Re: repairing cracks in dope finish, this is for dope only, no other top coat.
From the manual:
"Mix two parts J-3000 Butysolv Rejuvenator to three parts 9703 Butyrate Thinner. Spray one full, wet cross-coat (two passes of the gun at right angles). Wait 30 minutes until the coatings become soft, then you may be able to use your fingers to smooth out hairline cracks and small ringworms. (Be sure to protect your hands.) Wait two hours and spray on another cross-coat of thinned Rejuvenator. Let dry at least overnight. Fill any remaining small cracks with Rand-O-Fill Silver Butyrate using a small brush."
Those instructions are not good and probably will fail. I don't have near as much experience as Kevin, but I have used a number of systems and done complete and in depth rejuvenations on dope. They say to spray rejuvenator on and you "MAY" be able to smooth out the cracks. If you do it that way you are probably just healing the top surface of the crack and covering it over. The crack still exists deeper down and will reform to the surface. You can spray like they said, it's needed if you are refinishing the whole plane, but if doing a local repair I would just apply rejuvenator to the repair area. Then take a clean rag wrapped around your finger, dip it in rejuv and rub the crack. keep dipping in rejuve to keep wet, and keep rubbing till you get down to clean fabric. It will dissolve the dope completely and melt it so you can get right down to fabric. Only then is the crack gone. Then start building up the dope again by brushing it on. We would leave a brush in a jar of dope and every 1/2 hour put more on. Depending on the thickness of the original finish it could take 10 or more applications. Let it dry for a few days then go back and skillfully wet sand level with the surrounding surface. Then spray color top coat. If the original has faded, then a color match will be a problem. If respraying the whole plane, not a problem. This is a very laborious and time consuming job, so you need to decide if the cracks are bad enough to warrant it. Also if spraying the whole plane, the thickness is increasing, so tendency to crack increases. But you will be ok for a number of years until the rejuvenator starts to dry out again. If there are enough cracks, it may be time to consider recover.
Kevin is right, ALL finishes crack eventually, it's very frustrating. You need to decide on the lessor of evils for your intended use. A hangered show plane, in warm weather, is a different animal than a bush plane. I have two planes with old finishes, one dope and one Endura, both have some cracks. The dope, I do local repairs once in a while, color exactness is not a problem in the bush. The Endura, I can't really fix, so I cover cracks with vinyl, looks ok.
Re: tail LE cracks... In cold weather, (ski flying) it's even worse, edges of the tapes will lift. I now use a wide 4" tape on the LE, then another 6" wide over that. This way the edge of the tape is farther back from the LE and farther from the local stress of fingers, and I hope, less likely to lift. Just a few long winded ideas!
From the manual:
"Mix two parts J-3000 Butysolv Rejuvenator to three parts 9703 Butyrate Thinner. Spray one full, wet cross-coat (two passes of the gun at right angles). Wait 30 minutes until the coatings become soft, then you may be able to use your fingers to smooth out hairline cracks and small ringworms. (Be sure to protect your hands.) Wait two hours and spray on another cross-coat of thinned Rejuvenator. Let dry at least overnight. Fill any remaining small cracks with Rand-O-Fill Silver Butyrate using a small brush."
Those instructions are not good and probably will fail. I don't have near as much experience as Kevin, but I have used a number of systems and done complete and in depth rejuvenations on dope. They say to spray rejuvenator on and you "MAY" be able to smooth out the cracks. If you do it that way you are probably just healing the top surface of the crack and covering it over. The crack still exists deeper down and will reform to the surface. You can spray like they said, it's needed if you are refinishing the whole plane, but if doing a local repair I would just apply rejuvenator to the repair area. Then take a clean rag wrapped around your finger, dip it in rejuv and rub the crack. keep dipping in rejuve to keep wet, and keep rubbing till you get down to clean fabric. It will dissolve the dope completely and melt it so you can get right down to fabric. Only then is the crack gone. Then start building up the dope again by brushing it on. We would leave a brush in a jar of dope and every 1/2 hour put more on. Depending on the thickness of the original finish it could take 10 or more applications. Let it dry for a few days then go back and skillfully wet sand level with the surrounding surface. Then spray color top coat. If the original has faded, then a color match will be a problem. If respraying the whole plane, not a problem. This is a very laborious and time consuming job, so you need to decide if the cracks are bad enough to warrant it. Also if spraying the whole plane, the thickness is increasing, so tendency to crack increases. But you will be ok for a number of years until the rejuvenator starts to dry out again. If there are enough cracks, it may be time to consider recover.
Kevin is right, ALL finishes crack eventually, it's very frustrating. You need to decide on the lessor of evils for your intended use. A hangered show plane, in warm weather, is a different animal than a bush plane. I have two planes with old finishes, one dope and one Endura, both have some cracks. The dope, I do local repairs once in a while, color exactness is not a problem in the bush. The Endura, I can't really fix, so I cover cracks with vinyl, looks ok.
Re: tail LE cracks... In cold weather, (ski flying) it's even worse, edges of the tapes will lift. I now use a wide 4" tape on the LE, then another 6" wide over that. This way the edge of the tape is farther back from the LE and farther from the local stress of fingers, and I hope, less likely to lift. Just a few long winded ideas!
