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Jan 27, 2015, 04:34 PM
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Originally Posted by Asher Carmichael
Looking good! What did you use to adhere the foam and can you hotwire through it? If not, how did you hold the canopy segments together?
Hi Asher, I used Loctite Med. tac spray adhesive, similar to 3m77. It has acetone in it, tho, so it takes several light coats, with drying time between each, so as not to melt the foam. After assemblyand initial cutting, several places started coming loose, so I tried to dab a little in, but it started to melt the foam, and then went to white glue and taped it together for the repair. The hot wire goes thru it fine, but on the shallow angles, it does ride on glue a little before cutting into the next piece. This is shown by the wide black vertical reference line on the side of the fuse by the canopy front. Also, the glue stays a little rubbery, so isn't the best for final sanding. Not a deal-killer, tho. Before I glued the four 2" slabs together, I layed out and sanded out a 1/2 rounded groove using coarse sandpaper on a dowel in each of the 2 inner pieces along the line, from nose to end. When glued together, this left a 3/4" hole down the middle, which let me use a 3/4" steel conduit to mount it on the stand. After hotwiring the square fuse profile, I sat it back on the bottom shuck to hold it level, and gravity-cut out sectons. I just made paper profile templates from the one end-view plan, corresponding to the widthand height measurements of the top and side views, following Woo's method shown at the 1st of his 50% Diana build (thanks, Woo). I sliced the center, or largest one, cut it out on the bandsaw, 1/8" larger to allow for sanding, sprayed it with glue, threaded it back on the stand, and used the black slab lines to line it up. Then sliced another, and repeated it seveal times. I used a bit of masking tape to hold each canopy seciton to the fuse while cutting and glueing. Whew, starting to get a whole new appreciation for those posting builds. Thanks, all. Bob.
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Jan 27, 2015, 04:58 PM
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[ !

On a serious note what horizontal dihedral have you built in with the wing slot in the fuselage?[/QUOTE]
Simon,
The joiner will be 3/4" x 1 1/2"x 40", solid CF, flat rectangle, no dihedral, so the rod box in the fuse is also flat. The 3.5-14 airfoil thickenss will allow the flat rod & wing joiner box , when fitted with the end-grain balsa wedge, to yield a full 3* wing dihedral. I could increase it to 3.5* by tapering the end of the rod bottom slightly, if advisable. Oh, here are the "guesstimated" templates used for the fuse shaping. Thanks.
Last edited by flyingfever; Jan 27, 2015 at 04:59 PM. Reason: add
Jan 27, 2015, 06:13 PM
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Very nice.....following along! I'm in the middle of a small build...a 4 meter Arcus that uses a bit different construction method. The build is being done on facebook... https://www.facebook.com/Arcus4meter
Started in on the wings.....
Jan 27, 2015, 07:48 PM
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Originally Posted by SZD16
Very nice.....following along! I'm in the middle of a small build...a 4 meter Arcus that uses a bit different construction method. The build is being done on facebook... https://www.facebook.com/Arcus4meter
Started in on the wings.....
Thanks for following and posting your build link. Very nice--your method of joiner receptacle tubes might be the answer to my rectangular rod shape ones. Also I'm especially interested in how you used the thick foam to establish the wing dihedral with a flat base. The Nimbus has a 16" tip with additional dihedral, so I'll need to figure that out later. Oh, one thing I discovered--the factory 3-view drawing wasn't totally accurate. When I enlarged the front view to make the templates, the left side was not the same as the right. I had to fold it in half on the vertical center line and cut it out, making it symetrical. Thanks.
Jan 27, 2015, 08:12 PM
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Quote:
Originally Posted by flyingfever
Thanks for following and posting your build link. Very nice--your method of joiner receptacle tubes might be the answer to my rectangular rod shape ones. Also I'm especially interested in how you used the thick foam to establish the wing dihedral with a flat base. The Nimbus has a 16" tip with additional dihedral, so I'll need to figure that out later. Oh, one thing I discovered--the factory 3-view drawing wasn't totally accurate. When I enlarged the front view to make the templates, the left side was not the same as the right. I had to fold it in half on the vertical center line and cut it out, making it symetrical. Thanks.
The wing dihedral was something I thought a long time about........and the reason I arrived at the 4 meter span was that's the longest span I could get within the 3" thick foam I had. I used both AutoCad and Compufoil and went back and forth to make sure everything fit within the 3" foam.
As far as the joiner goes......yes, it will work just fine.....remember to wax everything real good and it will work. I have another project that is moving along on the other bench......I know.....to many projects...... Which has a 1.5" x .5" by 40" aluminum joiner. For that I have bought some carbon/Kevlar sock material that I am going to use to make the reciever tubes from.....
Jan 27, 2015, 08:19 PM
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Here's the aluminum joiner and the sock I'll use for the tubes.......
Jan 27, 2015, 11:47 PM
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Originally Posted by SZD16
Here's the aluminum joiner and the sock I'll use for the tubes.......
Where did you get the cf/kevlar sock? TIA. Bob.
Jan 27, 2015, 11:50 PM
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Originally Posted by flyingfever
Where did you get the cf/kevlar sock? TIA. Bob.
http://www.solarcomposites.com/compo...20sleeves.html

About half down the page......

Tom
Jan 28, 2015, 02:22 AM
I'm a glider pilot really.....
Hi Bob,
By "longitudinal dihedral" I meant the relationship between the wing angle of attack and the tailplane, not normal dihedral - this was another area I wished I had done differently.
I originally designed it with a zero/zero relationship but then was persuaded to add some positive wing incidence (and they were right). However, because I had already done the wing to fuselage interface the only way I could do it was to alter the incidence of the tailplane via its mounting on the fin - this has the effect of making it fly looking a little tail down.
So my strong recommendation is that you build in a least 1.5 degrees of positive wing incidence before you get too far (you may already have done so which was why I asked)

Simon
Jan 28, 2015, 02:26 AM
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Quote:
Originally Posted by swarrans
Hi Bob,
So my strong recommendation is that you build in a least 1.5 degrees of positive wing incidence before you get too far (you may already have done so which was why I asked)

Simon
+1 agreed
Jan 28, 2015, 02:48 PM
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Longgitudinal dihedral


Quote:
Originally Posted by swarrans
Hi Bob,
By "longitudinal dihedral" I meant the relationship between the wing angle of attack and the tailplane, not normal dihedral - this was another area I wished I had done differently.
I originally designed it with a zero/zero relationship but then was persuaded to add some positive wing incidence (and they were right). However, because I had already done the wing to fuselage interface the only way I could do it was to alter the incidence of the tailplane via its mounting on the fin - this has the effect of making it fly looking a little tail down.
So my strong recommendation is that you build in a least 1.5 degrees of positive wing incidence before you get too far (you may already have done so which was why I asked)

Simon
Simon, Thanks for this important info. This is exactly why I posted the build and am requesting all the help I can get. The info I need comes from experience, either personal or others'. As a 1st timer, anything I know about this project came from the builds on the various sites, including composite fabrication, so the value of everybody's posted builds is huge. I did note your having to re-mold the stab, and also that more times than not other builders had to change the tail, often to correct the wing situation. My 3-view side view did not have any kind of a "thrust" or base line to check the L. incidence with, so I drew a line from the nose tip to the center of the fuse rear (rudder hinge line) to use as a base line to set up the incidence. Not sure if this is right, but I figured that the horizontal fuse center line would represent the fuse, and if I set the tail to fly level, parallel with with the line, whatever that is, the wing would be angled up by 2*. This wing/aifoil position was also the position that was located on the enlarged plans, as far as I could determine. The picture below shows this location and horizontal center line. This is why I cut the airfoil profile out of the side profile template and the foam when it was in the square, as I couldn't figure out how I'd locate both sides properly after the fuse was shaped. So, the big question now is,-- Is it locatid correctly? It presently has a full 2* pos. incidence, in relation to the fuse horizontal center line I drew. I'm not sure how to locate teh stab and base yet, but will get into that soon. Thanks again.
Last edited by flyingfever; Jan 28, 2015 at 02:50 PM. Reason: add
Jan 28, 2015, 04:04 PM
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2 * is fine......1.5* would have been better. You can always set the tail at .5*+ and end up with 1.5* between the two and that will also give you a more "nose down" flight attitude which I feel looks better.
Jan 28, 2015, 04:12 PM
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My rule-of-thumb when setting a decalage is to angle the fuse how I would like to see it in the air. Place a long straight-edge not through the fuselage profile, but below it. Using that reference line, stand back and visualise the model flying and adjust the straight-edge angle until you're happy with how it looks and draw the line. This is very much a TLAR approach but it works.

Personally, I hate looking at a model with it's tail dragging so I tend to go for a slightly tail-high appearance. Then set the tailplane to zero degrees from the reference line. Think of the flights (feathers) of a dart. Their job is to keep the pointy end at the front. Same thing with the tail surfaces of a plane.

So as the model moves through the air, the tailplane sets the angle at which the wing will fly at ... to keep it in simple terms. The fuselage is merely keeping the tailplane and the wing apart from each other.

For the wing, I would use 1.5 degrees. No less than 1 degree and certainly no more than 2 degrees. Having a high decalage will require a more than necessary amount of nose weight to counter the pitch-up effect of the higher angles.
It was common from early scale designs to have as much as 4 degrees decalage!!!!

Struth!!! Why not put 10 degrees toe out on your wheel alignment while you're at it!!!

I think between 1.5 and 1.8 degrees. There are other factors that start using formulas and calculus blah blah blah ... not needed. If your tailplane area is in the TLAR range, then you'll be fine.

D.

Also, if you're having an adjustable trailing edge, you can vary the decalage with your radio
Last edited by Larrikin; Jan 28, 2015 at 05:18 PM. Reason: typo
Jan 28, 2015, 04:30 PM
I'm a glider pilot really.....
I completely agree with both those posts, and it sounds like what you have already done is fine. I suspect that even the 2 degrees will be fine with the additional nose weight - sure you might be compromising a fraction of purely aerodynamic efficiency but as it sounds like you will be mainly thermalling the extra stability and "correction" it will give you will be a bonus at height.
My ASG29 is so neutral (ie it goes where you point it and stays there) that when it is at altitude on flat field the only way I can tell if it is pointing down is when the sonic boom reaches me! Great fun on the slope though and an incredible roll rate for 7.2m!

I can tell this is going to be a great result...

Simon
Jan 28, 2015, 05:58 PM
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Thanks, guys. Feeling better now. Is the 1-1.5* measured from the fuse tip to tail center line, as I drew it , meaning I drew it in the correct place? I haven't glued in the wing "saddle" yet, so if it would make it better, or worth it, I could sand a little foam from the top , rearward foam surface of the fuse cutout, which would raise the back of the wing. reducing the incidence a little. It fits nice now, so will do it only if recommended.


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