Carbon Fiber Tip Repair
2016-07-10 How to fix a Carbon Fiber Prop
Ding the tip of your carbon prop? Is the prop in good shape otherwise?
This may work.
It's based on the same technique as covered in Chapter 12 of the PPG
Fixing a prop could cause injure or kill a bystander if the repaired
prop comes apart! Take this seriously and don't do it if you have any
reservations or it doesn't fall within the limits listed here. Even if it
does fall within these limits it may come apart for any number of reasons.
If in doubt, change it out!
Adhere to the following limitations and cautions unless you're willing
to hurt yourself or others.
- Don't try to repair damage to more than 2 inches of the tip(s).
- Don't use this technique for damage other than the last 2 inches
- If there is any indication of stress fracture or structural
compromise, toss it. Carbon fiber props may very well have crushed
parts of the interior honeycomb structure.
- Do test runs in safe areas. Departing pieces will go outward
initially but may also go forward or backward once they leave home.
Ensure there's nothing anywhere near the prop's plane that you want to
keep intact, especially soft, fleshy things.
- After each flight look for signs of stress cracks on your repair
along with a normal prop inspection. Unfortunately, repairs are still
more likely to fail without warning.
- If a prop repair lets go in flight, it will be vibrating severely
and may result in engine separation. Unless you're over really bad
terrain or large monsters are chomping at your feet, shut the motor
off right away and land.
Fixing the Prop
Here are the tool you'll want. A jigsaw is nice, too, if you're using
soft wood (like poplar) and have a way to clamp or brace the wood. We're
in a motorhome, a SMALL motorhome, so our options are limited.Belt sanders
rock but be wery, wery careful, they take a lot of material, especially
with the 80 grit sandpaper I use for shaping. Use a sanding block for
finer sculpting of the shape then use 200 grit or so for smoothing.
Here is a summary illustration of the repair
process. Below are some pictures from the actual repair. You're looking at
he prop from it's trailing edge.
Poplar works but probably isn't ideal--I'd recommend
something heavier. After I fixed the prop with this wood it turned out to
be too light and I had to add weight. Use at least pine which is harder
and heavier but not by much.
website with weights per unit volume of wood. The reason for buying it
in thinner pieces is so you can layer it in a way that requires less
Sand a shallow angle. It should be at least 2 inches to
give the wood a lot of surface to glue to. The belt sander makes quick
work of it. This face must be flat so the wood adhere's properly. If your
prop doesn't give this level of surface it would be unsafe to use this
The wood must go out far enough to be the same length
as the opposite tip. Size appropriately from measurements. Glue the wood
on with a good epoxy. If you don't have a thick enough piece of wood,
build up enough layers, gluing together with wood glue and clamp. Then
glue the block to the prop with Epoxy.
Sand to shape. This is the fun part that I enjoy so
much but is also the most difficult. It's a matter of
Balance. Add weight to the wood part. Avoid weakening
Sand, paint and fly!