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Jan 29, 2007, 03:46 PM
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chris williams's Avatar
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Slingsby Petrel plans


After a prolonged series of phone calls with Encanta, the new publishers of RCM&E, I managed to get my original plan of the Petrel back on the plans listing. It's not listed on the website, but if anybody wants one, then quoting the plan number SF543 to the webmaster should do the trick...

http://www.xlistplans.demon.co.uk

If anyone should get that far, I still have the original instructions which can be e-mailed...
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Mar 17, 2007, 08:33 PM
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BStaley's Avatar
Thanks for all the help. I e-mailed the webmaster for info on plans. Chris, what size is the model-it sure looks good! If you could e-mail me the instructions I would greatly appreciate it. Bill
Mar 17, 2007, 10:33 PM
TEAM GORGEOUS
SZD16's Avatar
1:3.5 scale......... 5 meter span.
Mar 18, 2007, 06:08 AM
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chris williams's Avatar
No prob Bill, just let me have your e-mail address.
At around 5m span and some 22lbs it's not a small model, but I never had a problem launching single-handed from the slope except in the very lightest of winds.
FYI: There are two full-size Petrels in existence, mine was based on the version with the original all-moving tail configuration. The red one has been recently restored to a very high standard and fitted with a conventional tailplane and a blown/moulded canopy. I have a copy of the drawing of the tailplane mods if you fancy that one...

This is mine at Crook Peak a few years ago in a fairly light wind (Bob Flook photo)
Mar 18, 2007, 12:30 PM
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BStaley's Avatar
Chris, thanks for the info. My e-mail is "bstaley24@cfl.rr.com". I found the web site with your plans. Any idea where I caould get a smaller set of plans, say around 2 or 3 M?
Thanks-Bill
Mar 18, 2007, 05:55 PM
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Wight's Avatar
2m span will not really work with a Petrel, it'll tip stall horribly with such a tiny tip chord. Even 3m is really going to push it.......
Mar 19, 2007, 05:41 PM
Ay up it's warped
mtbrider's Avatar
Wight

Thanks for that, I wondered why the old scale models are so big
Mar 19, 2007, 06:24 PM
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chris williams's Avatar
There's no reason why a small Petrel wouldn't work provided you used a much thinner-than-scale wing section and paid serious attention to keeping it light.
The compound curvature fuselage would be way too heavy in ply, so you would probably have to plank the whole fuz with balsa. Selig 3021 would be a good choice, as it worked pretty well for my mini-Bergfalke (1/6th scale, Traplet plan, see plans page, SSUK website http://www.scalesoaring.co.uk/Plans/.../CW_Index.html ) which was light enough to bungee on occasion...
Mar 19, 2007, 10:18 PM
henrykk's Avatar
Hi Chris - have you considered digitising your plans and making short CNC cut kits?
Mar 20, 2007, 01:48 PM
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chris williams's Avatar
Henrykk, there's a big difference between a plan drawn the old fashioned way (like mine) and a plan drawn digitally in CAD. With a pencil, ruler, French Curves and little or no knowledge of formal drawing procedures, my plans, like many others, are full of small (hopefully!) errors that to those used to the modern laser cut kits would probably find a little irritating. A plan drawn in CAD would be much more precise and well suitable for laser cutting. So, digitising my drawings would simply replicate those minor errors to no good purpose. One day, I might find the time to come to terms with CAD, assuming it doesn't cut into my building time...!
One more point, if this isn't getting too OT:

I reckon to cut out the parts to a model the old-fashioned way in about two or three evenings. The total build time might run, typically, to the equivalent of 150-200 evenings, making the time needed to 'kit' up for a project a pretty small proprtion of the total build time. Digitising makes sense, therefore, for a large production run, but not for a one-off...
Mar 20, 2007, 03:41 PM
Ay up it's warped
mtbrider's Avatar
Chris

I picked up your DFS Habicht plans for building later in the year as my first large scale glider, well to me

Mark
Mar 20, 2007, 03:49 PM
MTT
MTT
I care about rising air !
MTT's Avatar
Chris's answer makes perfect sense, I think...

Still if you shy away from cutting all those parts yourself, you can do, as I did:
I designed a set of ribs in compufoil, used compufoil's .dxf generating feature, which gave me a digital file, which I then sent to one of the laser cutting outfits. 2 weeks later I had a beautiful set of laser cut ribs...
I did this when I built a Bergfalke from Chris's plans. In the case of the Bergfalke, I also sent a copy of the plans to the laser cutter, they digitized it and also cut the fuselage formers for me.
See pics from the build here :Bergfalke build

I did the same again for my current project, a 1/4 scale Scheibe L-Spatz 55 (https://www.rcgroups.com/forums/showthread.php?t=469143)

Here a picture of the ribs :

Mar 20, 2007, 04:28 PM
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chris williams's Avatar
Mark, the Habicht is a beautiful glider, but my plan was drawn many years ago using the scale wing sections: since then I've learnt a bit!
I went on to build a bigger version with my favourite HQ sections which work so well on my other machines. Unfortunately, they're not much good upside down and the Habicht was designed for aerobatics, so I would reccommend changing the wing section to Ritz 2 or even Clark Y if you want to chuck her about a bit. It shouldn't be too difficult a job using Compufoil or Profili...
She will fly reasonably well on the plan section, but low speed handling needs care on the slope: aerotow would be a lot better...

MTT Enjoyed your Bergfalke log, did you ever get her finished?
I have had reports that the fuselage formers have some discrepancies, but obviously you overcame them, so it just goes to show that for you, digitising worked well. I'm planning to enlarge the model to 3rd sometime soon, but I think I'll rely on the desktop scanner and Profili to do the job...!
Mar 21, 2007, 07:29 AM
MTT
MTT
I care about rising air !
MTT's Avatar
@Chris: I got her almost finished, what remains to be done, is hinge the ailerons, and cover the wings.
It has been like this for quite some time, but I got sidetracked with other stuff....

Yes, the fuselage formers have some discrepancies. Not the formers themselves, but the jigging supports, they don't match the outline of the formers. but that is easily overcome, not a big deal.

Once I get done with the L-Spatz, and start covering the wings, i plan on covering the wings of the Bergfalke at the same time, and get them both in the air this spring/summer.
Mar 24, 2007, 09:38 AM
Ay up it's warped
mtbrider's Avatar
Chris
Thanks for the tips, if it designed to be chucked around it would be rude not to. Any suggestions for the angle of attack with the change of airfoil. 2degrees? It will be used for chucking off hills, there are some nice ones around here as I am sure you are aware
Mark


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