Strip Canoe advice - losing some shape after pulling staples

[NickN]

Hello. I've searched and haven't seen this particular issue discussed on the forum. Any advice will be appreciated.

I just finished pulling the staples on my first strip canoe. On the first two stations in from the stems, where there is a good bit of hollow, the strips have now lifted outward off the molds at the sheer. Maybe 3/8" at the worst spot. Ultimately, I'm not too bothered by it, but if I would prefer to correct it if reasonably possible.

Thus far my best thought is to glue a small block of wood inside the sheer and clamp or screw that to the mold before glassing. I would later have to remove the block with a chisel.

A few questions:
1- Has anybody faced this issue and come up with other solutions?
2- Even if I fix the strips back against the molds before glassing, will the outer layer of 6 oz. glass actually hold the shape or will it likely spring right back when removed from the molds?
3- Could I squeeze the shape back into the sheer when attaching the gunwales and breasthooks?


For reference, this is a bear mountain Huron cruiser which I shortened by 8" by tightening the station spacing. Thereby tightening all the longitudinal curves - Just to be sporting, I guess.

Thanks!

[Todd Bradshaw]

Re: Strip Canoe advice - losing some shape after pulling staples

I think you will find that strippers are pretty floppy until you get both inner and outer glass on and some structure in the way of at least temporary thwarts in. Chances are that trying to correct 3/8" isn't worth bothering with until you have glass on both sides and are installing the gunwales and thwarts. At that point, it won't be at all difficult to pull the boat into its designed shape. We used to find that a hot glue gun could be handy at times for temporarily sticking stuff together.

[Peerie Maa]

Re: Strip Canoe advice - losing some shape after pulling staples

Is it symmetrical? 3/8 both sides? If so, don't worry, be happy.

[Todd Bradshaw]

Re: Strip Canoe advice - losing some shape after pulling staples

A stripper with or without the first (outer) layer of fiberglass is way too floppy to be either symmetrical or asymmetrical. Unless you have built one (or more) you wouldn't believe just how mushy the shape is at that point. Set it upright on the ground and start to pick it up from one or both ends and it will fold in the middle.

[NickN]

Re: Strip Canoe advice - losing some shape after pulling staples

Thank you, Todd. I will see what can be done with a glue gun at this point. If that won’t hold it in place I’ll do what I can when the gunwales go on.

[JimConlin]

Re: Strip Canoe advice - losing some shape after pulling staples

Hollow sections of a strip planked hull will pull away from the mold when the staples are pulled. I think the only way to enforce hollows would be after glassing the outside, push the hollow sections back inwards with external station molds before glassing the inside of the hull. It’ll spring back outwards a little when the molds are relaxed,

[Peerie Maa]

Re: Strip Canoe advice - losing some shape after pulling staples

Taking a broader view of this issue: why is there hollow anyway? Did any birchbark canoes have hollow (personally, I doubt that they did)?
3/8'' at the sheer won't make much difference in the grand scheme of things.

I would just fair and glass the outside, fit the external gunnels and carry on.

[NickN]

Re: Strip Canoe advice - losing some shape after pulling staples

Taking a broader view of this issue: why is there hollow anyway? Did any birchbark canoes have hollow (personally, I doubt that they did)?
3/8'' at the sheer won't make much difference in the grand scheme of things.

I would just fair and glass the outside, fit the external gunnels and carry on.

I think some birchbark’s did have hollow in the ends. Consider the way the sheer was defined in some by gunwales that extended beyond the stem and were lashed there side by side. Necessarily imparts a reverse curve in plan view. And it’s certainly traditional from what I’ve seen of wood/canvas canoes. I don’t know that it does anything except maybe reflects a beneficial waterline shape. I guess it would make a drier and more buoyant boat without it, but this is not a sailboat or a whitewater canoe. Just a small boat for quietly paddling on quiet waters. I find the shape attractive. That said, the strips might be telling me this shortened hull has resulted in too much hollow. I wouldn’t be surprised if they haven’t found a nice line on their own.

as to why the issue bothered me at all, I suppose it’s just a blind desire to maintain control and arrive at the result intended. It’s all new to me so I thought it worth asking, and I appreciate the reassuring feedback.

[Peerie Maa]

Re: Strip Canoe advice - losing some shape after pulling staples

I don’t know that it does anything except maybe reflects a beneficial waterline shape.

3/8 inch at the shear will not do much of anything lower down.

That said, the strips might be telling me this shortened hull has resulted in too much hollow. I wouldn’t be surprised if they haven’t found a nice line on their own.

Clear straight grained timber usually know best.

as to why the issue bothered me at all, I suppose it’s just a blind desire to maintain control and arrive at the result intended. It’s all new to me so I thought it worth asking, and I appreciate the reassuring feedback.

Old school professional small boat builders did not bother much with moulds, may be one in the middle, or a set of key dimensions, They cheeked for symmetry and level, but all else was done by eye, to look right.

[Todd Bradshaw]

Re: Strip Canoe advice - losing some shape after pulling staples

Some hollow along the sheer line at the ends isn't unusual on traditional-looking canoes, even those with rather utilitarian end profiles like my 1972 Old Town Guide. Canoes with higher, more decorative end shapes will often have quite a bit more. This would include a lot of birchbark canoes, many of which carried some hollow all the way down to the waterline and below. Typically, they were built inside of a building bed with vertical stakes, set into position by using the pre-assembled inwale gunwale structure to indicate the desired shape, unlike modern canoes where the gunwales are usually a late add-on.

guide 013.jpg

[Peerie Maa]

Re: Strip Canoe advice - losing some shape after pulling staples

Some hollow along the sheer line at the ends isn't unusual on traditional-looking canoes, even those with rather utilitarian end profiles like my 1972 Old Town Guide. Canoes with higher, more decorative end shapes will often have quite a bit more. This would include a lot of birchbark canoes, many of which carried some hollow all the way down to the waterline and below. Typically, they were built inside of a building bed with vertical stakes, set into position by using the pre-assembled inwale gunwale structure to indicate the desired shape, unlike modern canoes where the gunwales are usually a late add-on.

[ATTACH=CONFIG]137245[/ATTACH]

Photos are tricky. What looks like hollow at the far end could just be a feature of the abrupt up sweep of the shear line. The near end does not look particularly hollow at all.

I have watched a couple of videos on birch bark building, on old black and white film from way back, and one by Ray Mears and with Pinock Smith. It is amazing how it goes from a flat bottom with straight sides to that fair form.

[Todd Bradshaw]

Re: Strip Canoe advice - losing some shape after pulling staples

Abrupt upsweep? Really? If this canoe has an abrupt upsweep you ain't seen nothing yet.

guide2 007.jpg

This is a shot from Adney and Chapelle's book "The Bark Canoes and Skin Boats of North America" published 1964 by the Smithsonian, page 36. You can see the hollow all the way down to the lowest waterline plane shown, as well as on the diagonals. It was created by the thwarts pulling in on the gunwales in order to create all that tumblehome, along with the gores cut into the sides of the bark skin. The canoe is a 16'8" Malecite canoe with a shallow arch bottom. The ribs were pre-bent to that bottom shape before ever being put into the staked-out bark skin.

Chapelle.jpg

[Peerie Maa]

Re: Strip Canoe advice - losing some shape after pulling staples

Abrupt upsweep? Really? If this canoe has an abrupt upsweep you ain't seen nothing yet.

[ATTACH=CONFIG]137246[/ATTACH]

This is a shot from Adney and Chapelle's book "The Bark Canoes and Skin Boats of North America" published 1964 by the Smithsonian, page 36. You can see the hollow all the way down to the lowest waterline plane shown, as well as on the diagonals. It was created by the thwarts pulling in on the gunwales in order to create all that tumblehome, along with the gores cut into the sides of the bark skin. The canoe is a 16'8" Malecite canoe with a shallow arch bottom. The ribs were pre-bent to that bottom shape before ever being put into the staked-out bark skin.

[ATTACH=CONFIG]137247[/ATTACH]

No fair! With such extreme tumbler home I doubt that any canvas covered, e.g. Old Town canoe, or stripper could be lifted off its build jig.

Compared to other craft your canoe does have an abrupt up sweep, as I said the near end in the photo does not look hollow. The sheer line and deck half breadths are the trickiest part of a boat's hull to get to look right from all angles, what looks fair from one angle can look humpy, or powder horn from another. So a photo can lie.

[Todd Bradshaw]

Re: Strip Canoe advice - losing some shape after pulling staples

Having owned that boat for 50 years and rebuilt it twice (including replacing the gunwales and decks) I can confirm that you are wrong and the photo is not lying. It is even visible in the shape of the decks where they meet the gunwales. Here is another one where you can't falsely blame it on the tumblehome, as there is none. Notice that again, the slight hollow goes all the way down to the lowest waterline and is also visible on both diagonals. In any case the topic of this thread is a 3/8" distortion up high when the staples were pulled. Having actually built numerous canoes and kayaks using this method and materials over the last nearly fifty years, I can verify that the problem will disappear when the gunwale and thwart structure is installed, and it is nothing to be concerned about.

DSCF4205.jpg

[Peerie Maa]

Re: Strip Canoe advice - losing some shape after pulling staples

Having owned that boat for 50 years and rebuilt it twice (including replacing the gunwales and decks) I can confirm that you are wrong and the photo is not lying. It is even visible in the shape of the decks where they meet the gunwales. Here is another one where you can't falsely blame it on the tumblehome, as there is none. Notice that again, the slight hollow goes all the way down to the lowest waterline and is also visible on both diagonals. In any case the topic of this thread is a 3/8" distortion up high when the staples were pulled. Having actually built numerous canoes and kayaks using this method and materials over the last nearly fifty years, I can verify that the problem will disappear when the gunwale and thwart structure is installed, and it is nothing to be concerned about.

[ATTACH=CONFIG]137258[/ATTACH]

I also have been saying that it is nothing to worry about, even if it does not disappear. Hollow offers no benefit at paddling speeds. If I understand the OP correctly, it really is a trivial amount over a small area high on the hull. So, as I have already said, let the wood do what it wants to do, so long as it is symmetrical.