Mylar Repair Liquid Formula and Making FFM Fixed Rotor

[AdithA]

Hi Coaches,

I have a few questions below.

1. I accidentally soldered a few small holes into my rotor while melting off the excess mylar after covering. I don't recall what the formula/ratio was for the liquid we used for Scioly between naphta and 3M77 to patch the holes and attach new Mylar down. Also, could you describe the process of how you apply this mylar to get as little added drag as possible?

2. I recall that Coach Brian mentioned that his team made the freedom flight rotor fixed because there is no difference in performance,and it makes usage/flying much easier, as I recall from experience with the J&H Hurricane. Would I be able to just glue the nose button of the lower rotor into the bearing and just make it fixed?

Thank you,
Adith

[bjt4888]

Hi Coaches,

I have a few questions below.

1. I accidentally soldered a few small holes into my rotor while melting off the excess mylar after covering. I don't recall what the formula/ratio was for the liquid we used for Scioly between naphta and 3M77 to patch the holes and attach new Mylar down. Also, could you describe the process of how you apply this mylar to get as little added drag as possible?

2. I recall that Coach Brian mentioned that his team made the freedom flight rotor fixed because there is no difference in performance,and it makes usage/flying much easier, as I recall from experience with the J&H Hurricane. Would I be able to just glue the nose button of the lower rotor into the bearing and just make it fixed?

Thank you,
Adith

I think Coach Chuck and I covered all but the film repair question in Discord. Process for repair that I use is same as for ultralight AMA FAI airplanes as it produces a good result. For SO it is probably not necessary to use this lighter and more complex process. I’ll describe the AMA process here in just a few minutes.

Coach Brian

[bjt4888]

AMA style ultralight covering repair process:

• 1. I use superultrafilm for SO repairs as it lays down flatter and bonds better to other covering than ultrafilm. You could use ultrafilm too.
  
  2. Sandwich a piece of ultrafilm or superultrafilm (maybe 6"x6" or so) between two pieces of newsprint. This allows small patches to be easily cut as it is easy to cut newsprint/film/newsprint with a sharp blade on a cutting mat. Then you get the patch the exact size you need (1/4" oversize in all directions).
  
  3. Once patch is cut out, slide one layer of newsprint away and gently slide the covering about 1/4" off of the remaining piece of newsprint. This give you a 1/4 inch"handle" of newsprint to pick up the patch with and gets a little of the patch ready for application.
  
  4. Thin a little 3M77 in naptha and brush on the area to be patched (1/4"each edge of the actual hole)
  
  5. Carefully pick up the patch film by the 1/4" handle of newsprint (newsprint side down and film facing you) and apply edge to the edge of the patching area and hopefully it will stick to the brushed naptha/77 area edge then slide the newsprint out from under the film. If it doesn't stick to the film area with naptha/77 glue on it that was brushed around the hole as the naptha/77 has dried, don't despair, just use thumb and finger to grip the patch film (one finger on each side of the covered surface).
  
  6. Don't touch the patch film, it is very unlikely that you will improve placement of the patch with your fingers and you might make a mess and have to start over). With your 000 sable spotter brush, apply some 100% naptha to the patch area adjacent to each edge of the patch film (don't touch the brush to the patch film). You will see the naptha wick under the patch film which will soften the previously applied naptha/77 and bond the patch.
  
  7. Let the patched area dry completely (all naptha to evaporate) before doing any trimming with a solder iron (if patch is near a spar) otherwise you might ignite the remaining naptha and have a bigger hole to patch. Naptha does not burn in flames in this small quantity, but you will see the naptha/77 area dissappear (bigger hole). I usually trim with solder iron the next day.
  
  8. Clean the brush thoroughly and repeatedly by dipping in naptha and wiping on shop towel so that it is usable for next time.
  
  Enjoy