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Old Feb 27, 2011, 08:55 PM
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Boise, ID
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NERF Bat SPAD - First SPAD

Hi all,

Intend to build my first SPAD, using a NERF bat. Note picture.

This isn't soft; it's a hard plastic bat, 32" long. I expect the plane will be about 36" long, from the tip of the spinner to the trailing edge of the elevator.

The wing will be the 44" wing from Spadflyer, which is in the mail.

I'm kind of stuck, getting started.

I'm thinking first thing is to cut a hatch in the front of the bat, for putting in the ESC and receiver. I envision the ESC two-sided taped to the bottom of the bat and a thin ply "floor" over it, for the battery. Then the receiver aft of the battery. Everything as far forward as possible.

But what about the cut for the wing?

Could I make one long cut, or opening, from, say 1/2" back from the top of the bat (the firewall) to the trailing edge of the wing? And a hatch at the front? I don't think it would be cut from the parting line to the opposite parting line; maybe would be a hatch of about 40% of the circumference of the bat. But, not sure.

Not sure where to start cutting. Of course, I won't do anything until the wing gets here, but that will be this week.

Any advice would be greatly appreciated.
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Old Feb 27, 2011, 10:46 PM
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LaGrange, GA
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What kind of tail will you have? Have you sized it for the wing you'll be using? I think the easiest thing would be to mount your tail surfaces, tape all your components where you want them to go, then use something like the coat hanger wing mounts to slide your wing back and forth to get your CG. Or you could tape the wing on, but the coat hanger deal is easier to move around. Once you get your CG close, then you can cut a hole opening under your wing like the SPAD originals on STTB. Once you get your CG established you can cut your battery hatch right on the CG in case you want to use different size batteries you won't be throwing your CG off. Taping everything on and getting the CG close means you probably won't have to add weight to balance and you won't be hacking holes in the wrong place that you'll have to cover up later. Good luck and keep us posted!
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Old Feb 28, 2011, 06:24 PM
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Boise, ID
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JohnsPop, Thanks for the suggestions and I will do exactly that. Makes sense.

Not sure about the tail yet. I'm waiting for the wing to arrive, and I don't know of any formula for the tail. It will be a conventional tail, however, (not a V), and I've been looking at the pixs on the SPAD sites. The horizontal stabilizor's trailing edge will go to the end of the bat, and then the elevator will extend past it a couple inches. At least, that's my thought.

The only thing I know is that the tail coroplast will be 4mm and it will be white, to begin with, until I apply the coating. (Plane will be blue and orange when finished.)

Now, I did have one question: I could not find anything about coat hanger wing mounts. What is that all about?
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Old Mar 01, 2011, 01:28 AM
Rusty
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Auckland, New Zealand
Joined Feb 2006
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Have a look at March 08 edition on rcsoaringdigest.com for a good article on a bat based corro sailplane. Could help with layout, wing attachment and even how to make a quality wing yourself.
Attached a tail calculator.
If you haven't designed a plane before, get back to us at each step!
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Old Mar 01, 2011, 11:08 AM
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Scroll all the way down to the end of this link: http://www.chrisspad.com/planes/main/mspp.html At the very end is a link that says How To Design Your Own Spad. Chris has a lot of formulas and stuff in there about how to size your tail to your wing.

You might attach your vert to your hor with some skewers through the hor up into the vert and gooped in. Or possibly use angles of PVC like they do on the Saturday Night Special. Or you could run some nylon 1/4-20 bolts through the hor into the vert like Dave McD does on the PBF. Then cut your slots in the tail end of the bat and slide the whole assembly in with some Goop to hold it all in. Or maybe some wood screws or skewers run through there to help lock it all in.

That's a good link to that glider article Rusty! I've got a buddy who wants to build one of those discus launch gliders out of coro so I'll point him to that article.

Wow, looking at the main RC Soaring Digest site..... what a find! Dang, they've got enough back issues to keep you reading for a WHILE!
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Old Mar 01, 2011, 07:49 PM
Rusty
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Auckland, New Zealand
Joined Feb 2006
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You might want to join the Yahoo group mentioned if you are going to download lots of Digests as it offers lower res copies of the more recent pdf files.

Corro is too heavy for a discus launched glider (100-300gms AUW, 1-1.5m span).
The go-to entry level scratch builds for DLGs are the Mimi, Quickflick (free plans) and the Gambler and DL50 kits - in the hand launch forum.

There are plenty of sloper designs that work well in corro, including Mugi, dAzi, Revert, Beetle, Waco, Fluteboy, Crossbow, Jart, Micro-slope Stik, Spaggy, and the scale WWII Mig 7 now on the slope forum. It may be possible to make other designs in Corro that can be tip launched into lift on the slope eg the Weasel.
Bex may give some pointers on making a thermal Spad if you have access to 2mm corro and go with a non-corro fuse.
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Old Mar 02, 2011, 11:23 PM
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Boise, ID
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Hi guys,

Got the wing today, and expect to get started this weekend. Will probably take my time, though.

After reading the suggested documents, (thanks!) have a good idea how to proceed.

Weighed the stuff I have, and approximate AUW will be about 60 - 65 ounces, with wing loading of 17 to 18.5 ozs. Don't have the tail stuff yet, nor the aileron servo, but weight will be something like 65 oz max, I'm pretty sure.

CoG and positioning of the wing might be fun, but installing the tail and taping the other things makes sense and I'll get the answer that way.

Thanks again for your help and I'll post pix as build progesses.

One other thing: I still could not find anything about coat hanger wing mounts. What are they?
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Old Mar 03, 2011, 11:19 AM
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Lawton, Oklahoma - USA
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you bend a piece of coat hanger into a u shape with little hooks bent at each end to fit around your fuse. you need two. you then put them onto the fuse, front and back of the wing, and use rubber bands from hook to hook to hold the wing on. you can easily slide the wing back and forth to find the correct CoG location. easier than taping the wing on to find CoG.

very quick image:
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Old Mar 03, 2011, 11:42 AM
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Oh yeah, sorry, forgot about the coat hanger hold-down links. Frost got it. And while they work with just a couple rubber-bands to slide back and forth to find your CG, they'll also work just fine as a full-time wing hold-down with an appropriate number of rubber bands. Believe it or not, they don't slide around like you would think. Not sure about on a tapered ball bat though!
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Old Mar 03, 2011, 12:03 PM
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Thanks guys.

That will work. I'll still have to make a guess about cutting the fuselage, where, and how big of a cut, but I was warned by Spadflyer I should just get a kit from him, with a rectangular fuselage, rather than use a bat, because using the bat is more complicated.

He's right of course. but the idea of using a bat just intrigues me.

I'm thinking I can adjust CoG with the battery placement too, if I need to. And the landing gear.

Thanks again.
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Old Mar 04, 2011, 12:25 PM
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Guys, one other thought:

My intention is to put two wood dowels through the fuselage, each approx under the LE and TE of the wing. Drill the holes through the fuselage and glue the dowels in. They'd stick out about a half inch, then use rubber bands to attach the wing.

Anybody have a better suggestion about that? Looking at battery fit, etc., I'm wondering how to slide the battery in and out, given the front dowel might be in the way. Haven't measured or cut anything yet, just wondering about wing attachment. Or if there might be a better way.

Those coat hanger links might be the answer, with glue or epoxy or something.
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Old Mar 06, 2011, 03:31 AM
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That front dowel is the tricky part with a fuel plane also because it often is right where the fuel tank is.... probably why they came up with the coat hangers in the first place. The dowels work well but you'll probably want to go about a 1/2" in front of and behind the wing or it's hard to get the rubber bands on. It'll be hard to get them drilled straight on a bat but unless you care what it looks like it won't matter unless you get them so cock-eyed the rubber bands come off. A small slot cut in the bat might hold the coat hangers in place ok but it may weaken the bat and cause a split if you fly like I do.

Something that's pretty interesting is Villa's method of mounting the battery and receiver in the wing itself. He cuts hatches in the wing and mounts stuff there. That would take the battery completely out of the fuse. You'd have to charge inside the plane or else make the hatch easy to open to swap batteries in and out but he's had a lot of success with mounting stuff in his wings. He's got some pretty good pictorials, right now I can't remember if I've seen them here, on RCU or on Spadworld, but if you're interested in going that route, I can track them down.
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Old Mar 06, 2011, 03:40 AM
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Here it is: http://www.rcuniverse.com/forum/m_9892444/tm.htm I guess that's just the RX battery for a fuel engine but no reason you couldn't mount a lipo in there as well with the aforementioned ease of access necessary for charging or swapping out to keep flying. Villa's done a lot of cool stuff. He's VillaPilote on here I think.
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Old Mar 07, 2011, 12:22 PM
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Thanks JP for that link!

That guy does have a slick setup. For cost reasons, and also because every SPAD flyer in my club, I think, has a single servo on the ailerons, that's what I planned also. So, Ill go with the servo sticking out the top of the wing, centered.

This weekend, CA'd and hot-glued the vert and hor stabs together. Now to cut the rear of the fuselage with slots for them. I should have followed Spadflyer's advice and just used a rectangular pipe for the fuselage. Ensuring I'll cut three perfectly parallel slots on this fuselage, perfectly aligned, with a fuselage with decreasing circumference, is more trouble than its worth.

The scrap piece of Coro a sign printer gave me had the coro running the wrong way for the horizontal stabilizer I believe. That is, the "rows" run front to back, not left to right. It seems like they are more flexible where they should be stiff, so I CA'd two carbon fiber strips to the horizontal stablilizer, running left to right. They will be covered by the covering or decals I have planned for that area.

Can this Coro be used either way, anybody know? For the main wing, the Coro rows run left to right AND it has a spar, of course. Seems like it would provide the necessary rigidity better that way.

Any concerns about running the hor stab coro front to back?
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Old Mar 07, 2011, 08:00 PM
Rusty
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Auckland, New Zealand
Joined Feb 2006
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Corro Wings

The bat will likely have a mold line on both sides that can be used for a datum to cut parallel slots.
The Corro is much stiffer in the direction of the flutes, but tends to kink and crease in the other direction. That is why your wing has those creases on the leading edge. This will adversely affect low speed characteristics. A conventional wing runs the flutes cordwise, sacrificing skin strength for airfoil integrity. The spar takes the loads and the skin bends naturally with some tension on it to keep a foil.
If you align the trailing edge with the flutes you can make a wing that includes ailerons and with a highly tapered wing, get a slightly diagonal flute direction, particularly on the top, that will conform to foil without creasing and give much more torsional stiffness (eg Mig7, dAzi).
To make a constant cord wing with spanwise flutes, it is necessary to use ribs or a wide foam spar web and heat to conform the foil without creasing, which is some more work.
See the previously mentioned Corro Bat (also May 2009 for a powered version) for how to easily make a performance wing.
Corro is cheap and readily available so I would get a new piece of 3 or 4mm for the tail surfaces. Try and keep this end light.
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