mooserider
Active Member
I thought I would make a post on this in case someone new to planes is intimidated by repairing a crash. They may look horrible and 'totaled', but often it's easier to fix than you might think. The big misconception for most people is that is has to be perfect to fly; it doesn't, trust me! Wings are the most difficult (for severe damage), followed by fuselage and then the tail feathers. At least, this is my general opinion.
What you'll see below is a 40 size Piper that I recently crashed (had the flap and aileron servos plugged in backwards and didn't do a surface check). This is an ARF (my first), and they're built so fragile that nosing it in crushed the front of the fuse up pretty badly. I have no plans/instructions, as this plane was given to me by a friend getting out of the sport.
Here's the damage after the flight. I start by removing the coating around damaged areas and see how things fit together with the broken pieces I have. You're not looking to fit it back together like a puzzle, rather you're looking for the larger pieces that will give you an idea of where things should be. Basically, examine everything, find the largest pieces and fit them together to get an outline. Even if the plane ended up an inch shorter, you'd be fine (though you would want to re-check and adjust the CG).
*See Note 1 at the bottom of post for additional info from Tony
Next, I start building back up the front (left side) by cutting plywood pieces to fill in where missing/broken pieces are. Instead of cleaning the edges of remaining pieces and trying to perfectly match a newly cut piece, just make a new piece that's longer than needed, and epoxy it to the inside/back of the remaining pieces. You can fill in gaps with balsa, or just ignore it and monokote over it. Also use balsa 1/4 inch stringers to beef up any areas of concern, or that seem weak. Epoxy is great for filling large gaps and stiffen'ing things up.
Next I attach the front engine section to the rest of the fuselage again. Be careful to try and keep the fuselage straight as possible. After gluing it in place, begin applying balsa and/or plywood across the gaps where major structural breaks were.
Take your time and do your best to cut pieces into shapes that fit well and don't leave any large gaps if possible. Again, epoxy helps here.
Next, I decided to replace the wind shield with balsa, as finding a replacement is pricey (and not going to be easy to find for an older plane). Take your time and fit things into shape. Then sand it down to be somewhat aerodynamic.
*See Note 2 at bottom of post - how to make a makeshift window from Smoogie.
There was a cowling for the motor that hid it; to replace it completely will take more time than I want (and I plan on crashing this again, so....), so I made a shorter, stubby version, that will at least hide the internals and add some aerodynamics to the plane, rather than a blunt motor block. To do this, I started by masking tape into positions pieces of balsa to match the 'engine' compartment.
I wanted to be able to get at my battery compartment a little easier, and to be able to remove the cowling if I needed to, so I added magnets to the back of the cowling. *Note: do not place any magnets near/close to the motor for electric builds. *Nitro: I would not trust magnets anywhere on a nitro build due to the vibrations.
Next, finish touches (paint and such) are added. I mask off the parts I want and spray paint it. Here, I'm trying to put 'lipstick on a pig', so to speak. You could monokote it and move on with anything. I chose a few minor enhancements, like painting on a window to the balsa replacement, and a few other things to make it 'sort of' look not wrecked and repaired. But if this is your first plane, just patch it and go. *Tip*: basic clear wide tape works wonders for holes in monokote.
Final picture before next flight:
Took the plane out on Monday, and it flew just fine. Few tweaks to re-trim, but that was it! Flew great!
--------- NOTES ------------
Note 1: On Rebuilding Structure after Crash:
*Tip from Tony: "Actually, i would say that putting them back is like a puzzle. The larger pieces are your corners since there are not many of them usually. the mid pieces are your borders and the small pieces are what is in the center. Start large and move your way down. Replace what you need to as not everything is going to fit back together." And he's right, do use the larger and mid-sized pieces to position things. You just don't *need* all of the pieces to accomplish your goal. Some pieces you may not find after the crash, even bigger pieces. But a fuselage repair is fairly forgiving. What can affect flight is the offset degree of the motor/engine due to torque. The only way to properly compensate here is to make sure your firewall is 90 degrees to your fuselage, and that the motor mount is then properly offset for the engine/motor torque. To check 'squareness' of your firewall (especially for curved body fuselages), measure the distance from the left side of the firewall to the rear (aft) tip of the fuselage. Then, measure the right side of the firewall to the right rear (aft) tip of the fuselage. The two measurements should be damn close. (Don't measure to your stabilizer tips, as your stab may not be perfectly square, and the error here will be worse the wider is stab.)
Note 2: On creating a Makeshift Window:
*Tip from Smoogie: "It's quite easy to form canopies over a wooden former. There are a few ways to do it, the simplest just uses a pop bottle (PET type plastic) and you shrink it onto the former in an oven. "
-----------------------------
Hope this helps someone out there!
Cheers!
What you'll see below is a 40 size Piper that I recently crashed (had the flap and aileron servos plugged in backwards and didn't do a surface check). This is an ARF (my first), and they're built so fragile that nosing it in crushed the front of the fuse up pretty badly. I have no plans/instructions, as this plane was given to me by a friend getting out of the sport.
Here's the damage after the flight. I start by removing the coating around damaged areas and see how things fit together with the broken pieces I have. You're not looking to fit it back together like a puzzle, rather you're looking for the larger pieces that will give you an idea of where things should be. Basically, examine everything, find the largest pieces and fit them together to get an outline. Even if the plane ended up an inch shorter, you'd be fine (though you would want to re-check and adjust the CG).
*See Note 1 at the bottom of post for additional info from Tony
Next, I start building back up the front (left side) by cutting plywood pieces to fill in where missing/broken pieces are. Instead of cleaning the edges of remaining pieces and trying to perfectly match a newly cut piece, just make a new piece that's longer than needed, and epoxy it to the inside/back of the remaining pieces. You can fill in gaps with balsa, or just ignore it and monokote over it. Also use balsa 1/4 inch stringers to beef up any areas of concern, or that seem weak. Epoxy is great for filling large gaps and stiffen'ing things up.
Next I attach the front engine section to the rest of the fuselage again. Be careful to try and keep the fuselage straight as possible. After gluing it in place, begin applying balsa and/or plywood across the gaps where major structural breaks were.
Take your time and do your best to cut pieces into shapes that fit well and don't leave any large gaps if possible. Again, epoxy helps here.
Next, I decided to replace the wind shield with balsa, as finding a replacement is pricey (and not going to be easy to find for an older plane). Take your time and fit things into shape. Then sand it down to be somewhat aerodynamic.
*See Note 2 at bottom of post - how to make a makeshift window from Smoogie.
There was a cowling for the motor that hid it; to replace it completely will take more time than I want (and I plan on crashing this again, so....), so I made a shorter, stubby version, that will at least hide the internals and add some aerodynamics to the plane, rather than a blunt motor block. To do this, I started by masking tape into positions pieces of balsa to match the 'engine' compartment.
I wanted to be able to get at my battery compartment a little easier, and to be able to remove the cowling if I needed to, so I added magnets to the back of the cowling. *Note: do not place any magnets near/close to the motor for electric builds. *Nitro: I would not trust magnets anywhere on a nitro build due to the vibrations.
Next, finish touches (paint and such) are added. I mask off the parts I want and spray paint it. Here, I'm trying to put 'lipstick on a pig', so to speak. You could monokote it and move on with anything. I chose a few minor enhancements, like painting on a window to the balsa replacement, and a few other things to make it 'sort of' look not wrecked and repaired. But if this is your first plane, just patch it and go. *Tip*: basic clear wide tape works wonders for holes in monokote.
Final picture before next flight:
Took the plane out on Monday, and it flew just fine. Few tweaks to re-trim, but that was it! Flew great!
--------- NOTES ------------
Note 1: On Rebuilding Structure after Crash:
*Tip from Tony: "Actually, i would say that putting them back is like a puzzle. The larger pieces are your corners since there are not many of them usually. the mid pieces are your borders and the small pieces are what is in the center. Start large and move your way down. Replace what you need to as not everything is going to fit back together." And he's right, do use the larger and mid-sized pieces to position things. You just don't *need* all of the pieces to accomplish your goal. Some pieces you may not find after the crash, even bigger pieces. But a fuselage repair is fairly forgiving. What can affect flight is the offset degree of the motor/engine due to torque. The only way to properly compensate here is to make sure your firewall is 90 degrees to your fuselage, and that the motor mount is then properly offset for the engine/motor torque. To check 'squareness' of your firewall (especially for curved body fuselages), measure the distance from the left side of the firewall to the rear (aft) tip of the fuselage. Then, measure the right side of the firewall to the right rear (aft) tip of the fuselage. The two measurements should be damn close. (Don't measure to your stabilizer tips, as your stab may not be perfectly square, and the error here will be worse the wider is stab.)
Note 2: On creating a Makeshift Window:
*Tip from Smoogie: "It's quite easy to form canopies over a wooden former. There are a few ways to do it, the simplest just uses a pop bottle (PET type plastic) and you shrink it onto the former in an oven. "
-----------------------------
Hope this helps someone out there!
Cheers!
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