This page describes a simple method of making a two bladed composite propeller. The basic idea is to make an open mold using an existing propeller as a plug. The curved side of the new propeller is made in the mold and the flat side is filled, ground, filed and sanded for the proper shape. This method requires the use of metal bushings (inserts) for propeller bolts instead of drilling holes and cutting fibers in the prop hub. The method was successfully used in making the propellers for the ATE-3 and JT-5 autogyros.
Since the laminating procedure is a pretty messy business I never took photos of the actual work. Instead I am using schematic pictures made using ClarisDraw and form•Z programs.
What are the characteristics of a composite propeller:
1) Easy to fabricate.
What are the drawbacks of a composite propeller:
1) It may be too strong! In an aircraft with retractable gear a belly landing may result in a damaged crankshaft.
THEREFORE, NOTE THE FOLLOWING!
1) Dont use polyester resins, they are not heat resistant. Always use the best heat resistant epoxies.
MAKING THE PROPELLER MOLD.
Make a copy of the propeller flange in steel or aluminium and bolt it
onto the curved side (pusher side) of the prop serving as a plug. In
some cases like VW based engines you can use the original prop flange.
|Laminating the Mold on the Plug|
LAMINATING THE PROPELLER IN THE MOLD:
When the mold has been completed take the following steps to make a composite propeller:
1) Calculate the desired pitch of the propeller at .75 R and at the tip. You may try the various propeller design programs in the net. Adjust the pitch screws as necessary.
|Mounting the propeller on the propeller flange.
The picture below shows the right and wrong method to install the propeller on the flange. It is dangerous to install the propeller so that the thin threaded portion of the bolts will carry all the torque loads. The propeller flange must have long nuts to carry the torque loads. In addition, use conical spring washers under the bolt heads to prevent any play from arising if the propeller shrinks due to an exessively hot flange.
|If you have any comments on this page, please, send me e-mail!
I've just found your composit propeller page and want to tell you my compliments. It is a wonderful page.
prop making ideas. I added a link to your site on our site. I might
suggest you orient the carbon cloth plus and minus 45 degrees for
increased torsional blade stiffness. Also use a metal blade as a mold
when ever possible to take advantage of the increased prop efficiency
afforded by the thinner blade. Thanks for doing that. Many of our
readers need that sort of information.
read you very informative article on the composite prop. I have one
question about post curing. I have been looking for plans or ideas to
build a home made oven for post curing.
live in sunny Australia land of Kangaroos and Koala bears. I have had a
bit of look around your website with great interest even the prop
design section it is amazing to see how easily people pick up on
things. I have been building props for homebuilt aircraft for nearly 20
years in wood and composite I use viynl ester resin for my propellors
good information you have provided the layman well done.
thank you so much to access an interesting page Making a Composite
Propeller from your web site. Although I am do research with prosthetic
limbs and related hardware, I am trying to fabricate a required
flexible L shaped composite strip, I can send a photo later.