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Old Nov 28, 2014, 03:19 PM
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SW-11 Swept Wing prototype

Using the very thin templates from the SW-2, this prototype will have much more wing area and a nearly pitch neutral full length flap. This flap arrangement requires that the elevons deflect down in order to compensate for the flaps, thus providing increased camber across the entire wing. Flap deployment will increase washout. Should come in handy.

Normally I'd build a 2m in one piece, but with a joiner no hatch is needed since access is provided thru the root rib. Should be clean. No plans for a main skid so final touch down had better be without flaps.

Stressed skin has been a problem with my weak Foamular 150 foam, so this one will have a full depth spar. Thinking about putting hard points out on the wing for ballast attachment, which will make for interesting slow speed roll control.

This will be a bagged wing so I hope I don't get too bogged down in the process. I'll be trying a disser treatment on this one.

Kent
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Old Nov 29, 2014, 08:33 AM
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Looks like a nice design to me. Good luck!
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Old Nov 29, 2014, 09:38 PM
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Looking good Kent. Keep the pics coming.

Greg.
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Old Nov 30, 2014, 09:51 AM
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Hi Kent - good to see that you are inspired to build again.
Depending on what you want to do with this model, you may not have enough twist.
If it's to be primarily a thermal design, you'd want it optimized for relatively slow flight.

So much of the wing is cambered and untwisted, that the twist in the relatively small outer panel is probably not going to balance it in slow flight trim. Of course you can manage it with the flap and elevon, but that introduces reflex which is not very desirable for slow flight.

All above just TLAR - not the result of any actual analysis -
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Old Nov 30, 2014, 10:54 AM
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Quote:
Originally Posted by HerkS View Post
So much of the wing is cambered and untwisted, that the twist in the relatively small outer panel is probably not going to balance it in slow flight trim. Of course you can manage it with the flap and elevon, but that introduces reflex which is not very desirable for slow flight.
Oh, this is good Herk. Yes, primary thermal, but fast thermal is good too.

There ISN'T much twist in this wing and the twisted outer panel IS quite small. So for high AoA (landing flare) there may not be enough "nose up" control surface available. I think that this is given. Although I'd be happy to live with such a configuration, even without flaps. If there weren't enough nose up to just float around at min. sink, then that would be disappointing. My TLAR radar tells that with a rearward CG and lots of elevon deflection, min. sink is doable. Your TLAR radar comments are noted and will tested soon enough.

Inasmuch as the flap is pitch positive, I could use the flaps for pitch control, thus increasing camber when nose up is needed. I see this as the "killer app" of swept wing design. The perfect combo. The SW-2 was an extreme configuration. This version should actually perform well.........( now I've done it , never say that out loud).

This is a THIN wing. Even a flat T7075 joiner barely fits.
SW-11 spar groove (1 min 11 sec)
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Old Dec 01, 2014, 10:44 AM
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Wire tube

For the fiberglass wire tube, a 5/16" music wire mandrel was used along with guitarcher's method. That's vaseline on the mandrel, wrap in food wrap and roll on a few layers of 4 oz. glass and 3m77, then vac bag.

For me, permanently attaching the glass to the mandrel is the norm at these small diameters, so I expected trouble in the mandrel extraction.

It slid right out. Found that running the mandrel thru again cleared the food wrap.

mandrel (2 min 10 sec)
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Old Dec 02, 2014, 03:34 PM
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Quote:
Originally Posted by Knoll53 View Post
For the fiberglass wire tube, a 5/16" music wire mandrel was used along with guitarcher's method. That's vaseline on the mandrel, wrap in food wrap and roll on a few layers of 4 oz. glass and 3m77, then vac bag.

For me, permanently attaching the glass to the mandrel is the norm at these small diameters, so I expected trouble in the mandrel extraction.

It slid right out. Found that running the mandrel thru again cleared the food wrap.
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Glad it worked for you Kent. RCGroups is a great place for learning and sharing.
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Old Dec 02, 2014, 03:39 PM
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That makes two of us that are glad.....
My guess is that I blew the food wrap removal part, though was able to get-er-done any way. Any tips for the next time?
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Old Dec 02, 2014, 10:45 PM
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Kent I haven't tried a tube as long as yours. My normal method is as you initially attempted. Grab the free end of the food wrap and twist gently without too much pulling. Remaining stubborn bits are pushed out as you did with the wire.

Also its a bit hard to tell from your photo but before you start to roll the glass or Kevlar or whatever if the free end of the glass is taped to the bench then after the roll is started on the plug you can pull back against the tape to keep the wrapping tight.

I have tried bagging as well as well as spiral wrapping with electrical/insulation tape/vhs tape.
The tape leaves a spiral imprint as opposed to a wrinkled finish that the bagging tends to do. Spiral wrapping will expel excess epoxy.

In winter I've had trouble removing the plug. If so, I put it in the sun for a few minutes to warm the Vaseline and then the plug slips out easier.

The amount of food wrap applied can be varied to give the desired tightness of fit if using a joiner bar/ incidence pin etc. You may know all this already.
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Old Dec 04, 2014, 09:27 AM
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Thanks for the tips guitarcher. Keep your eye on me, I'm liable to do most anything when it comes to FRP.

I DO have some incidence pins needed so tried again with a small carbon tube mandrel. this time extended the food wrap farther out beyond the glass but still was unable to "gently" pull it out from the end. Kinda amazed that you are able to do this. Think that I am using too much resin. With the vac bag, it runs out everywhere. Resorted to reaming with the mandrel and that works well with the food wrap.

Taping down the glass is a good trick to improve the roll up.
glass to mandrel (0 min 45 sec)
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Old Dec 08, 2014, 08:38 PM
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That is pretty neat!
Love how "thick" the wing is.
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Old Dec 21, 2014, 11:45 AM
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Wire Tubes....try #2

Yes I'm sure I'll love how thick the wing is too.........once I get it in the air. For the time being, that thin profile requires a whole different mind set to move things forward.

Initially I made a wire tube by rolling up FRP tubes around a spare 5/16" dia. music wire. This tube carries 2 servo wires and antenna wire. Didn't seem oversize at the time. but when a groove was sanded into the core to accept this tube, it quickly became a problem. Doable, but a problem.

Sooooo, I tossed them and made new wire tubes. I already have some black factory FRP tubes that are sized to fit the run to the elevon servo. But they are only big enough to take one servo wire and an antenna wire. So I used them as mandrels to roll up new wire tubes for the inner panel with it's 2 servo wires and antenna.

Learn by doing. A tapered wing with stepped wire tubes......who knew !
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Old Dec 21, 2014, 12:18 PM
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I also am learning thin wings can have some drawbacks, but I think the pain will be worth the effort in the long run.
Pretty neat trick Kent.
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Old Dec 29, 2014, 11:05 AM
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Groove for wire tubes

Tooling the groove for the new thinner wire tubes was a challenge. First tried sanding the groove with a special sander, which was slow and tore up the very thin edge of the foam.
Next, tried a hot wire tool, which showed some promise. The tool was sized to match the tube, but the more clever way would have been to undersize the tool and make 2 passes, one from each side of the core. That way you'd get a tapered groove with a close tolerance on each side.
SW11 wire groove (1 min 12 sec)
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Old Dec 29, 2014, 02:53 PM
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Thanks for sharing that. Love the old Weller soldering gun used a a foam tool great idea.
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