Wooden prop repair

I busted about 4 or 5 props so far.
two are completely broken, the rest only have small damages.

The completely broken prop was my fault. I fired up the OpenPPG on the ground without paying attention that there are no loose straps.

The two props that have each a tiny damage, I do not really know what happend, maybe a small stone or something when launching…

Anyways, since the props are made out of wood, I thought I should be able to repair them.


Here’s the damage already “cleaned” with a sharp knife, taking away some of the wood fibre.
I forgot to take a picture of the prop with the original damage.


this is some Putty specially for wood, which I purchased in a local hardware store. Akzo Nobel is the manufacturer (they make tons of chemicals…)


Using my finger, I pushed the putty into the hole… not so easy

Here are both sides of the prop after some smoothing with a wet finger.
I tried to make sure that there is excess material everywhere, so that the next step would be sanding.

I could also let it dry and add a second and third layer of putty, should the hole be a little larger.

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Next steps are:

  • let dry thoroughly
  • sanding
  • spray paint the sanded area
  • balance the prop with a balancer

I will post photos of the next steps once I am at it. need to let the prop dry first :slight_smile:

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…After some sanding…


And some more sanding, feels perfect.


The repaired propeller on the prop Balancer (Du-Bro TruSpin)
It’s the repaired side that is lighter. the Putty seems to be lighter than the wood. The sanding took some tiny bit of material away, as well.


Adding very gently some clear spray paint to the lighter side, making it slightly heavier (and protecting the repaired and sanded parts again)


Done

A fresh and perfectly balanced prop, ready to fly again :slight_smile:

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I broke this prop the same way as etienne did by running with a strap undone:

I decided to reshape the tip to look like some of the more efficient prop designs that I’ve seen. Of course the airfoil shape at the tip needed to be reshaped as well. I traced the tip onto a piece of paper to make a template to get the other side to match. Then I balanced it on the same prop balancer as etienne.

Good as new… maybe even better.

My other props had several dings on the leading edge which I fixed by sanding the same amount off both blades. After balancing they spin smoother than when they were new.

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Nice job Etienne. I fixed a powered hang glider prop some years back the same way. Lasted until I sold the machine. However, I didn’t think to do a weight balance and I love your spray varnish solution.

wasn’t my idea… saw that on a youtube video once, where they balanced a 1.35m diameter carbon prop that way.

after posting the pics, I damaged the same prop on the other side at about the same spot.
I know now where it comes from:

It must have been the netting, more precisely one of the knots in the last row right were the tension string is.
I thought I pulled it really tight, but it was still sort of close to the prop. In preparation of my flight today I connected the netting a couple of inches lower to the frame, and that allowed the netting to be secured a bit better behind the two lower arms.
I will have to make sure in the future to always pay really good attention of tightening the net and where I connect the tensioning strings to the frame!

I’ve repaired 8 of my props so far using your method, thanks @etienne ! Only step I did different was to cover the wood putty after I’ve sanded it with some thin ca glue. Then I sprayed with enamel and balanced.

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