Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Extreme Props


Old 02-07-2006, 01:47 PM
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Default Extreme Props

Hey Fast Prop People,

What's the most extreme prop situation that anyone out there has come across? As there have been some mention of planes in the ~200 mph range, it seems that those props must really be something special. As a curious guy who's always looking for the next RC project, I got to thinking about what this high speed really means.

I was looking at two specific situations with:
1) a 5 x 6 prop turning at 35.2 kRPM producing 1.81 lb of thrust at 200 mph and
2) a 5.5 x 6.5 prop turning at 33.0 kRPM producing 2.37 lb of thrust at 203 mph.

I came up with those numbers from propeller theory from one of my engineering courses but I don't think those equations were meant for such small props turning at such high RPM. Has anyone out there spun a prop this fast?

I've looked at props from Graupner, APC, and AeroNaut but haven't found either of these two. There doens't seem to be a very broad selection in the 5 - 6 in prop range. I'm also not sure what the max manufacturer RPM rating is for those props.

Has anyone clipped a high-speed prop? I suppose that I could cut down the Graupner 6.5 x 6.5 to 5.5 x 6.5 and do some precision balancing afterwards. This may cost some efficiency though...

So, for those who don't read long posts:

- Are there any 5.5 x 6.5 props out there that can take 33,000 RPM?

- Where can I get one?

-- Thanks, Ian

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Old 02-07-2006, 02:48 PM
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Default RE: Extreme Props

Hey there...... interesting post.

First - word of caution. There are VERY few commerically available props capable of the rpms and loads you noted.

When you get over 25K rpm, even in those 1/2A and old QM15 sizes, you want VERY good quality wood props, and preferably carbon fiber/glass props.

Two sources I have handy that may have what you are looking for - will require follow up contact to confirm they have something along those lines.

[link=http://pages.prodigy.net/gcleveland_grsmodels/_import/pages.prodigy.net/gcleveland_grsmodels/index6.html]GRS down in Louisiana[/link]. They are big into CL speed, combat, and generally fast little engines

The other is [link=http://www.supercoolprops.com/]SuperCool[/link] over in Australia.

Look around for other links to CL speed and combat specialty shops and suppliers. There are a handful out there. They all will offer or have links to suppliers for props similar to what you are looking for.

Use great care in modifying props. Be sure what you are starting with has a hub and blade design up to the task. Usually a larger prop. Then work from there (mainly refering to wood props).

There are very few prop driven r/c models that can reach the 200 mph range. Although not impossible, it takes a good deal of power, planning and hard work to get there.
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Old 02-07-2006, 06:33 PM
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Default RE: Extreme Props

You should also check out the F5D stuff (electric pylon). I'm running apc props up to around 40k.

My Excite F5D is turning apc 4.75x4.75 clipped down to just under 4.5 dia at about 39500 or so. Motor pulls a little over 100A and the batttery (8 cell IB3800 or 10 cell GP2200) is good for only about 2 minutes.

The F5D airframes are pretty low drag and sized only big enough for the competition rules for wing loading. I'm not sure, but I don't think they are running up at 200mph during the races. Perhaps with a high pitch prop and a HUGH dive, they might break the 200 mark.

You might try the High Performance Forum at RCGroups.com They have some sicko's trying to stuff 3 KW of power into gliders

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