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Advice needed on stretched skin that relaxed

Hi all, new here. Hailing from the lowcountry of South Carolina.

I recently built a SOF canoe using the Little Chief plans out of a magazine from the 1950's. I purchased a 10 ounce polyester fabric from George Dyson. The fabric was a little challenging to work with for a first-timer, but not too bad. I stretched it using a heat gun and steam iron. As I was doing that, it kept relaxing. I was under the impression that poly wouldn't do that. However, by going back over it a few times I was able to get it taut.

I applied three coats of Rustoleum oil based marine paint, and it looked great. About a week later, the skin relaxed again. Now it looks...disappointing. I am attaching some pics here, if anyone has any insight into what is going on I would greatly appreciate it.

TIA



Comments

  • edited January 14

    This doesn't make a lot of sense from a skin material perspective. Nylon will expand when it absorbs moisture, but polyester is unaffected by it. You can try using to heat gun to shrink it, but it's more difficult once it's been finished.

    Another possibility is that the problem isn't the skin, it could be the frame. Did you build the boat when it was humid or use any green/damp wood? Has the humidity dropped recently? If so, it may be the frame shrinking. One way to test it is the wet the frame really well and see what happens.

  • edited January 13

    Canoe looks great. Be judicious if you try the heat gun again it can cause further relaxation on the Dyson poly, "I have heard" .
    DId it get cold down there ? I have had poly relax in the cold (minnesota) but it snugged up again in warm.

  • @bnystrom said:
    This doesn't make a lot of sense from a skin material perspective. Nylon will expand when it absorbs moisture, but polyester is unaffected by it. You can try using to heat gun to shrink it, but it's more difficult once it's been finished.

    Another possibility is that the problem isn't the skin, it could be the frame. Did you build the boat when it was humid or use any green/damp wood. Has the humidity dropped recently? If so, it may be the frame shrinking. One way to test it is the wet the frame really well and see what happens.

    I like the way you think. The wood used is treated lumber. I did let it dry some, though, and by the time I got around to staining the frame the moisture content was 7-9%. I skinned after staining and varnishing.

    I do believe I have stumbled upon the cause, though, since I posted this. I built the canoe upside down, then turned it right side up to finish off the wood along the sheer line. Not long after this is when I noticed the relaxing of the fabric. I have since re-positioned the sawhorses to imitate the weight distribution on the frame. It is starting to tighten up again.

    As opposed to a more traditional bent rib construction, this method is less rigid.

    I think the moral of the story is, store the boat in the position it was in when you built the boat.

    Thanks for your input.

  • @Paatit said:
    Canoe looks great. Be judicious if you try the heat gun again it can cause further relaxation on the Dyson poly, "I have heard" .
    DId it get cold down there ? I have had poly relax in the cold (minnesota) but it snugged up again in warm.

    Another great comment. Yes, it did get cold after I skinned and painted the canoe, and that may have been a factor as well. I don't believe I'll try heating the fabric again. With my luck I'll burn the thing up, and then LOOK OUT! lol

    BTW, lived in Minnesota for many years. Grew up in Appleton but spent most of my life in the western suburbs of the TC. Move to SC to retire.

    Thanks

  • More recent pic, the fabric is starting to tighten up again. I believe this was all about how weight was distributed on the frame during storage.

  • Touch base with Jeff Horton over in Alabama - kudzu boatworks.

    Also consider posting on Facebook - skin-on-frame kayak builders (yes canoes are also there)

  • Eat more again.

  • Lots of advice on skin on frame building techniques (and issues) from experienced builders at the qajaqusa.org forums.

  • I used heat shrinkable nylon on my Yost design. Then painted it with 2 part epoxy per the instructions .Tight as a drum.

  • edited January 15

    The same that String described was used on my SOF Greenland replica kayak. The boat will be 10 years old this year and the skin is taut and smooth. I believe these are the same materials that boat designer and builder Brian Schulz of Cape Falcon kayaks has always used for his craft including canoes and guide boats.

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