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

PROP SIZE FOR OS MAX 40

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Old 11-07-2008, 04:03 PM
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newflyer
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Default PROP SIZE FOR OS MAX 40

I bought a Diamond Dust from a guy here on RCU and it has a old OS .40 MAX with a APC 10x6" prop on it. The motor has a rear exhaust with a tuned pipe on it. I'm not sure but I thought that the .40 MAX would need a 9x8" or so for top speed. I have never owned a Diamond Dust but seen several fly before. Could someone tell me where the CG is suppost to be and maybe what a good throw would be for the elavon's to start out with. I will be putting Hitec 5645 servos on the Dust and I am sure that they will be strong enough for it. I have never seen a OS .40 max with a rear exhaust before. Could it have been a duct fan motor? I have a Whiplash that I bought from a guy a couple years ago and I will be getting it ready to fly this winter so I thought the Diamond Dust would be good to fly first to get me use to the Whiplash. I have a guy painting a picture of the Green Goblin on the bottom of the Whiplash as we speak so that I can see it better. Any help you guys could give would help a lot. I do have a preditor that I have been flying for a couple of years now and I have had a Hobby Lobby projeti with a Mega 16/15/3 that I have flown several times so the speed in not an issue but the prop,CG and throws would be great

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Old 11-07-2008, 04:50 PM
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Mike Connor
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Default RE: PROP SIZE FOR OS MAX 40

Balance on the front spar or close to it.
3/8" for elevon and elevator with plenty of expo.
I believe that is a 40 FSR and the "V" is for rear exhaust. 9x6 or 9x7 prop and may get close to 17,000 rpm.
Do not need a 10" prop on a Dust.
Others may give more info on the engine.
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Old 11-07-2008, 05:16 PM
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Default RE: PROP SIZE FOR OS MAX 40

Mike,
Thanks for your help! I checked out you website and I love that orange Delta on the front page. Do you kit those? Here is a picture of my Whiplash that I am getting started on. Won't have it done until spring but I weighted it and it weighs almost as much with nothing in it as the Diamond Dust does with the motor on it.


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Old 11-07-2008, 05:53 PM
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Mike Connor
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Default RE: PROP SIZE FOR OS MAX 40


ORIGINAL: newflyer

Mike,
Thanks for your help! I checked out you website and I love that orange Delta on the front page. Do you kit those? .....
Newflyer
No kits for a few months now. I am on break and with Diamond Dust back it may be a long one. The orange delta on my home page was built by Denny (one of my customers) and he did an outstanding job.

Your Dust should weight under three pounds RTF. The Whip may be more durable but a little heavy IMO.
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Old 11-07-2008, 08:16 PM
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Default RE: PROP SIZE FOR OS MAX 40

Newflyer,
Looks exactly like my OS VF .46. Not a DF engine but it is a great motor.

Cody
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Old 11-08-2008, 09:36 AM
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Default RE: PROP SIZE FOR OS MAX 40

The engine is from the early 1980's - basically is a rear exhaust version of the OS .40 FSR engine designed for a few emerging .40 size pattern designs.

Good powerplant. The one shown here was cleaned up a bit. Looks like someone took time to polish parts of the exterior.

If the previous owner tuned the pipe for the 10x6, a swap to a 9x8 should be no problem.

Enjoy the plane

Bob
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Old 11-08-2008, 09:54 AM
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Default RE: PROP SIZE FOR OS MAX 40

Bob and Cody,
Thanks for your help! I got the motor started yesterday for a few seconds and then couldn't get it to restart. I put in a new glow plug and fuel line from the fuel tank but no luck. I checked the exhaust line and poked a T- pin in the exhaust nipple to make sure it was clear. I opened up the throttle and stuck my thumb over the carb and hand flipped the prop and could get the fuel to draw into the carb. I put a glow plug on it and the motor would start for a second and then die. I don't think it is drawing fuel on it's own. I checked the low speed needle and seen that it was 4 turns counter clockwise from closed. When I flip the motor with the carb open and my thumb over it (and the glow igniter removed) I think that there is a little fuel coming from the bottom of the carb where it slides into the motor housing. Not bad but a little. It looks like the screw is about stripped out. Is there a O-ring in there? Anything else that would make it not draw? I know that it could be that the clunk has come off but I can't see it without cutting the tank out from under the covering. Plus I don't thing that is it because if I fill the tank all the way up until it comes out of the exhaust line then the motor should run until the fuel made it past the top of the tank and it still won't run even with the tank overflowing?
Bob,
I will be getting ahold of you soon about a motor and pipe set up for my whiplash. I bought it from Bob Eckel here on RCU. It is the Spiderman one that is on your website. How far behind are you guys on getting product out the door?

Thanks
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Old 11-08-2008, 02:35 PM
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Default RE: PROP SIZE FOR OS MAX 40

Hi!
Try a 9x6 or 9x7APC!
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Old 11-08-2008, 03:10 PM
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Default RE: PROP SIZE FOR OS MAX 40

I found a APC 9X8 prop that I had bought for my Preditor and got it on the motor. A friend got the motor running for me. He took the exhaust line off and attached it to the nipple on the back plate of the motor and it pressured the tank to get the fuel to the motor. Once running and warmed up we noticed that the top of the head was leaking a little fuel. We took the head off and cleaned the head and the shim and haven't tried it since. The front of the motor where the case bolts together is leaking a little also. I haven't taken it apart yet because it looks like there is a gasket or a seal in there of some sort in between the crank case and the nose and I am afraid if I take it apart I might tear it and be in worse shape then leaving it alone. I still need to know where the balance point is on a Diamond Dust. Someone told me that it was on the spar but I can't seem to find a spar on the plane except in the rear of it. The mono coat is nice and tight and I can't feel or see one in it. I have the throws set at about 3/8" with 80% expo so I hope that will work.



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Old 11-10-2008, 10:36 AM
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Default RE: PROP SIZE FOR OS MAX 40


ORIGINAL: newflyer

I still need to know where the balance point is on a Diamond Dust. Someone told me that it was on the spar but I can't seem to find a spar on the plane except in the rear of it. The mono coat is nice and tight and I can't feel or see one in it.

Newflyer
The front spar is between the tank and servos or 8 3/4" behind the front of the engine mount. The plans show the balance point on the spar to a little in front of it.
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Old 11-10-2008, 12:29 PM
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Default RE: PROP SIZE FOR OS MAX 40

Mike,
Thanks for the help! The guy I bought the plane from is mailing me the planes for the Diamond Dust. I just tried to balance the plane on the spar and it is tail heavy. I put Hitec 5645 servos in it and I have 6 cell Hobbico Hydrimax 5-cell 1400 NiMH battery slid in between the servos infront of the CG to help balance it. I also put a small black prop nut on it to help get the CG where it needs to be. I am still tail heavy and not sure what to do next. The throttle servo is up close to the motor which is helping it out. I guess I could add some lead weight to the nose but I hate to do that if I can avoid it.




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Old 11-10-2008, 05:53 PM
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Default RE: PROP SIZE FOR OS MAX 40

what about trying one of those heavy hubs.
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Old 11-12-2008, 01:09 PM
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Default RE: PROP SIZE FOR OS MAX 40

I took the metal pipe brace off of the back of the pipe and bought a Mac plastic pipe hold down down and moved it forward about 5" and seemed to help out some. I am close to the CG but still just a little bit on the tail heavy side. Hopefully it will track good being slightly tail heavy! I don't want to add any more weight to the nose then I have to if I can keep from it. The DD weighs 3 pounds 3 OZ ready to fly minus fuel. That is with a 5 cell 1400 mah battery pushed all the way up onto the spar at the CG. I used the 1400 because I am running 2-Hitec 5645 digital servos and I will put 4 or 5 flights on it each time I take it to the field.





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Old 11-12-2008, 01:40 PM
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Default RE: PROP SIZE FOR OS MAX 40

I am surprised you are so tail heavy. Most Dust come out nose heavy with a side exhaust 40 engine and just about right with a rear exhaust 40. I always ran a 600mAH battery just in front of the rear spar and still needed a couple of oz. of lead in the tail with a 40 side exhaust engine. Your weight is a little heavy but it should fly good. Just don't let the CG end up much behind the front spar.
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