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Old Nov 24, 2013, 04:26 PM
let's FLY!
JimZinVT's Avatar
United States, VT, Castleton
Joined Dec 2007
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Build Log
SAL-Plank project

I've just started a new scratch-built project, and there has been some interest on the Wisel thread, so I guess I'll do a little build thread. I'm sure I'll need some advice along the way; your comments and suggestions are welcomed

It started out with the idea that I'd build a 2-piece Wisel Light for hiking or mt. biking in to check out the slopes around here (any slopes around here require a trek to get to....that's why I don't do all that much sloping near home.) Then I figured I wanted to be able to side-arm launch it, because at some slopes I fly, I have to fly from the bottom. So it needs a longer tail. Longer tail means weight will be needed forward so it needs a nose. I started playing with the design, and now it doesn't look much like a Wisel Light anymore. I've got a bad habit of over-complicating things.

So this is what I've got: I'm going with the PW-98 mod. airfoil because to my uneducated eye it looks like a liftier version of the PW-51. I've reversed the Wisel wing planform so it's less swept, which helps move some weight forward. Span is 48" (1.2m), root is 13" (33cm), tip is 7" (18cm). Ailerons are 20% at the root, 25% at the tip. The fuse is, from the side, a scaled-up image of the airfoil. And I gave her a stylized version of an Alula tail, which I think looks pretty cool

For the 2-piece wing I'm going with what some of the light Le Fish builds have done: airfoil-shaped recesses in the sides of the fuse to position the wings, and a joiner rod that will run through the fuse and into the carbon tube spar in the wing halves. Wing retention on this first one will be with magnets. I know that won't hold for a side-arm launch; If she flies well I'll have to put some thought into something more secure.

This first one will be XPS foam covered with laminating film. If she flies well, and once I work out all the details, I may try a composite vacuum bagged wing and molded fuse. THAT will be an adventure, since the only composite work I've ever done is one vac. bagged balsa DLG tail.
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Old Nov 24, 2013, 05:01 PM
Cliff
16141's Avatar
Australia, QLD, Pacific Paradise
Joined Oct 2011
342 Posts
Quote:
Originally Posted by JimZinVT View Post
I've just started a new scratch-built project, and there has been some interest on the Wisel thread, so I guess I'll do a little build thread. I'm sure I'll need some advice along the way; your comments and suggestions are welcomed

It started out with the idea that I'd build a 2-piece Wisel Light for hiking or mt. biking in to check out the slopes around here (any slopes around here require a trek to get to....that's why I don't do all that much sloping near home.) Then I figured I wanted to be able to side-arm launch it, because at some slopes I fly, I have to fly from the bottom. So it needs a longer tail. Longer tail means weight will be needed forward so it needs a nose. I started playing with the design, and now it doesn't look much like a Wisel Light anymore. I've got a bad habit of over-complicating things.

So this is what I've got: I'm going with the PW-98 mod. airfoil because to my uneducated eye it looks like a liftier version of the PW-51. I've reversed the Wisel wing planform so it's less swept, which helps move some weight forward. Span is 48" (1.2m), root is 13" (33cm), tip is 7" (18cm). Ailerons are 20% at the root, 25% at the tip. The fuse is, from the side, a scaled-up image of the airfoil. And I gave her a stylized version of an Alula tail, which I think looks pretty cool

For the 2-piece wing I'm going with what some of the light Le Fish builds have done: airfoil-shaped recesses in the sides of the fuse to position the wings, and a joiner rod that will run through the fuse and into the carbon tube spar in the wing halves. Wing retention on this first one will be with magnets. I know that won't hold for a side-arm launch; If she flies well I'll have to put some thought into something more secure.

This first one will be XPS foam covered with laminating film. If she flies well, and once I work out all the details, I may try a composite vacuum bagged wing and molded fuse. THAT will be an adventure, since the only composite work I've ever done is one vac. bagged balsa DLG tail.
Hi Jim looks nice I will be watching this thread with interest as I have just finished a 900mm straight le plank (Pewee 900) with pw51 foil and I am having a huge amount of fun flying it
Cliff
RC Pewee 900 flying wing glider northside (1 min 6 sec)
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Old Nov 24, 2013, 08:37 PM
let's FLY!
JimZinVT's Avatar
United States, VT, Castleton
Joined Dec 2007
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Cliff that looks like a great place to fly. Some day I'm going to have to get over to your side of the planet....so many cool places to see.

~~~~~~~~~~~~~~~~~~

I've been giving a lot of thought to the tail over the last week. The Alula gets away with an unsupported foam tail because the EPP is so flexible. The side loading from the side-arm launch bends the tail but it snaps right back. But even so it's not unusual for the fuselage to eventually break at the front of the tail. Trying the same thing with XPS I'm sure would result in a cracked tail.

Since I've just built a vacuum bagging system I decided to try a foam cored fiberglass tail combined with a fuselage "spine". This is only the second part that I've ever vacuum bagged. I used 1/4" (6mm) foamboard for the core, with the paper removed. It's covered with 3 oz. glass, with strips of 12k carbon tow added to both sides for stiffness. I used some yellow epoxy pigment in the resin. I'd call it a moderate success. It's stiff, and it's got a very nice shiney surface finish. And it's light, 31g out of the bag, untrimmed. But the foamboard core is very soft....it dents very easily. I'm afraid it will not hold up to the side loading of the SAL launch. But I'll use it for the prototype and see how it goes. I'll have to resist giving it a full-on DLG launch.
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Last edited by JimZinVT; Nov 24, 2013 at 11:15 PM. Reason: smaller pix
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Old Nov 24, 2013, 10:57 PM
Stirring the pot
johannlochner's Avatar
Port Elizabeth South Africa
Joined Jun 2008
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Go Jim GO!!!

Looking good!
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Old Nov 25, 2013, 06:42 AM
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MattyB's Avatar
United Kingdom, England, Hitchin
Joined Jan 2004
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Quote:
Originally Posted by JimZinVT View Post
Since I've just built a vacuum bagging system I decided to try a foam cored fiberglass tail combined with a fuselage "spine". This is only the second part that I've ever vacuum bagged. I used 1/4" (6mm) foamboard for the core, with the paper removed. It's covered with 3 oz. glass, with strips of 12k carbon tow added to both sides for stiffness. I used some yellow epoxy pigment in the resin. I'd call it a moderate success. It's stiff, and it's got a very nice shiney surface finish. And it's light, 31g out of the bag, untrimmed. But the foamboard core is very soft....it dents very easily. I'm afraid it will not hold up to the side loading of the SAL launch. But I'll use it for the prototype and see how it goes. I'll have to resist giving it a full-on DLG launch.
Personally I think you will be fine - after all, the foam at the centre of the foamboard is essentially Depron as used on the Alula mk1. Sure it might look a bit tatty after a bit, but it should still fly ok. If it's successful you can always redesign it to take a replaceable tail like the original Alula does.
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Old Nov 25, 2013, 07:20 AM
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United States, FL, Indialantic
Joined Dec 2011
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Design looks good, Jim, and your goal is a challenge for sure. After the tail final shaping is done you might consider rebagging to add a carbon fiber tow "U"-channel on the edges. That should really boost the longitudinal stiffness.

Always enjoy watching and learning from your builds and concepts.

Ken
(whose Weasel was eaten by a hotel, Alula "nose-jobbed" by a parking lot and has 4 Lost Model Alarms en route by mail)
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Old Nov 25, 2013, 07:28 AM
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Russia, Primorsky Krai, Nakhodka
Joined Apr 2010
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Will closely monitor the project.
Wings - my "secret love."

Embossing on paper towels can be imprinted on the laminate.
Good idea - towels without embossing.

I wish you success!
Eugene.
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Old Nov 25, 2013, 07:59 PM
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JimZinVT's Avatar
United States, VT, Castleton
Joined Dec 2007
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We'll see how it goes. I'm going to build out this "beta test version" using this part, and try not to break it until I can see how she flies.

Matty, I've never seen an early version of the Alula. The current version uses quite a thick tail. A thin tail seems like it would be a lot less draggy.

Udjin, I got a lot of paper towel imprinting on some DLG tails I made, using thinner mylars. On this piece I used 0.014" (0.36mm) mylars and I have no imprinting at all.
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Old Nov 26, 2013, 08:15 AM
left, left, oh, my other left!
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Old Nov 26, 2013, 01:44 PM
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MattyB's Avatar
United Kingdom, England, Hitchin
Joined Jan 2004
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Quote:
Originally Posted by JimZinVT View Post
Matty, I've never seen an early version of the Alula. The current version uses quite a thick tail. A thin tail seems like it would be a lot less draggy.
I will probably get flamed for saying so, but the Alula Mk1 was a better plane than the Evo - not as pretty and a longer build, but far lighter (30-40%), more aerobatic and launches just as high. Being hot wire cut EPP it was more labour intensive for Michael to produce, hence why it was replaced. Lots of Alula Mk1s are on Michael's archive page...

http://www.dream-flight.com/archives.html

As you can see the tail was quite different - 5mm Depron with carbon strip that extended fwd of the fin LE into the flutes of a small piece of Coroplast. This is a great method - it's light, and can easily be removed for travel and when it gets tatty or broken the Depron can be replaced on the field in seconds. In thousands of flights I've only ever had 3 tails and two pieces of Coro; works for me!
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Old Nov 26, 2013, 02:32 PM
Entropy Happens!
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Bellingen NSW Australia
Joined Aug 2008
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Nice project Jim, I'll be watching with interest as it progress's.

Have you started cutting the wing cores yet? The PW106 or PW75 are both worth considering as well. I see the PW98 has a higher camber than the Pw51, but both the above have an even higher camber.
I note that the PW98 is the one of the series most favoured for DS.
I have a plank flying with the PW75 foil, which I think I will choose for something like you are building, if and when I can fit it into all my other plans (or more accurately - dreams!)

edit:
I would love to see a design like this developed over time and a fully moulded version built. But now I really am dreaming..........
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Old Nov 26, 2013, 08:28 PM
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I believe PW1211 is purpose designed for SAL wings...

http://www.rc-network.de/forum/attac...9&d=1322944713

It has been used successfully several times...

http://www.rcgroups.com/forums/showthread.php?t=1261384
http://www.rcgroups.com/forums/showthread.php?t=749390
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Old Nov 26, 2013, 08:30 PM
Entropy Happens!
Jim.Thompson's Avatar
Bellingen NSW Australia
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[QUOTE=MattyB;26746820]I believe PW1211 is purpose designed for SAL wings...

.............................

Yes, thanks for the reminder. I had forgotten.

Do you have the co-ords Matty? If so, would you mind posting them please?
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Old Nov 26, 2013, 11:14 PM
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JimZinVT's Avatar
United States, VT, Castleton
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Jim, yes the cores are cut. Not my best cores but they'll do for the first trial. I did look at the whole range of PW plank airfoils but settled on the 98 as what looked to me like a good middle ground between the higher lift versions and the more aerobatic 51. I too have noticed that the DS guys seem to like it for their planks. I don't know near enough about airfoils and reading those colorful graphs to say why. We shall see.

Matty, the 1211 is also on my list to try. It was used on the "Sally" design that Johan and the Port Elizabeth, South Africa Slope Rebels had great success with, among others. It was my initial choice, but it's a pretty thin foil; I went with a thicker one for my first plank....should be a stronger wing for all the plowing into the earth I'm sure I'll do before I get it trimmed out. The 1211 will definitely get a try later....it's rumored to be fast.

The build will be stalled for a few days while I make the rounds of southern New England visiting family over the Thanksgiving holiday.
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Old Nov 26, 2013, 11:16 PM
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JimZinVT's Avatar
United States, VT, Castleton
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Jim, I'll PM you the 1211 coords.
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