Fiberglass cloth or not?

Discussion in 'Wooden Boat Building and Restoration' started by Barry Beard, Jul 7, 2007.

  1. Barry Beard
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    Barry Beard Junior Member

    I'm working on a 1945 plywood runabout. It may well not be worth restoring, but I've started into it now. I've used chemical stripper to remove the paint on the hull and gotten down to the fiberglass cloth. There are many divits in the fiberglass cloth. I'm thinking I need to remove this old cloth, sand the hull and start anew with new fiberglass cloth? (the boat is 14 foot) I'm looking for suggestions and advice regarding 1., alternatives to using the fiberglass cloth (or is that a necessity; I'm definitely a novice); 2., how to put the fiberglass cloth on properly (or best resource for that information); and so forth. I appreciate your response. Thanks. Barry *see the accompanying photos . . .
     
  2. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

  3. alan white
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    alan white Senior Member

    The cloth will need to come off. Once the hull has been de-glassed, the dings, dents, and gouges are filled. Then sand the hull. If it is fir ply (and it probably is), you must use a very coarse grit to avoid getting a wavy surface.
    Fir has both soft and hard grain, and sanding with too fine a grit leaves the harder grain standing higher. (filler--- West System Microlight).
    Once sanded, use epoxy and a layer of 10 oz E glass, and West System epoxy (105 resin and 206 hardener). Maybe a gallon of resin will do the job.
    Many other things could be said, but you should get the printed guide recommended by Raggi. Then you'll have more questions, I'm sure.

    Alan
     
  4. Barry Beard
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    Barry Beard Junior Member

    Thank you Alan.
     
  5. Barry Beard
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    Barry Beard Junior Member

    Fiberlass cloth or not?

    Thank you Kevdja.
     
  6. Barry Beard
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    Barry Beard Junior Member

    Thank you gentlemen.
     
  7. lewisboats
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    lewisboats Obsessed Member

    why remove the existing cloth...? Unless there is rot or some other adhesion problem...fill and fair everything with some slightly thickened epoxy and re-glass with a layer of 4 oz, fair it up, sand paint and polish and be on your way. Don't add additional work where it isn't needed.

    Steve
     
  8. Barry Beard
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    Barry Beard Junior Member

    Thanks Steve. There are adhesion problems in places and it seems the chemical paint remover also got after the cloth in places. Being a novice, I need to clarify something: Does "fair it up" mean using a long sanding device that keeps things contoured appropriately without making small sanding dishes?
     
  9. Flumixt
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    Flumixt Junior Member

    Practise.

    Practise glassing a piece of wood both horizontaly and at a steep angle like you have on your boat sides. Small pieces will do like a foot square. It's time extremely well spent; won't take long. If you can tilt the boat while doing the sides that'd be best.

    Especially on the sides the resin will tend to run down just after you think it won't. Put lots of thixotropic powder in the resin to stiffen it and have a couple (several?) heat lamps ready as soon as you've wetted out the cloth at any particular spot to aim on where you have just worked and start the resin to kick off ASAP. Figure about 30-60 minutes for this. Do small lengths to keep it under control. Then keep yer eye on it till it does kick off or you'll sure wish you had. Might have to keep working it uphill with a brush, blade or roller for a while till it stiffens.

    If you practice this on the spare pieces first you will learn a lot and won't get caught with a pot full of resin dripped on the floor. You can also go a tad heavy on the catalist which might hasten the kick off but practise that first. You'd have to keep track of the mixtures and reaction times ie make a chart. The practise boards will help you guage the thix powder too. You'll be amazed how much can be stirred inna the resin. You'll learn how close to set the lamps for effective heating w/o burning up your boat too.

    This turned out longer than I expected. -jimbob
     
  10. alan white
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    alan white Senior Member

    Regarding fairing: This is a matter of feel. Plywood, or any single curve surface isn't too difficult. Using a batten, check the hull over for low spots and areas and fill those first. I usually make a 24"-32" long longboard by cutting a 6" 36-50 grit sanding belt (normally used on a stationary belt/disc sander. This is then glued to (usu) a piece of 1/4" ply or masonite with construction adhesive and clamped overnight. Other sizes may be useful depending on curvature. In the case of ply, removal of wood isn't desired, so adding fairing compound is how to do it. Stick with a coarse grit because it is less suseptable to riding over harder surfaces. Running your hands over the hull is the true test of fairness. If you tape all corners before fairing with two layers of tape (3" is okay, offset so the first layer is an inch more on one side than the other, and then opposite with the next layer), you can run the big cloth (after fairing) up to, but not over (avoiding doubling) the corners.
    Fairing before glassing is a good idea because the glass has a perfectly smooth surface to lay on, and the weave is protecting the softer fairing compound underneath. It's also easier to guage your additional sealer coats for uniformity if you see the weave filling completely (two additional coats of pure epoxy finish the job ready for final sanding and prime/paimt.

    Alan
     
  11. Barry Beard
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    Barry Beard Junior Member

    JimBob and Alan, Thank you. I've got lots of tips and info; now need to get my butt out and into it. Just like jumpin' in that cold water. Barry
     
  12. barthautala
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    barthautala Junior Member

    Im a newbie. You only use fiberglass cloth on the surfaces you plan on painting correct? Otherwise, you wouldnt get the pretty wood shine. Am I correct here?
     
  13. alan white
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    alan white Senior Member

    Fiberglass is almost invisible. However, there's no need to use it above the waterline except for abrasion resistence or strength or water-proofing. Canoes that are strip built almost always are glassed and then varnished to add UV protection. They appear to be only varnished, however.
     
  14. barthautala
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    barthautala Junior Member

    thank you for the explanation. I never knew the cloth came out invisible. The only experience Ive ever had with fiberglass is the stuff on my dads bike. Which when broken looks white......that just must be the primer they use to paint over.
     

  15. Barry Beard
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    Barry Beard Junior Member

    Varnish over fiberglass cloth . . .

    Alan, I never realized you could varnish over fiberglass cloth. Do you need to get a special grade of fiberglass cloth to have it appear invisible? I guess I've never really looked closely at a varnished hull to try to detect the cloth. Thanks. Barry
     
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