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Rails for Fowler Flaps

Old 04-05-2014, 02:34 PM
  #1  
W7APD Alan
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Default Rails for Fowler Flaps

Long time back, I worked with a friend on plans for a full scale homebuilt. For various reasons, mostly financial, the project stalled (ha, made a pun!) One thing I always had in the back of my mind, was to build a prototype in 1/4 scale or so, to validate some of my designs. I'm thinking that might still be a groovy project even if the full scale bird never gets built.

One of the design items on the wing is large Fowler flaps. I'm attaching an animated GIF showing the essentials. (Hope it works here.)

In the full size application, the slotted rails would have been 1/4" aluminum. In a modelling application, I'm wondering if I still need to use aluminum, or would 1/16" plywood be adequate? Can parts such as these, made from plywood, be infused with CA (or other) to harden them? I'm pretty sure that plywood would be a whole lot more affordable...

Opinions?



Clicking the image should -- I think -- bring up the larger, animated, version of the image.
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Last edited by W7APD Alan; 04-05-2014 at 02:36 PM.
Old 04-05-2014, 03:27 PM
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b.bixel
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Hopefully this will work for you.... Robart #345.
http://www.robart.com/products/fowle...hinge-15-scale

Specs on Tower site.
http://www3.towerhobbies.com/cgi-bin...?&I=LXMRN6&P=7

Regards,
Bart

Last edited by b.bixel; 04-05-2014 at 03:30 PM.
Old 04-05-2014, 04:18 PM
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W7APD Alan
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Sorry, but I'm absolutely not interested in using pre-existing components. I'm seeking advice on the best way to prototype my own design. Thanks, though.

Last edited by W7APD Alan; 04-05-2014 at 04:37 PM.
Old 04-06-2014, 08:37 PM
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BMatthews
 
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For me it's one of those things that does not scale well. So right off the bat I'd suggest you upscale the track to something more like 3/32 or even 1/8 material depending on what you use.

I'm sort of thinking that you're still better off with .095 aluminium for a couple of reasons. First off it's more than strong enough. Secondly the running surfaces of the slots will be smooth enough to avoid undue friction of the runners in the slots.

I'm guessing that on the full size that you'd have used ball bearings as rollers? On the model that would be overkill. But even then I'd still use a roller sleeve over the pin that runs in the slot. The roller sleeve would reduce the friction of the flaps running by a big amount. It would also greatly reduce wear on the surface of the slots.

Or if you really want to stick to aircraft plywood then on a model of 7 to 8 foot span I'd suggest that you really want to use 1/8 ply, cut the slots oversize and edge them with some metal strip so the flap pin rollers don't tend to locally crush the wood and produce lumpy operation.

You MIGHT be onto something with the CA soaked wood. I know when I've done that the wood transformed to something more like plastic. Perhaps try hardening an edge like this and then roll the pin and sleeve you would expect to use on the scale model across it with two or three times the worst pressure you expect and see if it deforms or otherwise degrades the edge after a few hundred rolls. If it's still good and rolls with very little resistance or roughness then it would seem to me that it would be good for the model. I still like the idea of the 1/8 ply both for the reason that you aren't making it in aluminium and also for the added contact area for the small rollers on the flap linkages.

Unless it's quite a large full size design what about doing it as a 1/3 size? The bigger it is the closer to flying like the full size it would be. Also then you can use things like these fowler flaps with more confidence that the old scaling effect isn't going to alter how the flaps perform.

It all sounds like a great project. I hope that you'll post a build log if this goes ahead in whatever size you and your buddy decide on doing.
Old 04-06-2014, 09:01 PM
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invertmast
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3/32 or 1/8" G10 would be more than strong enough.
Old 04-08-2014, 07:38 AM
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Old 04-08-2014, 07:53 AM
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wings2an3
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Default Fowler Flap

Ziroli P-38
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