pretty confident that it will float great. i put a deck in and am gonna get some thick ply for the cabin roof and sides cos the 6mm stuff i used is rubbish for that, also it will hopefully push the bow down a bit because i was woried of the bow being too high and the stern being too low, so i'm starting with a 6hp british seagull which i will link to a steering rack of some kind...shudnt be too hard.the front deck will be replaced with decent ply, the stuff on it is rubbish. i recon i can do a good job of this boat with advice from everyone here and if i take my time. i'll try to add pics but summmit aint wurkin. grrr. lol :D
     
  10. floydrob
    Joined: Jul 2008
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    floydrob Junior Member

    pic thing aint working, i'l go on my laptop 2moz and post them.
     
  11. floydrob
    Joined: Jul 2008
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    floydrob Junior Member

    hi guys, i got my exam results today which were very good, so my dad let me put my boat on the trailer and launch it. i bought a trailer last week for $100, (i dont have a gbp sign cos i just reinstalled my computer to US keyboard format accidentally) but 50.00GBP its pretty tatty but does the job.

    we put it in the water down a slip, but the trailer has no winch, so we un-tied the rope and gave it a push, so it went in fine, sat it there with some weight in it for a good half hour, seemed fine, so i got in and took her for a spin...well thats an exaggeration, she's heavy, and with a 9.9hp yamaha (i borrowed from my grandad) she was going alot slower than expected, i dont have a spedo, but i wouldnt have thought any more than 8 or 9 kts.

    i now think i wanna make a full fiberglass one for myself, it would be lighter and i wouldnt need a big engine. what are your thoughts and where can i get fiberglass csm at the best prices? i pay $12 (6.00GBP) for 1M x 1M, which wont meke my nu boat cheap! lol. i want to double skin it and make fiberglass seats etc. also, where is the best place to order epoxy resin, and the best application process? rubber roler? i have no idea, i done the joints with a brush, which gave many air bubbles. thanks :D
     
  12. kengrome
    Joined: Jul 2006
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    kengrome Senior Member

    A 9.9 should easily get 500 pounds onto plane if the hull is properly designed to plane. Did you calculate your weights yet? How much did the boat + engine + you + fuel + other stuff weigh when you tested it?

    Who did you build this one for?

    Fiberglass is HEAVIER than plywood, not lighter, so you're going to need an even bigger engine if you make a similar boat in fiberglass and if you ever hope to get it to plane. I cannot help but wonder where you got the idea that you can save weight by building in fiberglass???

    Sure, if you make a composite sandwich with foam core in between two layers of glass your hull MIGHT weigh less than a plywood hull -- but even if you're lucky enough to get it to weigh less, the difference will be so small that it's not worth the time and money on such a small boat -- unless there are other reasons for using this technique (which do not apply to yours) such as a round bilge design for example.

    IMO you'd be better off building a second boat in plywood with epoxy/glass taped seams. But this time you might want to consider building it upside down on frames so you can start off with the correct shape. Then use high quality marine plywood of the proper thicknesses for each part of the boat.

    You might also consider using the right kind, type and thickness of glass tape (+45 -45 biaxial is best) on your joints inside and out ... and no more of that foam crap you used in the joints on this boat. Use good quality epoxy not polyester or any other cheap substitute. If you do what I'm suggesting you'll be finished faster with a lighter boat and you'll have saved LOTS of money over building one in fiberglass, that's for sure!

    Do you have any pictures of your boat in its current condition? After seeing the other pictures it would be nice to see the improvements you've made ... :)
     

  13. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    Couldnt have put it better myself!!!!

    Right on KG.
     
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