Problems and Questions

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doe4rae
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Problems and Questions

Post by doe4rae »

Fortunately the builders forum was down for maintenance at about 1 a.m. so I had some time to cool down a little. :frightened

It has taken me a very long time to work out the measurements so that I could install the inner gunnel in a way that the scuppers, seats, outwale screws, thwarts and decks are all appropriately spaced. I tried to start working on the taper for the ends (31") and felt I needed to sharpen my block plane so I took that apart and could NOT get it back together. Shaping the taper was taking forever. I have tried and tried to understand the diagrams in a couple different books how to do this on the table saw but it didn't make sense. I finally found a book in the library on how to do it. So I drug out all the stuff in the garage out into the snow... set up the ridiculously long tables. Hauled the 16' gunnels out and cut the tapers. Worked great.

You know where this is going.... so I'll cut it short(er).
I set up a system to steam and bend the inwales around a form and when I put the first one on it snapped right at the joint. I SO did not want that to happen to me!! I have read about it happening to so many other people. Those stories were on my mind a lot as I was bending the gunnel. But I kept recanting the words in CanoeCraft to myself, "Epoxy joints are forever." (p. 163) I was careful to wait all week, giving the epoxy plenty of time to cure. I kept the basement real warm. I don't think I starved the joint (turned the clamps until the glue squeezed out a little and then stopped.)
So I started thinking perhaps it failed because I didn't steam the center (only the ends where I anticipated more stress bowing in and up). So I steamed the other one. The entire length. (3 trips up and down the stairs with two kettles of boiling water. (Any better ideas how to steam 16 feet of gunnel?) They were in the steaming wet towels for half an hour. I had the second one in place and was feeling pretty optimistic that it worked. All the clamps were on and it hadn't shown much resistance. I leaned back to look at it and "SNAP". (Followed by explatives.)

OH, and if it HAD worked... all my pencil marks that I so carefully measured for scuppers and seats etc etc were gone. Use pen.

So I'm going to cut a few feet off the center of each gunnel and make a center piece. That way at leat I can keep the tapers that took me two days to work out. Is it because I put my joint in the center that this happened? I hate the idea of 2 joints on each side. Especially since I have completely lost faith in epoxy. Maybe I misunderstood which way the scarf joint lays. It seemed the long angle was meant to be visible from the side (after installation).
But when I saw how it twisted apart I wondered what the point of such a long joint is and if it was even in the correct orientation. I want to make shorter scarf joints if I am doing 2 per side. How could that be any worse than this? I was worried enough about the gunnels breaking that I didn't cut the scuppers yet. I would rather make them before I steam and bend but I don't want to go to all that trouble if I am going to break several gunnels before I figure out how to make this work.

Another big question I have is with the application of varnish. Using varnish is all new to me. I'm using Coronado Marine Spar and varnishing the seats. Directions say 18 hours between coats and light hand sanding with 220 grit paper between coats. Canoe Craft says to seal the wood first with varnish thinned with mineral spirits. So I did that. When I sanded I thought it was light, but by all appearances I sanded the varnish off completely. I am on my 2nd coat of varnish now and each time I sand I feel like I am going back down to the bare wood. What is the point of this ritual.... Varnish, sand varnish off, varnish, sand varnish off... etc. I feel like I am wasting varnish and sand paper. I wanted to put several coats on the canoe (6 I guess). But it seems like I could have stopped with one if I am ending up with only one coat anyway. When you sand do you want to remove all the sheen? Even if I sand very very lightly quite a lot of the shine is completely gone and then it seems wrong to have some shiny areas and some not at all. I really want to understand this before I even think about varnishing the entire canoe. The varnish really loads up the sandpaper fast!

Feeling kinda grumpy about this whole process right now and my canoe looks like some kind of awkward gangly adolescent. I feel bad for her.
:sad
Last edited by doe4rae on Sat Feb 13, 2010 4:38 pm, edited 1 time in total.
Dawne Olson

"The human soul needs actual beauty more than bread" ~DH Lawrence
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John Brice
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Post by John Brice »

You need to write a book on your experiences with this canoe - It would make a good supplement to "Canoecraft". All kidding aside I sympathize with you and can't help but wonder what's in store when I get to that point. I think the scarf joint would be best if you could see the joint from the top and you placed a clamp at the center point to hold it firm while you bend. As for the varnish question - I use waterborne lacquer for my cabinet and furniture but the process should be the same - The first (thinned) coat is a sealer that penetrates more than the full strength and sets up the grain for a light sand to just smooth it, the subsequent coats will be sanded (lightly) in between. It sounds like you are are a little to aggresive with the sandpaper. Good luck.

John


"Old age and treachery will overcome youth and skill"
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Adamv
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Post by Adamv »

Hi Dawne,

Can't comment on the joints, as I was lucky enough to not have to use joints in my gunnels.

For the varnish, I used a wet/dry sandpaper (220 grit I think, you can buy it in the autobody section) and wet sanded the hull just enough to dull the sheen. Keep dipping the paper in a cup of water to keep it from gumming up (it also results in much less dust).

Being a newbie to the whole varnishing thing, I also discovered another trick that probably everybody knows. I found it helpful to use a 3 or 4" foam roller to apply varnish to a section (say a couple of feet) and then use a foam brush to lightly brush out the bubbles. Worked great for providing an even streak-free coat.

Cheers,
Adam
Who travels not by water knows not the fear of God --- 17th Century Sailor
willo
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Post by willo »

Did you steam the joint ? Epoxy is not heat tolerant. Propperly done a scarf joint will be stronger then the the areas on either side of it. Did you coat both surfaces with epoxy and then recoat with epoxy thickened with fibers.If you can cut a taper with the tablesaw you can install an inwale , take a deep breath and go again.
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doe4rae
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Steaming...

Post by doe4rae »

... On the first one I did not steam the center where the joint was because I wasn't sure how the epoxy would handle it. I thought that it would be enough to apply steam to the last four feet at each end. When the joint failed I thought it was because I didn't steam the center where it snapped. I figured since I was going to be taking the table saw out again anyway I might as well find out if I would be needing to make two new gunnels or one. So I went ahead and steamed the ends AND center of the second one. I really thought that one was going to hold. I had it clamped in place and it gave me 2 seconds of satisfaction and then it snapped in front of my eyes while I was looking at it. Grrr.

Oh, and I did soak both joints with unthickened epoxy for about 5 minutes before a generous amount of thickened epoxy and clamping.

I was wondering about making a few narrow, shallow cuts in the joint parts that will face each other to fill with epoxy so that if the board tried to twist or break, there would be that kind of "mortise-and-tenon" joint as well, with the epoxy (in a hardened state) creating the tenon. Does that make sense?
Dawne Olson

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Larry in Champaign
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Post by Larry in Champaign »

Sounds like the joints might be starved. Try one small batch of epoxy (unthickened) to coat the scarf joints and keep them wet till the epoxy starts to set. Then mixed another batch, thicken this batch, and spread on the joints. When you clamp, use minimal pressure so the joint isn't starved of epoxy. Personally, I use T-88 for all of my epoxy gluing. It isn't cheap, but it sure works good.

Like was already mentioned, do not steam the joint.

As mentioned, the first coat of varnish is a sealer and will build with subsequent coats. Wet sanding seems to work best. Between coats, you might try some steel wool instead of sand paper.

Larry
sedges
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two mistakes IMO

Post by sedges »

1. I think, from your description of the joint twisting apart, that you did indeed have it oriented wrong. The long angle across the gunnel should be visible from the top. This way the forces won't be twisting the pieces apart.

2. Steaming the joint will soften the epoxy. Room temperature cure, marine epoxy is not able to tolerate high temperatures.

I also question whether it is even necessary to steam gunnels for this canoe. If you cut the sheer at it is shown in the plans it has an even gradual sweeping curve. It has no sharp up-turn at the ends like Red Bird. I have put gunnels on a half dozen prospectors, having a very similar sweeping sheer, and never had to steam them.

Start clamping in the middle and work your way out. A clamp every 12 inches is a good idea.

Cut your new scarfs the other way this time and have another go.

Good luck!
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doe4rae
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Post by doe4rae »

I uploaded a few images of the joint and how I approached this whole thing. I do agree that I wasn't sure if steaming would be necessary. I had hooked the inwale across the stems and put a fair bit of pressure pulling it towards the hull when it was dry and it was about 3 inches from making it before I started to feel really uncomfortable.I'd like to know (before cutting the scuppers) if having the scuppers cut will this make it easier to fit the inwale into the curve of the hull or will it just cause it to be more likely to break if I fit it without steaming it (with scuppers).

The reason I positioned the joint the way I did was because of this text: "By attaching the scarf joint to the hull so that one end lies on top of the other it will be virtually invisible from above." It seems counter-intuitive to me. And then after seeing the 'twist' off.... well. I just still don't know which way to lay it. I think my inwales are salvagable if I could re-glue them. Maybe they were starved. I can fix that without adding another section of board and re-calculating all the points and having to deal with 2 extra joints.
What do you think of that idea? As you can see from the picture it doesn't look like there is much epoxy to remove from the scarf joint surface.


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Dawne Olson

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Sherm
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Post by Sherm »

it may help if the joint is turned on "edge", it looks like from the photo it is
laying "top to bottom" making it easier for the joint to fail....I used redoak and the
only way I could get it to curve to the side of the canoe was to cut the scuppers first....

Happy Valentine's day to you and your family.....
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Larry in Champaign
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Post by Larry in Champaign »

If the joints were not starved, you would have had tear out in the wood, not a clean break. Try what I suggested earlier. I agree with others that the joint looks better when vertical, but this doesn’t appear to be the problem with your breakage.

Steaming is not wrapping in hot or boiling rags. The water itself will do little to soften the wood. It is the high heat from the steam that softens the natural glue in the wood that holds the fibers together. Also, your bending jig put undue stress on the joint. Try making a jig from a 2x4 that you cut to the profile of the shear at the ends (about 4’ long) and then clamp the steamed wood onto this jig for about 24 hours. If you cut the jig to a bit deeper profile than the shear it should account for spring back. The very ends are all that should need bent. For steaming I use a steam source and a 4’ length of 3” or 4”vent pipe. My set-up is a Coleman stove, pressure cooker, elbow, vent pipe, and rags stuffed into the end. Steam it for 20-30 minutes and get it clamped to the jig within a minute. Here are some pictures of my Bob.

https://netfiles.uiuc.edu/lwest/www/Bob ... index.html

Follow the other good advice by clamping from the center out when mounting and you should be fine.

Good luck,

Larry
sedges
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gunnel dimensions?

Post by sedges »

What are the dimension of your gunnels. They seem awfully big. I don't think there is any need to have gunnels more than 3/4 x3/4 even with scuppers. If yours are bigger than that you might find smaller dimensions easy to bend.

Above post about warm wet vs steam is right on. Steam in an enclosed space will heat the wood to temperatures that soften the natural resins in the wood which harden again upon return to lower temps. Wrapping hot wet towels will not come close to that. When people steam long pieces of wood they do it in a pipe or long box.
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doe4rae
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Post by doe4rae »

The gunnels do look big in the pictures. I always think that about other people's gunnels pictures that I've seen too! They are 3/4" by 6/8" (tapered to 3/8" on the ends). If the joints were starved then at least I have something I can work on correcting. I would not have thought I needed to steam the center until the first joint failed and I thought I had nothing to lose by trying.
:rolling eyes
If I am going to change the orientation of the scarf joint then I guess I can't reuse the pieces I have cut... I'll have to cut the joint off both 8' pieces and make new scarf joints plus an insert with scarf joints.
Dawne Olson

"The human soul needs actual beauty more than bread" ~DH Lawrence
Rick
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Post by Rick »

Bending the gunnels was the most frustrating step for me as well (an inwale snapped). To steam-bend wood easily, it should be HOT and steamed like described above.

Take it easy, you will get through this and your canoe will be fine... this step is part of the learning curve and after you've got it down, it won't seem so difficult.

With varnish, the sanding is done to remove high points that dust particles and wood grain create, so you don't need to overdo it by sanding too much.. I wouldn't agonize too much about varnishing since after some use there will be scratching on tne hull. Yes, there are appearances at stake here, but after it's been used for some time I think there will be real value in how it feels on the water and "character marks" from ongoing use will also be fine.

PS... don't forget to use blocks of wood to protect the soft fiberglass/cedar hull, when you're tightening the c-clamps to keep the gunnels in place with epoxy, since the clamps can squash the cedar, creating a white bruise mark.
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doe4rae
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Will re-think the steaming...

Post by doe4rae »

... I am going to take a look at setting up a better system of steaming the ends. I had opened the book up again last night to see what else I might have missed and made a note to myself concerning the title of chapter 9 on installing trim. Appropriately enough titled: "Character Development". Mr. Moores was probably referring mainly to the boat but the patience and perserverance being required right now must be doing something for my own character!
Dawne Olson

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Post by Glen Smith »

You should reorient the scarf joints. You should rough up the joints with some 60 or 80 grit paper. You should not apply too much clamping pressure to the joints. You should allow the joints to dry for 48 hours at 68 or 70 degrees. If you want to pre-bend the gunwales, use a form that is similar in shape to the canoe sheerline and not that joint torture fixture you are using. You are applying the greatest bending pressure right at the joints whereas when installed on the canoe, this will be an area of minimal stress.

Wrapping wet towels around the wood does not simulate steaming, just wetting the surface of the wood unless you keep it constantly wet with hot water for a minimum of 24 hours.

You should start over following all the good advice you have been given and take it easy.
Good luck.
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