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.
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.
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.
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.
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.
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.
Had both batteries mounted but conditions were less than perfect so i dismounted one set of bonkas but got to secure the strap for it. Just got air burn and whack! whack! No more strap. Landed immediately. One prop is cracked down the center about half way.
Can it be glued with CA (then the chip repaired as above) while I await a replacement set? I suppose I could try it and test it at full power on the ground.
The chip off the trailing edge has been there since my first flight.
Filled and sanded (320), repeatedly. Then water based polyurethane. More sanding, repeat.
Success!
Ran it up on the ground (motor on my back, leaning against a wall, in a safe location). First to 100 amp draw. Held that for a minute. Varied power a few times then switched off and checked it. Looked great. No signs of the crack reopening. Strapped back in. Ran it up to full power. Held it for a minute, varied power. Felt good. Switched off again and checked it. Seems perfect.
My leading edges are always getting sand blasted during takeoffs. I Just fixed one of them with Gorilla glue. It does not look like anything changed because the glue is translucent. It has worked for me so far.
That particular Gorilla brand glue is Cyrano Acrylic aka CA or Super Glue. Works a treat on pretty much anything porous and is particularly good for wood.
Phil,
My LZ on the beach has Lots of rocks and shells too. The clear 3M prop tape has saved my props…didn’t think it was going to help much, but it did. I was really surprised.
Bill
Now I need to find a way to separate my thumb and my index fingers😆
On a more serious note, the attached photo of the Gorilla repaired prop still looks bad but it is actually smooth after sanding. The dents are glue filled and the leading edge even. I don’t care about the look of it for as long as it works.
The lighter colored upper end section of the leading edge shows the damage high velocity vacuumed sand does to relatively soft wood fibers (sand blasting a work indeed!). First the original clear coat is blasted away and then it is the wood’s turn.
It only happens to the lower blades. I wonder how the SP-140 carbon fiber prop will fare in the same conditions?
That’s CA for ya. I heard it was originally developed to actually bond skin in battlefields. Do NOT get it in your eyes. If you want to fill a with it try dumping a few dozen milligrams of baking soda (sodium bicarbonate) into a drip of CA. It hardens into a crystalline cement instantly.
Just wood filler works to fill small nicks if you refinish with polyurethane. I have a couple flights on my repaired propeller now. Works as good as new!
I was really surprised.
