A Stripper and a Composite Copy

Kliff · Apr 12, 2023

Thanks guys.

Jim: Regarding weight management, I'm certainly a newbie to canoe building, but not general woodworking. With properties that matter, depending on application, I measure and/or test a variety of samples from my pile. I use density charts as a starting point:

Wood Density Chart

Wood Density and Specific Gravity The Following chart will tell you how much weight you can expect from your wood selection. A simple comparison of the lb/ft3 of cedar and any other species will t…

cedarstripkayak.wordpress.com

When I started thinking about woods for trim on my stripper, I tested samples from stock of Ash, Walnut, Cherry, Butternut, Teak. According to chart, Ash is 40-53 lbs/cu. ft. Mine all tested at or slightly above the high end. My walnut & cherry was mostly at the low end of 40-45. Of course for most woodworking lighter = lower density, something I don't want for many applications, so I have a pretty good pile of wood I've sort of put on hold that will be excellent for canoe trim.

I'm really anxious to get my stripper weighed. Even though I didn't set out to make it as light as possible, I think I'm going to be pleasantly surprised. Unfortunately, I didn't weigh my trim components before I put them on. I'm working on trim now for my next build, so I'll weigh stuff and keep track better on this one as I go.

Jim Dodd · Apr 25, 2023

So I have the stripper hull assembled, not varnished.

Put it on the scale, and the she comes in at a tad over 45#. It's not Obese, but average for a hull with Ash trim, flotation chambers, and a double layer bottom.

The gunnels are now part of the canoe, not something just screwed on.
By gluing, with filled epoxy, it gives it's full strength to the hull, and stops moisture, from getting between the gunnels and the hull.
Now to finish sanding and varnish.

I'll post a few more pics after varnishing.

Now to turn my attention to the Kevlar.
Flotation, and trimming the shearline next.
Going to Wisconsin Thursday, to pick up some Bell aluminum gunnels, anxious to see a final weight comparison.

Kliff · Apr 26, 2023

Beautiful Jim. Makes me want to rethink a solo for my next build. Where in Wisconsin are you getting the gunnels? Get this one varnished, and bring it along. I'd love to see it in person....

Jim Dodd · Apr 26, 2023

Kliff said:
Beautiful Jim. Makes me want to rethink a solo for my next build. Where in Wisconsin are you getting the gunnels? Get this one varnished, and bring it along. I'd love to see it in person....

Lacross. It's at the Bell canoe factory.

Plan to be there mid morning !

Cruiser · May 22, 2023

Jim Dodd said:
Spring is here, and the shop is warm enough to make working on the canoes, tolerable.

One of the main things that motivated me to build these two canoes, was to reduce the weight.

I must confess, I'm not very successful at that.

Setting out to the weigh everything.
First the hull. It is glassed with flotation chambers, and a double layer of cloth on the bottom. I do this with all my canoes. Not willing to change. Also added an extra 1" to the shearline Height. Why I don't know !?

The hull weighs in at this time 33.5 # with the trim, and seat, cut and laying in the hull. It weighs in at 45.5#.
Not what I expected with 3/16" thick strips, and 4 oz S-glass.
Hull at 33.5#, plus 12# for Ash trim including decks and seat. The seat alone weighs close to 3#.

I pulled out a set of Aluminum, Bell contour gunnels, I purchased a few years ago, to compare.
They weigh .4 # per foot. That figures out to be 6.4# for a 16' canoe.
My Ash trim including decks weighs 9 #. 2.5 # difference.

Though I made a comparison, between wood and aluminum gunnels, I won't put aluminum gunnels on a stripper. They may end up on the composite.

So in conclusion. Thinner strips and more expensive S-glass really made little difference.
I'll go back to at least 6 oz E-glass from here on.

For my gunnels, I glue and screw the inwhales, and decks. The outwhales are just glued. The shear of the hull is capped and sealed by the outwhales. This gives me the strongest gunnel system. It becomes the canoe, not something just screwed on.

No screws, or plugs will be showing. This seals everything. I like the look too.

Here are some pics, of my progress so far.

The decks will get shaped after the gunnels are installed.

More later, I need to put the scale to the composite next.

Jim

Cruiser · May 22, 2023

Jim, finally getting back into the shop and every time I look over at my strip shelves, I see the roll of S glass glaring at me .... with this quote from your post in the back of my mind, wondering if my next project is doomed for weight before I even start.

"First the hull. It is glassed with flotation chambers, and a double layer of cloth on the bottom. I do this with all my canoes. Not willing to change. Also added an extra 1" to the shearline Height. Why I don't know !?

The hull weighs in at this time 33.5 # with the trim, and seat, cut and laying in the hull. It weighs in at 45.5#.
Not what I expected with 3/16" thick strips, and 4 oz S-glass."

Spent some time developing a hull model to give me a realistic view of what is actually happening here. Fortunately, I have actual measurements from the last several builds to provide empirical data to keep me on the right track. Please keep in mind, these are just working numbers, to give an idea of magnitude .... every build/builder is different, but these should be a reasonable guestimate, for strip construction.

First up, the weight saving from S glass versus E glass are likely real, just not as high as expected. The cloth thickness of 8 mil (6 oz) and 6 mil (4 oz) suggests a 25% layup reduction. So for a 6 oz layup at 6 pounds, a weight reduction of 1.5 pounds is the first thing to come to mind, unfortunately, it isn't just the cloth thickness/layup to be considered. There is significant epoxy absorbed to the wood substrate, then the actual cloth/epoxy layup, then the additional layer to bury the weave. So 3 distinct sources of weight and only that middle cloth/epoxy realizes any weight savings, the other 2 are always about the same. My model suggests the weight savings from a layup perspective will be in the range of 10-12% or in this case ~.6 pounds per layer.

Second up, reducing strip thickness from 1/4" to 3/16" strips. This is a pretty straight forward calculation, assuming the same sanding regime and assembly techniques you will save about ~5 pounds on your 16' boat.

Third ... "Also added an extra 1" to the shearline Height. Why I don't know !?" ... with a standard glassing applied, that additional 1" along the sheer adds ~1.6 pounds to the hull weight.

So overall, your steps should have netted you a ~4.2 pound weight reduction, I suspect moving to a heavier cloth for the additional layers is where some of the added weight came from .... my model suggests that hull with a single additional 4 oz layer on the football should weight in the neighbourhood of 28-29 pounds, so I still think something else is going on there. There is just no way to get to the 33.5 pounds you measured without adding in another weight factor. There seems to be about 5 pounds unaccounted for, on the bare hull.

So while I figure I can still make the next boat work weight wise, it isn't as rosy as I thought ... but I still am of the belief that I will save weight with S glass, just not as much as I had hoped. I also think you took all the right steps to make a decent weight reduction in your boat and that there is still a missing piece to that weight puzzle, the additional 1" sheer didn't help, but certainly won't account for 5 pounds .... FYI the football piece adds ~1.5 pounds and is included in the estimated hull weight.

But the bright side is that you are on to my favourite part, final finishing.

Brian

Jim Dodd · May 23, 2023

Thanks Brian !

A good evaluation !

I looked at Kliffs weights of different woods, but weight is only part of the equation. Ash will out preform Walnut, and Cherry, in abrasion and flex.
I picked up some Aluminum gunnels for the composite. This will be a significant weight reduction.

I've been so busy with other things at the Nokomis Wood shop, I having a hard time getting back at the canoes !

Jim

Jim Dodd · Jun 3, 2023

Finally getting back to my canoes !

Applied varnish, inside and out, on the stripper. Have it set on stands to Watco the gunnels. These Scissor stands are AWESOME ! No masking tape, and no Watco running down the sides of the hull !

Now for flotation chambers in the Kevlar hull.
I use Owens Corning 1/4" building foam, as the core with a layer of 4 oz S-glass cloth, on both sides.
The side with the writing needs a good sanding as it is coated with a very thin plastic. Epoxy doesn't like it !
It's cut to fit the hull, and then epoxied into place, with a fillet of thickened epoxy. Covered with Kevlar, and another layer of 4 oz S-glass.
I've done better, but these are rock solid.

stripperguy · Jun 4, 2023

Jim,
Did you reinforce the other side of the foam as well?
I’m in the middle of making a total of 4 carbon/glass/Divinycell hulls. One of the future owners (my nephew) likes those teardrop shaped bulkheads, but we’ll use some excess 1/8” Divinycell for that. I’m curious how you held shape while you (if you) reinforced the back side.

Patrick Corry · Jun 4, 2023

Jim Dodd said:
Finally getting back to my canoes !

Applied varnish, inside and out, on the stripper. Have it set on stands to Watco the gunnels. These Scissor stands are AWESOME ! No masking tape, and no Watco running down the sides of the hull !

Now for flotation chambers in the Kevlar hull.
I use Owens Corning 1/4" building foam, as the core with a layer of 4 oz S-glass cloth, on both sides.
The side with the writing needs a good sanding as it is coated with a very thin plastic. Epoxy doesn't like it !
It's cut to fit the hull, and then epoxied into place, with a fillet of thickened epoxy. Covered with Kevlar, and another layer of 4 oz S-glass.
I've done better, but these are rock solid.

I made a pair of scissor stands after seeing yours in an earlier post. With the carpet strips mine function as upright hull supports or, partially closed and inserted under the inverted hull like your first picture, the carpet pads the interior of the canoe as well.

Here, I'm washing a Chestnut Chum prior to making planking repairs.

Jim Dodd · Jun 4, 2023

stripperguy said:
Jim,
Did you reinforce the other side of the foam as well?
I’m in the middle of making a total of 4 carbon/glass/Divinycell hulls. One of the future owners (my nephew) likes those teardrop shaped bulkheads, but we’ll use some excess 1/8” Divinycell for that. I’m curious how you held shape while you (if you) reinforced the back side.

Yes, 4 oz S-glass on both sides of the foam. then one of Kevlar, and another 4 oz S-glass on top of that.

I had a scrap of the double sided foam, that I cut the inserts from. Seemed pretty stiff, but when I put pressure on it ? The foam failed catastrophically ! I sure wouldn't use it for a hull ! The basic reason I used the foam, instead of 1/8" cedar ? I could prebend it, and with one coat of cloth. It would hold the shape. I wanted more flotation on the composite, and so this was my answer. This works as I've done it on 4 other composites.
To get the shape ? I just used two cleats fastened to a base board. By sliding the cleats closer together ? I could match the shape of my Story stick with the 1" markings.
Here is a pic of a previous build. I was lack on taking pics of this process.

Good Question, and I should have explained it earlier !

Jim

Jim Dodd · Jun 4, 2023

Patrick Corry said:
I made a pair of scissor stands after seeing yours in an earlier post. With the carpet strips mine function as upright hull supports or, partially closed and inserted under the inverted hull like your first picture, the carpet pads the interior of the canoe as well.

Here, I'm washing a Chestnut Chum prior to making planking repairs.

View attachment 135872

So simple and they work.
I always hate to see a hull resting on a solid saw horse.
The Carpet is so much easier on a hull.
They store easier too.

Jim Dodd · Jun 7, 2023

With some foam laminated trimmings, from the flotation chambers, I put them through an impromptu stress test.

They were pretty stiff with almost no give. When I increased the pressure they broke.

Definitely not what you want for a hull !

Jim Dodd · Jun 9, 2023

The Stripper is finished.

It's been awhile with this build Glad it's done !

The final weight, what I and everyone else is waiting for !
46 lbs. I'm deducting the 6 oz, for the weight of the strap

A quick rundown on build thread. 3/16" strips.
4 oz S-glass inside and out.
One addition inch, to shear height.
Double layer of 6 oz E-glass on the football.
Flotation chambers,
Ash trim.
Two bias strips on the stems.
Varnish one quart.

Soon as I get aluminum gunnels on the Kevlar copy ?
I'll post weight of it also.

Glenn MacGrady · Jun 9, 2023

Jim, maybe you addressed this somewhere above, but what are those two dark areas on the stripper's thwart? Natural features of the wood? Dark wood inlays? Spilled caviar? Maybe you can show a close up picture of the thwart.

Jim Dodd · Jun 10, 2023

The dark, is some Walnut lamination.
Just for decoration. I liked how the router made the taper.
I didn't take a pic of this one, but here is one of my earlier canoes.

memaquay · Jun 10, 2023

Very nice looking canoe! I think 46 pounds is a very good weight, anything under 50 I consider to be top notch!

Jim Dodd · Jun 10, 2023

memaquay said:
Very nice looking canoe! I think 46 pounds is a very good weight, anything under 50 I consider to be top notch!

I was hoping for less weight.

My last composite was 36 #.

The 4 oz S-glass, and thinner strips ( 3/16" ), being the main difference on this build.
I like the thinner strips, but will likely stick with 6 oz E-glass from now on.
Thanks !

Jim

Jim Dodd · Jun 18, 2023

The 38 Spl. modified, made it out of the shop today.

A little Sexy shot.

Kliff · Jun 29, 2023

That is a beautiful boat! Now you've got me thinking of trying a composite after my next build. Something for tripping places like BWCA. Rocks everywhere, and more portaging than I like doing with a stripper. Just got back from a week with my stripper, and now I'll be buffing and recoating varnish, which I expected.

One question that keeps nagging at me. Seems like all the Kevlar surfaces you topped with 4 oz glass, either E or S. Isn't one of the biggest advantages of Kevlar its superior abrasion resistance? If that's the case, why put glass over it?

A Stripper and a Composite Copy

Kliff

Wood Density Chart

Jim Dodd

Kliff

Jim Dodd

Cruiser

Cruiser

Jim Dodd

Jim Dodd

stripperguy

Patrick Corry

Jim Dodd

Jim Dodd

Jim Dodd

Jim Dodd

Glenn MacGrady

Administrator

Jim Dodd

memaquay

Jim Dodd

Jim Dodd

Kliff

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