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

Diamond dust cg check

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Old 03-26-2011, 05:50 PM
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BlackB12
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Default Diamond dust cg check

I'm building a Dust and plan to use a sport Jett 46 on it. I'm using the red Jett muffler. I'm at the point of laying out where to put the throttle servo so I laid the engine in and servos in to get some idea of how it was going to balance. Its looking very nose heavy already. Is this typical? If I cut a hatch on the top sheeting I can push the receiver pack (3.5 ounce pack) behind the rear spar and it should get me closer. Just wondering if this is needed or do people fly them nose heavy with the heavier engines on them?

Mike
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Old 03-27-2011, 04:50 AM
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Default RE: Diamond dust cg check

The DD was originally designed for a .32 which is based on a .25 case. A lot of us used the MVVS .40 becuase it was a very light .40 and it made us stuff everything far back. Yes you will have to be creative in your placement. Also using a full tuned pipe over a muffler moves weight back.
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Old 03-27-2011, 06:28 AM
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Default RE: Diamond dust cg check

Hmm. Good point. I may have to go that route or look for a lighter .40-.46 size engine. I jumped the gun and widened the motor mount for the Jett 46 so now that's probably too wide for a .32 or .25 huh? I just messed with putting the battery on the trailing edge and it's still way nose heavy even without a prop on it and I don't feel like adding lead to the tail.

Mike
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Old 03-27-2011, 06:52 AM
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Default RE: Diamond dust cg check

IF you want to continue to try using that motor you can move it back a good 1/2 inch maybe more. Also you could side mount the servos and move them back some. Side mount the throttle servo between the two elevon servos.... heavier battery since you'll need the weight you might as well get benefit...

But even with all this she's going to be tough to balance, shame it should be quick with that motor.


Second choice is to get a Magnum w/o motor for the Jett and get a lighter motor for the DD....
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Old 03-27-2011, 12:32 PM
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Default RE: Diamond dust cg check

Hi Mike
The DD is very CG forgiving, I have seen your configuration fly with the battery forward or aft of the rear spare. Some rational: the Jett engine is one of the lightest engine in it's class, you don't have the ultra coat covering or control linkage weight accounted for, you are using 2/3 A size batteries (good choice,instead of AAA) and for easy access batteries, therefore I think I'd put the batteries just ahead of the rear spare. Placing the batteries aft of the rear spar is OK too if it makes you feel better, but do a more thorough balance mock-up including covering, linkage, prop, rubber isolation(fuel&electrical), it may surprise you.

I have used a 46VXDF engine(dang heavy) in the clipped wing version, and it is mandatory aft of the rear spare.

I never had to add any lead weight to balance a DD.
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Old 03-27-2011, 12:50 PM
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Default RE: Diamond dust cg check

I like to use an 8 oz. tank centered behind the engine for more flight time. The throttle servo is then mounted between the eliveron servos. Don't forget to use a genuine OS bubbless clunk and isolate the tank with real 1/4" foam rubber. You wont need a bladder tank that way, not even with a DF engine.

You may need to make some wood shim wedges (thin & thick) for use under the engine lugs to rotate it so that the rear bell of the muffler is not resting on the wing.
You could also drop the left engine lug through a notch and lap(glue) a ply on the bottom, you still need some wedges to not distort the mount.
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Old 03-27-2011, 03:43 PM
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Default RE: Diamond dust cg check

freakin,
Thanks for the advice. I think I'll give it a go then. Also, until this evening I didn't even know if this Jett even ran. I bought it used off the classifieds here. the muffler is has a ding and a couple fins are dented like it was dropped, but I mounted it and it fired right up and ran perfectly. Never had an engine run so crisply. It gave me motivation to make it work in this Diamond Dust.

evan,
As far as mounting the servos laying down, how exactly is that done. Would I need to cut out the ribs so the servos can go in them? Seems some have done that but I'd worry about weakening the ribs.

Mike
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Old 03-27-2011, 04:39 PM
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Default RE: Diamond dust cg check

Cut the rectangle out of the rib and the add some lite ply to stregnthen it... Here is a pic before I cut the slots for the servo arms...
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Old 03-27-2011, 04:46 PM
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Default RE: Diamond dust cg check

Yeah, I think your gona have fun Mike
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