Prop makers?

So who out there in the prop world is probably the best to work with as far as asking them questions, getting data and getting a prop made fir something that is not the normal run of the mill set up.

As I'm thinking on a direct drive "lawn mower" engine for my prodject it won't be a easy one.

 

You might also inquire of Culver's (Missouri). Wood props, and they have some experience with alternate power since the build one, as well as airframe -- good folks, but the trick is (sometimes) getting them on the phone, so be patient if you call...

 

When is saw this thread a few prop makers came to mind but Culver jumped to the top. Some very nice people at Culver. The lady I spoke with was willing to go above and beyond to help her customers. They are also affordable. Second would be Dana's choice. I have owned one of those props and loved it. Not as easy to setup as say an IVO but a very good quality prop. Then you have IVO. What I like about IVO you can get different size blades in not only length but width. Ivo offers a narrow, standard, and wide blade. This gives one more of a selection of blades to get prop loading just like you want it.

There are many other makers of props but in the small aircraft style using the engines we speak of, these are the makers I would be looking at. If you were talking more on the lines of a VW or Continental ect, I would have a different list.

 

Arrowprop they have direct dirve hubs and props for low hp

 

Propeller design is a classic "garbage in, garbage out" process, so the quality of the end product will be reflective of the quality of the data used as inputs. The better you can quantify the power/rpm curves for the engine, and the drag/speed of the aircraft, the closer they can come to providing a prop that meets your needs.

The reality is that we often don't have good data, and this is where the adjustable props can be very helpful. You might not get the maximum efficiency that you would from a properly designed fixed prop, but you can at least tweak it to improve performance within the constraints of the design envelope of the adjustable unit.

 

^
+1

 

What fly2kads says is spot on. Give any decent prop maker the RIGHT numbers, he will make you a pretty good prop.

Engine hp is very often overstated and will be the biggest unknown if you improvise an engine. The prop makers will know the real hp of off-the-shelf engines. Have a look at Eiffel wood bar props as a crude dyno. Rectangular square edged lengths of wood with a very predictable hp vs rpm requirement. Easy to make yourself.

 

Performance propellor probably makes the best but not the cheapest. Meglin1 here could probably do a good job too.

 

The turd of it is I will be starting with a 17.5hp engine but I'll be putting if I can find one the 20hp crank in, opening up the ports, exhaust will be more open then stock, but I can't quite get a solid number on what that will do to the engine, could get 5 more hp or 10 more hp.

 

When you do your testing, it's probably a good idea to record the barometric pressure, temperature and humidity, so you can compare testing from different days or different aircraft.

 

Good point

 

You are going to have to try more than one propeller. If it is crank driven most likely best to stay with two or four blade wood (blades perpendicular do not have to be in same plane) because wood goes from tip to tip uninterrupted and is usually best for crank driven small engines. But if crank drives a PSRU then you could use a adjustable propeller. The more I am educating myself on fixed pitched props for relatively high rpm low hp engines, the better I am liking multiple blade small chord propellers. Maybe it is just me? But any rate if you go solid wood for prop 2 blade, or more blades, you are going to have to try a few to get it right, there is no way to adjust them and have a propeller that dampens the loads. Fortunately others have gone before so you have a lot of empirical data to study to limit your choices to just a few.

 

Wondering why people always talk about buying props instead of making them. Maybe there's some reason that's not obvious to me?

 

I started carving props for my control line models when I was 12 years old ( 1952) and I still don't know what I am doing carving props. Think its more of a black art

 

Not sure I will ever carve a prop. Would like to but will have to make a carving machine or pick up a cnc machine and bribe a programmer first. If you put your engine on a dyno, then you could have a reasonable chance of carving a prop by hand (chisel and sanding) and getting it right the first time. Otherwise you have to guess your best at the truth from the lies about the power available and it is most likely going to take at least two attempts, probably more to get it right. Talking crank driven props that need the forgiveness of wood to not to crack something. With all the factors involved in sorting out a prop how do you think it will happen correctly the first time? Sure it will work, but you know you are going to want it different. So for those that it fits probably best is http://www.aeromatic.com/ because one and done without all the math.

 

I carved about 6 props for lawn mower type engines. Carving isn't that hard, but yes it might take a few tries.
The prop can be repitched somewhat after rpm and or the flight test.

 

Aeromatic props just don't work, they are tuned to work because they have to balance the centrifugal balance weights with aerodynamic loading. If you look at the blades and the hub there is an offset that this all works on to keep the forces from just making flutter. I think they are cool, but you just can't throw one on. Those forces are tuned to the hp/ rpm of the engine.

 

I've carved props for model airplanes. However, this was rubber power, and I have a rubber stripper, so it was easy to adjust the torque to match the prop and the model. I wonder if it's really necessary to have fancy machinery to carve a prop. Seems like a drawknife, plane, etc. should be sufficient if one uses enough care to make the blades close to identical. But, not having done it on a large scale, I could be completely wrong.

I also wonder why there aren't more homemade carbon fiber props. Seems like the material is so strong that they should be fairly easy to get right.
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There used to be one of those Aeromatic props with just one wooden blade. That way you wouldn't have to make identical blades!
http://www.rexresearch.com/unibladeprop/onebladeprop.htm

I guess they'd be a bit heavier than a regular prop, but maybe not heavier than a variable pitch prop? The mechanism for the single blader could be quite simple, I think.
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NACA TN-212 discusses designing and making wood props. Go to the NTRS server and search for "Simplified propeller design for low-powered airplanes".

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There's also Simplified propellers for low speed home built aircraft by a Mr. Hovey. I think this one is on the web someplace, or used to be.

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I don't know if these are correct about everything, but I know they're out there. I suspect anything by Eugene Larrabee would be correct, but may be too technical.

 

Anyone have a link to the Eiffel club props? I'm getting no where with google.....:ermm: