Extending the rotor blade diameter from 3.6 meters to 4.4 meters

[chinsettawong]

My 4 meters diameter blade hit the pole and I had to cut the diameter down to 3.6 meters a few months ago.  Now I'm trying to glue back but make it a little bigger.  I'm not sure if it will hold.

My pictures tell the whole story:

After gluing the two parts together, I apply some resin and a layer of fiberglass.

I'll sand them well and paint the whole area with new paint.  I hope they will stay.

Wachara C.

Bangkok, Thailand

[wdyasq]

Wachara,

If you used epoxy it will probably bond and carry the load.  Polyester and vinylester resins will not bond to wood. If I were doing the repair and had a choice, I would have cut a 'scarf', as opposed to a key, and tried to find a linear glass or carbon fiber for the overlay.  Lacking that one could use a glass 'cloth' as opposed to mat and use as little epoxy as possible to increase strength and reduce weight.

A boatbuilder named 'Dynamite' Payson used to join plywood by 'butting', using a belt sander to reduce the thickness, adding glass and epoxy then sanding back down to original thickness.  He did this on both sides with good success.

Ron

[coldspot]

Bummer about them breaking!

But it looks like they will be fixed.

I would have used a "dove tail" for the joint.

good luck!

have a great Day/Night !

[hvirtane]

Good epoxy should work with this.

Fiberglass with or without

resin will not add much.

If you would glue there some

new wood or plywood over the joint

with epoxy it should become stronger

than the rest of the blade.

- Hannu

[zap]

A dove tail wouldn't be a good choice for this situation, Ron's scarf joint would be the better choice. A scarf with a shoulder would help with any bending the new tip would want to do along the blades long axis as would a scarf that has dowel pins. The dowels would also increase the shear strength. IMHO

[dinges]

Sorry, don't want to spoil the party,

But I don't see a problem here. Why not simply carve new blades? Seems simpler, easier, better, but most of all, safer.

The joint itsself doesn't look to bad, it's just that I wouldn't risk it.

And for really important repairs on wooden gliders (even main spars, but I've never had to do those, thank god), the ends are made in a -glue- shape, with the angle of the joint being at 1:40. 1:20 being used for less critical repairs. So, for every mm of thickness you would have 40 or 20mm of overlap.

Just some thoughts. But, judging from a previous post on building fiberglass blades and moulds, I suspect you like playing around with epoxy better than wood

Peter,

The Netherlands.

[chinsettawong]

Thanks to you all for the comments.  I thought about joining or not joining for a long time.  I know that this method is not that good but I just wanted to see how it would work.  

Wachara C.

Bangkok, Thailand

[dinges]

say WHAT?

Polyester won't bond to wood?

walking into the shop, checking the boat, returning to the computer

Hmm, could have fooled me. So far it has adhered very well. I'd better explain this to the boatbuilders in my country as well, since their boats may be unseaworthy.

I don't know if you're using different polyester from mine, but I think I could trust my life to such a bond...

Peter,

The Netherlands.

[dinges]

Wait,

I DO trust my life to such a bond.

Polyster 590; katalyst Butanox M50.

Peter.

[coldspot]

So no "DoveTails".

That "Scarf" joint looks easyer anyway, I could never get a dovetail straight.

Learned something new AGAIN here today, lol, cool.:0  

[chinsettawong]

Just to update with you guys.  It has been about 8 months since I fixed the extra length to the blades using my method.  I put the machine up right after it's done.  It's been flying great without any problem.  

Wachara C.

Bangkok, Thailand

[ghurd]

It is very nice to hear if something worked or not!

G-