The Woodshop Shed
home << Woodworking << auto airplane propeller rework

Airplane propeller rework
Furnished content.
(from Lumberjocks.com)


Airplane  propeller  reworkBeen a while since I've been here, too many other projects to do much woodworking, but some might find this interesting.I've owned my Hatz biplane for about a year and a half now. It originally came with a metal propeller, but it wasn't quite matched to the plane and for various reasons I wanted a wood prop so I bought one, custom made to my specs. The new prop is birch with a polyurethane leading edge for abrasion protection. After testing, it still wasn't quite right… it needed to have the pitch (the theoretical distance it moves forward in one revolution, 47” in this case) reduced, kind of like downshifting a car to a lower gear. It was better, but still not quite right, so I decided to make the final adjustment(s) myself, bringing the pitch down to 44”.A metal prop can be adjusted simply by twisting it, but for a wood prop the pitch can be reduced (but not increased) by shaving a bit of material off the back face trailing edge of the blades. The leading edge and front face are untouched. It's a tiny amount, which varies by where you are on the blade, from .014” at the tip to .075” 12” from the hub… and it needs to be accurate. Of course I practiced on a scrap pine board first!The modification starts with precise saw cuts 3” apart to establish the depth. I used one of Dad's old Zona saws, to which I clamped an aluminum strip, which I adjusted with a dial caliper to set how far the teeth protruded. I then used an orbital sander to sand the back face down until the cuts disappeared. An orbital sander really isn't made for heavy material removal so it's slow, but it makes it less likely to accidentally take off too much. Thinning the blade leaves the trailing edge too sharp, so I rounded it back with a scraper, in the process making the blade slightly narrower.After final sanding, 5 coats of rattle can polyurethane, checking the balance and adjusting it with a bit more varnish on the light side, then I put it back on the plane for further testing. It's considerably improved, it turns about 75 rpm faster and the plane performs better. It's now “good enough” but there may be room for further improvement, I need to do more testing first. If I do rework it again I'll likely trim a bit from the diameter to get the rpms up rather than reducing the pitch any more.



Read more here


edit: Woodworking/auto___airplane_propeller_rework.wikieditish...

Password:
Title:
Body:
Link | Image | Paragraph | BR | Return | Create Amazon link | Technorati tag
Technorati tag?:
Delete this item?:
Treat as new?:
Make old?:
home << Woodworking << auto airplane propeller rework