Hello, I'm doing a little research on DFs to help evaluate the feasibility of using them as a model powerplant. Can some one direct me to some info on ducted fan engines and fan units. I'm trying to find details on engine outputs with fan units. So far I've been digging around on the internet for days without much info. The small bits of information I can find is scattered about. Mainly i'm looking for information on all sizes of nitro DF engines and fans (smallest? Largest? and where you can find these). Also information about power to wieght ratios and speeds on those models like you guys fly. So far i can find some information on .91 sizes. Very little on .46 on JHH's site, no numbers on power. I even seen a .15 (wow). The problem I've found is most sites focus on one powerplant, which is usually a .91. One said 15 lbs of thrust? Anyway I'm more curious about fan sizes smaller that 5" (i'm guessing thats the "sweet spot" size). But I'd love more information on any of them as I'm designing around the engine I'm going to use. Is there a ducted fan site or store that offers various products and information? Any input would help! Thanks

Hi,
I think you will find most d/f fliers experience is of either the 5" Ramtec here in europe
or the Dynamax in the US, the Ramtec suits the OS91 that most people use the best, but the Dynamax appears to allow a slightly smaller inlet to be practical. If you are looking for a smaller fan unit then your best bet would be the Thorpe Brothers here in the UK, I may be wrong but I dont think anyone else produces a suitable unit anymore. Their website www.thorjet.co.uk appears to be down attm but their tel no is +44 1572 822291, they have never been less than helpful so you could give them a call??? Mike

Any takers on power to wieght on the ducted fans? For example.


My model has a _______ engine with a _______ fan unit. My model weighs ## and goes _____ mph. (also try to add a guess at thrust)

So powerplan, wieght, speed, thrust if possible.

This would help me out a lot.

What is an idea power to wieght ratio for a model?

This information would help a lot. Thanks.

Jus10: I know you prefaced your question for glo DF, but most developments & advances in DF of late have been with the electric side. Some examples of those on the market of varying delivery time are:
-WeMoTec :--Midi (90mm class or 3.63in dia), 1200 to 1350 watts, 4.7 to 5.5lbs static thrust
-Schubeler:--DS1 (90mm class), 1200-1500+watts, up to 7lbs thrust
-JePe: --Spider (90mm class, I have no figures)
-WeMoTec: --HW730, HW750(?, check supplier site), up to about 5" diam), 2.3 to 3kw, reportedly up to 14-lbs
-Aeronaut: --TF4000 (about 5" dia)
Also don't forget Kress' RK & JHH's electrified Turbax.

Your question re thrust to weight ratio is, in my opinion, the key for DF. From my own limited experience & postings by others, a T/W of 0.5 to 0.6 means bungee launch & limited vertical performance, T/W of 0.8 to 1.0 will give good vertical performance. A few have attained T/W>1.0, mostly by omitting landing gears, but may not be the case for too long. Max speed depends also on airframe drag besides dynamic thrust. 100 to 120 mph are now routine, with a few hitting 140. Good luck with your survey.

Phil

My JMP Starfire II had an OS.91 engine with a Dynamax fan unit. My model weighed 12.75# and was clocked at 196 mph.
My 1st Miller F-4 had an OS.91 engine with a Dynamax fan unit. My model weighed 16# and went about 115-120 mph.
My 2nd Miller F-4 had an OS.91 engine with a Dynamax fan unit. My model weighed 14.75# and went about 115-120 mph.
My Regal Eagle had an OS.91 engine with a Dynamax fan unit. My model weighed 11.75# and went about 120 mph.

This is perfect... keep it comming if possible!