Need advice on how to repair the tail on this twin and the glassed fin crack.
Okay, while larger and clearer pictures would help, a lot, lets get you started -
Our story so far:
I cut loose shattered bits out at the tail but the bottom of the tail remains damage free , just the top part of the tail. Do I sand the bottom down and make a cone shape with fiber and patch it on? or do I cut the corner glass from the bottom off as well ?
Bzzzzt- wrong answer. If I’m making sense of the picture, you cut the foam and crunchy glass away flat to the bottom, with a saw, right?
Wrong, you don’t want to do it that way. In the future, ditch the saw and get out the x-acto knife.
Lots of well meaning people do untold damage by ‘cutting away anything broken’ - which loses the shape it was, loses the color it was and gives you this major chunk you need to replace. It’s kinda like stubbing your toe and amputating your foot to fix it.
In the future, take an x-acto knife and use it like a scalpel to pull the crunched glass out to the original position as best you can, then fill ( cabosil/aerosil and resin is best ) behind it, then glass over the whole thing after sanding it a bit. Salvage as much as possible, always. Among other things, the old glass usually has the color and such, which means you can make an almost invisible repair.
For future reference, the less work you do on a repair, the better it generally comes out.
In any event - chuck the saw. Break out the sandpaper. If you can get a wee chunk of compatible foam, stick that on there, shape it with coarse sandpaper, then glass over it. I wouldn’t try to match the color.
If it happens that you’re a reasonably skilled woodworker, I might make a matched set of mini-tail blocks and install them on both swallowtails, as swallowtails are notorious for getting those tail crunches and a tail block arrangement will not only help prevent that in the future but if you do those, chopping off the tail like you did can become an ‘I meant to do that’ kind of thing. It’s always good to look good, y’know?
The fin is not loose , but a hair line crack runs to the back in the hot coat.
The key words here are ‘not loose’. No major work required, so don’t do any major work.
What you want to do first is sand the hotcoat some, and down onto the bottom a bit and up the fin a bit. No more than an inch and a half on either one.
Cut two strips of glass the length of your fin base. One maybe twice the width of the other, same as the width you sanded from up on the fin to where you stopped on the bottom. . With a 1" throwaway brush, brush in a very little resin thinned with a very little acetone. That’ll fill the crack nicely, whatever remains of it.
Then, brush on full strength resin while that thinned stuff is still wet, set the wide strip on that straddling where the fin meets the bottom and kinda baste it with resin. Put on the second strip, brush it with a very little resin so that there’s no air bubbles and the weave of the second layer is saturated but not so much that it’s drooling resin, y’know? Let that dry to a hard gel, cut the cloth even with the leading and trailing edges of the fin.
Let it dry hard. Sand what you’ve done, feather the edges some so it’s nice and smooth. Then, hotcoat it with a fairly fast batch of resin. When that has dried hard, sand and wet sand to the point of ‘good enough’ and there you are.
Hope that’s of use