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Author Topic: Comet 12"w.s. Folker DVII  (Read 1371 times)
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Grabber
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« on: February 26, 2013, 12:00:42 AM »

Here is the plane that is under construction, it will be the first biplane since grade school, hope this one will fly!

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Comet 12"w.s. Folker DVII
Comet 12"w.s. Folker DVII
Comet 12"w.s. Folker DVII
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Grabber
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« Reply #1 on: February 26, 2013, 12:04:28 AM »

This is the kit wheels weight v.s. balsa wheels.

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Re: Comet 12"w.s. Folker DXII
Re: Comet 12"w.s. Folker DXII
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Pit
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« Reply #2 on: February 26, 2013, 05:33:13 AM »

Looking GOOD!  One thing to watch out for, is the LACK of decalage on the plan - one of the main reasons that the kit, build exactly to plan, was a bear to get flying at all.

The wing(s) could use a bit of POSITIVE incidence (leading edge higher than the trailing edge) and /or the stab a bit of NEGATIVE incidence (leading edge lower than the trailing edge, but not easy to accomplish on this aircraft).  You want to get about 3° total.

Hopefully, some others, who have built and flown the D-VII will chime in, as I have heard that the decalage of this particular aircraft goes against popular conventions.

Pete
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« Reply #3 on: February 26, 2013, 10:00:06 AM »

Pit,

Thank you for that info. I built a Curtiss Robin a while back from a Comet plan and really did not get any dihedral angle on that plane! The plan on that plane said that spare brace W 5 would set the dihedral angle, and it is very slight! What should a Fokker DVII have? I think Comet tried to build in a small amount in the inner most lower wing ribs by angling these slightly in relationship to where they join the side of the fuselage. But the plan does not indicate what the height of the wing tip should be like on a Guillow plan! Comet got me on the Curtiss Robin so I do want to make a learning experience out of it. I also want to thank you for not telling me that Fokker never made a D XII since I messed up the subject line and could not figure out how to fix it! Thanks again for your help and if you know of a better way to determine dihedral angles please teach it to me.

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« Last Edit: February 26, 2013, 10:15:22 AM by Grabber » Logged
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« Reply #4 on: February 26, 2013, 12:31:03 PM »

Yes I can say from experience that the decalage does go counter intuitive, that is to say instead of the negative incidence in the stab (trailing edge up) you use positive (leading edge) up. I could not get my DVII to fly till I fixed that. After that I noticed that the real plane had the same settings back there and all the good model designers followed suit. I cannot back this up with equations and aerodynamic theory, just suffice to say, Reinhold Platz knew something about the why and that suits me...plus now all my DVII's fly right!
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« Reply #5 on: February 26, 2013, 06:08:57 PM »

The actual dihedral for the Robin does not need to be very much, since it's a high-wing configuration, and the fin/rudder is of adequate size. Dihedral is the angular difference between the main wing panels looking from the front (or rear), whereas decalage is the angular difference between the main wing and the tailplane (stab) looking from the side (in simple terms).  My round-nose Fairchild 24 dime-scale only has 1/4" under each panel and has NO stability problems.

The D-VII probably only needs 1/4 - 3/8ths" on each side.  You can do a little experiment in appearance by blocking up the wing panels at various heights and view from the front.  When the angle starts to look ridiculous, go back one step and use that angle (dihedral does NOT hurt - only the senses Roll Eyes)  The plan for the 16" Dime-scale version only calls for 1/2" per side and this model is next on my "sport-build" list - probably start this week (I need another dimer Grin).  I DO know that the DR-1 (Fokker Tri-plane) flys quite well without ANY dihedral.
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« Reply #6 on: February 26, 2013, 08:12:14 PM »

Crabby,

 Thanks for looking at my post, I have seen from your previous post that you appear to be a biplane builder and I will probably need more advice. I have read the cabane struts are what really makes the models look good (believe you said that, and I agree) so I will need to master this since I have a lot WW1 models planned. (Guillows WW/ 100 series and 201 thru 205 from Guillow as well)I have seen pictures of builders using cardboard or corrugated templates that hold the top wing in proper position to the lower wing. Guess the secret would be to properly position lower wing? Also very nerved up about the thread rigging! Will do some more research before doing these things. Thanks for taking the time to explain things as it is very much appreciated. Just to be clear on the stab did you say T.E. up ? Or L.E. up? I think if I'm reading Pits reply right the T.E. of the stab is up a few degrees? I'm not sure?I just learned the word dihedral last month so I have a long way to go on jargon and building skills / techniques, I would like all the planes to fly so it is important to learn every thing I can.

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« Last Edit: February 26, 2013, 08:36:40 PM by Grabber » Logged
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« Reply #7 on: February 26, 2013, 08:17:36 PM »

Pit,

 Thank you for the information as I said to Crabby , I will need all the help I can get building these type of models since they seem to be more challenging. I have a SIG29'er that I'm kind of afraid of so mono wing planes are still very challenging , guess just want to do a biplane. With all the details and wing braces, rigging wire etc. I'm far from good at mono wing models but I do like the looks of the bi planes so I'll just have to learn to do it! Once again can use all the tips tricks and help you all are willing to part with! Please let me know when you start the 16" Fokker DVII it would be great to see how it is done.If you have time look at the pictures of the front and side views of the Curtiss Robin let me know what you think.

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« Reply #8 on: February 27, 2013, 04:52:39 AM »

Crash Caley is starting a build of the Mike Midkiff design of the D-VII (x3!): http://www.hippocketaeronautics.com/hpa_forum/index.php/topic,13904.new.html#new
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« Reply #9 on: February 27, 2013, 07:03:29 AM »

Grabber don't be afraid. Dive right in. The DVII is as good a plane as any to start with as is the 29er. Pit has given you some great advice...Build the thing the best you can, it's gonna break a few times. Its a good design that has proven to fly as is the 29er. Don't worry too much about looks because you are going to be bending the stab, twisting the rudder, and biting the trailing edges of the wings. The undercarriage of a DVII has another wing between the wheels, be careful that one doesn't get set in some strange angle as you attach it to the fuse. The key thing is to do out and have yourself a ball. Just don't fly around pretty women if you are the proud sort. Model airplanes have been known to make chumps of the proud!
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« Reply #10 on: February 27, 2013, 12:17:55 PM »

Pit,

 I will be looking at that build thanks.I'm confused about the stab angle, but I was able to follow what you said and decided to start out that way , if there are problems changes will have to be made. You have been a great help, thanks for the info.

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« Reply #11 on: February 27, 2013, 12:27:37 PM »

Crabby,

Your reply made me laugh! Do not fear no proud type here. Still confused about the stab angle in relationship to where it mounts on the fuse, should it be L.E. up , or T.E. up on the stab ? Maybe able to follow Crash Caley's build and get the idea down. Thanks Crabby!

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« Reply #12 on: February 27, 2013, 01:06:47 PM »

There have been a few builds of the D-VII in the past, both here and on SFA.  Also a number on the Yahoo Groups Comet site.  Take a look thru the FF Scale and Dimescale boards here - if I come across a thread, I'll post a link.

John Ernst has also built the model - I think more than once - and has his own site with full documentation of most of his builds.  It's worth a look: http://mysite.verizon.net/vze8ljo4/johnsmodels/id59.html
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« Reply #13 on: February 27, 2013, 08:25:15 PM »

  With all the details and wing braces, rigging wire etc. I'm far from good



Grabber, just a reminder that if you're only building for yourself, rigging is entirely optional. Fortunately with the D-7 there are no worries either way because the real plane had no rigging  Smiley .

I think FAC rules state that Mass Launch WW1 aircraft models must have rigging if the full scale version had it.

I'll readily admit that well-done rigging looks very nice on a model and I admire those who make the effort. The price they pay for it is enormous amounts of drag which hampers flight performance.

So, whatever rings your chimes  Grin . Personally I don't do rigging because I don't care about competition or contests and like to engineer the little birds to suit my own self-gratifying idea of FUN  Cheesy .

As Crabby said....the whole point is to go out and have a ball. +1 on that.


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« Reply #14 on: February 28, 2013, 09:32:03 AM »

Jim,

  Thanks for the info. It may make sense for me to try the rigging on a bigger model, and one that is supposed to have it. A plane with a 22" w.s. will hopefully be better to learn on than a plane with a 12" w.s., do not know for sure yet. But I can always go back and add rigging to models latter after they are retired from flying, due to one to many wrecks! Then the rigging will serve two purposes, Scale appearance and hold remnants of plane together!!!

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« Reply #15 on: March 01, 2013, 07:33:34 AM »

just to be the wet rag that I am and to be clear/specific...

for FAC WWI Mass Launch, the Fokker D.vii MUST have the landing gear rigging, and the struts and rigging on the tail (and 3D guns and exhaust).

It is true (and perfectly legal) that the D.vii did not have wing rigging, but the other rigging must be present.

however, for sport flying - no rigging is ever necessary Smiley

--george

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« Reply #16 on: March 01, 2013, 06:11:49 PM »

George, no wet rag at all, and thanks for the heads up  Smiley . Didn't know that the D7 was rigged as you pointed out. That's good info to know, far better than taking an unrigged D7 model to a FAC contest only to be disqualified  Shocked !



however, for sport flying - no rigging is ever necessary Smiley




Just so I understand, you're talking here about informal flying among FAC (or other org.) members after regular contest events at a meet have been completed, rescheduled or canceled....is that correct?


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« Reply #17 on: March 01, 2013, 08:26:24 PM »

...or your backyard or local park - yes, correct.

--george
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