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Old Jun 17, 2015, 10:53 PM
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Micro Wing for Mini Vapor GB and Brick ( IT FLIES VIDEO!!!)

Hi Everybody!

I am building a little micro wing for a comission. Here is a video of the glide testing. This will be my first scratchbuilt wing, so any suggestions are greatly appreciated!

Micro miniature RC wing glide test (0 min 13 sec)
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Old Jun 18, 2015, 08:06 PM
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How much does it weigh?
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Old Jun 18, 2015, 09:20 PM
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(edit:just trimmed off .3 grams) 2 grams without the ailerons, brick, motor/gb, control rods etc... The ailerons will be added tonight and I will weigh again with them attached.
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Old Jun 19, 2015, 09:53 PM
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I was able to do a maiden this morning. The wing flew OK, but still tail heavy. The CG is further forward now. The ailerons did not have equal throws, so the model kept turning left and would barely go straight. This may have been caused by the motor breaking from the mount.

I also added some standoffs for the control rods. They were bending a little causing improper deflection. They are just a piece of shrink glued to a piece of foam. I can add a filet if that is not enough.

The motor broke off from the mount on the first landing, and was causing problems that I didn't notice until 5 or 6 flights later. I think I have the CG correct now. I have not flown the model since the mount broke. Hopefully I can get my Wife to take some video this weekend!

AUW is 13.6 grams as flown on the maiden flight(s)...
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Old Jun 19, 2015, 10:05 PM
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The brick and M/GB is from a mini vapor I crashed and salvaged the electronics from. The wing and winglets are 2mm depron with 2mm reinforcement pieces. The tailfin and ailerons are 1mm depron reinforced on one side with glued paper. There is a piece of 1/32 plywood under the M/GB. After gluing on the reinforcement pieces, I ran a piece of .45 CF rod down the middle of the airframe and tailfin, glued to the plywood under the M/GB, and embedded in the surface. Each leading edge has a piece of 1.2mm CF rod glued into the leading edge by splitting the wing and reinforcement piece and wedging it in there. The LE was then sanded down and taped. CG is about %25 from the LE.
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Old Jun 20, 2015, 03:03 AM
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I flew the wing indoors tonight. The control was much better, but still not good enough. It wants to nose dive and it porpoises around pitching the nose up and down. I have to hold full up elevator just to keep it "level" and the angle of attack is too high, so it does a stall-recover-stall. When turning left or right, it will lose altitude and not recover. It does OK in a straight line, but still does the stall-recover-stall thing.

I suspect the CG is too far forward. It is at what I am guessing is %25 of chord from leading edge. I want to fiddle with battery placement to see if I can get it to fly level. The 1mm depron control surfaces may be too floppy as well. I hate to add weight, but I think I will try making stiffer elevons to see if that fixes the controls. I have jacked with the z bends so much they are ruined and I will need to make some new ones.

I could use some help here. I have a few questions about wings. Since I am a newb to wings, I probably made some silly mistakes or took something for granted. I need some ideas! How do you find the CG on a wing? Is it different than on a regular airplane? Any suggestions are appreciated! Thanks!

I will get some video up of the flying tomorrow...
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Old Jun 20, 2015, 07:06 AM
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What's your wingspan, I'm trying to calculate your COG roughly.
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Old Jun 20, 2015, 07:10 AM
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I measured the top view picture, and the COD is roughly a quarter of the wingspan from the nose, Your setting is way too nose heavy.
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Old Jun 20, 2015, 07:54 AM
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Wingspan is 13" and weight is 13.6 grams.

The wing balances just in front of the brick with the battery as pictured. If I remove the battery, the cg drops back behind the brick.
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Old Jun 20, 2015, 08:00 AM
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Quote:
the COD is roughly a quarter of the wingspan from the nose
OK, that makes sense based on the observed behavior. I used 25% of chord not span. That changes everything! Works out to 3.25" which is about 1/8" behind the brick. I think I will rebuild the elevons using some Balsa. Maybe the added weight will allow me to use the current battery mounting position.
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Old Jun 21, 2015, 04:36 AM
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When I added the Balsa Elevons, the cg moved back quite a bit. I had trouble getting the balance forward enough. The AUW was 19.5 grams for the attached video and the CG still wasn't right. I think my launch technique was causing issues as well. That is improved on the new model.
Micro Mini Wing tail heavy Mini Vapor AR6400 (0 min 15 sec)

I decided to do some major surgery. I was able to shave 2.2 grams off over all and add some reinforcement to boot! The wings are removable from the central pod, and are held on by tape. The glide is much more even now and nose is pointed slightly down. Tomorrow morning I will get some video of the new version.
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Old Jun 28, 2015, 04:42 AM
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Here is a new video of the wing flying much better, still underpowered I think. The CG is within 1/32 of that recommended by the calculator. I noticed one of the servos on the brick would periodically spazz out and chatter, causing the elevon to flutter. That explains why the wing would nose dive randomly. The chatter got much worse during the flights in the video.

Micro Mini wing development 1s AR6400 (1 min 36 sec)


I took the little servo apart and cleaned it real good. It works much better now. The linkages are a little problematic still, but much better now that the control horns are straight and the travel is closer to parallel with the servos. It would be better to have two individual servos, but also too heavy. The bread tie control horns are not very good either, and heavy.
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Old Jun 30, 2015, 06:39 AM
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Just a thought, have you considered changing the wing planform to a tapered swept plan? I suspect a tailless flying triangle would be pretty tough.
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Old Jun 30, 2015, 05:18 PM
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Your glide test looked good, correct CG. I would rebuild a new one same as this. Mark your CG location then tape your battery and RX close to the nose.(like you had it) Now you can lay your motor on the plane moving it forward or backward till you hit your CG. mount the motor in that location. Your thrust line(prop shaft) needs to point right at the CG mark.
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Old Jun 30, 2015, 09:13 PM
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Quote:
Your thrust line(prop shaft) needs to point right at the CG mark.
The current configuration has the thrust line pointing just aft of the correct CG. I had the wrong CG figured when building the model. I had missed that, that is an excellent observation! The thrust line comes up short of the CG. Correct me if I am wrong, but that would pitch the nose up. That is definitely one of the problems I am experiencing.

The control rods are too long and oriented in an awkward, angled way. The elevons are probably not big enough and situated in a way that makes them hard to actuate. The power from the motor/GB is barely adequate. Everything needs to be just about perfect for the wing to fly well.

Quote:
I would rebuild a new one same as this. Mark your CG location then tape your battery and RX close to the nose.(like you had it) Now you can lay your motor on the plane moving it forward or backward till you hit your CG. mount the motor in that location.
The wing is apart now. I will rebuild taking the things I have learned and your suggestions into account. I may replace the 6mm x 10mm MV motor with a 6mm x 15mm J3 motor, but I don't want to go that far. The whole point is to see if there is an application for the MV GB outside of an actuator stick model.

Quote:
have you considered changing the wing planform to a tapered swept plan?
The model is apart being rebuilt now, so changes are possible. What do you mean by tapered swept plan? Do you mean like this?
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