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General Category => Plans, Projects, Building and Flying Tips => Topic started by: Flypaper 2 on September 29, 2016, 11:26:27 AM

Title: 3DR1 Fokker Triplane
Post by: Flypaper 2 on September 29, 2016, 11:26:27 AM
The idea behind this was, an aerobatic 3D type plane. I figured with a short span with lots of wing area would fill the bill. Don't get much better than 3 wings. :D
 Light weight was one of the other criteria. That's where this foam from Home Depot pays off. It's normally used for under floor insulation. It has a film of thin plastic on either side.
 It's only very roughly semi scale. I wanted to be able to fly at very slow speed too, so I made the control surfaces oversized to enable that.
 Bottom wingspan is 26 in. span.
 Middle span is 30 1/2
 Top is 36 in. not counting the ail. outer tabs.
 The total ail. span is 38 1/2 in.
  Wing chord on the bottom two wings is 8 1/2 in.
 Top wing outer is 9 1/2 in. inner part is 8 1/4.
These numbers are not critical. 1/2 in. either way is not going to matter. One of the joys of scratch building. ;D
 Fuselage is 5 in. deep and notched out for the bottom wings.
Length is 24 in.
 This one turned out a little nose heavy, so I'd move the wings back by 1 in. So the bottom wing will be 4 1/2 from the firewall. Middle wing is 3 1/2 in.
 Now, if you put a ruler between the bottom and the centre wing, the top wing leading edge will be in line with the two bottom wings. Wings are about 4 in. apart.
 Here are some pics. If you need anything specific, let me know.
Rudder hinges have very little area so I used the heavy nylon hinges with the brass cotter pin that you would normally find on the larger 1/4 scale planes.
 I think everybody knows what the tail skid is.
 I forgot. The motor is a BP 2217-7T and 1250 KV and sold by Leading Edge.
 By the way, the plane weighs 1 lb. 2 oz. W.O. batt.
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on September 29, 2016, 04:44:00 PM
This plane flies like it is on rails and follows the sticks as thought it was reading your mind. I was so impressed when Gord let me fly it, I started building my own. Foam is cut, assembly next. If anyone wants plans, I could figure out how to copy the templates. Easiest just to borrow them.
Photos to follow.
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on September 30, 2016, 12:53:34 PM
Gord:
Are all your servos 9gm, or 5?
I've cut and glued most of the foam. Here's the "Fokker-Werks"
Title: Re: 3DR1 Fokker Triplane
Post by: Flypaper 2 on September 30, 2016, 01:32:52 PM
All 9 gram Reg. Looks like you might be needing a bigger workbench. ;D
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on September 30, 2016, 03:36:41 PM
Gord:
Those doublers, do they go all the way back to the TE of the midwing?
And did you put any spars in the wings?
Title: Re: 3DR1 Fokker Triplane
Post by: Flypaper 2 on September 30, 2016, 04:10:40 PM
The doublers go to the leading edge of the bottom wing. There no spars in the wings. The only strength is through the carbon rods that go through outer wing struts. They go through the upper and lower wings to the outer surfaces. They're about 1/8 in. dia. or 3mm.
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on September 30, 2016, 07:31:55 PM
Thanks Gord, I'm getting there slowly. I'm also going to make the wing struts larger as you suggested.
The joining worked out well., but I might put a bit of rod in the upper wing.
Title: Re: 3DR1 Fokker Triplane
Post by: Flypaper 2 on September 30, 2016, 07:52:34 PM
The upper wing didn't have enough support due to the narrowness of the centre strut, So, this morning I put a carbon rod through the wing and into the fuselage, at the back of the wing. I cut around the foam where it goes through the wing and fuselage. Sort if a tapered hole. then filled it with hotglue. The wing will bend no more. ;D
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on September 30, 2016, 08:00:02 PM
Hot glue saves the day again!
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on October 01, 2016, 07:56:22 AM
So, what do you think about making the struts a bit wider to help with the flatness across the chord? I'll post a sketch.
Title: Re: 3DR1 Fokker Triplane
Post by: Flypaper 2 on October 01, 2016, 08:21:12 AM
That's more like what I should have done. I did more like that on the smaller one I have, that this was copied from, other than they are curved at the front also.
 The carbon rods are to tie the wings together for stiffness, so they won't bend, as in unwanted dihedral in a tight loop.
With the longer glue surface that you have, may not need them. If they are needed, they would be easy to install later.
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on October 01, 2016, 08:37:46 AM
Thanks Gord - I thought it might be too much weight.

I'm just working on the tailplane now. You are right, that hinge has to be super strong, and I might put a light carbon rod vertically for extra stiffness.

Contact cemented the doublers in, and I'm looking around for an engine.

I wonder if Gary has a neat way to hot wire the leading edge so we don't have to cut and sand?

This plane is fun to build! I can hardly wait to get airborne.
Title: Re: 3DR1 Fokker Triplane
Post by: Flypaper 2 on October 01, 2016, 09:13:22 AM
Sort of like building an indoor flier on a slightly larger scale.
 Where else can you cut out/build a 3 ft. wing in about 3 mins. ;D
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on October 01, 2016, 12:27:05 PM
Well, due to my dumb error, it was more than 3 minutes, but I take your point.
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on October 01, 2016, 01:41:45 PM
Elevator - Gord did you double bevel that like the rudder?
Title: Re: 3DR1 Fokker Triplane
Post by: Flypaper 2 on October 01, 2016, 03:18:14 PM
No. Hinged at the top like the ails.
 Put four more flights on it today and the more I fly it, the more I like it. I think it's getting used to me. :P
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on October 02, 2016, 09:20:26 PM
It  looks like you have 3 hinges on each ail, what are they, and is the ail slit open or did you close it with tape or hot glue?
Thanks
Title: Re: 3DR1 Fokker Triplane
Post by: Flypaper 2 on October 03, 2016, 05:08:54 AM
I use the open weave drywall tape. I believe it's fiberglass threads.
 I left the plastic over the hinge line but slit it at the hinge line. One needs to glue the tape to the foam itself, so I made a slit through the plastic, fore and aft about 1/2 in. from the hinge line and 1 1/2 in, apart, then peel back to plastic so the foam is exposed. Now, cut the tape about 1 by 1 1/2 in. and hotglue to the foam. While the hotglue is still melted, put the plastic back down over the tape, using a plastic card to push it down rather than the fingers.
 I found that the glass fibres will loosen up too much with use, across the hinge line, so I put a thin strip of hotglue across the threads.
 You might as well do this now.
 On the elevator. I put the glass tape all the way across the hinge line, using the method above.
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on October 03, 2016, 06:32:33 AM
I did that on the Zagi, but was wondering how you made the surface look so neat - secret revealed! I'm going to use 3 of the mini-hinges on the rudder, and probably add a couple of pin hinges on the outer end of the ails to help with the "wandering" problem of fiberglass drywall tape.
On the elevator, you must have joined the halves with a rod?
I tried a sample of the Krylon yellow spray on both sides of the material, and I think it will cover my mistake nicely.
Thanks
Title: Re: 3DR1 Fokker Triplane
Post by: Flypaper 2 on October 03, 2016, 06:51:30 AM
On the elevator , there is a 1/8 in. carbon joiner tube bedded into the foam at the 45 deg. bevel.
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on October 03, 2016, 08:35:57 AM
Thought so, I'll have to focus my camera better next time!
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on December 13, 2016, 09:01:17 AM
Nose Job:
Well it's extended about 2 inches, and balances at the same point as yours Gord without all those lead weights. I'm just trying to figure a btter way to mount the foam cowl without hot glue, but otherwise, raedy to go!
I'm not painting the new nose until she flies well!
Herman is grinning again.
Title: Re: 3DR1 Fokker Triplane
Post by: Flypaper 2 on December 13, 2016, 03:01:44 PM
Looking good Reg. You may have to put skis on it. :o
 I wonder if Velcro would hold the cowl on. If it gets hurt, I still have lots of that foam.
Title: Re: 3DR1 Fokker Triplane
Post by: ganguy on December 13, 2016, 04:12:47 PM
Here's what I did (no photo):
I pinned the top of the cowl to the body with a bamboo rod, which I disguised as a gun sight for Herman!
At the bottom of the cowl, I glued on two small magnets which stick to the LG rods. So the whole thing comes off quickly, if needed. Ain't I smart?
Skis for everything now, I guess.
Title: Re: 3DR1 Fokker Triplane
Post by: Flypaper 2 on December 13, 2016, 05:01:11 PM
Then , we can always take off on the tables. I won't tell anybody. :-X :o

  Gord.