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Old Jan 05, 2010, 11:27 AM
G_T
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It sounds good so far! I'm guessing with a cleaned up fuse and possibly airfoiled tails you should easily get up over 100 seconds, and have a lot better L/D at speed. I'm curious to see if you can hit 2 min dead air time.

Gerald
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Old Jan 06, 2010, 09:49 AM
Launchpad McQuack
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Netherlands, Moordrecht
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Originally Posted by Berrie View Post
But for the coming weeks because of the weather in the Netherlands my schedule will be like: sleep-work-iceskating-sleep-work-iceskating-sleep
Model name suggestion: M-ice
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Old Jan 18, 2010, 09:15 AM
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Berrie's Avatar
Schoonhoven, the Netherlands
Joined May 2006
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Not much to tell, but a post to show some progress:



Second set of wingcores is almost finished for bagging. Hardpoints of balsa to attach and some sanding at the carbon tipsparcaps. As you can see it is very hard to keep the very thin trailingedge free from damages. But is not important for bagging. Just cosmetic.

Dennis made a mandrell and I made a new boom with this mandrell. This boom is made from two layers 45 25grams glas and one layer UD HM 80gram carbon. In my opinion a quit scant boom. Not much left for "construction safety".
With a lengt of 570mm and outside diameters from 8.8-12mm it weights 4.8 gram. I like that weight. Dennis will build another wooden fuselage to test this boom and a new tailgroup. The tailgroup is simply a shrunk version of the full size Zone and made of 2mm balsa.



If it works, we than know:
- that it is usefull to fly with a smaller tail as we do now with the actual version of the Mini zone (with MIMI tail) So I can build a composite tailgroup with nice airfoil.
- The nice light weight boom is strong, stiff and light enough.
- we can decide about the composite fuselage noselength and build this fuselage.

It is all some sort of "Flinstone style engineering proces". Sorry for that...
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Last edited by Berrie; Jan 18, 2010 at 12:33 PM. Reason: add some comments about the boom
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Old Feb 11, 2010, 02:37 PM
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Berrie's Avatar
Schoonhoven, the Netherlands
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The storie continues......

We could test the second version a little. So far now problems. Altough the tailgroup seems pretty small, no real problems occur. But I need to say we would test more. The test conditions were not very good......

http://www.modelbouwforum.nl/forums/...ml#post1556316

The fog also caused also curved balsa elevator and rudder. We could not fly long enough.

The small tailgroup did help to get the target weight:



The boom was strong enough. It is not the type of boom that you can test between your tumbs.....

I will also ad a short piece of 54grams glas in the boomlayup at the part thats mounted in the pod. That boom will go into the vacuumbag tonight.
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Last edited by Berrie; Feb 11, 2010 at 02:45 PM.
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Old Feb 11, 2010, 03:50 PM
G_T
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Just FYI, but you might find the need to increase the size of the tails a little. Particularly the vertical. Relatively flat plate surfaces will stall at much lower AOA than airfoiled surfaces. That would rather negatively affect launch height.

Also flat plate horizontal airfoils tend to have dead-band issues. That may lead to issues on trimming in airspeeds. If the airspeed becomes a little unstable due to dead-band, then performance will go down. Also the drag of flat plate airfoils is likely a fair bit higher than for full airfoils.

Looking forward to more reports!

Gerald
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Old Feb 11, 2010, 03:54 PM
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Berrie's Avatar
Schoonhoven, the Netherlands
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Thanks for the reaction Gerald. We intend to increase the surface of the vertical. Also to make a tailgroup wit "real" airfoil. But we go step by step.

It's time for the fuselage.

A question. What angle between the airfoilchord and fuselagestreamline is preferenced?
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Old Feb 11, 2010, 04:09 PM
G_T
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Berrie,

It seems I forgot to answer this at the start of this thread. My bad!

I'll have to pull up the model and look at the numbers to give you an answer. But in general the answer is going to be quite close to the answer for the Zone 2P design, except the nose should droop probably nearly half degree more due to the lower L/D of the smaller wing.

Gerald
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Old Feb 12, 2010, 05:06 AM
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Schoonhoven, the Netherlands
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Originally Posted by G_T View Post
quite close to the answer for the Zone 2P design, except the nose should droop probably nearly half degree more due to the lower L/D of the smaller wing.
Gerald, is this the post you refer to?

http://www.rcgroups.com/forums/showp...&postcount=114

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I'll have to pull up the model and look at the numbers to give you an answer.
I would be happy if you take a close look. I think, because the fuselage is almost as big as the fuselage for a fullsize DLG , it matters even more on a small plane.

Just to share the idea: I am considering Supergee's tailfoils, with fixed elevator (like the Apogee Elite?!). The difference between the wingfoil and the tailfoil (in speedmode) should be about 1? (always difficult to understand for me...)
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Old Feb 12, 2010, 11:28 AM
G_T
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Yes, that is the post. I need to dig out the "simple formula" as I didn't keep a copy. IIRC, the downwash angle is dependent on the aspect ratio, and the 1M wing is enough lower than 1.5M wings to make a difference in the numbers.

For some raw numbers, for speed mode:

Alpha, the angle of attack of the wing at the root, is 3.5 degrees upwards.
Gamma, the glide angle, is 3.1 degrees downwards at best, neglecting all sources of lift/drag except the wing (the penalty of small wings is a steeper glide slope).
The lift coefficient is 0.4.

These numbers assume a plane with the target weight of 115g and the design of the lower aspect ratio 8 wing I published.

To get the plane to perform to its best potential, you need to do everything you can to minimize drag. That includes slimming down that fuselage as much as you can manage. Make it so you have to shoehorn in D-47 servos! And change the tip peg to a blade. A blade has far less drag. The blade need not be built to the same standards as a blade for a 1.5M plane as the loads during launch will be lower.

Ok, looked up my simplified formula for downwash angle:

downwash_angle = 36.5 x coefficient_of_lift / aspect_ratio

Plugging in the numbers yields about 1.8 degrees. So the tailboom should droop about 1.8 degrees compared to the nose of the plane, and the wing should be mounted at 3.5 degrees up compared to the nose of the plane. This should give a minimum drag configuration for speed mode, which is where I generally choose to minimize drag. It is not very far off for other flight modes, except for launch climb where Cl is essentially zero or close to it. Anyway you end up with the classic slightly banana-shaped fuselage.

With a fixed elevator, probably the required mounting angle for the fixed part of the stab would be with its bottom fairly close to parallel to the flattish portion of the bottom of the wing.

For the vertical you would probably be better off with the Edge-Vertical airfoil. It has less drag than most anything else, and you can use a rudder or not, as you choose.

Gerald
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Old Feb 13, 2010, 03:33 AM
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Schoonhoven, the Netherlands
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Thanks Gerald, that will help!

Good that you mentioned about the trowing pin/peg. I was in a lazy mood and almost glued in a 3mm peg. Now I need to saw'nsand again

If we are lucky, we could mill aluminium fuselage molds with a CNC milling machine at Dennis his work. That would be cool!

Here is the second wing, same layup, 47.6 gram. Ready to build in the servo's, horns and peg.



[edit] The dihidral from this wing is 8. We both think that 6 is not enough.
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Last edited by Berrie; Feb 13, 2010 at 07:05 AM. Reason: comments on dihidral
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Old Feb 13, 2010, 12:22 PM
Walter Roos
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Canton, Ga.
Joined Aug 2004
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Hi Berrie,
On the 8 degrees of Dihedral, would that be 8 degrees total or 8 degrees per side ? If that's the total, seems like not very much vs the 60" DLGs I fly.


thanks, glad you're working all this out.

walt
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Old Feb 13, 2010, 12:52 PM
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Originally Posted by ROOSWH View Post
Hi Berrie,
On the 8 degrees of Dihedral, would that be 8 degrees total or 8 degrees per side ?
It is per side. Each wing half is tilted 8 from the horizontal.
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Old Feb 18, 2010, 11:19 AM
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I just start my project.
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Old Feb 18, 2010, 01:32 PM
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Muto

That doesn't look like your S8 pod, is it a DLG?

Richard
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Old Feb 18, 2010, 01:33 PM
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Muto

That doesn't look like your S8 pod, is it a DLG?

Richard
Not yet
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