C-Forum

For my Shacho, I decided that I wanted the lower thigh strap loops close to the saddle, so I got some materials and did what I thought was a reasonable job of glassing in a set of loops, following the instructions on the box, so to speak. However, what I did will not withstand the force exerted by rolling practice (I'm a lefty, and many roll attempts eventually pulls up the left floor thigh strap loop). I did it over again with more cloth but it's still pulling up.

Now maybe no loop is going to hold up under a lot of rolling practice, but I'm willing to concede initially that I'm doing it wrong. Can anyone here give me some detailed instructions on installing a loop that is going to have to bear a lot of stress? I've been assuming that you have to glass it in, but maybe there is some kind of glue that would work?

How well did you rough up the kevlar on the hull? Sand it with some 60 grit and then use a hacksaw blade to rough it up more.

These guys definitely know what they are doing.

http://www.riverelf.com/RiverElfStrapAnchorInstall.pdf" onclick="window.open(this.href);return false;

If it's an epoxy boat you need to make doubly sure you abrade it well with 60 grit because in it's natural cured state epoxy develops a waxy amine coating that nothing bonds to - you need to abrade that thin layer off first.

Also when/if you do expose the kevlar in the resin, it is difficult to wet out thoroughly, rough it up plenty and work the resin well in before laying the glass fibre strips into the resin (and then work resin into them until they become clear).

You can also have bonding issues with different resin systems. Even after abrading, polyester resin doesn't play well with existing epoxy (but epoxy over polyester is fine) - I have never used vinylester resins so not sure how they are for compatibility.

I would never use anything but high quality epoxy for such a job. G-flex is great, but may not wet out some cloths readily.

Polyester resin is easy to get, but is junk. I've used vinylester for patching with great results, but it has no advantage over epoxy whatsoever.

Maybe some thought should go into the rolling motion if it is tearing the outfitting off the hull.

I had the same problem. I finally had Kaz glass the loops in and they have been solid for the last ten years. Visually the job requires that additional layers of glass cloth be laid over the strands of the loops you have prepared. Just think you are applying all of your body weight to the 8 sq in of area that you epoxied.

As others have stated, sand the boat. If it's Kevlar, you've gotta get it fuzzy. I use West System epoxy. I like to use S-glass over the rope so I can see the frayed ends. Mine are similar to the River Elf method, but my loops lay down more. If you get it right, the loops become part of the boat. You will not pull them up. If they pull up, you didn't get it right.

This is not my best work, but it's the best photo I have:

https://www.facebook.com/photo.php?fbid ... permPage=1

Instead of rope I have used 1" wide tubular nylon webbing for thigh strap anchors. Although rope has a circular cross-section more like a D ring, I find that the webbing works just fine.

I like the webbing because when the ends are frayed properly there are a lot more fibers to allow a more secure bond to the hull. I also use S 'glass to cover the ends of the anchors which leaves them visible beneath the glass.

After cutting an appropriate length of webbing, put the end on a piece of scrap wood and thorough fray about 1 1/2" at each end using a razor blade or sharp utility knife. After appropriate sanding and cleaning of the hull as others have described, I fan the frayed ends of the nylon webbing out into a semi-circular shape and thoroughly saturate them with epoxy. To avoid getting epoxy on the webbing loop cover it with tape or plastic wrap or waxed paper.

I put the 'glass on as a separate step so as to be sure that the bond between the webbing ends and the hull is completely filled with epoxy, and sand that joint if necessary to assure that the 'glass lays over it smoothly. I haven't had any anchors come loose as yet.

Forgot to say that you should assess the overall stiffness of the hull where the strap anchor will be glued in place. My Millbrook Edsel has massive Spheretex stiffening on the bottom, so a strap anchor will not distort the hull contour.

I have not seen a Schacho, but perhaps the bottom is not reinforced much beyond the basic SSKK layup. If so, then the pull on the strap anchor will dimple the hull upward, and in my opinion, make it more likely that the strap anchor will be peeled loose from tension along the anchor edges.

The solution to this is to lay one or two layers of glass or Kevlar to produce a wider stiffened area where the anchors will go. This will prevent upward dimpling of the hull, and make it less likely that the anchors will be peeled loose.

I also agree with pblanc that strap or webbing will allow more fibers and more area to be incorporated in the ends of the anchors.

Someone mentioned the problem of residual amine blush in epoxy. A Schacho is vinylester, so blush is not a problem. And amine blush washes off easily with detergent and water or any number of solvents. On the other hand, aggressive sanding may not remove blush. So wash it!