On Monday, March 18, 2019 at 7:07:16 PM UTC-6, wrote:
Hi John,
I have repaired and recovered a K-6 and a K-13, both were licensed in Standard Category. Simply stated, the rules are you must do what the manufacturer did and use the same materials originally used, or get written permission from Schleicher or the FAA to deviate. I had to get FSDO permission to use epoxy glue to rework the ribs and check with Stits Fabric to see they had aTSO for each ship in order to use their Poly Fiber covering materials. All this can lead to problems with the IA who will be asked to sign off your form 337 and the Feds who must accept the work done, methods and materials used, as stated on the 337.
If I were you I would ask my local FSDO to change the ship over to Experimental, exhibition & racing. I’d tell them you wish to do this in order to use modern glues, materials and coverings. I have done this a couple of times with no problems at all. Once your licensed Experimental, an A&P can sign off all the work with a log book entry, no form 337, no IA, no TSO’s needed!
JJ Sinclair
BTW, covering the D tube with fabric is not allowed on your type certificated ship (you must do what the manufacturer did)........bad idea anyway because after shrinking, the fabric will bridge over all low spots and the dope will form a ring at the edge of these low areas and show up as very ugly rings in your final paint Job!

I would prefer to keep this standard certification if possible. I hope that once the glider is restored, it will be a club glider, that can be rented out to club members. Possibly even in a commercial setting. Thus the desire to kept standard certification.