Demon Knockoff for a 67
05-25-2010, 04:17 AM
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Demon Knockoff for a 67
Well I did want to buy a Demon.... But I'm not terribly patient.
I have access to a laser cutter so I figured that it couldn't be that hard.... Right?
Some things I'd like to do different. First off I want to use a different airfoil. The NACA 0006 (and a half) is too thin IMO. I think I can get the same performance with a MH51 which is 8% thick. This makes more room inside and provides for a stronger structure (not that the SD is weak).
I also want to fully sheet the wing to get a better profile. Lastly I want to build it without the carbon spars.
First off: Get Profili to draw up the reasoning for the airfoil choice. While I'm at it - make the DXF for cutting.
Second up: Fire up SW and do a model. See what I'm up against.
p.s. Mike, I hope it's o.k. by you. If everything goes well I'll send you the plan.
I have access to a laser cutter so I figured that it couldn't be that hard.... Right?
Some things I'd like to do different. First off I want to use a different airfoil. The NACA 0006 (and a half) is too thin IMO. I think I can get the same performance with a MH51 which is 8% thick. This makes more room inside and provides for a stronger structure (not that the SD is weak).
I also want to fully sheet the wing to get a better profile. Lastly I want to build it without the carbon spars.
First off: Get Profili to draw up the reasoning for the airfoil choice. While I'm at it - make the DXF for cutting.
Second up: Fire up SW and do a model. See what I'm up against.
p.s. Mike, I hope it's o.k. by you. If everything goes well I'll send you the plan.
05-25-2010, 07:53 AM
#3
RE: Demon Knockoff for a 67
I think your ideas will work...if you can create more room and preserve the sleek aerodynamics at the same time.
I'll bet the engine in your drawing will need to move back a little bit. If you are figuring your loading plan on the computer can you come up with an "as designed" CG?
I'll bet the engine in your drawing will need to move back a little bit. If you are figuring your loading plan on the computer can you come up with an "as designed" CG?
05-25-2010, 07:56 AM
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RE: Demon Knockoff for a 67
ORIGINAL: combatpigg
I think your ideas will work...if you can create more room and preserve the sleek aerodynamics at the same time.
I'll bet the engine in your drawing will need to move back a little bit. If you are figuring your loading plan on the computer can you come up with an ''as designed'' CG?
I think your ideas will work...if you can create more room and preserve the sleek aerodynamics at the same time.
I'll bet the engine in your drawing will need to move back a little bit. If you are figuring your loading plan on the computer can you come up with an ''as designed'' CG?
I think so too. Right now the CG is too far forward. I want the prop to be as far forward as possible to reduce the slipstream-wing interaction. Probably end up with both the battery and servos bunched up at the TE.
06-02-2010, 08:23 AM
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RE: Demon Knockoff for a 67
Small updates...
Got the ribs done and I'm not happy. The quality is fine but I should have stuck with MJD's method with the carbon spars. Building tabs are a pain!
I'm going to try cutting foam cores and see if the result is better. Meanwhile I reduced the sweep by 2". This should allow me to install the engine without too much CG issues. Stability is another matter
Got the ribs done and I'm not happy. The quality is fine but I should have stuck with MJD's method with the carbon spars. Building tabs are a pain!
I'm going to try cutting foam cores and see if the result is better. Meanwhile I reduced the sweep by 2". This should allow me to install the engine without too much CG issues. Stability is another matter
06-02-2010, 09:07 AM
#6
RE: Demon Knockoff for a 67
Those are good looking ribs. I would snip the tabs off after the framing is complete and move on to the next task. I don't see the problem with them?
The down side to break away tabs is the building surface has to be most perfect. If a tab gets parked in just a minor dent on the table, it could throw everything off. With the tube spar system, those tubes are so perfectly straight that they will "signal" allignment trouble to the builder before it's too late.
The down side to break away tabs is the building surface has to be most perfect. If a tab gets parked in just a minor dent on the table, it could throw everything off. With the tube spar system, those tubes are so perfectly straight that they will "signal" allignment trouble to the builder before it's too late.
