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Old Nov 14, 2007, 05:13 PM
What tree?
Rampage's Avatar
Yucca Valley, California
Joined Aug 2005
2,467 Posts
I was thinking about tying the sweep to throttle..

DX6, you can activate mixing with the right-side two-position switch. I was thinking of mixing the sweep servo. Fully extended at low-throttle, full sweep at full throttle, but only toggling the mix after the handlaunch.

Think that'd work for the mix? I'm seriously thinking about building one of these. Going to hunt for foam tonight.
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Old Nov 14, 2007, 05:44 PM
medium-sized Lewbowski
USA, CO, Denver
Joined Jan 2005
300 Posts
Interesting idea. I'll try it and tell you how it goes. Not sure how it would work with high alpha because you need the ability to work the throttle to maintain pitch angle and altitude. Heck... why not try it though... I am going to rip out the HS-45 wing servo tonight and replace it with something much larger. This should allow sweep changes at any wing loading. Make sure you download the latest plans before building.

m
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Old Nov 14, 2007, 05:46 PM
Have Fun! Land, Sea or Air
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United States, TX, Austin
Joined Jul 2006
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Very Cool!
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Old Nov 14, 2007, 07:11 PM
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smkn951's Avatar
United States, HI, Kapolei
Joined Jan 2007
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while messing with the wing sweep, i noticed that the Cg shifts rearward, is this normal?
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Old Nov 14, 2007, 07:23 PM
medium-sized Lewbowski
USA, CO, Denver
Joined Jan 2005
300 Posts
I have no noticeable shift on mine. How are you determining this? Where do you have your CG at when balancing?
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Old Nov 14, 2007, 09:32 PM
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Joined Jan 2007
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Quote:
Originally Posted by smkn951
while messing with the wing sweep, i noticed that the Cg shifts rearward, is this normal?
Yes. The CG will be in the most forward position when the wings are fully deployed to their most forward position, i.e., least amount of sweep. It will be in the most aft position when the wings are in their most aft position.

Cheers,
Bill Segraves
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Old Nov 14, 2007, 09:35 PM
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Joined Jan 2007
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Quote:
Originally Posted by Maybz
I have no noticeable shift on mine. How are you determining this? Where do you have your CG at when balancing?
The amount of shift from full forward position of the wings to full aft position of the wings is independent of the initial location of the CG. The wings would have to have zero mass for there to be no shift at all, or more reasonably, would have to have balance weights to make the CG of each wing coincide with its hinge axis. The little triangular pieces to which the sweep-control clevises are attached could be sized to achieve this perfect balance of the wings, if it were deemed necessary. You're the designer, though, and it's reasonable to expect you've considered all of these design alternatives in your excellent design.

Very nice work! Thanks.

Cheers,
Bill Segraves
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Last edited by segraves; Nov 15, 2007 at 12:04 PM.
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Old Nov 14, 2007, 10:01 PM
medium-sized Lewbowski
USA, CO, Denver
Joined Jan 2005
300 Posts
Sorry guys, I misunderstood... I thought you were experiencing CG shift in flight, i.e. noticeable changes in pitch.

Yes, when balancing on the bench it is normal for the CG to move fore/aft slightly in conjunction with the wing position. Hopefully it will all balance out in flight for you guys when you go to fly. In theory, it I think it is desirable for the CG to move aft when the wings are swept since the center of pressure is moving aft at the same time. I'm curious to see if you get the same performance as I have on my prototype. Thanks for all of the great input.

I'll be posting a gen-2 version within the next few weeks. Got a few more refinements I want to make.
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Last edited by Maybz; Nov 14, 2007 at 10:16 PM.
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Old Nov 14, 2007, 10:36 PM
Fly now crash later
davecrash's Avatar
Canada, ON, Newmarket
Joined Nov 2006
2,245 Posts
Good, I can finish up what I have on the bench and wait for Gen2 to come out..lol. excellent job on this. looks like you have it ready to go to kit?
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Old Nov 15, 2007, 05:56 PM
medium-sized Lewbowski
USA, CO, Denver
Joined Jan 2005
300 Posts
new wing servo

Replaced the HS-45 wing servo today with an HS-65HB. This is a 30 in/oz servo and has roughly double the torque of the HS-45. I can now change wing position pretty much any time I want. The next step up would be an HS-80 but I don't think the weight penalty is worth it. Got in two flights today just cruising - average flight time was 16 minutes with TP1320.

Here is what the Gen2 version is looking like. When I built plastic models as a kid I always liked the ones that were molded in color and didn't require painting. So that's the idea here.. made from white and grey foam. New top deck design also. Still toying with the idea of a 3D top fuselage but haven't come up with anything I like yet....
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Last edited by Maybz; Nov 15, 2007 at 06:06 PM.
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Old Nov 15, 2007, 06:03 PM
medium-sized Lewbowski
USA, CO, Denver
Joined Jan 2005
300 Posts
Here it is with classic white bottom... you could also laminate the wings from 3mm grey and white foam (I'm sure someone has already thought of this)
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Last edited by Maybz; Nov 15, 2007 at 06:18 PM.
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Old Nov 15, 2007, 07:00 PM
dare to be dull
bigjohn's Avatar
Deland, FL
Joined Jun 2002
695 Posts
Quote:
Originally Posted by smkn951
while messing with the wing sweep, i noticed that the Cg shifts rearward, is this normal?
Yes, it's normal. Since the wing is moving rearward, not only the CG, but also the center of pressure is moving back. As long as they move roughly in proportion, everything is fine.
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Old Nov 15, 2007, 07:26 PM
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smkn951's Avatar
United States, HI, Kapolei
Joined Jan 2007
1,440 Posts
not an artist but,

here it is. thanks for the wonderful plane.
i had to do something, it was all white and it's hard to see.
i toss it in the back yard and she flew short but at least it wasn't dorked.
it's really windy today, hopefully this weekend would be nice.
as you can see the M2 on it. right now all the memory on the tx is full. wonder which one would be nice enough to donate it's guts........
again thank you everyone.
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Old Nov 16, 2007, 01:42 AM
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Joined Nov 2007
9 Posts
utterly Brilliant

Thats a Great design you got there.

I think it pretty much preforms like the real thing. in F14 the Wings shift back to cause the delta Shape for highspeed and Extend to get more lift and a slower landing speed. Ideal for Carriers eh.

The CG shift is large is a problem, however if is slight is an advantage. When wings are swept back into the Delta Formation the Centre of Lift shifts back. Usually you load the main weight in the centre or axis of lift to get Max performance and not throw around too much weight when you turn. Thats why usually(with a few exceptions) you put a battery(heavy one) third into a wing for all rounded flight performance as thats usually where the centre of lift is.

This model is a great mixup for a half Delta Half Sport. Got a half sized model built with some styrofoam(Yes I said Styrofoam as in TM) I've been looking around for a nice model to build for my current power system, and have yet found a good one. This one is tempting, but I probably need way more RPMS and Lipo... Oh well.
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Old Nov 17, 2007, 07:02 AM
Winging it >
leadfeather's Avatar
Joined May 2006
9,470 Posts
Decals

I'm still hoping for a printed version of this jet, but in he mean time here is something to help put the finishing touches on an F-14.

GotrekGurnisson has created decals in his blog for several planes and several variations of the F-14 http://www.rcgroups.com/forums/member.php?u=89637 His artwork is very, very good.
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