PPG Troubleshooter

Solutions to problems for paramotor pilots  | suggestions? send them along.

Motor Problems

Redrives & clutches

 

Propeller Problems

Prop Repair

 

Related

Chapter 12: Setup & Maintenance
Parts & Service
Tools

Tips on non-motor hardware improvements

Winterizing your Paramotor by Alex Varv

 

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 Bible.

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 of tip.
  • 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.

Tools.

 

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. Here's a 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 sanding.

 

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 technique.

 

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.

them

 

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 the joint.

 

Sand, paint and fly!

 

 


© 2016 Jeff Goin & Tim Kaiser   Remember: If there's air there, it should be flown in!