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bwillis
11-15-2011, 02:26 AM
What glue and prep techniques are best to use for laminating propellers. I've been told that dampening wood with water and letting it dry to raise the grain is a good practice. Is this true?

KosPilot
12-04-2011, 11:41 PM
I have the same question! With this rate of answers, we may have to wait a while... ;) (see other post)

Anyways, since some of the old manufacturers of propellers started as furniture carpenters, maybe some old trade knowledge is still available if looking in that direction.

Dave
12-05-2011, 06:51 AM
Yeah, I think you'll find this is more of a propeller collecting forum than it is one of manufacturing or of design theory.

bhunt
12-12-2011, 11:25 PM
Many of the experimental prop makers are using hardware variety resorcinol glue or a high grade epoxy such as the West System. Some manufacturers use a cascophen G1131 two part resorcinol glue which is much more expensive and can only be purchased in large quantities. Wood should be straight grained and quarter sawn is best. Slope of grain should be no less than 1 to 10. The best prep for the wood is to plane the wood to open the pores the same day as gluing it. Don't sand it and don't put water on it to try to raise the grain. Hard woods such as maple, birch, oak and walnut are satisfactory for props. This subject could take 4 or 5 pages to fully explain. Hope this helps you get started.
I agree this is not a subject for this forum. You can send me a private message if you need more info.
Thanks.
Bob

Garuda
06-19-2012, 08:51 AM
Hi guys,

In addition to Bob's excellent response, I did a lot of research work on such issues when I was researching the Garuda propeller, of which I am making a replica.

Many, but not all propellers were planed with a toothing plane, which helps to increase the surface area of the planed surface, and removes the compressed, smooth surface left by machines such as jointers and thickness planers. I have also found that compressed air can help to remove dust etc from the grain of the timber, although a freshly planed surface probably only requires removal of excess debris simply by brushing.

I hope this is also of some help!

Regards,

David.

bwillis
06-19-2012, 06:16 PM
Thanks to each of you for you rinsites. I have been laminating sled runners for dog mushers for some 40 years. I have to admit that I do have some delamination problems. I want to solve these for the sleds of course but must solve it before I build propellers. The idea of wetting the surfaces to raise the grain came from Chad Willie of Rhinebeck. In the mean time I visited Iceland where they have very active and skilled aircraft builders. The propeller guy said that glue starved joints are a problem with delamination and to solve that when using West System for instance he applies a layer of resin to each surface and then as it soaks in applies another layer mixed with micro fibers to one surface before clamping. I haven't tried this yet but it does make sense to me.

Garuda
06-19-2012, 10:10 PM
You're very welcome. It's great that you find the advice helpful.

It's interesting that you've been building sled runners for 40 years or so. What types of aeroplanes are they building in Iceland? The propeller builder is correct. A joint which is starved of glue will potentially be a weak joint. A common mistake when laminating propellers is to clamp the laminations too tightly. Unfortunately the tighter the joint is clamped, the less glue will be in the finished glue joint. The glue is actually stronger that the timber, and laminations must not be tightened excessively. I also apply the glue to each surface and allow it to soak into the timber. Although I don't use West Systems epoxy, it is available here, and is a common choice. I think the modern epoxy glues are all very similar to each other, and are certainly far superior to glues used in the past. The micro fibres certainly would make a difference.

Regards,

David.

bwillis
06-20-2012, 02:47 AM
Regarding the homebuilts in Iceland - I saw PA-12 replicas, Stits biplanes, a couple French wooden trainers, a British WWII plywood twin, a Baby Great Lakes and a cabin Waco. Wooden props seem to be the first choice. One fellow claims 145 mph with his 150 hp tripacer with his custom 3 blade wood prop. Another with an L-4 (WWII observation plane, American cub variant brought over from Germany) claims his wooden prop flexes at high power settings to give a flater pitch, sort of contant speed. I flew it and with a 90 hp cont. it really performs with two normal size guys in it. Any thoughts on shape, cord or pitch for performance. Oh yes, The builder of the three blade has a home made router set up for copying blades. It was basically a three dimensional box set up on steel rails with pullys for wheels and a plastic knob that was in alignment with a router blade. The knob was passed over the pattern and the router made a copy on a blank. He swamped ends with the blank and cut both ends identical. I imagine this is old stuff many of you but it was exciting to me.

dairwin
06-24-2012, 06:58 PM
David/Bob,

Can you advise on what glue you are using? I understand that Resorcinol is used, but I can not find a supplier in the UK?

Regards,

David

Garuda
06-24-2012, 10:09 PM
Hi David,

I use Techniglue, which may not be available in the UK, since it is made here in Australia. I understand that other adhesives such as West Systems are very similar to Techniglue. The only difference I am aware of is that the Techniglue already has a filler added, which I wanted because I use a system of adding surface area to the glue surfaces, in very much the same way as many of the original propellors were planed with toothing planes. Some other adhesives such as West Systems need to have the filler added, if required.

Regards,

David.

dairwin
06-26-2012, 02:20 PM
Hi David,

Thanks for the info. I can not find a UK supplier of Techniglue, but have found a West Systems supplier.

Regards,

David

Garuda
06-27-2012, 12:27 PM
Hi David,

You're very welcome! I don't think you will be disappointed with West Systems adhesive. Although I haven't used it, my understanding is that it is very much the same as Techniglue, and a variety of other adhesives. The only difference I am aware of is that if you require filler with the West Systems glue you have to add it manually, whereas Techniglue already has it in the mixture. I decided that slight, or even more substantial gaps in the joints are inevitable, and in some cases such as toothing plane grooves (or a very close substitute, as I have devised, since toothing planes are not as readily available as they once were) are added intentionally. The filler will ensure that any such gaps, whether added intentionally or not will not result in an inferior joint. If you choose to use the West Systems epoxy you will have more flexibility, since you will have the choice of adding filler if you deem it necessary, or omitting it if you feel it not to be necessary.

I am exceptionally happy with Techniglue, and I'm sure you will find the West Systems epoxy to be just as good. Interestingly, I have talked to several other builders who have also decided to use Techniglue, and have not heard any bad reports about it.

Regards,

David.

dairwin
06-27-2012, 04:08 PM
Hello David,

Thank you for your detailed answer David, I very much appreciate your experienced opinion.

I have never fabricated a propeller before and consequently, these types of epoxy(?) glues are new to me for this application.

The filler used for the West Systems; from reading the web and viewing a video, I understand the filler is a thicker mix containing a powder/filler component when one mixes resin and hardener.

Is there a specific brand number of West System epoxy I should be considering for a propeller (given the dynamics of propellers), and what filler type?

Thanks,

David

Garuda
06-27-2012, 11:42 PM
You're very welcome David. I have some experience, and am trying to become an expert WW1 propeller builder, but I'm just like you really, asking people and trying to learn as much as I possibly can.

I think you're right, they are epoxy adhesives, as far as I know. I don't know which specific glue and filler you should use. I could go to the fibreglass supplies shop and ask the owner. I have heard that they all have very similar properties to each other, and the modern two part epoxies are stronger than the timber, so it's very difficult to go wrong I would suggest. The only real danger is adding too much hardener, which results in a glue which ironically never sets properly. If measured carefully this will never be an issue.

I grew up in England, and usually spell propeller with an or at the end. I'm not sure if I learned this spelling at school or if I just made it up somehow. How do you spell propeller over there?

Regards,

David.