delamination in Jabiru wooden prop

[Bruce Tuncks]

There is an area on my prop ( about a ten-cent coin size) where the fiberglass sheathing has delaminated from the wood. I reckon an injection of resin followed by clamping till it sets would be a good fix.

 

But what resin to use? I think it may be polyester but I don't know for sure.

 

 

[Jaba-who]

I had a similar event with my first wooden prop. I think it originated from a stone strike if I recall. Anyway I spoke with Stiffy and he advised just using the epoxy that came with the kit.

 

I just injected it in with a needle and syringe then clamped it down.

 

As best I recall it worked fine.

 

 

[Head in the clouds]

Bruce - please note that polyester resin is NOT an adhesive, but epoxy resin is ...

 

Poly will join a layer to a layer if it's abraded or similarly a long scarf but if you just want to bond an unprepped poly matrix to timber ... well, I'd inject epoxy.

 

 

[Downunder]

I believe you can use epoxy over poly but not vice versa..... so you should be good.

 

 

[Oscar]

There is an area on my prop ( about a ten-cent coin size) where the fiberglass sheathing has delaminated from the wood. I reckon an injection of resin followed by clamping till it sets would be a good fix.But what resin to use? I think it may be polyester but I don't know for sure.

Unless Jabiru has changed, they use Araldite LC3600 ( but best check with Kody). CG Composites sells it in small quantities at reasonable price - the postage for 1 litre of it may well be more than for the resin itself because of the 'Dangerous Goods' classification. Note - LC3600 has a definite shelf-life, don't use 'old' stuff!

 

 

[Kenlsa]

Bruce, I will be at my hangar tomorrow and have all the gear to fix it. I did mine 200 hours ago and all is still good with the repair.

 

Ken

 

 

[Oscar]

With respect to the knowledge you and Kensla obviously have, may I suggest a couple of things.

 

Optimum ambient conditions for this work would be around 22-24C and not a lot more than 30%RH. Preferably, several days of RH around that figure before the repair.

 

Prop off the aircraft and the repair set at zero degrees to ensure the resin flows evenly around the de-lam area.

 

Drill with around 1mm holes at the peripheral of the delaminated area to ensure the influx resin gets to the edge of the de-lam area, and inject from the centre until all peripheral holes exude resin.. Work it around by thumb-pressure.

 

Wrap with cling-wrap - and if you can organise even a crude vac-bag using a vacuum cleaner and some builder's plastic blanket ( but have the vacuum-cleaner running on low vacuum setting so it doesn't burn-out!), you'll get a damn good result. You'll need to run the vac.bag for around six hours at about 22C to ensure the resin has gone off.

 

Take a test coupon of the resin - if it breaks cleanly (not shatters into shards but doesn't just indent), you've got a good result.

 

 

[Kenlsa]

Oscar, what you have said is close to what I did. Seems most of the problem isn't delamination of the cloth on cloth but the oil in the timber causing separation of the timber from the first layer of cloth. If the delam is close to the hub the easier it is to fix. But if close to the tip, it's off to the manufacturer to fix. I have done 2 props, one at 150mm and the other at less than 300mm from centre, certainly in the first third where prop speeds are lower.

 

Ken

 

 

[Bruce Tuncks]

Thanks Ken, I was set to go today but the humidity is too high ( raining as I type this) for a critical epoxy job, and yes the repair job is close to the tip.

 

The damage was done at Wentworth when I moved off the runway to allow a CT to take off. There were a few weeds which were woodier than I thought, and they did damage to the prop tape near the tip as well as triggering this delamination. If I had not fixed up the tape, the glass might well have been lost from the tip with a serious loss of balance. Mine is an early prop where the leading edge rubber is just butt-jointed on.

 

I reckon the repair will be ok, anyway its worth a try.