I have a 1/4 DR1 Fokker that Im going to put a xoar ww1 prop on. It has a dle 30 and now weighs 16lbs. Options are a 20x6 or a 20x8. The larger is the reccommended max for this engine so I dont want to over do it especially in a slower flying ww1 plane.

20 X 6. The lower pitch will not overload the engine, and will give better pulling power at the lower speed.
This for all of the same reasons that full size constant speed props have a lower pitch for takeoff and climb (at the lower speeds in those situations) then go to a high pitch for high speed cruise. Considering the drag of the DR1, I'd recommend staying with the lower pitch. Of course, you'll probably try the 20 X 8 anyway. .

Dash

18X10 would probably do best on a 30cc engine. A 38cc or above would do better with a 20" prop, but your going to have to make the choice. Sometimes the "best" prop for a plane with a particular engine will require experimentation. Xoar Simitars in those sizes are'nt that expensive to experiment with, but in general, the 18" prop should be fine for a 30cc engine.

Thanks, you guys are both reading my mind. Funny, it has an 18x10 on it now but not a scrimitar. Reg xoar. The 20x6 was my next choice but dont want to load the engine too much. Then again I rarely use more than 1/3 throttle in flight. I suppose which ever one would make keeping even smooth airspeed on landing is the one that interests me most. Flown this one for a whole season now but as anyone with ww1 exp knows they can all be hairy!!!

I have found lower pitch larger dia works better on bipes. I do try different prop sizes until I am happy with the performance of the specific plane. When I change pitch I usually change dia to keep the rpm's as close as possible to recommended prop size rpm. Up in pitch down in dia, up in dia down in pitch. Once in a while just more pitch makes the difference to better performance.

I have been running a 20x6 semi simitar prop from RedWing RC on my DLE 30 and the engine loves it . WOT RPM's are around 7800 and a lot of power . I had been using a Zoar 19x8 which worked very well but the RedWing 20x6 is even better . I am not sure who makes the prop for RedWing RC or how the Redwing will compare to the Zoar WW1 prop. But the DLE should be able to handle it after a good break in on a 19x8.

I have a couple of the Scimitar style xoar props and found that they shake a lot. I also found that my DLE 30 shook more than the other DLE engines I have.

I agree with low pitch as well. I had my DLE 30 in a BUSA tripe. Not very long though as I lost it to radio failure. I contribute that to the vibration.

I have experienced some "more than usual vibrations" on the DLE 30 during initial tuning and break in on all of my 30's . I balance all of my props so that the will stay in any position you put them in on the balancer . So prop induced vibration on mine didn't seem to be the cause of the engine vibration . Through prop swapping from engine to engine on other DLE 30's , some with much more run time , I was able to pinpoint the vibration to state of tune and break in on each engine. After they all had a few gallons of fuel and some more retuning along the way the vibrations lessened to what I determined as a normal level . The engine with the most run time (probably 10 gallons of fuel ) is now and extremely smooth running and very strong engine . On that engine I have seen tach readings over 8200 RPM with the Redwing 20x 6 prop. A note on the tuning of the DLE 30 or any DLE engine . Be sure to use an NGK CM6 plug gapped around .020 " and set the ignition timing between 28 and 32 BTDC . ALL DLE engines I have checked new out of the box have had the timing set too high ,some as high as 45 BTDC . I feel that the incorrect timing makes the engine more difficult to get through the engine break in and tuning stages. Now I set the timing and discard the DLE spark plug as soon as I open the engine box .

CK1,

Great info on the DLE 30. I just ordered one for my new P51. First gasser. I know what TDC (top dead center) means but what is BTDC? And what prop (19X8) would you use to break in the engine for the first gallon of fuel. BTW, I would do the break in while flying the plane, never on a test stand. Thanks.

Gene

Gene ,
I would tune it and break it in flying on a Xoar 19x8 prop beach or laminated ,although I find that the laminated is a much more efficient prop and is more resistant to hub crush from tightening prop bolts . BTDC = before top dead center.

Hmmm....my 30 runs almost completely vibration free. Must have a good one. Now for the dumb question ...are you actually using a degree wheel for timing?

CK1,

Thanks.

Jeff, I have found most people have widely differing perceptions of what levels of vibration are considered normal or vibration free . You may be the lucky one that got the smooth engine we all want . . Yes I used an actual degree wheel.

I have a 20x6 on a DLE 30 powered H-9 Taylorcraft. Runs very happy and is about 5 years old. Plenty fast and outstanding pull.