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A new speed plane under developement

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A new speed plane under developement

Old 03-05-2014, 05:19 PM
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Originally Posted by aspeed
You're wondering about dm 2. It is square decimeters. A decimeter is 10 cm, or 3.94 inches. About the size of a cigarette pack. The wing loading is Grams per square decimeter. Like oz. per square foot, except in the dreaded metric.
It had been so long since I had worked with metric measures that large I had forgotten all about DM, I was reminded of it shortly after I asked the question. I knew 92.9 cm - 1 ft^2 but I was sitting here going what the heck is a dm. Talk about feeling stupid.
Old 03-05-2014, 05:24 PM
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Originally Posted by combatpigg
You can always stretch the aft end if it comes out nose heavy, or with too much area forward of the CG. A big fin that sweeps back would help with that.
If all this plane wants to do is flat spin upon release, then that is the symptom of the side area inbalance.
Getting the CG right shouldn't be all that hard given the brick (battery) that it going to have to carry.

You must be a mind reader on of the things that is a concern to me is the side area forward of the COG. While I have a fairly large fin planed (and the cooling duct and exit on the rear should add a bit of side area) but still this is the type of thing that keeps me worried.
Old 03-05-2014, 08:32 PM
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Originally Posted by combatpigg
You can always stretch the aft end if it comes out nose heavy, or with too much area forward of the CG. A big fin that sweeps back would help with that.
If all this plane wants to do is flat spin upon release, then that is the symptom of the side area inbalance.
Speaking to the side area issue.
I have planed on using a vertical stabilizer that is about 11% of the wing area, figuring I can trim it to size as flight test proceed.
Do you think that is large enough to start with or too large?
I know you and Mike Connor liked going with a fin that was closer to 9% because of the whetted area but I don't know it I can even get close to that with this one.
I got to get the test model built there are so many questions with this one.
One major one for me is roll stability, no dihedral at all in this design and a pretty narrow beam. I don't think what is left of the swept wings are going to help all that much as far as sweep = dihedral.
Old 03-05-2014, 09:15 PM
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All I can do is offer guesses and ideas. Lord only knows what shape will work the best.
I would be sure to make the center section big enough to allow the battery pack to be moved fore and aft, but I realize you want the tail to end with a smooth taper.
Honestly, I think there is so much side area ahead of what I reckon is your flyable CG, that the leading edge of the wing ought to be brought forward to form more of a classic delta configuration.
Either that or shift the existing wing that you have already laid out forward.
Again, these are just my general impressions and nothing but that.
Going strictly from what I know about this stuff there never would have been a flying witch on a broom or a flying lawn mower.
Old 03-06-2014, 07:12 AM
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About the only caution I was given is that I need to centralize the mass moments as much as possible because of the possibility of pitch issues, to reduce the amount of trim force to keep the drag lower. From that I gather that I should use the mass to trim it so I don't use the control surfaces to do it, which is pretty much what I did on the original and what I will do on the SD when I get it airborne. The center section was designed so that I have a large amount of flexibility in the battery position. From what I have going now I can have the battery (about 1 lb) fully behind the COG if I need to, and I have a fair amount of latitude as far as the placement of the servos as well. As it sits the airframe balances right around 50% MAC right now, granted hanging 8 oz on the nose will change that quite a bit but I hope I can offset that a bit with the fin and control setups so the battery will go fairly close to the COG. As I get more of the structure (ribs installed) I will be able to cut out a good part of the flat foam in the center section as well as the 45 degree swept portion so that may help a small bit. I figure only on leaving what I need to mount the servos and what I wind up with that will be part of the framework itself. The back is going to be for the most part trailing edge except for the portion where the cooling duct exits this portion will be an 1.25 diameter duct setup pretty much as my SD was done.
My main fear is this thing will end up flying like a boomerang if I don't get the vertical stabilizer right.
Old 03-07-2014, 02:30 PM
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Default Angular stryker

Iron Eagle


I'm building something similar to your design, but my center section of the aircraft has an angular design to it. The wings I'm going to use our from the older stryker model aircraft. So it's going to be sort of like an angular design striker aircraft, Powered by an 80 mm E-flight ducted fan.


The base of the model is going to be made out of 3/16 gator foam material, which I found is stronger than your standard posterboard material. It has a paper on the outside with a foam core on the inside, which to make it stronger I am impregnate it with Z epoxy finishing resin. I use a poor man's vacuum bagging technique it's wax paper pressed on top with some type of a flat plastic Sheet material laid on top of it, and then I put some weight on top of it keep it flat.
I know where the center of gravity is on a stryker model so hopefully on this model I shouldn't have too much of a problem with it.


How are you going to power your model with a prop or a ducted fan?
Old 03-07-2014, 03:00 PM
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That sounds like a fun project.

The foam poster board I used has paper on both sides of a foam core, sounds very very similar to what you described, I picked it up at Staples. The plane I am building at the moment is only to work out some of the design ideas. The actual airframe will probably either be composite foam cores wire cut then glassed, or molded layups with a balsa/composite framework. (still thinking about it)
Your method of using the resin to beef it up sounds like a great idea. I had already decided to use some carbon tow to reinforce the swept wings but I think I am going to do as you have and use resin on the entire wing as well.
As far as the COG Vincent posted a link to a online calculator http://wingcgcalc.bruder.com.br/en_US/? which has no problems with odd shaped airframes, if you want to get a better idea of what might work.

This and the actual model will be powered by a prop, but a DF version would definitely be cool to do as well.

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Old 03-07-2014, 09:26 PM
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The Gater Foam I picked up at a sign shop, and by itself it is a lot stronger than the posterboard material. I just fiberglass the bottom of the fuselage, and on the foam wings I'm going to MonoKote ( TowerKote them because of the low temperature). Thanks for the center of gravity calculator but I think I'll be okay because I know where the center gravity is on the Stryker wing.
Old 03-08-2014, 07:06 AM
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Post some pictures if you will this sounds very cool. Thanks for the tips about adding strength to the airframe!
Old 03-08-2014, 09:56 AM
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Here are some pictures of this angular stryker aircraft working on. Please excuse they little metal items in the center of my model I am using that just for weight purposes. I am a machinist by trade and I have a lot of little metal things laying around.
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Old 03-08-2014, 10:44 AM
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Did you laminate foam with balsa for your fuselage formers?
A machinist, now there is a skill I wish I had...
Old 03-08-2014, 06:00 PM
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No I didn't laminate the balsa wood formers, I probably will hit it with some thin CA glue to make them a little stronger.
Old 03-09-2014, 05:47 AM
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It must be the way the light hit them they looked like they had foam cores.
Old 03-09-2014, 05:48 PM
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The reason I started this whole project, was that I had some success with a stryker with a 70 mm ducted fan on the back of it that went extremely fast. It has E-Flite Delta V 15 fan with a 3600Kv motor running on a 5 cell 2700 Mah Li-po 35C battery. We had a jet event at our field and a person with a fiberglass Habu jet could not catch me.
Old 03-09-2014, 08:24 PM
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I seen a couple of DF setups done like that with a tuned duct that were quick.

I spent most of today working on the main body structural elements for the framework of mine.
When I finish with the structure I will cut away all the parts of it that are not needed to keep the weight down.

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Old 03-10-2014, 09:26 PM
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The set up that I have does not have any thrust tube on the end of the ducted fan unit it's just the fan sitting there by itself and it goes pretty darn fast as it is, I couldn't do much work on my model today because my cordless Dremel tool went out on me and I have to take it apart and fix it.
Old 03-11-2014, 07:35 AM
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This is one which I had seen.
http://www.rcgroups.com/forums/showthread.php?t=1966775
Old 03-12-2014, 05:25 PM
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Thanks for the thread on that flying wing, That person put a lot of work into that model. I don't think I would go with the rudder on the end of the wing like he did, With my design I think it's a lot simpler since I'll have the wing basically already made and the installation spot to put the rudder on. I have the wheels semi recess and unfortunately on the nosewheel there is no steering so take offs can be a little hairy.
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Old 03-12-2014, 05:26 PM
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Here's the picture of the bottom of my plane from some unknown reason it didn't upload.
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Old 03-12-2014, 07:41 PM
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Those are just winglets on his, all of the control is via the elevons.
Old 03-13-2014, 09:10 AM
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What I meant to say if the winglets are off on their angle a little bit, I believe it would cause the plane to roll. But they act like a stationary Rudder.
Old 03-13-2014, 09:42 AM
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In this type of application the winglets have to be washed in about 1 -2 degrees for them to work right. This is done to reduce the amount of outward lift they produce to keep the drag at a minimum. All they are intended to do is to give the airframe yaw stability. In my design if I had the mechanical aptitude I would eliminate the vertical surfaces altogether by using drag rudders/spoilers and a gyro to provide yaw stability to eliminate the whetted area of the vertical surfaces entirely. Not having that mechanical ability to machine the parts needed I have opted for a single central vertical stabilizer to keep the interference drag to a minimum.
Old 03-14-2014, 07:08 AM
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Default A bit of progress

Slowly it is starting to evolve into a airplane. The equipment bay is working out to be just what I anticipated.
What CP did for his tail has really got me thinking about what to do on this one.
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Old 03-14-2014, 07:00 PM
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A swept back racy looking clipped delta fin on center at the aft end of the tail section? A really low aspect ratio fin has a long junction line with the fuselage therefore more interference drag. Also more induced drag during yaw. A modest aspect ratio fin compromising between stiffness and aspect ratio with a reasonably long bond-line for strength would be the direction I'd go, keeping the underside clear for sliding on the belly and bungee launches. Well, maybe a dorsal keel widening to the rear would be cool. And a little green alien head in the cockpit.
Old 03-14-2014, 07:27 PM
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Instead of having drag rudders with mechanical linkages on the outer wing panels, I would go with wings servos in there and that would eliminate the mechanical linkage aspect of it, and then I would control it with as you said with gyros.

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