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Author Topic: Help designing/building a foam-wing F2D airframe  (Read 12709 times)

Offline Bill Ervin

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Re: Help designing/building a foam-wing F2D airframe
« Reply #50 on: August 27, 2016, 02:36:57 PM »
Thanks for the tips and pics guys, the compartment measures 1.25"x5.25".

Offline Rich Perry

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Re: Help designing/building a foam-wing F2D airframe
« Reply #51 on: August 27, 2016, 02:53:56 PM »
Your dimension should be fine for a .15.   Mine are 1.375" x 6" , and that gets me over 5 min  for a .36.

Offline Bill Ervin

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Re: Help designing/building a foam-wing F2D airframe
« Reply #52 on: August 28, 2016, 08:20:43 AM »
Thanks Rich, relieved to read that as I had committed to sealing and closing off the compartment.  Cutting the  bladder compartment out with hot wire looks like a much better method!

Offline phil c

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Re: Help designing/building a foam-wing F2D airframe
« Reply #53 on: August 29, 2016, 01:18:37 PM »
A couple more things Bill.  Bass is fine for a motor block, but you need to loosen the mounting bolts after every flying session or the wood will compress while it sits.  Then tightening the mounting bolts will torque the case.  The boom should go almost to the front of the block and have the bolts go through it- a .113 or so numbered bit will just clear 4-40 bolts.  But since it has a metric engine and mounts, use 3mm bolts in a slightly bigger hole. Most Euro F2D planes use pieces of 1.5mm(,062in) fiberglass plate epoxied top and bottom back to the spars.  The motor block really need to be made very precisely, especially parallel top and bottom so the beams don't torque the mounting tabs on the motor.  Ball bearing motors particularly don't like to have the case twisted.

To fix the motor mounting bolt probem you can use Dubro brass inserts.  They screw into the right sized holes and use some epoxy on them.  It needs 4 short bolts though.  Or you can cut some 3/16in. aluminum wire, cut the wire to length, and drill a through hole and tap it into place with some epoxy.  Sand the ends flat and parallel with the block.
 
The original designs like this(Steve Hill's Arrowplane) used a piece of hardwood dowel pressed lightly and epoxied into the front of the boom and extending far enough back that a through bolt could be used to mount the bellcrank directly on top of the boom.  Another way would be to cut a strip of 1/32in. aluminum.  Half wrap it around the boom with the ends to the left.  Bend the ends to into a zig-zag shape that will take the bellcrank and pushrod and attach with a short 6-32 bolt.  Hold the mount in place by figure eight wrapping some carbon tow around the aluminum and the boom and then soak it with thin epoxy before installing the bellcrank.  Or you can run a piece of 3/32 aluminum welding rod through the BC mount and boom and afix with a bit olf epoxy.

1/8 x 3/8 bass, spruce, or pine is fine for spars, although a bit heavy.  For flat spars you need to add a doubler laid flat in front of the spars about 1.5in. long and tapered back to the main spar.  Either that or cut quarter inch deep slot in the block under the spars for vertical doublers to lock the spars in place.  You need at least a 3/4in. square of gluing area to hold spars to the motor block.

Anyway, the planes you are putting together should fly just fine.  Just some tips to make them more durable.



Dacron fishing line won't do much for holding the wing together in a crash.  It's too stretchy.  Needs to be carbon fiber, Kevlar, or possibly Spectra fishing line, but that is hard to glue.

phil Cartier

Offline Dane Martin

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Re: Help designing/building a foam-wing F2D airframe
« Reply #54 on: August 29, 2016, 01:44:45 PM »
Great advice phil,
What about lead out guide position.  I've read 3/4 inch behind the CG. Is that reasonable?

Thanks

Offline Bill Ervin

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Re: Help designing/building a foam-wing F2D airframe
« Reply #55 on: August 30, 2016, 10:05:15 AM »
Yes that's great advice and appreciated.  Looks like Dane and I will have many improvements to make in our refinement program.  The scale tips right at 15 1/2 oz.   With any luck the second airframe will be delivered to him this afternoon so he can put a couple trim flights on each before leaving for Lubbock.

Offline Fredvon4

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Re: Help designing/building a foam-wing F2D airframe
« Reply #56 on: August 30, 2016, 11:23:28 AM »
I get small quantity of size 207 .018 64 LB Kevlar, and size 346 .026 135lb Kevlar here

http://www.thethreadexchange.com/miva/merchant.mvc?Screen=CTGY&Category_Code=Kevlar-Thread
"A good scare teaches more than good advice"

Fred von Gortler IV

Offline phil c

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Re: Help designing/building a foam-wing F2D airframe
« Reply #57 on: September 28, 2016, 07:29:14 PM »
One of Fred V's posts reminded me.  The original stab hinge you were talking about was made by Roy Henderson in Nevada.  He was making dies for a molding company and made a complete set- bellcrank, stab mount, and horn.

The planes look fine. 

The bladder compartment was supposed to go into the right panel during assembly.  T-12 fluorescent light covers are 1.5 in and 5in. long is plenty for F2D.  Or you can go with T-8 covers, 1.15 in. in diameter, 6-7in, long.

Way back when I did some experimenting.  1/8 x 3/8 spars set flat, as you did flexed about 1/8 in. with a weight on the spar and the tips supported.  The same wing with a 3/16 x 3/8 vertical spar tapered to 1/8in. at the tip flexed 3/16in.+ with the same weight.  With either type of spar vertical webs at midspan and at the tips cut the flex to almost nothing.

Phil C
phil Cartier

Offline Ken Burdick

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Re: Help designing/building a foam-wing F2D airframe
« Reply #58 on: September 29, 2016, 09:41:38 AM »
Hi Phil.\Do you mean Hepinstall? I may have ruined the spelling. Last I saw of him was at Top Gun. Anybody hera from him nowadays?

Ken

Offline Bob Mears

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Re: Help designing/building a foam-wing F2D airframe
« Reply #59 on: September 30, 2016, 08:03:25 AM »
A couple of tings I might add. First, I would glue some formica on the top and bottom of your motor mount. That will stop your wallering out. And a great little tool I use for cutting out fuel cells is a hot knife. Mine is a bit different, but its 25 years old too. Here's one thats similar...  http://www.ebay.com/itm/Nordstrand-Electric-Styrofoam-Cutter-Hot-Wire-Styro-Foam-Cutting-Pen-Knife-/272341308733?hash=item3f68ce953d:g:rNUAAOSwIgNXsJXE
Home of the control line combat museum.

Offline phil c

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Re: Help designing/building a foam-wing F2D airframe
« Reply #60 on: September 30, 2016, 07:02:54 PM »
Hi Phil.\Do you mean Hepinstall? I may have ruined the spelling. Last I saw of him was at Top Gun. Anybody hera from him nowadays?

Ken
Yeah, that sounds righter.  I think it was Heppenstal.
phil Cartier


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