Just a few questions

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Robbie
Posts: 46
Joined: Sun Jul 15, 2007 5:38 pm

Just a few questions

Post by Robbie »

Do you precoat the canoe with resin before you start galssing? How long before do you do this and do you sand before you put the glass down? 24 hrs? 12 hrs?
My canoe is a square stern so my thought here when doing the transom is cut a piece of 4 oz cloth to put on the back and then cut the glass at the transom at angles to flap over the transom piece. I hope you under stand what I'm trying to say here. I think it will be the stongest way to do this transition area if the canoe.
Thanks for your ideas and help in advance.
Cheers, Robbie.
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ealger
Posts: 387
Joined: Sat Aug 14, 2004 5:14 pm

Precoat

Post by ealger »

Robbie, you're at the most exciting part of your venture.
There are 2 camps on pre-coat; some do, some don't. I have done it both ways and think that the wet out is easier with a pre-coat done.

I let the precoat sit 24 hours and then scuff with a Scotch Bright pad. As I precoat, I squeegee off the excess epoxy after brushing on with a chip brush. I think for first time glassers this pre-coat gives a better feel for how the epoxy goes on and how long it takes to mix.

With regard to the stern: Laying on the glass on the flat end is OK. However, wraping around the edges, with the fabric is problematic. I would suppose that if the 4 oz piece is layed on in the bias direction, then it might wrap around OK.

If you find that it bubbles, then you could trim it off square with the stern edge and lay on a bias cut strip to tie the fabric around.
Ed...
Ed Alger
canoeblderinmt
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Joined: Sat Jul 03, 2004 12:04 pm
Location: Butte, MT

Post by canoeblderinmt »

Robbie,
I'm not a pre-coater, and even going over double layers in the football section I've done OK. You have to watch that you don't starve the glass.

I would recommend that when you buy your glass, buy some bias cut "tape" as well. This is nothing more than glass strips cut on the bias or on a 45 degree angle to the strip. This helps the tape mold around corners easier. I use it on my stems, as I build stemless and like the extra reinforcement. You will probably end up cutting darts in this tape, especially at the bilge areas, but it will behave much better than regular glass. Feather the edges in and nobody will know.


Greg
" Choose to chance the rapids, Dare to dance the tide..."
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Jim Dodd
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Location: Iowa

Post by Jim Dodd »

I'll go with the precoaters !
I precoat, and let dry.
You will always have specs of dust, If you don't take them off, it will raise your cloth!!!
Don't sand the specs,! With a gloved hand, I go over the hull, and SCAPE off any imperfections.
I am then ready for the glass!

As for glassing the transom, I would do the main hull first, and then the transom, When it comes time to feather the edges, you will not be sanding into the main layer of cloth, just the over lap from the transom piece.

Good Luck
Jim
Keep your paddle wet and your seat dry!
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ealger
Posts: 387
Joined: Sat Aug 14, 2004 5:14 pm

Precoat

Post by ealger »

Robbie, with regard to whether or not to scuff a pre-coat, you should consult your epoxy manufacuture for the maximum length of time epoxy can cure and still permit a chemical bond.
Ed...
Ed Alger
Robbie
Posts: 46
Joined: Sun Jul 15, 2007 5:38 pm

Post by Robbie »

Thanks everyone!
I'm going to precoat then.
I better get some bias tape at the store too.
I still have to fit the outside bow stem yest and splice in a keel but things are moving in the right direction again.
Thanks again!
Cheers, Robbie
AlanWS
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Joined: Thu Mar 17, 2005 4:30 pm
Location: Shorewood, WI

Post by AlanWS »

Whether there is any benefit to precoating possibly depends on the epoxy you use. I can see several disadvantages to precoating, but don't see any advantages with the epoxy I use (sys 3 clearcoat or silvertip). Precoating takes longer, and the bond is either worse, or in the best of circumstances, equal to that of the single step method -- though I'm sure it's good enough.

I suppose precoating lets you become familiar with the way your epoxy behaves before you get to the critical wet out process. That could be useful if you have not used it before. If you don't have a helper mixing the epoxy for you, precoating might be useful by reducing the rate at which you need to mix the epoxy.

If you precoat and wait a short enough time that you will get a good chemical bond between layers of epoxy, you will still have a slightly sticky surface that makes getting the glass smoothly laid out a lot more difficult. Having the glass in exactly the right place avoids wrinkles, lifting, and shifting on wetout -- much more important, in my mind, than whether or not you precoat. So if you precoat, letting it harden long enough that you need to scuff it sounds like a very good idea.

I don't understand the idea that dust might hold the glass out from the hull. That would need to be pretty big dust particles, and even if true, why would precoating help? I do agree that you want to get rid of dust carefully.

One circumstance where precoating sounds useful to me is if your epoxy has trouble soaking into both the glass and the wood, and there is some problem with bubbles or glass lifting when you do it in one step. With fairly non-viscous epoxy, this has never been close to a problem. I suppose really thin epoxy might have more of a tendency to drip out and starve the cloth, but even with sys 3 clear coat, one of the slowest and thinnest epoxies around, this doesn't seem to be a problem.

With regard to the square stern, I would not wrap the glass around the corners. I'd run the glass close from both surfaces, smooth it after cure, then apply bias-cut strips over the edges. These can deform a lot without wrinkles, and have much less tendency to pull off during cure.
Alan
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Jim Dodd
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Location: Iowa

Post by Jim Dodd »

Hi Alan
I precoat for several reasons.

First, to fill any voids that I may not have filled.

Secound, I do not fill my staple holes with putty. I precoat, wait about an hour or two, mix a 6oz batch, and paint over the staple holes. This fills the holes, and eliminates those nasty weep holes.


Thrird, I have no bonding problems this way.

Four, I use System Three Clear Coat. No BLUSH. I think blush causes a lot of problems.

And yes, if you don't scrape the dust particles that are inbedded in your precoat, they will lift your cloth . You can overcome this by extra layers of resin, I prefer not to.

These are lessons I've learned the hard way.

I hope this helps !
Good Luck

Jim
Keep your paddle wet and your seat dry!
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