Stem questions - with pictures!

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ptsmith
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Stem questions - with pictures!

Post by ptsmith » Wed Jun 22, 2016 10:26 am

Hello, builders! I've been slowly progressing through my first canoe build - a Freedom 17, following Canoecraft. Between the book, this forum, and a few key builders' pages, there's plenty of info on what to do/not to do, etc. However, the wealth of info can be overwhelming, and I'm concerned I may have problems with my stems already... Looking for advice.

Here's a list of my "issues" (some potential). I'm crossing my fingers that those with more experience can tell me what I've done wrong, and how to fix a couple things. (Note, I've only laminated one stem in case I wanted to improve on the second...)
  • 1) I deviated from Canoecraft by using 1/8" laminate strips with the intent to dry-heat bend, but aborted the heat bend for steam. I am stuck with 24 1/8" stems (6 for each stem). This may have led to the next issues...
    2) When laminating, I epoxy coated all mating surfaces. It was my first time epoxying... I didn't think I was using much, but apparently it was A LOT. Epoxy was everywhere. The stems were basically glued together and to the mold. I did follow advice of Canoecraft and used lacquer thinner to clean up squeeze-out. Should I have simply epoxied one surface of each joint? (Also think I had so much glue because I had 6 pieces per stem, rather than 3). (Note, I'm using West System 105/207 with 403 filler... not much filler at all, not even to ketchup stage).
    3) When forcefully splitting the stems from the mold, the inner cedar stem split at the tightest bend (see photo below). The split is exaggerated in the picture. How should I fix this? (Assume epoxy somehow with 403 filler). Note the split crosses layers.
    4) Lastly, I'm not sure what is normal for spring-back post gluing. The stems sprung back on the bottom (photo below). I assume this may be normal, but want to be sure in case I should redo the stems. My guess is the hull kind of holds the stem in place when formed around the molds, then the outer stem must be screwed on.
I'm hoping you experts can help me decide if I can salvage these stems and take a deep breath, or if I should redo these stems, and change my method. Should I use thicker strips? Should I use less glue? Should I use more tape to prevent gluing to the mold?

Thank you for your help! I'm excited to post more build pictures as this progresses!

Inner cedar stem split when pried from the mold. The stem is flexed in this photo to exaggerate the split (click to expand):
Image

Inner and outer stems lying next to mold showing spring back at bottom, and outer stem spring back around bend (click to expand):
Image
Last edited by ptsmith on Thu Jun 14, 2018 8:54 pm, edited 1 time in total.

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Jim Dodd
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Re: Stem questions - with pictures!

Post by Jim Dodd » Thu Jun 23, 2016 6:26 am

I'm no expert on stems, as I build stemless.
But I'm no stranger to the technic.

First cover your form with clear packing tape, or duct tape. You should not have trouble pulling the stems from the mold. Correct that first.
Is the broken stem salvageable ? You could saturate the split with epoxy, and a little filler, and get by.

Me ? I'd probably make another, inner stem. And chock the first one up to experience.

It is my understanding that the inner stem is fastened to the form while stripping to hold it in place, until you are done stripping.

Jim
Keep your paddle wet and your seat dry!

JesseP
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Re: Stem questions - with pictures!

Post by JesseP » Thu Jun 23, 2016 8:45 am

Hey ptsmith,

I'm certainly to expert in the art of canoe building, but have just successfully completed my first build. Personally I don't think it matters one bit whether you use 1/8 or 1/4 inch think strips for the stem as long as you get the the correct dimensions in the end. As for the split in your inner stem.. I would personally just redo it.(That's just me.. It's the start of your build and cheap and easy to redo now.) Dry bending has never really worked that well for me so I went straight for stem bending right off the get go. You'll probably be steam bending your gunwales anyway so you might as well get the practice now. As for the spring back when you take the clamps off.. from the pictures you provided that seems perfectly normal, there will always be some regardless. The stems will be screwed and clamped to the molds anyway keeping them to the form as you strip.

Good luck


JP
I'm up to my torch.

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Cruiser
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Re: Stem questions - with pictures!

Post by Cruiser » Thu Jun 23, 2016 6:41 pm

1) IMO strip thickness is not an issue from a "will it work perspective", however, going thinner means more strips and that means more surfaces to epoxy, more potential for things to slip and slide .... in other words, you just make the job more work and increase the potential for issues. If you research dry heat, you will find that it is only suitable for some woods, as a process it seems easier, but in practice I had to give up on it as mostly unworkable for me.

2) When epoxying the stems pieces (I use epoxy, but many people just use glue) you use unthickened epoxy for the initial application, after the strips are saturated, apply thickened epoxy (peanut butter) in a thin coat. You will get squeeze out, i wouldn't use thinner, just clean off the excess with paper towels or a rag. Clean up the edges, with a scraper, when it cures. Don't put more epoxy on than is required to cover the wood.

3) If the strips got stuck, you have an issue with how you did the gluing/epoxying. You need to make very good separations between the stacks with plastic or something the epoxy can't penetrate or stick to (painter tape, vapor barrier tape etc.). If you did a cleanup with thinners, you can actually move the epoxy around and have it soak in where you don't want it.
Finally, the canoe will be the sum of each step ... all mistakes or fixes remain and accumulate ... redo the stems and get them the way you want them, you won't regret taking the extra time to get it right.

4) That spring back is within the normal range, you will be clamping/securing them to the exact shape when you start stripping.

Good luck, it is a nice build, I am a little ahead of you on my Freedom

Brian

ptsmith
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Re: Stem questions - with pictures!

Post by ptsmith » Thu Jun 23, 2016 11:10 pm

Jim Dodd wrote: Me ? I'd probably make another, inner stem. And chock the first one up to experience.
This is mainly what I needed to hear. And:
Cruiser wrote: Finally, the canoe will be the sum of each step ... all mistakes or fixes remain and accumulate ... redo the stems and get them the way you want them, you won't regret taking the extra time to get it right.
I'm going to redo the strips and stems. I'll go back to the 1/4" strips for simplicity and less glue... And as Jim said, now I have "experience" :wink

By the way, thanks, guys, for the replies. I lit up when I saw this actually worked. I've seen your other posts on the forum and have already been studying your advice. I feel like I'm getting advice from famous people!

Cheers,
Patrick

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Cruiser
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Re: Stem questions - with pictures!

Post by Cruiser » Sat Jun 25, 2016 8:19 am

On the topic, just a few pics and maybe a useful tip.

Image

I like to add a few guide blocks when I get ready to steam bend the strips, this makes alignment a bunch easier IMO

Image

When you do the bending, don't forget that sacrifice strip, it is pretty important and saves a lot of potential issues.

Image

And lastly, once you get the epoxy on and clamped, you can see the heavy plastic tape extending out to keep the pieces separate ... and the sacrifice strip on top ... it helps distribute the clamping force and takes the marks left by the clamps. I leave the blocks on until this stage, once they are clamped and not going anywhere, I just remove the screws, take off the blocks, wipe that area and then leave it to cure. This set only got wiped down with paper towels and separated just fine.


Brian

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Denis
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Re: Stem questions - with pictures!

Post by Denis » Mon Jun 27, 2016 6:43 pm

this video clip shows gluing up stems and may be of interest to those of you dealing with this issue

Denis

https://www.youtube.com/watch?v=GzthTJxyi3c

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Cruiser
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Re: Stem questions - with pictures!

Post by Cruiser » Mon Jun 27, 2016 7:31 pm

Good video, but I would suggest a slight change up.

I like to use unthickened epoxy on the joints first, then thicken the epoxy and apply a light coat, before I assemble the stack.

I think the unthickened epoxy absorbs better, then adding the thickened epoxy provides the gap filling.


Brian

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Denis
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Re: Stem questions - with pictures!

Post by Denis » Mon Jun 27, 2016 8:36 pm

true esp with cedar inner stems, however I have built many canoes and kayaks just precoating all mating surfaces once with runny thickened epoxy and have had no issues. Hardwood doesnt require as much as it doesnt absorb as much as cedar does. Makes cleanup a whole lot easier as well.

The key point which may have been missed in the video is to coat all mating surfaces. Which means the center piece of the inner stems and the outer stems is coated on both sides. Doing it that way I feel ensures there is adequate epoxy to soak in and not leave a dry joint.

The video was taken at BearMountain boat shop during the last course. What the video doesnt show clearly is the clamping of two 1/4 by inch pieces of scrap on each side ot the stack and moving the clamping blocks along as you clamp the stems down. Usually we use two sets of clamping blocks and leapfrog down the stem. keeps everything nice and smooth on the sides which helps cleanup.

We all have our own preferences and the beauty of this forum is it exposes several different options to potential builders :thinking

Denis

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Jim Dodd
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Re: Stem questions - with pictures!

Post by Jim Dodd » Mon Jun 27, 2016 10:29 pm

Not to critic the video, as there are many ways to skin a cat !
But at the very end a student is applying resin to a stem piece, without gloves. A real NO NO in my book.

I really hate it when I accidently get resin on my skin !

Jim
Keep your paddle wet and your seat dry!

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Denis
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Re: Stem questions - with pictures!

Post by Denis » Tue Jun 28, 2016 4:02 pm

that was no student :-) that was me, I just cant seem to keep my hands off :-) I did put on gloves later during cleanup and all students were gloved, but a very good point, gloves should be worn at all times even when just doing something for a minute :-)

Denis

ptsmith
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Re: Stem questions - with pictures!

Post by ptsmith » Fri Jul 08, 2016 10:40 am

GENTS -

Just (FINALLY!) popped bow stems 2.0 off the mold and they're light years better. Plus, while still messy and frustrating at times, the process was a lot more enjoyable. Thanks for your advice. I used bits and pieces from all of your input!

Main changes from first attempt:
  • -Used 1/4" thick strips
    -Packing tape in lieu of green 3M painters tape (I do not recommend the green tape for this process, it sticks way too much)
    -Precoat with unthickened epoxy, then coated with peanut butter epoxy (minimal coats)
Those were the major game changers. Some imperfections, but pretty good! :tu

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Cruiser
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Re: Stem questions - with pictures!

Post by Cruiser » Fri Jul 08, 2016 8:24 pm

Glad it all went better, you won't regret the extra work ... going forward now you know they are better.

Keep enjoying your build, and keep us updated.


Brian

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