Questions on skin-on-fabric with light fabric

[dr_innovation]

I'm working a paddleboard design where I hope be using recycled polyester posters for the skin. These are 118g/m^2 which from an online calculator is about 3.48oz/y^2 fabric. Its quite strong, does not stretch much (<5% under 200lb load on 2' strip) or shrink much (<5% under heat gun).

Three questions
1) I've seen a few posts using such lightweight fabric but most seem to be using heavier. But paddleboards don't get as much abuse a kayak (where I've used SOF before). What experience do people have with ~4oz polyester fabric on a mostly flat-water boat?

2) If I find 4oz is too thin, especially for the bottom, would adding a second layer be reasonable? If so should it be bonded/glued together (laminated) before of after application?

3) In other applications/forums (e.g. teardrop trailers) people use fabric but use waterproof glue as a first coat, e.g. titebond 2. It both bonds the fabric to the surface but it also stiffens the fabric But I've not seen anything like that for skin-on-fabric boats. Anyone use glue as a coating, then paint? I remember reading, but cannot find the thread, that said skin movement was important. Is having the skin movable important, if so why?

[Dusty Yevsky]

Re: Questions on skin-on-fabric with light fabric

I remember reading, but cannot find the thread, that said skin movement was important. Is having the skin movable important, if so why?

Probably not important on an SUP. Important for the performance of SOF kayaks because the flexing of the frame of traditional lashed construction allows a kayak to go over waves rather than plow through them. Skin glued to frame would stiffen it and inhibit flex. I'd imagine the longer the boat the more important flex is.

Another consideration is the lifespan of the skin. Frames last much longer than skin and trying peel off glued-on skin without damaging the frame sounds dicey.

[Woxbox]

Re: Questions on skin-on-fabric with light fabric

Aircraft dacron is about that weight and works well, but I don't know if puncture resistance is the same. And by all means, make it easy to reskin.

[dr_innovation]

Re: Questions on skin-on-fabric with light fabric

Thanks.. I had considered the flex issues and figured reducing flex was important but I still have waves to deal with on my board (and it will be 11-12 ft), so I'll go glueless.
am planning on an internally lashed framing (using PET-strips that I can heat shrink to get the frame under good compression since my skin will not be as tight.

And I had not though about the reskinning issues; especially important if I am using unproven skin material.

[amish rob]

Re: Questions on skin-on-fabric with light fabric

It would be very simple to make a section of mock up frame and skin it.

You could test your planned fabric attachment scheme and the durability/suitably of the fabric fairly simply, with little investment.

[Woxbox]

Re: Questions on skin-on-fabric with light fabric

The quickest and easiest way to put the skin on would be with staples. Also quick to replace. You can cover them with good tape or fold back a flap of the fabric and glue it down.

[amish rob]

Re: Questions on skin-on-fabric with light fabric

Oh, I’d argue that sewing (especially with a double cord type seam) is WAY faster than staples; and especially on something like a kayak or board. Honestly, though, the description in the OP doesn’t sound like something that could be sewn.

I have made square frames to testa variety of cloths and finishes over the years. It’s a cool way to test fabric.

If you do staple, the type with the saw teeth edges seem to split wood less, in my experience.

[Kudzu]

Re: Questions on skin-on-fabric with light fabric

Biggest concern is punctures. I will not use aircraft fabrics on my boats. Just to easy to puncture and the last thing I want is to be down the lake a few miles from the ramp with a hole in my boat. I did that once and it is no fun. While I am not worried about drowning or sinking the boat, it is long swim back to the launch or a long walk through the brush!

3.48oz per yard sounds light but one thing I have learned is there is a lot more to it than just the weight of the fabric. -Just as important is the weave of the fabric and the yarn used. Are these posters even a woven polyester of some soft of extrusion? Will it stop a rip of just keep going? Important thing to consider.

Are they waterproof? If not can apply something on them and it stick?

I sell some fabric that is just just under 6 oz per yard but it far superior to an 8 oz per yard I used to sell. It looks flimsy but it is strong, very strong.

You have heard you can't judge a book by it's cover, same with fabric. Weight is just one indicator.

Also consider abrasion. I have not see anything that really stands up beaching over and over well. That why I use ande sell bronze for rub strips.

All that so say there is no way to answer you question without seeing the fabric to know if it is suitable.

[amish rob]

Re: Questions on skin-on-fabric with light fabric

I have one boat in what seems to be permanent limbo, bit when I do get around to skinning it, Jeff, I’d love to try that cloth you have.

It looks nice.

[dr_innovation]

Re: Questions on skin-on-fabric with light fabric

Biggest concern is punctures. I will not use aircraft fabrics on my boats. Just to easy to puncture and the last thing I want is to be down the lake a few miles from the ramp with a hole in my boat. I did that once and it is no fun. While I am not worried about drowning or sinking the boat, it is long swim back to the launch or a long walk through the brush!

3.48oz per yard sounds light but one thing I have learned is there is a lot more to it than just the weight of the fabric. -Just as important is the weave of the fabric and the yarn used. Are these posters even a woven polyester of some soft of extrusion? Will it stop a rip of just keep going? Important thing to consider.

Are they waterproof? If not can apply something on them and it stick?

I sell some fabric that is just just under 6 oz per yard but it far superior to an 8 oz per yard I used to sell. It looks flimsy but it is strong, very strong.

You have heard you can't judge a book by it's cover, same with fabric. Weight is just one indicator.

Also consider abrasion. I have not see anything that really stands up beaching over and over well. That why I use ande sell bronze for rub strips.

All that so say there is no way to answer you question without seeing the fabric to know if it is suitable.

Thanks.. great feedback and thanks to every one else that offered insights as well. Kudzu I love your many videos which help inspire me to skin-on-frame instead of XPS-foam-based board.


The fabric is definitely woven/coated Terylene. It has very very tight threading and a smooth coating on the "printing" side. Spects of the most common one I use is at https://bciimage.com/product/kapco-w...CABEgLbUvD_BwE. It will not tear and if cut will not propagate. It was strong enough to pull the staples back out of the wood where I attached a piece to the frame for testing and did not rip along the staples.

I did some testing, inspired by your " Yes its tough Video" when stretch on a frame , a 12"x3" section of the uncoated fabric can be hit with the claw side of a hammer at maybe 1/4 swing without puncture, a modest attack with large phillips head screw driver leaves dents but no hole, but the tip of a scissor will go through it pretty easily. Does that sound puncture proof enough/ Does painting add much protection h from sharp puncures? Latex/Oil or varnish any better in that regard?



Its quite waterproof even without a coating, I put water on top of the surface over a paper towel and let it sit ~ 24hrs. No seepage and no drip. I assume the coating, designed for inkjet printing, is very intentionally designed to limit water flow which would lead to ink bleeding. With the back side coated with waterproofing/paint I would expect it to be even better. It glues well with titebond II (PVA glue) and I could also consider that for waterproofing/coating the inside to add strength even if I don't glue it to the frame.

For abrasion I think I will be fine. SInce I'm used to an inflatable I do try to avoid hitting anything but sand/mud so already have that mindset now so not as worried as hitting stuff with this as I would with a Kayak.
My design already calls for wooden rub-strips all along the outside of the frame, covering the overlapping seams. I was planning on something for beaching as I do that occasionally with the paddleboard, with either some recycled custom formed HDPE, or even just some glued on PET strips (from soda bottles) along the stringers, but have not really worked that part out yet since I'm still working on the Bow design and may change after I try getting cloth stretched without creases. (My questions in design on that have not been answered so I'll eventually be experimenting).