Carbon Fiber Tape

[Guest]

I bought some West System epoxy yesterday to glue up my new stems that are all white ash. I recently realized that I needed to make my stems over because I was previously going with basswood for the inner stems to have an easy wood to work with to make the rolling bevel.

I am going to have permenately mounted rudder gudgeons on the stern stem. I learned after reading Todd Bradshaw's book that I needed a hardwood inner stem as well, because of the forces exerted from the rudder gudgeons.

While at the marine store yesterday when I was getting my West System supplies, I noticed that they also had carbon fiber tape. I'm considering using this stuff on the inside of the canoe over the stem areas when I do my inside fiberglassing and on my paddles. This stuff is not cheap by any means, but will I make my stems stronger laying this stuff up over the stems on the inside of the canoe?

Originally, my plan was: after my inner stern stem was mounted to the stem station, I was going to cut a section of the station out and replace it with a wider piece of ash and transfer the rolling bevel onto that extra piece to get the extra stiffness at the stern stem. But, this carbon fiber tape would be much easier of a task if it does what I hope to accomplish. Any thoughts on the matter would be greatly appriciated, thanks.

[Glen Smith]

Hi Dean, me again. If that carbon tape isn't bias cut then it won't want to conform to the shape of an inner stem.

[ChipSandresky]

my plan was: after my inner stern stem was mounted to the stem station, I was going to cut a section of the station out and replace it with a wider piece of ash and transfer the rolling bevel onto that extra piece to get the extra stiffness at the stern stem. But, this carbon fiber tape would be much easier of a task if it does what I hope to accomplish. Any thoughts on the matter would be greatly appriciated, thanks.

Hi Dean. Whatever you do, fix it now. It will be a hassle to add extra reinforcement down in that narrow crack when the hull is stripped. Personally, I would consider cranking up the steamer and just redoing the stems in hardwood. Or you could split the basswood stem down the middle (carefully) on your tablesaw or bandsaw and then laminate it back together using hardwood to fill in the saw kerf... If you use CF, do a neat job because it is going to be terrible trying to tool that stuff.

I don't know if this helps. Good luck with it.

Chip

[Dean in Eureka, CA]

I don't think it was, but I could be wrong. I do remember that it said it was unidirectional (whatever that meant) and that it added stiffness in only one direction. I think it had something like 144,000 fibers per inch and they have it in 3" and 1 1/2" widths x 12' in length. It also said that the fibers were held in place by polyester thread to make it easier to wet out. I thought about putting it inside the lamination or in between the inner and outer stem, but I think it would be a bear to cut or raise cain with my tools when shaping.

Do you have to log on twice, to really be logged on? I'll log on and the forum index shows me as being logged on, but when I go to the forum I'm not shown as being logged on.

[Todd Bradshaw]

Dean, I don't think you're going to gain enough extra strength (of the type you need) to bother with carbon tape. The stem area is very stiff, just because of the geometry of all the various pieces/parts coming together. The main thing you want is screw-holding power in the form of enough bulk in the stems or their reinforcements (as is sometimes provided by added interior blocking, etc.) and a reasonably broad-based transition into the surrounding parts of the hull. Carbon might stiffen your stems and make them less prone to breaking if you want to park a truck on top of your hull, but isn't going to do much for keeping rudder gudgeon screws from being pulled out.

Gougeon carbon looks like a flat bundle of really fine straight hair. The new stuff seems to be sort of "stitched" loosely into a flat band by the polyester threads. This is good because the old stuff, like the roll I've been using for about 20 years, only had a light sizing on it and brushing the resin onto the strands without the brush hanging up and pulling some of them kitty-whompus was a real pain. Think of it as primarily a unidirectional stiffener, rather than generating the type of strength that you might get by switching from your normal fiberglass weight to say, 12 oz. cloth. The last slalom racing kayak I had was S-glass, reinforced with transverse rings of carbon tows about 8" apart. The boat weighed about 16 lbs. The deck, in the spaces between the rings, was about as stiff as a plastic milk jug. You could deform it with your finger. But the areas where the rings of carbon were were quite stiff. Same on the bottom, except the glass there was heavier so that the underwater portion of the hull wouldn't deform in use. That's the kind of use that carbon tows are really good for, along with uses like stiffening wooden masts for multihulls and iceboats. On a typical stripper there really isn't much need for increasing hull stiffness in that way.

The best bet for gudgeon strength is most likely going to be using a tough wood and having enough of it in the form of the stem dimensions or glassed-in blocks to make sure the screws really get the best possible bite on the boat. Gudgeons that fit the hull well will help and for a long-term installation, I might even bed them in 5200 to also glue them to the hull. A good kick-up rudder system helps a lot as well.

[Dean in Eureka, CA]

Thanks Todd,
I just finished glueing up the last set of new stems with epoxy. I went with white ash throughout this time, so my rolling bevel is going to be fun. I am going to be casting my own gudgeons like the Willits Bros. shown in your book. So I will have the luxury of deciding where to place the screw holes. A thought that comes to mind is to offset the screw holes on each "wing" of the gudgeon so no two screws from opposing sides of the hull will meet or hit on another. I did come across an old picture of the gudgeon, but it only shows one side and I belive that their canoes had two layers of strips on the hull. If I need to add the additional blocking behind the inner stem, I will have to wait until I get the inner stem shaped with the rolling bevel to see exactly what I need. It would be nice to tranfer the rolling bevel right into the additional blocking.

As far as the carbon fiber tape goes, I think I will use that on my paddles.

Did you get my message I sent you through this forum?

[Guest]

Yes, the message arrived. I'm working up a plan and will send it soon. If your rudder gudgeons turn out well and the casting isn't too much of a hassle, there is a market for them. About half of my customers end-up hunting all over for gudgeons and those which are available aren't as nice as that style. You wouldn't get rich, but it's not uncommon for good canoe gudgeon sets to sell for up to $100.