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XF VIPER - Foamboard F-16 EDF

willsonman

Builder Extraordinare
Mentor
No idea. Give it a try! It's normally around 80% here in the summer. A bit drier in the winter. I've seen folks wet using a spray bottle, some wetting their finger and wetting the surface with that, and others using a damp cloth to wipe the surface before application.
 

willsonman

Builder Extraordinare
Mentor
Progress continues. I added bamboo sections to the lip of the intake. When I lay down the heavy glass I’ll loop over these to blend things in a bit better. I also added bamboo to the LE of the V-stab to stiffen it up. I’m still contemplating a section at the TE as rigidity is still not the same as with the paper-backed foam. Base layer of glass is on all the parts now.
 

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Another skewer at the tail TE is probably warranted, for the reasons you stated. Also, in concert with the one on the LE and the glass, they will work together to resist torsion as well.
 

willsonman

Builder Extraordinare
Mentor
Working on a number of cosmetic spots but took time to add to the build too. Bottom strakes are installed and servos too. The wires were secured with cable ties so the fan would not suck any slack into it. The push rods for the elevons will be slightly off angle but should work just fine. I wanted the servos a bit more flush to clean up the drag a bit more.

I need to figure out how I want to hinge the elevons too. No tape. No hot glue. Pin hinges will likely flutter a bit as well as my usual floppy disk material. Open to suggestions here.

With the ESC and servos secures I’ll move onto the top of the fuselage that remains. Installation and glass work there and I can move onto the hatch while I figure out hinges. The duct inlet needs a little cleanup work too.
 

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willsonman

Builder Extraordinare
Mentor
I settled on hinging the elevons with heavy glass cloth and WBPU. The stiffness from the application should eliminate any flutter in the tail planes and should be mostly strong enough. Hopefully the glass will not peel off the foam. I used my covering iron to melt a bevel on the bottom side.

I tried to move onto the remaining fuselage former... not realizing that my ESC to battery leads were too short. Supplies ordered to do that. I hope to wrap up the tail surfaces this weekend and final installation of the v-stab.
 

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rockyboy

Skill Collector
Mentor
I had never thought of doing hinges like that... :unsure: WBPU never struck me as a structural adhesive before.

Are you going to bother covering in the weave or just spray some paint on it and go fly? Wonder if lighter weight cloth would work just as well and be less fill work.
 

willsonman

Builder Extraordinare
Mentor
Lighter cloth would create a much more fragile hinge. With the WBPU, it would be more prone to ripping. The thicker glass can be filled a bit but I am not going to worry about it. I'll sand it a bot to clean up the edges but otherwise I'll leave it alone.

WBPU can be structural just like anything can... to an extent. I already have fears about the strength of this one as the glass is tending to wrinkle as I slightly bend the foam. This application Is really testing the waters in terms of what can be done here. For sure this will be much lighter than a normal one. I hope it holds together. With the carbon spar and some added strength in the form of a paint stick in the wing, I'm hopeful but I do have my doubts. Another one is the strength of adhesion. If it does not hold as strong as I hope it will, the glass will pull away from the foam at the hinge and start fluttering anyway. At least I know it will not pull away due to getting wet or even the humidity in my area.
 

willsonman

Builder Extraordinare
Mentor
I did finish up installing the elevator control horns and push rods this weekend. Any notes on throws and for different rates? Feeling lazy today and do not want to comb through 17 pages of building here.

I also glued on the V-stab. Looks good and seems stable enough. Parts to extend the power leads should arrive today. Hope to get that done as well as programming the throws. I'm hopeful that I can wrap this up this week. Maybe shoot a little gray paint on her. I suspect the hatch will need some re-building but I'll cross that bridge when I get there.
 
For max low-speed and high-alpha maneuvering I try to get about +/-45° surface deflection, but that is by NO MEANS required for 'normal' flight, and even more normal aerobatics.

For normal deflections I would target something in the +/-30° range.
 
I'm assuming that is deflection of elevator or aileron input only. It will extend further when combined. Correct?
Actually, I was thinking of the total max surface deflection. If you can get 45° total max surface deflection, you'll only need it at low speed. Even then, I usually fly on mid-rates, which I have set to 75% throw, and I switch to low rates for high-speed passes, which I have programmed to 50% throw.

Can you get 45° deflection if you move the servo horn to pointing up?
 

willsonman

Builder Extraordinare
Mentor
She is about finished. The side panels for the hatch were bowing out so I added some wood the make them straight. Added a magnet to the back of the hatch and a wood paint stick piece to the front to secure the hatch. Just a little bit more glass work and she will be ready.

Without a battery she comes in just shy of 2 pounds for those wanting a reference for weight. I hope she flys as well as she looks.
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