Konrad
Very Strong User
It pains me to admit this, but as a result of my poor piloting skills I’m rather good at repairs!
While learning to fly Thornton Beach I had a few rather abrupt arrivals. The fuselage to my new 3 meter ship took the brunt of the abuse.
forum.alofthobbies.com
Most landings weren’t bad just not good. These showed what we already knew that the fuselage was made with improper fiber lay ups. That is there wasn’t adequate fiber aft of the wing fairing to spread the load as a result of the stress riser formed by the rear of the wing fairing. Also that the bond between both sides of the fuselage was sub par! (Note that the buckling stops at the part lines. This is because the sides split apart at this joint because of insufficient fiber content at the part line)
The other damaged area was as a result pilot error where I lawn darted the plane as I did not trust my flaps (crow) to slow down the ship for landing. This was compounded by the fact that I was fully ballasted. While the nose did suffer some damage I’m actually pleased at how well the nose performed under those challenging conditions.
To the repair.
I first fit the parts as well as I can. That is try to regain the shape of the fuselage. I then saturate the fractures with a thin glue. Normally I would use heated up epoxy to lower the viscosity so that it will flow into the fibers much more easily. As I’m against a dead line, I have another race at Thornton on Sunday and I bent my ship on Friday, I used CA to hold the fuse shape.
To properly repair a composite fracture one needs to replace or support the damaged fibers. Normally we just lay a patch across the damaged area. I did this where I could gain access from the inside, like the nose area. I don’t like to add fibers to the outside surface as these alter the shape of the part.
I try to add fibers by giving them space to lay down while not violating the outside shape. To do this I grind troughs into the fuse across the fractures These troughs give the fiber a place to go and not sit on top of the desired surface shape. I do grind the troughs deep enough as to break through to the inside in spots. I’m trying to give these fiber strips as much depth as I can.
I then place the fiber roving into these troughs. After the epoxy cures I block sand the area until I just start to hit parent material (paint).
I will repeat this grinding and filling of troughs between the troughs until the fracture area is about 70% filled with new fibers. Note you do not want the end of the troughs to line up. You want to place the ends so that they make fingers between the new and old fibers.
Once the fracture zone is filled with new fibers, I then block sand the outside surface to remove all paint. I will then make a bandage from a very light weight fiber to cover the area. I like to use 0.2 ounce carbon tissue as the random direction of the fibers helps tie the new and old fibers of the splice together. The bandage needs to of a very fine fiber as the bandage will only be as thick as the paint or gel coat layer you previously sanded off.
The patch/splice will be stronger than the original area as there will be some fiber dimension that has gone towards the inside.
Photos are of the first part of the repair.
All the best,
Konrad
While learning to fly Thornton Beach I had a few rather abrupt arrivals. The fuselage to my new 3 meter ship took the brunt of the abuse.
Soaring USA gift certificate (Strega purchase?)
Hello Guys (and maybe Gals), I've acquired $100 gift certificate from working the 2018 ISR from Soaring USA. My hope was to use this to pay for the shipping and taxes to buy a 60" MOM Racer. It pains me to say that Soaring USA only stocks one 60" plane I would want and at the same time risk MOM...
forum.alofthobbies.com
Most landings weren’t bad just not good. These showed what we already knew that the fuselage was made with improper fiber lay ups. That is there wasn’t adequate fiber aft of the wing fairing to spread the load as a result of the stress riser formed by the rear of the wing fairing. Also that the bond between both sides of the fuselage was sub par! (Note that the buckling stops at the part lines. This is because the sides split apart at this joint because of insufficient fiber content at the part line)
The other damaged area was as a result pilot error where I lawn darted the plane as I did not trust my flaps (crow) to slow down the ship for landing. This was compounded by the fact that I was fully ballasted. While the nose did suffer some damage I’m actually pleased at how well the nose performed under those challenging conditions.
To the repair.
I first fit the parts as well as I can. That is try to regain the shape of the fuselage. I then saturate the fractures with a thin glue. Normally I would use heated up epoxy to lower the viscosity so that it will flow into the fibers much more easily. As I’m against a dead line, I have another race at Thornton on Sunday and I bent my ship on Friday, I used CA to hold the fuse shape.
To properly repair a composite fracture one needs to replace or support the damaged fibers. Normally we just lay a patch across the damaged area. I did this where I could gain access from the inside, like the nose area. I don’t like to add fibers to the outside surface as these alter the shape of the part.
I try to add fibers by giving them space to lay down while not violating the outside shape. To do this I grind troughs into the fuse across the fractures These troughs give the fiber a place to go and not sit on top of the desired surface shape. I do grind the troughs deep enough as to break through to the inside in spots. I’m trying to give these fiber strips as much depth as I can.
I then place the fiber roving into these troughs. After the epoxy cures I block sand the area until I just start to hit parent material (paint).
I will repeat this grinding and filling of troughs between the troughs until the fracture area is about 70% filled with new fibers. Note you do not want the end of the troughs to line up. You want to place the ends so that they make fingers between the new and old fibers.
Once the fracture zone is filled with new fibers, I then block sand the outside surface to remove all paint. I will then make a bandage from a very light weight fiber to cover the area. I like to use 0.2 ounce carbon tissue as the random direction of the fibers helps tie the new and old fibers of the splice together. The bandage needs to of a very fine fiber as the bandage will only be as thick as the paint or gel coat layer you previously sanded off.
The patch/splice will be stronger than the original area as there will be some fiber dimension that has gone towards the inside.
Photos are of the first part of the repair.
All the best,
Konrad
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