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Author Topic: 1960s Coupe d'Hiver Postal  (Read 154246 times)
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billdennis747
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« Reply #75 on: June 14, 2014, 01:55:14 AM »

I see on the plan there is to be a 1/16" wash in at the outer rib of the right wing inner panel at the leading edge?  I have never seen wash out or wash in given for a leading edge before.  Then there is to be 1/8" wash out for both outer panels?  I understand the wash out part but why the leading edge wash in on the right inner panel? Isin't leading edge wash in the same as trailing edge wash out?  I am going with building the Barron Knight II myself and hope to learn a bit from you two.  As stated above the Garter Knight has tapered longerons but the plan for the Barron seems to also as drawn.  The width of the longerons at the front of the fuselage is a bit wider than at the rear but the plan says just 3/32". 
Hi Bingo
I think the washin confusion is down to convention. It is normally shown at the TE but as drawn on this free plan, there is no room. Wherever the words are written, it means the same thing - more incidence, not less. I suppose in practical terms, the LE is the best place to signify washin because you pack up the LE, and vice versa! I just got off the phone to our John O'Donnell who knows one or two tips, and he flies flat wings with just a 1/8 washout on left inner (flying right/right)
John also says the prop is inefficient. I shall be making an alternative two blader for other events; 18" x 20" with 1 1/2" wide blades
No longeron taper! I never met John White but looking at the picture of this Yorkshireman with his model, he doesn't look the kind of bloke to taper longerons! Life is too short to taper longerons, or stuff a mushroom for that matter
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ffkiwi
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« Reply #76 on: June 14, 2014, 07:03:11 AM »

Because it is easier to build by propping up the LE the required amount at the dihedral break than by doing the equivalent to a tilted TE......in other words, suppose you require 1/8" washin on the starboard inner (on a polyhedral wing obviously!)-you can build this in (which is the only safe way of doing it BTW) by propping up the LE 1/8" at the dihedral break, or the TE at the centre-both options generate 1/8" washin at the starboard dihedral joint-but if you're building an undercambered wing, then you've already got the TE shimmed up to match the airfoil underside camber as you build. [of course if you have the luxury of a cambered building board, this doesn't apply...]

Just make sure you know the difference between washin and washout-and the roles both warps play on the wing, and consequent model trim....

 Personally, I think 1/16" is way too inadequate for the Baron Knight-I'd go with 1/8" (which is what mine has-and most of my other locked down Coupes). Coupes-being about the lowest powered of the traditional rubber duration classes, seems to need generous amounts on washin on the inner wing under power-amounts that would be considered excessive on faster flying models. They also seem to need a lot of right thrust-though that has a lot to do with the relatively short nose moment...
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ffkiwi
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« Reply #77 on: June 14, 2014, 07:20:03 AM »

I fully agree with Bill's comments above-and fully endorse his quotes from the great J O'D. The BN-II prop is a bit of a shocker-but under the rules we can't really change it, so are stuck with a pretty inefficient SB folder. On my original built 30+ years ago-as detailed earlier in this thread, I changed to a two bladed folder-simply using a spare prop blade-and got improved performance,. These days I'd use a Bob White Coupe prop (another man who knew what he was doing when it came to Coupes...)

  I can also report that the old-new Baron Knight had its maiden flights this morning, on a soaking wet Rayner's farm- and survived more or less in one piece, though the thrust line still needs a bit more right sanded in (which I couldn't do accurately on the field) and a surprising amount of right rudder was required to get a decent right-right pattern-surprising because it already has a lot of tail tilt built in. Cost me about 5 motors blown though, and a broken prop in the end brought things to a halt.

 Heading up to Levin tomorrow to fly P-30 with the Palmerston north FFers, and will continue trimming there, having repaired the prop, and sorted the thrustline earlier this evening, as well as having modified the stooge pin position so the wing doesn't interfere with it.

 I can tell you the glide is definitely as good as I remember from all those decades ago......it just floats (but then it needs to, as it struggles to get much above telephone pole height on that less than ideal prop....!)

  ChrisM
  'ffkiwi'
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Bingo Fuel
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« Reply #78 on: June 14, 2014, 04:40:15 PM »

Hi all,

  Thanks Bill and ffkiwi for your input on the wing of BKII.  With the negative comments on its propeller, I don't know if I want to continue with it.  I know its a great flier but I sure don't like that low ceiling it reaches with the motor run.  Garter Knight is also appealing to me and I have the plan with its much higher pitch prop.  I also have the full size plan for Deuzio which is nice .  There is zero info on the plan about the nose block and only the blade shape for the prop.   I wasn't even sure if it was a single or two blader.  I see from the article posted earlier that it is two.  I need the info in the 69-70 AM annual for that information. I guess it is now a toss up as to Deuzio or Garter Knight. I'm sort of glad I didn't go too far into the BKII project.  I better get going though.  Again thanks for the help.  Bingo
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billdennis747
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« Reply #79 on: June 14, 2014, 05:06:54 PM »

Baron Knight was apparently a winner in its day though
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Mark Braunlich
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« Reply #80 on: June 16, 2014, 08:53:40 AM »

Baron Knight was apparently a winner in its day though

Must have been successful enough to inspire the name of this Swedish Cd'H.
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billdennis747
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« Reply #81 on: June 16, 2014, 09:16:34 AM »

My money would be on the Swedish model! I just wish it wasn't tubes. I used to have a snooker (pool) cue but no longer
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ffkiwi
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« Reply #82 on: June 16, 2014, 09:44:21 PM »

Baron Knight was apparently a winner in its day though

Must have been successful enough to inspire the name of this Swedish Cd'H.

Indeed-definitely a BN influence-but I see they had an attack of commonsense and used a two bladed prop
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dputt7
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« Reply #83 on: June 26, 2014, 08:26:42 AM »

Well its cold out here in the shed  so it must be winter, so I've finally settled on what to build for this postal. After seeing the few photos of Dave's lovely Drobeck  and rereading some of the posts I decided on what I think is the Ziac version of this Coupe, I like the sheeted forward fuse and the extra dihedral. I have used the Ziac plan with extra info found in this other version http://rc-model.rajce.idnes.cz/Almanach_planku_Radoslava_Cizka/#Drobek_-_volny_vykonny_model_s_gumovyn_pohonem_kat._Coupe_d_hiver_-_1961.jpg   its a pity I can't read any of the notations on the plan as they are to blurry but I can make a reasonable guess, and of course there's all of you to help me out. My main problem will be building it light enough, I've put away my cyno and opened the Titebond, fired up my scales and weighed some wood, I would have ordinarily used .062" wire for the cabane on a model this size but I bent the first one from .055" wire then bent one from .047" wire and finally settled on .039" wire saving nearly 2 grams. As it stands in the photo it's 25 grams so I guess I'm already behind the eight ball  Shocked Grin
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THB
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« Reply #84 on: June 26, 2014, 11:00:13 AM »

1960s Winter Cup Postal Rules
those living in the Southern Hemisphere will fly June-Sept, 2014.
Yep, the pressure is on Down-Under. And the winter is definitely here as Dave says. 
Getting organised for this one I even bought a short pool cue at a market last week to use as a rear tube form.
And tonight spent a very relaxing evening cutting 30-odd ribs for the wing. (A Guy Cognet Coupe. I'm assuming that the rear part is a tapered tube because the dimensions talk about diameters...  but the front is square... so the join will be interesting.)
cheers
Tim
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sparkle
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« Reply #85 on: June 26, 2014, 04:27:27 PM »

 Grin Good to see you boys having a go! I expect it is cold down there as it's cool up here too! I don't have a big enough local field up here, so I'm just going to watch!
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mike
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« Reply #86 on: June 28, 2014, 06:47:18 AM »

........your Barron Knight IIs, I see on the plan there is to be a 1/16" wash in at the outer rib of the right wing inner panel at the leading edge?  I have never seen wash out or wash in given for a leading edge before.  Then there is to be 1/8" wash out for both outer panels?  I understand the wash out part but why the leading edge wash in on the right inner panel? Isin't leading edge wash in the same as trailing edge wash out? .......

This caught me out when I built my first one in 1966.  I built 1/16th in. washout into the right inner.  The first part of the flight was tight flat right-hand circles every time!  I got the second one right in that regard and made it a two blade prop.
Placed 11th in the Aeromodeller postal in 1967!

I just pulled out the plan........

Mike F
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Bingo Fuel
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« Reply #87 on: June 28, 2014, 10:44:26 AM »

dpuut7 and all,  Wow your fuselage for Drobek is fantastic.  I do agree that it is one very good looking Coupe.  I can't wait to see more of it.  I've seen Dave's in person and it is really nice.  Regards.  Bingo
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billdennis747
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« Reply #88 on: June 28, 2014, 11:10:35 AM »

I am interested in the long/short tail moment thing. The Drobek is very short - the Baron Knight long. I can understand a long tail on an area-limited class like F1A but not on Coupe, or indeed the British 50g class. My guru is John O'Donnell and he flies a long fuse 50g because he says it flies more nicely - but longer? I like shorter fuses, like Matveev's wake in the 1965 WC. If I am struggling to build down to a weight, it seems perverse to carry all that wood around.
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THB
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« Reply #89 on: June 30, 2014, 05:37:22 AM »

Bill - are you saying I shoulda bought a longer pool cue?
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Tim
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billdennis747
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« Reply #90 on: June 30, 2014, 05:43:54 AM »

Hi Mark
No, but my long-fuse models always end up with 150% cg!
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THB
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« Reply #91 on: June 30, 2014, 09:26:14 AM »

Hi all - good times - glue smell everywhere - balsa shavings - we'll get there!
That's a pretty complicated tailplane just saying...
Tim
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Tim
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sparkle
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« Reply #92 on: June 30, 2014, 04:27:30 PM »

 Grin very neat work as usual Tim!  Cool
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dputt7
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« Reply #93 on: July 01, 2014, 04:00:57 AM »

Hey Tim, we should get together, your flying surfaces and my fuse  Roll Eyes
I have a question about wing joiners, the Dobrek has each wing joined in the center with 2 short dowels to locate the wings with what looks like a single tube and dowel wing joiner to carry the load, Can I use some Aluminium tube and a 3/16 hardwood dowel or would it need something like 3/32 wire.  Thanks
Dave
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Mark Braunlich
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« Reply #94 on: July 01, 2014, 07:32:26 AM »

Dave,
How about ΓΈ1/8 bamboo skewer in paper tube?  I did that with the two halves of 1936 Judge Wakefield wing with no problems over many years of flying.  Overlap of dowel in tube was one full rib bay.
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Mark
dputt7
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« Reply #95 on: July 01, 2014, 08:07:39 AM »

Thanks Mark, I just found some bamboo Skewers that fit nicely into 3/16 O.D. Alum. tube that I'll probably use, If you think that 1/8th is OK as I tend to over engineer things anyway. My previous use of paper tubes was a disaster  Shocked
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Mark Braunlich
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« Reply #96 on: July 01, 2014, 10:53:54 AM »

Dave,
Dope the paper before rolling, let it dry and then use cellulose based cement while rolling the paper.  Never had a problem.
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Mark
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« Reply #97 on: July 01, 2014, 11:03:49 AM »

Reference reply #94.

Dave,
All my Coupes, except the very early ones, had two piece wings plugging onto a straight wire joiner that fitted in a tube in the fuselage.  Now I know that you are only talking about a wing joiner but the main points are the same.  My wings were 50" span and the joiner 1/16" diameter piano wire, about 4 inches long.  Joiners 3/32" dia are too heavy and too strong.  In a strong wind, or heavy landing the 1/16" joiner will flex amazing amounts and I don't think I have broken a wing since using them.  I did try 1/16" carbon rod joiners but they broke. I don't know if it was poor quality carbon but as it was such a job getting the broken pieces out (they broke off flush with tube ends) that I stayed with wire. The wires went into aluminium tubes.  I strongly recommend using a straight joiner wire, not one bent for dihedral - they are a pain.  Angle the tubes in the wing instead.  It is not relevant to your set up but, for completeness, at the root trailing edge I fixed a short piece of 0.032 dia which plugged into the fuselage side to set incidence.

John
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dputt7
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« Reply #98 on: July 02, 2014, 03:18:47 AM »

Thanks Fellas, Mark, I made some paper tube for a Easy B many years ago and they worked perfectly, then recently I tried again and ended up with a sticky mess. I even reread the original article to see what I was doing wrong but it was no help.
John, that's familiar territory, just wasn't sure about the stiffness required. Fully agree about bent joiners, can end up with anhedral.
regards Dave
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THB
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« Reply #99 on: July 02, 2014, 09:54:01 AM »

Just a bit more work...  leaving the prop till last as I don't know how to do that bit
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Tim
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