Propeller Fabrication

Some people cut pipes lengthwise and use them as blades.

 

It's a pipe dream.

 

.

I'd think one of these curvy shapes would be best.



After Gonzo's post I googled it and apparently people do make propellers out of pipe, but I've only found them for for wind turbines.

http://www.morse-code.com/id182.htm



If a guy was to make one for an ultralight, I would try it out first on an airboat to make sure it might be a good idea.

 

https://www.youtube.com/watch?v=NolB5BbQnBc

I think he means this.

 

I have built two propellers for experimental aircraft and can say that you really need to do some study before doing anything like you are planning. That was the most precise woodworking that I have ever done in a long lifetime. There is no danger of shooting you down as you will not get that high. Wood is the only material that should be considered by an amateur with minimal experience in propellers. Go to this site and look at what home builders are actually doing.

https://groups.yahoo.com/neo/groups/propeller/info

Some ultralights are so near to gliders that they don't need much thrust and so the props are less critical but still need to be done well for decent performance. Aircraft of any kind are far less forgiving than boats where just about anyone can make one that will float.

 

I hear the Wright Bros homemade prop had 90% efficiency, but only at their flying speed.

Just copy that.

 

As part of the 2003 First Flight celebration, VPI, Virginia Tech, made some detailed testing of the Wright Flyer propeller. It tested at a max of 85% which is remarkable considering that most others attempts were pretty sad by comparison. They were one of the very few would be aviators to recognize that pitch was related to distance from the hub and so their props had twist in them.

 

Some friends and I built an electric paraglider in 2003. Flew it on the same day as the folks in Kitty Hawk were flying the Wright Flyer replica - we flew further than they did, but not by much. I found a place in Canada (GSC Systems) that makes ultralight props that are adjustable. You can set the pitch on the ground. That is extremely useful for fine tuning when you are not sure what the optimum pitch should be. The cost was quite low, under $300 I think. It had to be low cost, we had no money.

I'm all for DIY, but in the case of an airborne propeller, either you do it yourself (the right way, out of wood or composites - not using plastic pipe) or you buy one from someone else that knows what they are doing.

 

buying a prop, even a used one in good condition, is a far better option. 300 lb thrust is actually a really big requirment for a small prop.

Many have made wood props, you laminate quality strips of wood with epoxy to a good blank. As stated the carving and shaping becomes critical, but it has been done for many years by home builders. There should be detailed plans available on making your own wood prop, go find them and make one.

wood is the only low cost material that is suitable to build a prop. all others are not strong enough or costs much more or a too difficult to hand work.

good luck.