Thread: Heine replica
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Old 07-05-2014, 02:11 PM   #5
maxim08
 
Join Date: Aug 2009
Posts: 23
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Hi David, nice to see you 'over here' on woodenpropeller.

Yes, that's me on the Aerodrome and much of the technique was shown there but I will do a quick recap for others.

Honduran mahogany is still available in Canada although a restricted wood in the US. It can be found masquerading as 'Central American' mahogany. I am fortunate to know a very good cabinetmaker who has helped greatly by selecting much of the wood for me. In Canada the difficult to get species is white Ash. A nation wide infestation of the Emerald Ash Borer beetle has decimated the species with massive culling and burning taking place in an attempt to slow down this invasive species from Asia. The next prop will use Birch instead of Ash, one of the traditional German prop woods.

I have been using West Systems 105 epoxy with their slowest hardener, #206. While WS recommend fillers be added for laminating, I declined due to the whitish colour that they add to the glue line.

I laminate on pair of boards at a time with a 24 hour cure between. It is slow, 7 days to glue 8 laminations, but it is safe and helps to ensure that each lamination is aligned correctly to the next.

The basic process involves wetting the back of the top lamination using a flexible autobody spreader to ensure an even coat. Next comes the bottom layer which is treated the same followed by re-coating the back of the top board. The WS eopxy has quite low viscosity and it flows out quickly and is absorbed quickly into the wood. That is the reason for the reapplication to the first board which ensures plenty of epoxy. The curse of laminating is a glue void. If you find one, the prop is scrap unless you plane off everything above and start over. Trust me, with the price of wood and the difficulty in finding boards large enough, I use lots of glue!

I have never grooved or deliberately raised the grain when making laminated wing spars, but the original Heines that I have inspected all show definite tooth marks between layers. Unfortunately no picture. What I used was a fine tooth dovetail saw that had symmetrical teeth ie identical tooth angle both directions. I grooved each board with overlapping strokes and quite a bit of force pulling the blade sideways toward myself. When grooved, I run a scraper lightly over to knock the peaks off the grooves as I don't want them to collapse into the grooves when clamped.

I use moderate/strong clamping force. WS does not have as good gap filling abilities as T-88 and by pre-wetting the boards I can avoid dry glue-ups.



The above clamping rig is really for clamping 28' spars, so the 2.8m prop is easy.

Note that I responded to your PM. I hope that the above is of interest to you even if it took me a month to see your note!

All the best,
john
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