New Member - staining strips?

[Ric Altfather]

Experiment...

Barry,

Most of the Epoxy companies have sample kits that you can buy for $10. Try them before you buy the big kit. I did that and was able to make a very good evaluation for the project at hand. Also, I end up with a little epoxy for those one off jobs like a paddle, kayak saddles, repairs, etc. I have tried every one and in the final analysis, they all work, again depending on your job. You can save money with some, others offer better advice/support, all can blush depending on the hardner you use...my personal choice (unsolicited) is MAS with Raka (unsolicited) a close second. Buy the glass from the company you get the Epoxy from.

Ric

 

[Todd Bradshaw]

A 16' canoe with one gallon??? I'll believe that one when I see it. I don't care what brand you use, but unless you're using some sort of exotic, super-light cloth (and willing to take the strength reduction that comes with it) that's just dreaming.

You're also preparing (unknowingly, I assume) to toss about half the strength and durability of your hull right out the window..... I've been round and round this topic on several strip forums with new builders, but the last thing you want to do on a stripper hull is use less reinforcement on the inside than on the outside - unless you have some sort of desire to later start another one of those "Dude, my boat split...what do I do now?" posts.

People assume that the outside needs more strength than the inside because that's where the rocks are. This is only half true. Yes the rocks are outside, but the strength needed to survive them needs to be on the inside of the hull. When you hit a rock or when your hull flexes or it's bottom bounces there is a certain amount of compression on the outside. The inside layers, however, are in tension, not compression, and due to the thickness of the sandwich, they are getting far more destructive force than the outside is. An encounter with a beach or a rock may scrape the outside layer, so some thickness and beef out there helps the boat survive impact and abrasion, but the inside layers are likely to split wide open (both the glass and the wooden core) long before the damage on the outside even gets serious.

The typical assumption that you can reduce the inside layup on a stripper to save weight is a huge mistake from a durability standpoint. Don't make it. If you want a lighter boat, use lighter trim, or thinner strips or lighter, more expensive cloth, but don't try building an unbalanced sandwich construction with less beef on the inside unless you have the experience to selectively reinforce a composite layup without losing strength and rigidity on one side.

 

[Dan Lindberg]

Barry,

Listen to Todd.

BTW, on my projects it was closer to 2+ gals resin, for 17.5 and 18.5 canoes.
Back then a 2 1/4 gal kit of MAS was available.

Dan

 

[BarryB]

2 Gallons

Hi Ric, Todd, and Dan,
All good information. Thanks for the replies. I got the "one gallon for a 16ft canoe" from a thread in December 2005. It was a reply from a person named "jackbat" to an "Epoxy" thread and it sounded like he knew what he was talking about. Todd, you were in that thread but never replied to the one gallon post. I presume because it was too ludicrous to warrant the attention. Regardless, I always intended to buy two gallons.

The discussion about the double layer of glass on the bottom is new to me too. Canoecraft only discusses one layer of 6oz inside and out. I don't want to be one of those "Dudes" as Todd puts it, whose boat splits down the middle. Especially since this canoe is for my Daughter. I have an Old Town Yankee to restore for myself. So since the genie is out of the bottle, should I use two layers on both sides, one layer, or two on the inside and one on the outside, or what? I had intended to go with the recomendation in the book but now I'm not sure.

I'm presuming this topic is well covered in the threads so I'll look around a bit to see what the concensus is but I really like getting direct information from you guys. The tone can be a little harsh sometimes but good coaching is often harsh in my experience. I'm not afraid so let me have it. You'll save me a load of time and trouble with your valuable experience. That's why I'm here.

Thanks,
Barry

 

[BarryB]

I Beam

Hi Todd,
I just read your excellent discussion regarding how stripper construction is really an I Beam. I found it in a thread titled "Big Crack... OUCH" from February. Fantastic. It sounds like our 17' canoe will benefit from the suggestion to use your "bilge-cookie" method with the inside bottom double glassed.

I don't want it to get super heavy, even though my daughter is 5'11" and very strong, but the extra strength sounds like it's worth it. I noticed that you used that method on both sides but after reading your discussion it seems that taking a double layer past the bilges on just the inside would be plenty.

I did quite a bit of feathering on my sailboat since it had double layers on all the seams and it looked fine. You mention that you lay up the double layers at the same time. Does that give you a hard line where the first layer of glass ends? The taped seams in my sailboat were all sanded after curing to feather the edges, allowing the cover layer of glass to lay up without a visible line.

It might not save much weight since the bilge is only a few inches from the sheer line. Perhaps its best to simply double glass the entire inside?

Your time is much appreciated.

Thanks,
Barry

 

[Todd Bradshaw]

Barry, the method I've always used was to lay the bilge cookie on the wood, drape the full layer over the top of it and saturate both at the same time. You do need to work carefully to remove any bubbles under or between the layers and you don't want to agitate the resin too much and add more little ones, but when you're done, there isn't much of a "step" left where the layup transitions from two layers thick down to one layer thick. I use a Gougeon foam roller to apply the resin and follow it with a squeegee cut from a slab of ethafoam or minicell foam to gently "comb" the glass down tight to the hull. As soon as the main layers are on, the stems are wrapped with bias-cut fiberglass strips.

Filler coats are added as soon as the glass layers are stiff enough that the roller won't disturb them. I never pay any attention to the number of filler coats and personally believe that trying to pre-determine how many you will add is crazy. I roll on thin filler coats until the weave of the cloth is totally covered - and then add one more. If the temperature, rolling style and resin type happen to require five or six coats to get to that point, so be it. I usually use WEST epoxy and if I have to wait overnight between coats, I'll take a few minutes to go over the hull with water and a Scotchbrite pad and then wipe it down before the next coat. This removes any amine blush, but I would do the same thing on any resin to remove anything which might have settled on the surface overnight. Whether your resin is one that blushes or one that theoretically doesn't, fiberglassing is a heat reaction and heat reactions quite often cause moisture to condense out of the air on their surfaces as they cool down. Before I roll another filler coat on a cold hull, I want to be sure that there is no crap on the surface.

By the time you're done filling, the step-down where the bilge cookie ends is nothing but a very minor hump that will sand smooth in a flash when you go to finish sand the hull. I never sand between coats of resin or to try to feather out layers during the glassing process. Epoxy doesn't fully harden for several days and you run the risk of bruising the fresh fiberglass and creating little whitish fractured fibers along the transition that will never go away.

I firmly believe your best bet is one full layer of fiberglass cloth and one bilge cookie, both on the inside and outside of the hull. Until you have built and used enough boats to have the experience to experiment with something more exotic, it's a good, safe all-around choice.

 

[Dan Lindberg]

Barry,

I'm a bit reluctant to throw this out but, the 2 best ways to reduce weight are 1) reduce the volume of wood, and 2) use a thiner/tighter weave cloth.
But both take a bit more finesse to work. I'm not sure they should be used on a 1st project.

My 1st, 17.5 ft, using the std 6 oz and a 2ed layer in the football in and out plus a lot of trim ended up at 72 lbs, way too heavy.

Dan

 

[BarryB]

Bilge-Cookies

Hi Todd,
Thanks a million for the extensive description. I'll follow your advice and do the bilge-cookies on both sides. I worked with West System on the sailboat and recall wiping it down between coats. I'll do that this time too even though MAS slow hardener is supposed to be blush free. I don't want a milky finish.

I installed the accent stips yesterday and added a couple more on top of that today. It looks great. I'm building without staples and it's a lot of fiddling with clamps and wedges but I think it will be worth it. So far it's working out perfectly. I'm a little concerned about getting around the curves of the bilges and may use a staple or nail if it's needed.

I was worried about the fit at the stems. I had a hard time spoke shaving the stems while they were on the forms so took them off and put them back on a hundred times to get the right angle. It was a lot more work than I expected so, just to be as accurate as possible, I attached a batten about 5 feet long to my reciprocal saw and taped a hunk of sanding belt to the other end of the batten. My wife ran the saw, I guided the batten, and sanded a perfect bevel on the stem. Thought that was a pretty clever idea so won't somebody pat me on the back for that one? Getting familiar with you guys and girls on the threads makes me believe you probably all do something like that so maybe I'm feeling cocky a bit prematurely. It's been a pleasure so far and seeing the strips going on so well makes me very happy. Perhaps the bilges and the football will tame me.

Thanks,
Barry

 

[BarryB]

Weight

Hi Dan,
I just saw your post and understand the weight issue. My daughter doesn't plan to portage much. We live near Seattle and she'll use the canoe for day trips in some of the lakes up north and an occasional overnight. I'd rather trade the weight for a strong canoe if she's going to be out there on an overnight, especially if it's far away.

This is a pretty big canoe to start with and it specs at 55 to 65 pounds with one layer of 6 oz. We knew it was going to be heavy when we decided to build it so we loaded up the Old Town to 65 pounds and carried it around. She didn't think it was all that bad so we'll see. All this stuff seems to boil down to trade-offs and Gougeon Brothers says that 50 square feet of 6oz glass weighs 2 pounds more than 4oz glass. I suspect there would be savings of 4 or 5 pounds if I did the cookies in 4oz glass. What's the concensus on that tradeoff?

Thanks,
Barry

 

[Todd Bradshaw]

Assuming that the cloth layers are tight together and tightly down on the surface of the wood (in other words, well squeegeed so that they're not floating in excess resin) I don't think switching the cookies from 4 oz. to 6 oz. will save you that much weight. You still have a thin layer of reinforced resin (the saturated cookie) under the main layer and the difference in weight is simply due to the difference in thickness between this partial layer and the resin it holds and a similar, but very slightly thicker or thinner layer. Fiberglass as pretty darned thin in the type of use we have in mind for it, and the weight of the cookie material has no effect on the number of coats needed to eventually fill the weave of the six ounce outer layer, so I can't see it being that much of a weight issue.

One good practice exercise for folks learning fiberglassing is to lay up a couple layers of cloth maybe 12"x 12" or so on a flat surface (plastic, waxed paper, waxed formica or something else that resin won't bond to). Squeegee it down neatly and tight to the surface, add filler coats if desired or just squeegee the top surface removing the excess resin until you have a nice, even weave showing and let it harden. Then peel it off and you'll probably be surprised at just how thin it is. Two layers of six-ounce only has about as much bulk and backbone as the wall of a plastic milk jug. This flimsy chunk of stuff represents one half of the "beef" in your canoe and clearly demonstrates the rigidity gained by using a cored sandwich construction. Keep in mind though, that the increase in stiffness provided by the core doesn't directly correspond to an increase in strength. The wooden core is not a major strength provider, but more of a spacer. The impact resistance and true strength of the construction is still in the inner and outer skins.

There is an old boatbuilder joke where a worker develops an incredibly strong, lightweight composite test panel. He takes it to his boss and says "Watch this!" He sets it down and hits it really hard with a hammer. Nothing happens. His boss then says "Watch this", turns the hammer over and with relative ease, drives the claw part right through the panel. This scenario is worth remembering when you're building canoes.

 

[BarryB]

Weight 4oz vs 6oz

Hi Todd,
Again, you are giving great advice. I did some quick calculations and found that at 54 square feet or 6 square yards, the difference between 4oz and 6oz glass, in the fabric alone, is only three quarters of a pound. Using your method of laying them up together the amount of extra resin required would be a minor factor in the wight. After reasoning it out like that it seems the strength versus weight issue is not really an issue at all.

Thanks,
Barry