OS 91 VRDF experts wanted
05-26-2014, 06:34 AM
#103
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Airfoil thickness not calculated. It is cut and try, Maybe 10% at center. Brake in prop was a zinger 12 X 6 cut to 10 x 6. RPM around 17500.
Launch with nose at about 30 degrees high, right wing down about 20 degrees, just let go. Landings are long, flat, and smooth with skid on grass.
Launch with nose at about 30 degrees high, right wing down about 20 degrees, just let go. Landings are long, flat, and smooth with skid on grass.
07-08-2014, 02:59 PM
#104
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Usually a tuned piped needs a longer header pipe, upwards of several inches. You have the pipe directly to the engine. Add say six inches to the header then cut 1/4 inch off it until rpm's quit rising. It is tuning and needs to be done to each engine/pipe combo individually. There is no set length for a given setup as even glow plug or fuel can change it. Also you would normally run a glow plug with a cooler heat range.
07-08-2014, 07:21 PM
#105
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Usually a tuned piped needs a longer header pipe, upwards of several inches. You have the pipe directly to the engine. Add say six inches to the header then cut 1/4 inch off it until rpm's quit rising. It is tuning and needs to be done to each engine/pipe combo individually. There is no set length for a given setup as even glow plug or fuel can change it. Also you would normally run a glow plug with a cooler heat range.
If you're saying that the prop load on the bench was too much for static running with the pipe, I'd agree with that from the description - overheating on bench running. But the fact that it gets on step once unloaded in the air and stays there indicates the system is set up okay for speed flying. You don't tune to maximum ground rpm (on the flight prop) for best flight speed, but that technique is appropriate to aerobatics where the boost is more needed under load such as in climb or accelerating from low airspeeds. Also pretty much bang on for sport flying. But for higher timed engines and fast fight you just optimized the system for a bigger prop. So to bench run and tune the pipe system you reduce the prop load a bit and go for peak rpm. This simulates the unloaded condition in the air and gets you closer to optimum.
06-27-2016, 07:24 PM
#106
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I am hoping there are few of you that are still doing this kind of setup. So here is what I am after.
I am building a silver warbird pylon racer and got one of these engines for a steal so I thought I would give it a shot. I am after 120-125mph on a 40size Mig-3. This is the data that I have found from others in my area. A fellow racer is using a 11-9 spinning 16000ish and is too fast for the gold class which is 150mph. I have tried a 13x8 cut down to a 11-8 ( I had one to do this to) and i got 13800rpms with 10% fuel and 4turns on the needle very rich setting at this point. I have found that it seems that 20-22% oil and 10-20% fuel would be max any other ideas, thoughts, and/or input would be great.
thanks
I am building a silver warbird pylon racer and got one of these engines for a steal so I thought I would give it a shot. I am after 120-125mph on a 40size Mig-3. This is the data that I have found from others in my area. A fellow racer is using a 11-9 spinning 16000ish and is too fast for the gold class which is 150mph. I have tried a 13x8 cut down to a 11-8 ( I had one to do this to) and i got 13800rpms with 10% fuel and 4turns on the needle very rich setting at this point. I have found that it seems that 20-22% oil and 10-20% fuel would be max any other ideas, thoughts, and/or input would be great.
thanks
06-28-2016, 06:55 PM
#107
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Too large of a diameter prop 10" is the max diameter depending on the air frame smaller is better.
This motor should be spinning must faster 18-21K is where the real power is produced.
20-25% oil
This motor should be spinning must faster 18-21K is where the real power is produced.
20-25% oil
An APC 10-10 isn't meant to spin that fast either - 19k tops according to APC safety warnings (190,000 divided by diameter). Cutting down a wooden 11" prop is a good idea for bench running so you have lots of hub strength. Not ideal for a flight prop but it will get you in the air. Also note that for setting up the pipe is it normal practice to use your intended flight prop cut to 85% diameter to allow the engine to achieve flight rpm on the bench and thus allow you to set up the pipe to optimum length on the bench.
It is standard practice in prop speed applications for 15cc engines to run CF props only of no more than 9" diameter, typically in the 9-10 range, or smaller/higher pitch.
Sources:
RocketRob (CF 9-10 based on trimmed/reshaped APC 10-10 I believe)
These two have props designed for AMA D C/L speed which are pretty much what you want:
Steve Wilk / Eliminator props
Mike Hazel / ZZ Prop
and there are European sources at EU $18+ per prop and shipping [:-]
It is standard practice in prop speed applications for 15cc engines to run CF props only of no more than 9" diameter, typically in the 9-10 range, or smaller/higher pitch.
Sources:
RocketRob (CF 9-10 based on trimmed/reshaped APC 10-10 I believe)
These two have props designed for AMA D C/L speed which are pretty much what you want:
Steve Wilk / Eliminator props
Mike Hazel / ZZ Prop
and there are European sources at EU $18+ per prop and shipping [:-]
Last edited by iron eagel; 06-28-2016 at 06:59 PM.
