Jarrah

I just saw this motor, can u put a reglar prop on it for speed planes? I wanted to put it into one of the new Kyosho Kelly Racers. What size prop would be best for speed in this size plane? http://www.kyoshoamerica.com/airplanes/gp/11075B.asp

Cheers

nitro junky

My Feedback: (3)

I was reading a review about the DD and they used a OS. DF engine. [link]http://webpages.charter.net/rcfu/KitReviews/DiamdDust.html[/link] Maybe this can will help you with a prop selection maybe not.

I-Love-Jets

Well, the Kelly racer seems to be designed for moderate speed only considering the balsa wing and balsa stab. That is strong enough for a .70 four stroke at maybe 120 mph but the wing most probably will break using the OS .91 VR-DF engine.

So if you accurately reinforce the wing (strong spar + sheeting) and stab (also firewall, all linkages, maybe also landing gear), I don’t see any problems using about 4.5 HP on this airframe.

Recommended prop size for this airframe to go quite fast would be 9x10. I recommend a carbon fibre copy of the APC 10x10 cut down to 9“ of diameter. Using this prop size involves several advantages:

- the OS will run in its best powerband between 18000 and 22000 rpm
- a 9“ sized diameter prop will prevent prop tip speeds approaching supersonic (that really absorbs peak rpm).
- the prop hub thickness of the APC 10x10 (carbon version) already provides sufficient tensile strength. Thinner hubs would be too unsafe using this engine.

I would like to recommend the JMP 2 tuned pipe which makes the OS run cooler than the BVM DF pipes.

I personally would select an inverted mounting position of the engine.

Here’s addtitional info on the OS ducted fan engine for break-in:

http://www.rcuniverse.com/forum/fb.asp?m=5250897

rmenke

My Feedback: (13)

Jarrah:

You are getting great info regarding your prospective project, especially from "I-Love-Jets". The guys on that side of the pond have much more experience with the fan motors as they are not limited to 200 mph as we are here in the states by AMA. Note that the VRDF used on the diamond dust was nose heavy and it was a 45. You are considering a 91, a bunch more heavy, and more of everything (twice as much except rpm) I suggest you re-evaluate your goals and equipment, or at least start with the basics befor investing a lot of mony into equipment. First, find a source of carbon fiber props for a 10 X 10 that can be cut down to 9 X 10. If you find some at a affordable price, please let me know where and how much, I have two of the engines in the engine cabinet waiting for me to gather experience and equipment for a go faster project, one to learn on, and one hopefully will survive for intended use. The JMP 2 tuned pipe information was priceless to me, a OS VRDF being somethat user friendly makes a big grin come to face. There may be someone somewhere that has taken on a project like this with some success, keep looking, the information gained may save you many hundreds of bucks. Yes, this is going to be a big buck project at the finish line. If I lived down the street from the go-faster guys in Germany, I would not hesitate to go for it, but not with a "dust". If you want to fly something quick, why not start where design and equipment availibility is available, a Q-500 plus Jett or Nelson Q-500 engine, only $400.00 or so for the engine and 150 to 800 for the airframe, props available with a phone call to APC. Remember, you can modify these airframes, like reducing the wing span to 40" (you arn't going for a legal bird). That in itself will put you in the 200 mph range with a good engine. Landing will not be as bad as you think. A formula type airframe would be better looking, but not necessarly much faster. Why I said 40" is cause I have one flying, Jett powered, and its docile landing, just a little faster than the typical Q-500. A Jett 60LX powered version is in the engine cabinet and starting on the workbench, but will begin with a 45" viper wing. I want something that has a good chance of surviving a season or two, and not skid out in pylon turns. Yesssssss, a sneaky one just for the local gang. There is some truth to the old and tretcherous thing!! Regarddless, ENJOY

Jarrah

thankyou every for your replys, they are very helpful and i have been thinking and maybe i wont go for the DF. Seems a little to involved for my first project. The other planes are ok but i really love the look of the kelly racer so i will stick with this airframe, just tone down the speed that i want out of it. Hopefully something round 150mph will be possible? Do you have any suggestions on what motor prop combo would be good for this application. Would the OS 91FX be sutible, id rather not pay $400 for a motor unless i have too haha.

Cheeers

bob27s

My Feedback: (19)

My general suggestion to folks looking for a high powered plane that can exceed 150 mph --- is to build it yourself from scratch/kits/plans. Modifying an ARF is usually not a good option.

With an ARF there are too many variables - by the time you get done stripping the covering off, beefing up the firewall, ensuring the wing structure is suitable or is beefed up, making sure the tail (usually the first thing to fail) is up to the flight loads ----- you might have just as well built the plane in the first place.

Airbike

My Feedback: (6)

Bob, I'm at that stage now, trying to decide to modify the heck out of an existing arf or build from scratch. I just need some suggestions for plans.

My target is to get over 200mph using the old mantra.....power is good, more power is better, too much power is just about right.

I have picked up a used K&B 1.00 DF engine and pipe from a local flyer and then also came across a very good deal at the AMA Convention a few weeks ago for a New in box Rossi .81 DF engine with a short staight exhaust pipe ($120).

Now I can go and modify a Quickie 500 (add wing fillets, carbon/glass the wing as needed, move firewall back and strengthen tail, etc..)or just build something nice. Whats a good speed ship to build? I don't have any foam core cutting equipment so that might limit the choices.
but building from plans is enjoyable to me if I can get some of the fiberglass parts (my mold making skills suck).
Needless to say, I don't have to follow any racing rules, This is just for fun!

Meanwhile, I'll just go and try to stuff 2KW into my electric F5D to keep some adrenalin going...

I-Love-Jets

Hello Airbike,

it turned out that without fully enclosed engine/pipe even a .90 sized powered speed plane will hardly reach real 200 mph.

For that a glass fibre cowling is mandatory to reduce drag and to fully take advantage of a high pitched custom speed prop of 8 to 9“ of diameter.

I-Love-Jets

Just for completion...

Strykaas

Why no spinner [:-] ?

bl10

I don’t think an unmodified Q500 will ever go 200 with an IC engine. Just too much drag. The wing is thick and not the proper planform. The fuse is about as streamlined as a brick. The Vortex, composite wing and tail, Q500 is probably the fastest Q500 around. On a perfect day with a great Nelson pulling a 8.8 x 9.25 (19.6K) APC pylon prop they are hard pressed to break 170. Keep in mind the Nelson or Jett Q500 engines are pretty darn good. A while back some one had a good Q500 with a Rossi Q500 engine on it and it topped out about 150. The largest prop it would pull was a 8.8 x 8.5 and even with that was about 2k down from the Nelson.

The current crop of F3D (40 size FAI) will exceed 200 in level flight but not by much. These airframes do conform to FAI rules but are streamlined to the nth degree including, in most cases, retracts.

If I really wanted to go fast, say 210 to 220, I would start with a proven F3D airframe like a Bruce Dechastal EVO or one of Harold Sattler’s planes. Add a MB modified by machining a revised head to lower compression (FAI rules do not allow Nitro) so about 30% nitro could be run. Probably run the MB “fat” full pipe but that would be subject to experiment. Get a bunch of spare parts because at these HP and RPM levels things break. Next I would get some prop molds and start experimenting with continuous strand carbon props. (These are the only props that will stand up to the 35K unload rpm of the MB that includes the current crop of APC Q40 props). I would not cut down or modify existing props as the efficiency and strength would probably be destroyed.

Faster yet (I think) would be one of the current crop of Q40 airframes modified to accept the same MB and Pipe in a fully cowled configuration with retracts or no gear hand launch (catapult). It would probably be 5 to 10 mph faster.

The ultimate, in my opinion, would be a Q40 wing and Stab mounted on a fuse design similar to the current crop of F2A U-control speed planes.

I don’t know how fast an IC powered plane is capable of. I just looked at the thread for the 2006 German Speed Cup and top speed with a 91 was 222.
http://www.rcuniverse.com/forum/m_37...tm.htm#4930340

In the German Speed contest the 91’s were clearly faster than the 40’s. I am not familiar with the engines used. The fasted F3D plane was 208 the fastest 91 was 222. I’m not convinced with all the development done on the F3D engine lately that it doesn’t have the potential to go as fast as a 91.

Every one talks about how easy it is to go fast. I disagree, average 428 Q500 speeds are 155 to 165, Q40 speeds are 180 to 190 and F3D speeds are 190 to 205. The best F3D in the above referenced contest was 208. I suspect the guys in that contest spent a lot of time and MONEY to get the speed they did. Hope you notice there are no DD, Magum, Rifle or any other inexpensive ARF’s in the field. You need purpose built engines and planes to truly go fast.

Just my opinion

Barry

Airbike

My Feedback: (6)

Hi Barry,

Your opinion is much appreciated. I would definitely be modifying the Q500 to resemble one of the German speed planes. Fully enclosed engine and pipe, wing fillets to the fuse, strengthen everything as needed, maybe retracts, etc.

If I had the skills like some of the Dynamic Soaring guys that are laying up their own full carbon wings & fuse to withstand whatever G's they're pulling (60+G's??) I'd be designing a composite speed plane.

I'm up for scratch building from plans but find it easier mentally to just bash a kit or arf.

The good thing is that I have no racing rules to follow. Even the German speed planes had to follow some rules for their competition. I'm just a hack.

As for props, thats another area I'm limited in. I was planning on cutting down some wood props from 11x8 to a 9x8 or whatever testing would get the engine to 22 to 24K. I couldn't find any carbon props in sizes larger than the Q40 props. I don't want to order custom props from Europe. I remember that a lot of racers used to make or customize wood props before the carbon props were available, so I hope that would be a way to go for me.

Everytime I see you guys (Scott, Lee, Mathias?, haven't seen you at Whittier for a while) practicing, I want to go fast too.

I'll try to create something with what I have to work with. Hope to see ya sometime.

Dan

bl10

Dan:
I was at Whittier a couple of times prior the PHX Winterfest, Sorry I missed you.

If you’re going to use an ARF Q500 wood wing on your plane I would go with the Viper wing. It is much stronger than the Predator wing. Super T makes a laser cut Q500 fuse kit for the Viper wing. It is an excellent design and very strong. The nose is already very short. I would mount the engine as much like we do in Q500 / Q40. They definitely run better for us mounted a little below horizontal as opposed to vertical Again look at the U-control FAI speed planes. You can still cowl the whole thing in. If you cut the wing down I would still use the Viper wing tips, they are a good design.

As far as RPM goes it all depends on engine exhaust timing. Nelson and Jett Q500 engines use about 166 degrees of exhaust timing and we prop them to turn a little above 19k on the ground and about 22k in the air. The Q40 engines have about 200 degrees of exhaust timing and we prop them to turn about 23.5k to 24K on the ground and about 27k in the air. I don’t know what the exhaust timing of your engines is but you can use the above as a reference. If you are going to modify an existing wood prop Darrol Cady has a good description of the process on his web site. You will see from his description there is much more involved than just cutting the dia down. Be very careful about the grain. If it’s not pretty straight you stand a chance of throwing a blade. Something else to keep in mind is prop tip speed. If you get anywhere close to super sonic, actually anything above 70% if super sonic is bad, prop efficiency drops way off and drag goes way up. The U-control speed board has a pretty good spread sheet on this. At Q40 RPM you can’t go much past 7.5” to 8” dia with out approaching to high tip speed. Generally speaking you want high pitch with small dia.

I would keep a close check on the lower end of the K&B. I know there were some problems with broken rods.

Good Luck

Barry

I-Love-Jets

Yes, in addition the good .60s RIRE engines are also considerable faster than modified MB.40 Profi FAI engines.



Here's a list of potential SpeedCup engines. Some of these types are used since about 25 years successfully.

http://www.rcuniverse.com/forum/m_52..._1/key_/tm.htm



Well, an unmodified OPS .60 VAE does eat a modified MB .40 (latest version) for breakfast. [sm=tongue_smile.gif]



Why disagreeing, Barry? Just buy one of those 200 mph deltas... [sm=wink_smile.gif]