Firstly understand that I live in the UK"
I have been building combat models and covering them with nylon for at least 50 years and I have a pretty well sorted method:-
dope structure, wet nylon in tub of water, lay on towel to remove loose water, lay on model and fix around the edge with more dope pulling tight.
Then leave for some hours to dry when the nylon will be drum tight ready for a couple of coats of thin dope followed by a couple of coats of thicker dope.
This has always worked for me until last year when the covering of my
Razorblade 64 failed to tighten and no amount of dope would tighten it. The dope didn't seem to go into the weave and just laid on top
I am currently building 4
Supermongers and am just getting sorted to cover them. I don't want to suffer the same problems again so I have done some experiementing:-
The nylon I had problems with was supplied by Flair and appeared to be OK. I cut a strip 495mm long and 1" wide, soaked it in water for 30mins then laid it on a board to see if it had expanded in length. The result was no change of length.
I did the same test with an offcut of the nylon I used some 20 years ago. the length dry was 310mm and the length wet after 15mins was 317mm. after leaving to dry it shrunk back to 310mm long - much what I was expecting. a shrinksge of 2.25%
Next I cut a new 495 long strip of the Flair material and washed it well in detergent and warm water. This time it had lengthened to 500mm when wet. so a shrinkage of 1% - not ideal but better than the "as suppllied" material.
My suspicion is that modern nylon material is treated with something that stops the nylon thread absorbing water and that is the problem. Raw nylon can expand as much as 5% when immersed in water.
Has any one else seen this problem or any more information.