Removing Hysol

[Goldendale-flyer 6]

I have an Avid MK IV that had the old tanks removed (mostly) and I need to put the new tanks in. I want to use a heat gun to remove the hysol that is still stuck to the spars. What is the appropriate temperature to use? I want to soften the Hysol but the ruin the temper of the spars.

Best,

Rick

[EDMO 1078]

Totally unofficial - But best I know is to keep it under 250F.  You can use a sander and not have to heat it - It don't have to be perfectly clean because the Hysol or Silicone will bond to the old too - I would rather use the Silicone caulk since it is easier to remove tanks later on.   EDMO

Edited 10 Apr 2018 by EDMO

[Goldendale-flyer 6]

Since the tank replaces several ribs and I think a drag tube, which would indicate to me that the tank is providing mechanical strength to the wing assembly. That would seem to indicate Hysol. Am I missing something? 

I thought scratching the spar with sand paper was bad since it helps for a stress riser in the spar.

 

[EDMO 1078]

Since the tank replaces several ribs and I think a drag tube, which would indicate to me that the tank is providing mechanical strength to the wing assembly. That would seem to indicate Hysol. Am I missing something? 

I thought scratching the spar with sand paper was bad since it helps for a stress riser in the spar.

 

I believe my Kitfox manuals say to sand any scratches on the spars with 100 grit sandpaper - I believe that sanding was also recommended in the places where you apply Hysol, followed by an alcohol wipe?  I would have to check the manuals for the exact instructions.  You probably only need to sand the high spots of the Hysol, and try the tanks for fit before gluing them in.  My 12 gallon Kitfox tanks only replaced one rib for each tank because Kitfox ribs are about 17 1/2" apart.  EDMO

Edited 11 Apr 2018 by EDMO

[SuberAvid 617]

Rick,

The Avid manual says to scuff the spars with 360 grit sand paper when preparing them for gluing so I would be cautious about sanding them with100 grit.  I agree with Ed that you probably don't have to totally remove all the old glue, just the high spots. Insert the tanks and see if you can strap them together in the spars and get the center to center distance to be correct. (I used ratchet straps to do this and to hold the spars in tight when gluing.)  Once you get that you can drill the bolt and pin holes (with the tanks strapped in place) and can glue the tanks in after you do the spar inserts (unless these are still in the correct locations). Then you have to completely wrap the tanks and spars with fiberglass- 1 random sheet and 1 woven sheet to get the structural strength.

Randy

Edited 21 Apr 2018 by SuberAvid

[Geoffrey Thorpe 31]

I want to soften the Hysol but the ruin the temper of the spars.

Aluminum is annealed at temperatures on the order of 650F - wouldn't want to get that hot

Fabric is shrunk at around 350F - should be safe.

[Goldendale-flyer 6]

Thank you Geoff.

[Goldendale-flyer 6]

Thank you everyone for your input on this. 

Rick

[EDMO 1078]

Rick,

The Avid manual says to scuff the spars with 360 grit sand paper when preparing them for gluing so I would be cautious about sanding them with100 grit.  I agree with Ed that you probably don't have to totally remove all the old glue, just the high spots. Insert the tanks and see if you can strap them together in the spars and get the center to center distance to be correct. (I used ratchet straps to do this and to hold the spars in tight when gluing.)  Once you get that you can drill the bolt and pin holes (with the tanks strapped in place) and can glue the tanks in after you do the spar inserts (unless these are still in the correct locations). Then you have to completely wrap the tanks and spars with fiberglass- 1 random sheet and 1 woven sheet to get the structural strength.

Randy

Just to clarify my post about sanding the Hysol high spots with 100 grit - Although Kitfox says to sand out scratches on the spars with 100 grit, that is to be followed by finer sanding and polishing.  I didn't mean for you to sand close enough to scratch the spars - just to take off the high spots of Hysol.  Also, tightening fabric with a moving iron at 250F is not like holding the heat gun in one spot directly on the spars at that temperature.   EDMO

Edited 24 Apr 2018 by EDMO

[nlappos 413]

From my experience, Hysol is pretty soluble in MEK, as long as you can keep it away from the other stuff in the area.