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Aug 27, 2004, 09:32 PM
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Cessna L-19 Bird Dog


For the last several weeks the "drawing board" has been consuming the vast majority of my spare time, but now that there are 3 new designs roughed in, and a fourth well under way, it's back to the workbench to make a bit of sawdust.
The first new design up for proto-typing is the Cessna L-19 (you'll just have to wait to see what the other ones are!!) with a 40" span and 200 sq." of wing area.
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Aug 27, 2004, 09:37 PM
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Framing is just about finished


The model is about 90% framed now. The only thing left is to carve the cowl nose block, get the wing hold downs in place, and make up the wing struts and mounts.
Framing is typical "stick and tissue" style, shooting for a flying weight in the 8-10 oz range.
Aug 27, 2004, 09:41 PM
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Lots of Sticks!


The tail section is framed using a laminated outline made up from 2 layers of 1/16 x 1/8 balsa, with the rest done up in 1/8 sq. and 1/16 x 1/8 balsa. The rudder will be controled by pull/pull and a wire pushrod running the elevator.
Aug 27, 2004, 09:49 PM
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Fuselage Frame


The fuselage is built around a basic stick frame with formers and stringers top and bottom. The main frame is 1/8 sq. balsa with 1/16 x 1/8 vertical and diagonal braces. The stringers are 1/16 sq. balsa, which I was a bit skeptical about going in, but now that everything is in place, they look plenty stout. The wing will be bolted in place, retained by dowels up front.
Aug 27, 2004, 10:00 PM
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The Wing


The wing assembly on this one is a whole new deal, based on the Dumas method of doing the wing on their Mister Mulligan. The spar is one piece instead of the typical upper and lower front spars with a single rear spar. 1/16 sq. balsa diagonal bracing adds all the torshional rigidity that will be needed to keep things nice and straight at the speeds the model will fly, and by using a "semi-functional" lift strut, there's no danger in braking the wing.
The center section is sheeted top and bottom at the rear section, and the top only at the front.
So far, framing has gone well, with no major glitches. So, the next step will be to get the radio gear in and hooked up. Stay tuned.......
PAT
Aug 28, 2004, 01:08 AM
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Pat, gorgeous airframe, as seems to be your habit! I love those lightweight airframe designs of yours! Anxiously awaiting more pictures and words. I don't see how you do it, it would take me years to get this far, starting from scratrch, and apparently you have whipped this out in just a matter of hours!

Keep it up, we want to see more!

AmpAce
Aug 28, 2004, 08:10 AM
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Amp, Thanks for the kind words. Actually, I've had this one "in the works" for awhile. Learning CAD has been an uphill trek for awile, which is why there are 4 designs in the works and only one going together (for now -- but that's going to change real soon). I figured the best way to learn the drawing program is to just dive in and go till my eyeballs started bugging out. Well, there buggin' out now, so it's time to get off the chair and back into the shop!
The beauty of building CAD designed p-types with laser parts is that it cuts the building time dramatically. The thought of cutting all 14,000 of those stringer notches makes me cringe, and we haven't even discussed the wing spars yet! It's funny though, "a large collection of sticks, all flying in close formation" looks alot tougher to build than it actually is, and it goes together alot faster than one would think, once you get used to the building style. The good news is, they're light, and strong, all at the same time!
PAT
Aug 28, 2004, 11:39 PM
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Well, I have to hand it to you for learning CAD. I haven't tried this yet. I absolutely agree with you about the "collection of sticks"! It's surprising how fast things go together. The thing that slows me up is when I'm treading in "uncharted territory" and am not sure how to best do something. Takes a lot of trial and error, and cogitating!

I really like the lightweight stick built airframes. Usually they much more closely resemble the real thing than anything else, plus they are amazingly strong for their weight.

I suppose once you learn CAD, and have laser cutting availablde, it's much easier to go back and change something if you don't like it. You don't have to cut all of those notches over again!

I just aquired some line drawings for a 1928 TravelAir, and may have to make a try at scratch building one. Looks like a fairly straight forward design. Not too many curves or complicated parts.

AmpAce
Aug 29, 2004, 12:08 PM
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Beautiful Bird Dog bones, Pat. As always I'm blown away by your ability to crank out super quality models in record time. I started CAD-ing out the Comet 54" Taylorcraft last night with the intention of having it laser cut. I'm wondering where you get your laser cutting done, or do you own your own machine?

thanks,
Jim
Aug 29, 2004, 02:57 PM
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Jim, I get the majority of my laser cutting done at Teccut in Baltimore. Contact David at [email protected] and he'll fill you in onwhat you need to do to make the files compatable.
I got to fly a 54" Comet "Tea kettle" at SMALL this year. It was powered by an MP Jet .061 deisel and flew way better than words can describe. Your's will definately be a good one!
PAT
Last edited by P. Tritle; Aug 29, 2004 at 03:16 PM.
Aug 29, 2004, 03:02 PM
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Power and Guidence is just about all in.


The servos and control hook-ups are all in place now. The servo rails mount on the lower longeron, allowing plenty of clearance between the servos and belly stringers, and don't use up alot of space in the cockpit.
My first choice in servos would be the Cirruss CS-5.9's but I had a couple old S-80's laying around so I desided to use those instead.
The rudder will be actuated using kevlar pull/pull cables, the elevator uses a Sullivan #507 pushrod tube with a .032 wire pushrod.
Aug 29, 2004, 03:09 PM
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Motor Mount


As always, the motor mount is simply a 1/16 balsa platform suspended between the first and second formers. The MPI EPU-6 drive unit is glued to the mount with silicone with a little right thrust. The Jeti 05 ESC will be secured in the fuselage as dictated by the battery location.
Aug 29, 2004, 03:13 PM
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The Nose Bowl


With the motor mounted, the nose bowl was carved, hollowed and fitted over the front end. With that, the motor mount and eqipment installation is pretty well complete. The Rx and battery location will be dictated by the C.G. so that won't come until last.
For now, the only thing left to do is bolt the wing down and build the lift struts and it'll be time to start covering.
PAT
Aug 29, 2004, 03:22 PM
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Kit Kit Kit Kit Kit!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!

Beautiful work Pat.

Regards,
Scott
Aug 29, 2004, 04:42 PM
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Kit Kit Kit Kit??????????????


Scott, You never know just what might happen, now can you
?????PAT?????


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