Tips for cutting into and repairing a glass/CF fuse
07-14-2014, 07:02 AM
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Tips for cutting into and repairing a glass/CF fuse
Gents, Looking for some pointers...
I have a really big Clark Spitfire with a glass/CF fuse that I need to cut into to access tail feather controls. The spot I'm going to cut into is under the horizontal stab just behind the last bulkhead there. The plane is designed with a pull pull elevator and rudder setup in the rear across an axle glued to that bulkhead.
My goal is to cut into the fuse, remove the pull pull setup and use arrow shafts (fiberglass or carbon fiber) directly connecting the control linkages to the servos.
I've never cut into a glass fuse and some of the videos I've seen (mostly jet threads) show using an exacto blade scoring the surface until it cuts through... I've gone through 3 blades now and haven't made any progress beyond seriously scratching the surface. If I use a cutting wheel on a dremel the cut will be too wide (I'm guessing) and my patching abilities are very weak.
If I use a dremel and cut a 4X3 inch square out of the fuse back there how should be panel be re-installed... do I glue/epoxy strips of balsa or light ply to the inner surface with over lap on the edges to glue the panel I cut out back on?
I'm also worried that I'm going to be weakening the structure substantially so what do I do to bolster the strength?
any help is much appreciated. links to how-to's even more so.
I have a really big Clark Spitfire with a glass/CF fuse that I need to cut into to access tail feather controls. The spot I'm going to cut into is under the horizontal stab just behind the last bulkhead there. The plane is designed with a pull pull elevator and rudder setup in the rear across an axle glued to that bulkhead.
My goal is to cut into the fuse, remove the pull pull setup and use arrow shafts (fiberglass or carbon fiber) directly connecting the control linkages to the servos.
I've never cut into a glass fuse and some of the videos I've seen (mostly jet threads) show using an exacto blade scoring the surface until it cuts through... I've gone through 3 blades now and haven't made any progress beyond seriously scratching the surface. If I use a cutting wheel on a dremel the cut will be too wide (I'm guessing) and my patching abilities are very weak.
If I use a dremel and cut a 4X3 inch square out of the fuse back there how should be panel be re-installed... do I glue/epoxy strips of balsa or light ply to the inner surface with over lap on the edges to glue the panel I cut out back on?
I'm also worried that I'm going to be weakening the structure substantially so what do I do to bolster the strength?
any help is much appreciated. links to how-to's even more so.
07-14-2014, 04:53 PM
#2
Gents, Looking for some pointers...
I have a really big Clark Spitfire with a glass/CF fuse that I need to cut into to access tail feather controls. The spot I'm going to cut into is under the horizontal stab just behind the last bulkhead there. The plane is designed with a pull pull elevator and rudder setup in the rear across an axle glued to that bulkhead.
My goal is to cut into the fuse, remove the pull pull setup and use arrow shafts (fiberglass or carbon fiber) directly connecting the control linkages to the servos.
I've never cut into a glass fuse and some of the videos I've seen (mostly jet threads) show using an exacto blade scoring the surface until it cuts through... I've gone through 3 blades now and haven't made any progress beyond seriously scratching the surface. If I use a cutting wheel on a dremel the cut will be too wide (I'm guessing) and my patching abilities are very weak.
If I use a dremel and cut a 4X3 inch square out of the fuse back there how should be panel be re-installed... do I glue/epoxy strips of balsa or light ply to the inner surface with over lap on the edges to glue the panel I cut out back on?
I'm also worried that I'm going to be weakening the structure substantially so what do I do to bolster the strength?
any help is much appreciated. links to how-to's even more so.
I have a really big Clark Spitfire with a glass/CF fuse that I need to cut into to access tail feather controls. The spot I'm going to cut into is under the horizontal stab just behind the last bulkhead there. The plane is designed with a pull pull elevator and rudder setup in the rear across an axle glued to that bulkhead.
My goal is to cut into the fuse, remove the pull pull setup and use arrow shafts (fiberglass or carbon fiber) directly connecting the control linkages to the servos.
I've never cut into a glass fuse and some of the videos I've seen (mostly jet threads) show using an exacto blade scoring the surface until it cuts through... I've gone through 3 blades now and haven't made any progress beyond seriously scratching the surface. If I use a cutting wheel on a dremel the cut will be too wide (I'm guessing) and my patching abilities are very weak.
If I use a dremel and cut a 4X3 inch square out of the fuse back there how should be panel be re-installed... do I glue/epoxy strips of balsa or light ply to the inner surface with over lap on the edges to glue the panel I cut out back on?
I'm also worried that I'm going to be weakening the structure substantially so what do I do to bolster the strength?
any help is much appreciated. links to how-to's even more so.
Before you do any cutting layout an area about an inch larger all the way around than your planned cutout, next perform a wet layup of 2 or 3 plies of 4 to 6 oz. cloth and a laminating grade epoxy of your choice, next allow to fully cure before removal. Now you have a doubler that can be trimmed and bonded to the inside of the fuse after you are done cutting and modifying everything. If you are careful with the piece you cut out, you can use it to replug the hole by bonding it to the doubler previously boned in, next perform your cosmetics and be on your marry way.
Bob
Last edited by sensei; 07-15-2014 at 02:51 AM.
07-15-2014, 09:58 AM
#3
Senior Member
Bob's is one good way.
In your statement you actually describe another good way. Conventional planes (stab in the back) don't carry a lot of load back there except if you are using a big block up front, the shakes can get to the tail. What I've done in the past is a similar repair as you suggested in your statement but I always come back after scraping the paint and add another layer of 2 ounce kevlar over the repair, overlapping the edges. One such repair has lasted 1000 flights give or take.
BTW- why are you removing pull-pull? A properly executed pull-pull is the best arrangement you can have. On an elevator you have 4 point adjustability, twice as many as any other set-up. You can get absolute precision in the amount of throw at just about any servo throw. ANY other set-up is much heavier, adding the weight in the tail (wrong place). Over 45 years I've tried all control systems and always return to pull-pull on elevators, rudders. Would use pull-pull on ailerons too but it's trickier there and makes less sense
In your statement you actually describe another good way. Conventional planes (stab in the back) don't carry a lot of load back there except if you are using a big block up front, the shakes can get to the tail. What I've done in the past is a similar repair as you suggested in your statement but I always come back after scraping the paint and add another layer of 2 ounce kevlar over the repair, overlapping the edges. One such repair has lasted 1000 flights give or take.
BTW- why are you removing pull-pull? A properly executed pull-pull is the best arrangement you can have. On an elevator you have 4 point adjustability, twice as many as any other set-up. You can get absolute precision in the amount of throw at just about any servo throw. ANY other set-up is much heavier, adding the weight in the tail (wrong place). Over 45 years I've tried all control systems and always return to pull-pull on elevators, rudders. Would use pull-pull on ailerons too but it's trickier there and makes less sense
