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Author Topic: Keil Kraft Elf: Cook-Up  (Read 20011 times)
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Pete Fardell
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« Reply #325 on: September 05, 2016, 06:12:34 AM »

Many thanks, Russ, for the idea of putting an Elf in the rubber ratio comp yesterday. It wouldn't have occured to me otherwise. No great flight times yet, but more to come I think, and good enough for 3rd on the day. My poor elfin pilot is still recovering from flying in conditions so at odds with his elf 'n' safety ethos, but it probably handled the wind as well as most things and was no disgrace in the final 'flying swarm' mass launch event either. (Thank you, OZPAF John too- it was your suggestion of more right-thrust that started to get it going properly.)
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Russ Lister
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« Reply #326 on: September 05, 2016, 02:56:31 PM »

Well done Pete ... yesterday was definitely a case of 'who dares'.
I'm sure that on a better day the Elf will have so much more to offer. I'm sure it's the turbulence more than the actual wind speed that causes the problems ... especially for such a small model.

I hope that you as hooked on the event as I am now (though I must admit to a bit of a moody on the way out because of the conditions!)
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Pete Fardell
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« Reply #327 on: September 05, 2016, 04:34:34 PM »

Yes, after attending twice, I think I am hooked, Russ! It may well become an event I'm prepared to organise my holidays around.
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OZPAF
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« Reply #328 on: September 05, 2016, 07:24:48 PM »

Good to hear that your Elf and Safety flew well! Of course if he had a few swigs of good Oz Beer (the night before of course) he wouldn't have noticed the conditions Smiley
John
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cvasecuk
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« Reply #329 on: September 27, 2016, 07:03:16 AM »

At the BMFA SW Area indoor meetings we hold a "One Model Comp" every December. This year, inspired by this thtead we chose the KK Elf. Here are some which turned up on Sunday
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Pete Fardell
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« Reply #330 on: September 27, 2016, 07:16:50 AM »

Love them! Especially Elfis Presley- wish I'd thought of that one!
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ffscale
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« Reply #331 on: December 10, 2016, 11:08:32 AM »

OK - the cookup may be long over, but I finally got round to building an Elf.  It only took a week as well, so I don't know why I kept putting it off.  We had an indoor meeting in a local school today and I didn't have anything to fly (well, anything that wasn't broken).  So I thought I'd see if I could get an Elf done in time.  It was a fun build, and Andrew's laser cut parts fitted well.  I kept the colour scheme simple, but red and green seemed appropriate for a Christmas Elf.

I didn't make any effort to keep it light and used any wood I had lying around - I also used domestic tissue.  All up weight with a loop of 3/32" rubber and a scraped Easybuilt 6 inch prop was a touch over 15 grams.  How on earth Keil Kraft came up with their 1 oz figure on the plan (28 grams) is beyond me, and two loops of 1/8" rubber is frankly ridiculous!

The model trimmed out easily, with the leading edge of the wing needing to be shimmed 1/32", plus I added a small amount of tail weight.  If I give the prop another good scraping, I may be able to get rid of that.  I couldn't put more than 800 winds on or it was up in the roof structure.  Mine wanted to circle right, so I let it.  What a charming little design!

Mike S

 
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OZPAF
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« Reply #332 on: December 10, 2016, 05:46:25 PM »

Very nice - like the wheels and the coloured window framing.

One week - hmm! I won't tell you how long mine has been underway Sad

John
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gossie
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« Reply #333 on: December 10, 2016, 06:04:07 PM »

Looks nice in those colours. Smiley
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Art356A
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« Reply #334 on: December 11, 2016, 09:11:22 AM »

Christmas Colors.
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My arms are so weak, it's like that pushup I did last year was a total waste.
Jack Plane
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« Reply #335 on: December 11, 2016, 01:46:35 PM »


One week - hmm! I won't tell you how long mine has been underway Sad

John

Not as long as mine!!  :'(

Nice version Mike - plus you've actually just solved my problem of what to fly in small halls!
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« Reply #336 on: December 11, 2016, 01:58:42 PM »

Looks great Mike.  A charming design indeed.  I was really meant to set a date for this cook up to end, but more keeping popping up  Grin Grin

Andrew
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Russ Lister
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« Reply #337 on: December 11, 2016, 04:34:41 PM »

Love the one model comp collection  Smiley

Nice job Mike ... Christmas colours as Art said Smiley

Going to have to get mine done before next September .....
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OZPAF
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« Reply #338 on: December 11, 2016, 04:59:47 PM »

Good grief - I may not be the last to finish Smiley
Merry Christmas everyone.
John
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ZK-AUD
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« Reply #339 on: December 11, 2016, 06:06:49 PM »


I  How on earth Keil Kraft came up with their 1 oz figure on the plan (28 grams) is beyond me, and two loops of 1/8" rubber is frankly ridiculous!


I have a fair idea - I was given a KeilKraft Robin by someone (you build model planes don't you....)  I was shocked at the weight - the kit parts (cut out) and wood weighed 43g unbuilt.  I used my own wood and flying weight with rubber was 23g  The U/C supplied was 20swg!!

Last seen heading to Australia unfortunately!!
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pedwards2932
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« Reply #340 on: May 27, 2017, 09:45:30 AM »

Not sure if I should post this here....but I built an Elf and it looks like everything is aligned and straight but under power it wants to spiral right?  You would think under power it would want to go left.  I tried adjusting the thrust angle which originally was set at about zero.  Seems to help but as the I up the number of winds it still wants to spiral right.  The turn is so sharp that it doesn't get much altitude and eventually dives in.
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Hepcat
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« Reply #341 on: May 27, 2017, 06:22:05 PM »

Ped,
I would say that must be washin on the left wing or washout on the right wing or both. If it is not please let us know what other fascinating misalignment you have found.
John
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pedwards2932
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« Reply #342 on: May 28, 2017, 07:12:33 AM »

To my eye the wing looks pretty straight, I will check it to make sure.  The test glides on it seemed like it was going to be fine.  At lower winds I don't notice the hard right turn but at about 400 turns it starts the hard right.  It was a little windier then I would like when I was testing so I may wait for calm air to try and see.
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Prosper
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« Reply #343 on: May 28, 2017, 09:19:07 AM »

That's mysterious. As Hepcat says a subtle warp would be the likely culprit. A wing can be twisted along its whole length in a way that's as good as invisible: leading edge and trailing edge dead straight - and yet produce a rolling moment. If you get the calm air you need, it might be possible to tell in the first few seconds of flight whether the action is primarily a roll, or primarily a yaw leading to a secondary roll. Other factors are thrustline and unequal weight left and right. Less likely, since the wing is held on by rubber bands, a displacement of the whole wing to one side. Or the tailplane being strongly tilted relative to the wing. My Elf turns right; not for preference but because I built an unintended warp into the wing which resists all steaming/soaking/cursing. It's just easier to let it have its head.

Stephen.
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pedwards2932
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« Reply #344 on: May 28, 2017, 02:09:06 PM »

Flew better in no wind but still not consistent.  Needed some more nose weight and downthrust.  I think I have it figured out when I sight from the front of plane the right side of wing is lower than the left.  I need to adjust the wing rests so the wing sits level.  I am guessing the smaller planes are a bit harder to get flying right.
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pedwards2932
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« Reply #345 on: May 28, 2017, 03:57:39 PM »

Okay I sanded it down a bit so the wing sits level.  It looked at first like that had it but as I added the winds to it the right spiral came back. So I twisted the wing so right wing tip was up more and left was down more.....that really seemed to do it so Hepcat and Prosper were correct.  The final flight where some of the twist settled out it flew one circuit right and then started to go left.....I had about 600 winds on it and it got about 35 ft of altitude which doesn't seem like a lot but it stayed up about 30 seconds which is about max for the field I was in.  Added a picture......I tried it stock using the rubber band to hold on elevator and just found it to not work so well so I glued on the elevator.  I think I want to build another and use magnets to hold the wings on.
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Hepcat
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« Reply #346 on: May 28, 2017, 05:47:08 PM »

P, (sorry about 'p' but I am terrible with names; was it Patrick?)
I typed this answer before #343 but forgot to press the button  so here it is now because it is still a bit useful. On a wing with dihedral  if you push one tip forward then that side gets more incidence and the side with the tip moved back gets less.  This is the sort of thing we did in the 1940s and tend to forget about doing it over the decades as our builds get a bit better.  I have seen it mentioned recently in connexion with fast climbing electric models.  It is useful to have in your box of trimming tricks because it allows you to try the effect of wing warps without much effort and it is easy to work in small increments when the model is sensitive to trim changes.
John
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« Reply #347 on: May 28, 2017, 05:56:33 PM »

Both the Elves I have built were very stable, certainly no spiralling in.  I think both wanted to fly in right hand circles, so I just let them, and some nice flights were had...

Andrew
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pedwards2932
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« Reply #348 on: May 28, 2017, 06:43:01 PM »

The last flight was pretty promising......I have the parts set up for laser for this so I plan to make another and incorporate some changes.  It's a cool little plane I must have gotten some sort of warp in the wing.....it was hard to see but when I twisted the wing it seems to fly pretty good.  I want to use magnets to hold the wings on and I want to redesign the nose section.  I also feel like gluing the elevator worked a lot better.  I know the original premise of this cook up was build as original but I can't help myself......  I don't know how it goes for you guys but I learn a lot from the first build and try to improve with successive builds
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« Reply #349 on: July 09, 2017, 06:00:24 AM »

I also had trouble with the Elf spiraling in and found that a warp had crept into the stab. After it had been flattened the model has flown well until I became too ham fisted and blew a motor at Peterborough in June. I have just rebuilt the fuse and look forward to getting going again. I was getting about 49 seconds.
Ricky   
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