Propellers for the DE

[MrG]

Im am using Frank form Performance Props in TX and i need to order this week
A couple questions
1: Are we using dowels ? what size and looks like 5/16th bolts?
2: where do you get the dowels if needed
3: do we glue in the dowels

I have a 1919 cc if you used Frank what prop config and HP do you have and does it work ok
any info would be good

Its a long way to ship a prop to Australia and or get another made love some info if you have a
DE and what setup you have, would love to get it right the first time.

[Tom H]

Mr G, here is some experience we had/are having with our DE Stubby:

Engine is Great Plains 2180 w/ Force One Hub.

We currently have a Sterba 62x26, which we modified by shaving a small wedge from the trailing edge.  The wedge starts at the tip and is about 6" long.  At the tip it was 1/4" wide, tapering to zero at the 6" mark, and then the blade was re-contoured and balanced.  The performance improved from the original, and flies great with one person.  Wide open static is 3150 rpm, climbs about the same rpm at 400+ fpm average.  Cruise is about 75 mph at 3000 rpm.

We purchased a prop from Frank, he suggested 60x24.  We tested it, but it seems too low a pitch since it statics at 3400, climb is not much improved, cruise at 75 requires way more rpm.  Full throttle rpm at level exceeds the engine red line of 3600.

Frank thinks that the Sterba may be closer to a 28 pitch, per his methods, based on our performance numbers.  He is now building a 62x26 prop for us, which he thinks will be a slightly less pitch than our Sterba, but more than his first prop that we tried.  The diameter is larger, but there is an option to trim it shorter if it makes noise or vibration.

There are other design parameters from one prop maker to another of a prop that are not easily quantified, such as blade profile, thickness, width, material properties, etc., so it is hard to make clear comparisons.

I believe this next prop from Frank will be real close to what we want, which is a stronger climb to try to carry a second person.  Don't worry, I'll report the results.

I don't know if this defines the right prop selection for a 1919 engine, but may help.

[Sam Buchanan]

You might consider a ground-adjustable prop since it is so difficult to return a prop for remake.

Years ago I flew an IVO prop that had adjustable composite blades. It worked nicely on my Super Koala and the pitch could be changed in a matter of minutes.

[MrG]

@ Tom
Well least Frank is getting better with practise  - all info is good info, hardest thing for me is guessing the HP rating
Least if prop is wrong and only needs a trim there is a guy in Queensland that could do that if needed - thou Frank
is cheaper option even if i need a 2nd one sent over - good info  and guess he only gets better with each prop made
Im guessing you have 80hp  same as mates Onex with same engine, 
 
@Sam
i did ask Leonard and he said dont use - only company said they would try one was Bollie here in Australia
but would be there first and around $1800 (had to make the reverse blades ) they do nice props thou
If Paul was a bit closer flying and wanted to do same that would of got cost down a bit and gone that way

Looks like i just have to suck it up and try one - least i get to go flying  Thanks guys  good info

[Tom H]

Mr G, the DE Stubby engine is a Great Plains 2180, w/ Force One Hub, rated 75 hp at 3600 rpm.  I have not done anything to verify that number, though.

[Steve]

Mr G, the DE Stubby engine is a Great Plains 2180, w/ Force One Hub, rated 75 hp at 3600 rpm.  I have not done anything to verify that number, though.

This is a good point for me to recount that Tom was the first Eagler to try testing an engine with the Wood Bar Dyno (see Downloads, Forum Toolbar tab) and remind that knowing engine HP is vital to the Prop Maker's decisions...

On the 4 cyl engines that require a bigger bar the woodworking is simple - MrG the ball is in your court...

[MrG]

Morning
the maths behind the prop (scary) it nearly makes we want to dyno the engine to find the HP  
guessing engine HP is a science in its own - for the $150 it may be the best way to get the correct prop 
Next door neighbour built a jodel and took 4 props to get it right - The Hoffmann prop is still on that plane

[Tom H]

Finally got a flyable day to test the new Performance Prop 62x26 on DE Stubby.

Here is a summary of the testing, essentially what I sent to Frank Johnson at PP:


2180 Great Planes engine, about 75 hp at 3600 rpm, per the GP manual.



Temps were mid 40's, dew point 34 degF.  Field elevation around 700 ft MSL.



Static pull tests were done.  Be advised that none of the instruments we used were certified, but they are the same ones used in all our testing, and I believe they are fairly accurate.



RPM     pounds pull
2500    170
2750    185
3000    200
3070    235    This was full throttle.


Take off acceleration was better than any previous prop.  Lift off was sooner than any other prop.  Climb was way better than any previous.  It looked like a climb from Joe Spencer's Putt-Putt video. 



Several test climbs showed rpm about 3200 and climb rate between 700 - 1000 fpm.  Previous Sterba 62x26 gave 3140 rpm at around 500-600 fpm.


Level cruise at 3000 rpm was 80 mph (5 mph more than before), 3100 gave 84, 3200 maybe 86.  Wide open throttle was 3400 rpm at 90-92 mph.

Two others of our group flew it and were similarly impressed with the improvements.



Have to keep in mind that this was in very cool temps, and may degrade in the summer heat.  But, I have flown the airplane enough to know it is performing much better.


Prop seems balanced well, no vibration.  No tip noise/vibration.


Overall the rpms were maybe a bit lower than Frank and I were trying for.  I wonder, if slightly higher rpms across the board would result in even better climb, but maybe lose some cruise.



But, at this point, we don't want to mess with a good thing by doing any other mods to the prop.  We'll try to fly it a bit more for further evaluation, then send it back for final finishing.

If you have any doubts, this is an endorsement for Performance Propellers.  No kick-back yet, though.

[MrG]

Tom you are a legend 
that looks pretty good  i would be very happy with that 
Ill give Frank a ring and thanks for the feedback