Jacobs 1800 down for maintenance

[Tom Sullivan]

I developed a bit of an obvious "out of balance" quite a while ago, but it was only evident at slow speeds.  I had my log home project in the way to drop the thing, and recently moved the home to it's permanent site and finally got time to take the turbine down.  It looks like the bolts and screws loosened up on one blade and it worked out a bit on the shaft.  I communicated with Mick about getting another set of blades, but for the production I get in my light winds, I just can't justify $1100 for another set.  He mentioned something about an "Epoxy Glue" that works better than the outdoor waterproof glue I used when building the blades 3 1/2 years ago.  Anyone know where I can find an epoxy glue?  I think I can repair the blades for now and maybe get some solid blanks for building a new set in the spring.

Tom Sullivan

[SparWeb]

In glue, strength = $$.  How strong do you want to buy?

There are structural epoxy resins that can bond steel to aluminum so wel that the aluminum will break before the glue joint does.
... when applied properly ...
There is enough variety that you can usually find what you need.

Can you elaborate on exactly what joint you want to repair, what materials are involved, where you intend to apply it?
A photo would be very valuable here.  Even though I think I can picture what you mean, this isn't something to get wrong by making assumptions.

[Tom Sullivan]

I may need a couple different types of glue.  I need something to fill the mounting hole where it has egged out, and a couple spots where the stainless steel wood screws attach the blade to the mount.  But, the blade is cracked at the end grain mounting hole and I also need to re-glue one of the lamination joints near the root (still looks good out farther on the blade).

There is a crack crossways on the blade where there is extra wood laminated on it for the mount, but I believe this is from flexing of the blade.  The actual blade is NOT cracked, and the lamination appears to be fine.  It is just the paint that has cracked at that flex point.

Tom Sullivan

[SparWeb]

That didn't go flying to kingdom-come? 

This will be difficult.  There are long cracks and a lot of weathering to deal with.

Early thought, about the bad hole:  Consider how a brass/steel bushing could be made up to support that better.  You'll need two bushing, one on each side of the axle.  Diameter of bushing to rest firmly on a slightly bigger hole in the wood, depth of bushing to allow clamp-up against the wood not the bushing...  but still not confident I'm on the right course, just bringing out the idea because I don't think glue will solve this alone.

I need to let this "simmer" in the back of my mind before I come back with a solution that I can justify.  Can't guarantee it's easier than building a new blade.  Do you have a link handy for the photos you posted of the project, a few years back?

[Tom Sullivan]

I searched pretty hard on this forum, but can't seem to locate the long thread I had going while building during the summer of 2010.  I have quite a few pictures on my own website, several of the blades being built.  http://www.aluminum-solar-absorbers.com/wind-power-projects.html

Tom

[Mary B]

The amount of glue needed to fix that is going to throw off the blade balance badly.

[Royalwdg]

I have built built blade that went on a few jacobs machines.  The root bolts right in.  Email me at Royalwdg@netsync.net to discuss the application.  The pricing is way better than what you just mentioned.    Dave Moller

[SparWeb]

Here's what I'm worried about:  The long split can be re-bonded, and sure you can get strong epoxies, but the base wood has been weathered significantly, suffered a fair bit of surface damage from the fitting being dragged across the root, and then there is the bad hole, of course.  Seeing all of these things together on the same blade, you have a reduced cross-section of wood, reduced bearing area to support the bolt's pressure on the wood, and reduced material strength due to exposure to the elements.  Moisture has entered the core of the blades through the cracks (on either side) and reached the hollow bore.

The structural reason to say goodbye is that wind turbine blades undergo not just radial load, but thrust.  That thrust is like an airplane propellor, it just pulls backward, not forward.  On a Jake it's probably 300 pounds or so in a really strong wind.  The thrust pressure is spread along the blades, it bends them back a little.  If you were to put that cracked blade back on the shaft, and press back, you would see the cracks spread open.  Thrust loads will encourage the glue joint to open up.  Even with the root fittings clamping it together, the cracks extend way out the span, and I think the axles do too.

Even if you fix the crack now, there is still a load on it, so you have a fatigue mechanism that will just find a new (parallel) path to crack again.

Sorry.