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Old Jan 20, 2012, 09:08 AM
Just call me crash for short
Quick61's Avatar
United States, OH, The Plains
Joined Jan 2011
1,697 Posts
Quote:
Originally Posted by boingk View Post
Quick question guys... as you might have garnered from a previous post or two I'm building a flying wing glider using a Peter Wick airfoil. I've cut a stack of PW-106(?) ribs from 1/8" balsa and have my 1/4" spars ready to go, as well as all electronics for the build.

Now, how should I space these ribs out? Chord is 12 inches and I'm shooting for a wingspan of around 60 inches. I'm thinking of a rib spacing of around 4 inches, giving me approximately 16 ribs for the entire ~60" span.

I'm not looking for this thing to be overly aerobatic but would like it to be reasonably strong. The plan for spars is for them to be 1/4" square balsa, with one 2" back from the LE and another 2" behind it. LE will also be 1/4" square stock. TE will be the most suitable triangular stock I can find.

Does that sound about right to you guys? Any help is much appreciated.

Cheers - boingk
TheNightowl and Captain Canardly are pretty much on target here unless your building a free flight and are trying to save weight. Maybe I should ask, where are you wanting to fly this wing and under what conditions? If your planing on sloping on a nice grassy hill in moderate winds, you should be shiny with a strong LE (like 3/8" hardwood dowel or 1/4"x1" balsa strip) and D box. Now, if you plan on launching with A 2m high start into a headwind with a single hook close to the CG, your in trouble and it will fold up on you like a cheap suit. In either case, I would get the ribs closer together, like 2.5", even if your sheeting the entire wing with 1/16" basswood. Now,if you recall, I just mentioned "a single hook". If you use dual hooks, and a bridal tow,not a bad idea with any flying wing, your wing loading will be reduced by better than half (3 -5 x depending on wing and hook placement) I'm attaching a .pdf that will explain this a little. Still, getting rid of that first balsa spar and replacing with a basswood or spruce 1/8"x1/4" upper and lower with either "C" or better yet, "I" beam spar would be much better way to go. Here is a link on some testing done with spars. - http://www.rcgroups.com/forums/showthread.php?t=1431515. (worth reading ALL the way through). You have a build log anywhere? You also might want to take a look in the new Nurflügel forum here - http://www.rcgroups.com/nurfl-gel-762/ as there are several sail-wing projects going on, and these guys are serious about their wings.
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Old Jan 20, 2012, 09:43 AM
I need some building time in t
scaflock's Avatar
United States, AZ, Douglas
Joined Nov 2007
1,617 Posts
That's one thing about aero-towing that I really like. That being that you don't subject the wings to nearly the same forces that you would with a winch or high start. You could built a much lighter spar system and not have to worry about it folding on you during a launch. Granted, that plane would be pretty much be stuck being used for aero-tow launching only, but think of how light of lift it could soar on!

I'm thinking that something like a Hobby Lobby 12ft Telemaster would make a great tow plane for just about any size model sailplane. Of course it's just about big enough to use for flying in the hooter girls as well so it could serve dual duty.
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Old Jan 20, 2012, 10:15 AM
≡LSF8067≡
dwells's Avatar
Bedford, TX
Joined Oct 2007
2,851 Posts
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Originally Posted by Windependence View Post
On a slightly different note I have made a little progress on my woody build. I now have two outer wing panels and will begin working on the inner panels soon. Overall they came out pretty well. I still need to add the tip blocks. I used formica templates glued to each end of the wing panel to use as a guide in shaping the LE and the wing airfoil. It worked really well and is easy to do and best of all, it is easily reproducible. Here are a couple pictures of wood for all of you.

Wayne
Beautiful, Wayne, very precise! This is a great idea and will use it on my Oly wings. I can almost smell that balsa dust through me screen....I want to go home and build!
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Old Jan 20, 2012, 10:24 AM
Making wood fly since 2007
Windependence's Avatar
USA, MN, Rochester
Joined Mar 2008
2,543 Posts
Thanks Dwells,

I first got the idea over in the hand launch forum. I figured if they can cut super accurate airfoils in foam using templates why can't I? It really takes the guess work out of that LE.

Wayne
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Old Jan 20, 2012, 10:44 AM
Just call me crash for short
Quick61's Avatar
United States, OH, The Plains
Joined Jan 2011
1,697 Posts
Quote:
Originally Posted by Windependence View Post
Thanks Dwells,

I first got the idea over in the hand launch forum. I figured if they can cut super accurate airfoils in foam using templates why can't I? It really takes the guess work out of that LE.

Wayne
I've come to realize that there are more than a few building techniques that can be ported from the DLG side of the sport when building a woodie. Like CF disser on the D-box sheeting, tail boom construction, pull string/sping setups, (nice, light and simple for spoilers), ultra light tails, etc.. Pays to study what others are doing in different areas. Nice work on those LE's.

Mark
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Old Jan 20, 2012, 10:44 AM
≡LSF8067≡
dwells's Avatar
Bedford, TX
Joined Oct 2007
2,851 Posts
Well, it makes perfect sense. My first set of wings had very accurate LE's but it took me several hours to get them just right. This will help with the shadows and eye strain trying to eyeball every inch of the length.
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Old Jan 20, 2012, 11:18 AM
AMA 3959
alstrahm's Avatar
United States, CA, San Jose
Joined Oct 2002
1,471 Posts
Quote:
How's towing the Oly 650 working out? We tried towing an RES ship years ago but the problem we experienced was a combination of roll coupling and a tug unable to fly slow enough to make it work.

Sean, I read that after I had done 5 or 6 tows with no problemsJust drop a little flap on the Fun Cub and off we went!

Al
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Old Jan 20, 2012, 11:28 AM
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boingk's Avatar
NSW, Australia
Joined Feb 2011
2,120 Posts
Thanks quick61, very helpful. I should probably have mentioned that this will be an electric powered ship as I will need noeweight anyway. Thinking 35mm 1100kv outrunner with 10x6 prop on a 3s 2200mah lipo or thereabouts. Could even use a 1000mah 3s if I as only doing a motor run to altitude.

My main concern isn't with launching, then, but with actually flight loading. Does this change anything?

Cheers - boingk
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Old Jan 20, 2012, 12:49 PM
Just call me crash for short
Quick61's Avatar
United States, OH, The Plains
Joined Jan 2011
1,697 Posts
Quote:
Originally Posted by boingk View Post
Thanks quick61, very helpful. I should probably have mentioned that this will be an electric powered ship as I will need noeweight anyway. Thinking 35mm 1100kv outrunner with 10x6 prop on a 3s 2200mah lipo or thereabouts. Could even use a 1000mah 3s if I as only doing a motor run to altitude.

My main concern isn't with launching, then, but with actually flight loading. Does this change anything?

Cheers - boingk
Yes, it does a bit. you can get away with lighter spars if your not planing any high G maneuvers, but then again, things don't always go according to plans. Spinning down from a spot out or pulling out of a dive can put just as much load on the wings as a launch. If you really want to go with the lighter spars, make sure that it's HARD balsa and not just any 1/4" stick and I would also be thinking about CF strips / tow laminated to the bottom at the minimum. A couple-3 wetted out strips of 12K CF tow "wax paper bagged" the the spar should go a long way to keeping things together for normal motor glider operation. Personally, I'd still go with at least a C-beam spar, but maybe it's just me.

Of course, as with everything, your mileage may very

Mark
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Old Jan 20, 2012, 03:19 PM
life long racing nut & modeler
granada don's Avatar
Granada Hills Ca.
Joined Nov 2009
2,042 Posts
Your Main Spar is your wing, put in some shear webs to build a C-spar - I Beam - or a Full Box spar. Like Quick says at least a C spar.

Your 12" cord wing will never know the difference in the weight of some balsa pcs for a lot stronger wing, if you don't put them and you fold the wing pulling out of a dive you will feel really bad that you did not do a little extra work.

Maybe a 3" - 3 1/2" rib spacing too as 4" might be a bit much.

Better to be safe than sorry and fly another day!!

G Don
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Old Jan 20, 2012, 03:24 PM
ein flugel schplinterizer
seanpcola's Avatar
USA, FL, Pensacola
Joined Sep 2004
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Quote:
Originally Posted by alstrahm View Post
Sean, I read that after I had done 5 or 6 tows with no problemsJust drop a little flap on the Fun Cub and off we went!

Al
Yeah we had too much tug and zero flaps. That's why I was thinking about a smaller, lighter EP tug.
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Old Jan 20, 2012, 09:02 PM
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boingk's Avatar
NSW, Australia
Joined Feb 2011
2,120 Posts
Thanks again quick61 and G Don, and a bit of a sorry on my part as I was planning shear webs but did not know that they were known as a 'C spar' once fitted to an upper and lower mainspar arrangement.

Calculations are all being made off my first 100% selfbuilt model - the 'Kombat Kid' by ProBroJoe. Build thread on that one is here:

http://www.rcgroups.com/forums/showt...1425370&page=3

And the micro version of it is here:

http://www.rcgroups.com/forums/showt...1425370&page=3

So the natural progression after making a smaller version is of course to make a larger one! Both large and small wings fly very well and I can only imagine the current build will fly better as its using a dedicated flying wing airfoil and will have an equal or lower wing loading when finished.

Cheers - boingk
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Old Jan 20, 2012, 09:09 PM
ein flugel schplinterizer
seanpcola's Avatar
USA, FL, Pensacola
Joined Sep 2004
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Uh, boingk, I think I have one of those wings in my shop. I'll pull it out this weekend and take a photo. Long story as to where I got it.
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Old Jan 20, 2012, 09:17 PM
ein flugel schplinterizer
seanpcola's Avatar
USA, FL, Pensacola
Joined Sep 2004
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Quote:
Originally Posted by scaflock View Post
That's one thing about aero-towing that I really like. That being that you don't subject the wings to nearly the same forces that you would with a winch or high start. You could built a much lighter spar system and not have to worry about it folding on you during a launch. Granted, that plane would be pretty much be stuck being used for aero-tow launching only, but think of how light of lift it could soar on!

I'm thinking that something like a Hobby Lobby 12ft Telemaster would make a great tow plane for just about any size model sailplane. Of course it's just about big enough to use for flying in the hooter girls as well so it could serve dual duty.
Jeff, you'd be surprised what a ST can pull. MY Ask-13 is a little under 20' span and weighs around 30# and an 8 footer ST pulled it up without too much sweat. Don't remember the motor size but it was a single lung gas.

I have no problem with building a dedicated aerotow bird. Something I've had on the drawing board in my mind for a few years is a cheap, easy to build full house aerotow model of around 20' span for fun towing. Wouldn't have a lot of build time to it, no details (cockpit, pretty paint), just a big majestic cheap to acquire glider that's big enough to see way off with a tow release. Balsa sheeted foam wings, simple fuse layout, maybe flaps and spoilers both. Knock out a few sets of wings, tail feathers and fuses. Pile one in, slap the next one together and keep on soarin'.
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Old Jan 20, 2012, 11:46 PM
life long racing nut & modeler
granada don's Avatar
Granada Hills Ca.
Joined Nov 2009
2,042 Posts
Hi Sean

Do you go to Len's Aerotow site & forum as they have a ton of build's going on, and some really big one's too.

G Don
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