Tiny Curare
 

Hi RCU members.
I have flown many modern patternships but I believe you agree with me that nothing could be compared with flying a classic one specially when built in a smaller size.
I have read and followed many of RCU's perfect detailed threads and they motivated me to start mine. this will shows all procedures during building a small curare powered with a TT GP-07. I was very concerned with the proper wingspan and finally after consultation with some expert guys a 33 inches wingspan seemed to suit. I'm not a skilled builder so all opinions are helpful. stating with the wing andthesee images shows my last night efoort,

RE: Tiny Curare
 

Hi,
Nice work so far. Will the wing be fully sheeted?

Jamesf

RE: Tiny Curare
 

Hi Jamesf
I'm working on the wing pannel.No the wing won't be compeletly sheeted. I'm gonna use the "D" structure with shear webbings. Hope be strong enough. I guess I will upload some more pics of the wing progress tonight.
Ehsan</p>

RE: Tiny Curare
 

Any chance you might upload your scaled down plans? I would be interested in building on myself

John

RE: Tiny Curare
 

John
PM sent
Ehsan

RE: Tiny Curare
 

More progress but very slow.

RE: Tiny Curare
 

Let me suggest the following:

Wings- use 1/32" sheeting maybe 5-6 lb density. Taper sand the tips to thinner than 1/32". Shoot for a weight of5-6 ounces for a 300 square inch wing
Ribs look awide to me which will result in a thicker section than the original wings in 60 size. Shoot for about 12-14% section
Thin walled 1/8" carbon tubing as spars and 1/4" LE should shed more weight; albeit more costly.

Fuselage- . I'd use 3/32" medium balsa (8-10 lb density) as sides and double the front.. I'd use 1/32" for top and bottom. Some 1/8" thin walled carbon tubes possibly as longerons. Fuse plusfinweight should not be more than about8-10.. ounces

75 square inch stab shouldn't weigh more than 1-1 1/2ounces

Empty weight should come in at about 1 1/2 lbs +/-. Flying weight should be around 2 1/2# for better flying with a 300 square inch wing

RE: Tiny Curare
 

Mattk
Now I'm back home from work .unfortunately I glued the main spars and L.E.&amp; T.E.last night, But as you care I'll Try to keep weight light.
I agree with you.3/32" (2.5 mm) balsafor sides or even thinner sheets like 2mm balsa may be allright. I will use a layer of epoxy and light cloth like 75gr or lighter from inside instead of balsa doubler. I use this method for lager planes up to 50 size engine - a hard 1/8" balsa with 120 gr cloth and epoxy doubler- 2 of the following pictures show my .46 curare built this way. you can see the cloth texture in the photo.unfortunately I didn't complete thecurare .46airframe and construction has been stoped almost from 2 years ago. just 1 week working makes it a flying bird.
Ehsan

RE: Tiny Curare
 

2 wing pannels are now glued to each other and the shear webs are placed. Note the dowel is not cemented. It'll be glued after carvingthe L.E.
Ehsan</p>

RE: Tiny Curare
 

Nice work Ehsan!

I had no problem bringing a 40" span Tipo airframe in at 16 oz. I used foam core wing and stab under 1/32" skins. The all up weight was 26 oz without its 3s battery (4 micro servos). Battery added another 4-6 oz. I had an area closer to 400 squares (375 if memory serves).

David

RE: Tiny Curare
 

Matt,

40 oz on 2 sq ft of wing (300 squares) equates to a loading of ~20 oz/sq ft. I suspect Ehsan might be happier with a 32 oz model all up. 12-14 oz airframe and 18-20 oz of equipment. The landing gear might be a factor. 3/32" rather than 1/8" music wire might help.

David

RE: Tiny Curare
 

Lighter is practically always better in Pattern. If he can do it, I agree... 2 lbs all up or less is much better for that wing size....I haven't built anything this small in a very long time.

I am mostly basing my opinion on recent commercial offerings of similar size, that were heavy/overbuilt, and flew poorly. Loadings typically in the 24 oz / sq ft. Fine for larger models but not the tiny ones

Your little tipo should have flown very well

RE: Tiny Curare
 

David

In fact I'll do my best to save more weight. that might some times be difficult to choose between a stronger structure or a lighter airframe. But as Matt said lighter weight always brings you best results.
Before starting the project I reviewed your Tipo 40. But I prefered to use a glow engine instead of an electric onecos from my point of view though it has less power than an electric motor in this size but can betterreproduce the sense of a classic pattern.
there is one question left: did you hollowed some windows in the wing core or not? cos itreally weighs well. This is what I couldn't see in your tipo's pics.
Ehsan

RE: Tiny Curare
 

Ehsan,

No I didn't. It was the first time I did 1/32" over foam and I was really surprised at how light it was. The foam I used was of very good quality and so was the wood. I didn't use contest though. I didn't see a need for it. The weight of the epoxy was under 1 oz as I used a 1/4 oz per wing skin but had some left. For the stab I probably used a .3 oz of glue. The tips and ailerons contribute a fair bit so watch that wood weight.

Your wood wing will likely weigh about 5 oz. Torque rods and LG are also something to watch.

David

RE: Tiny Curare
 

wing pannel is now ready for skin. To prevent any distortion of the wing during glueing the skin a jig must hold the structure butusually don't use the common jig in this size. I simply use 2 thick sheets of balsa attached to the wing with some pins. one sheet to the L.E and 1 to T.E. the picture attached shows this better than any word. I used 1mm balsa (1/32) to skin the wing. first I glue it from the front edge with some C.A. then the entire skin joints the ribs with epoxy resin. I guess skinnig the wing will be finished in the next 2 days.

Ehsan

RE: Tiny Curare
 

Ehsan,

Should be rock solid!

I'm surprised your 1 mm can support those weights between rib bays. Must be pretty strong wood.

I find that wood glue (aliphatic type) is a little lighter and easier to use than epoxy for the LE and TE skins. It does require pins though at least on the spar and sometimes on the rib contacts.

David

RE: Tiny Curare
 

David,

If wood glue saves me more weigh I'll use it for the rest of the procedure. moreover wood glue seems to have a higher cyclic fatigue cos its more flexible than epoxy based resins. This is important while you are using a glow engine instead of an eletric one which produces more vibration.

Ehsan
</p>

RE: Tiny Curare
 

Ehsan,

Good points. I was going to mention that I also am generally not wild about fast set epoxy's due to their more crystalline (non plastic) nature once cured and as they age. So you wind up with a "cracking" stiff wing. Once one joint fails though one ends up with a faulty wing.

Wood glue is less dense than fast epoxy (probably even slow epoxy) but one tends to use a little more due to its low viscosity. Used carefully though I think it's a fair bit lighter as much of it evaporates. With epoxy, the weight applied is the weight used. I actually find myself using wood glue more and more as I no longer use CA as much as I used to. Wood glue has become very good and has improved drastically in the last 30 years. Then again, so have epoxy resins...

David

RE: Tiny Curare
 

Not sure if you knew or not but Eureka has a baby Curare kit available for $80. 42" ws, you can get it with a built up wing or a foam core wing,
http://www.eurekaaircraft.com/eac_kits/babykits.htm

RE: Tiny Curare
 

If you can get your hands on one the Norvel .074 is a lot better engine for your build. Way more power and lighter. You can find them NIB on ebay for around $80.00 US. However if your talking about a 35-40 oz plane you will be alot happier with a .15 to .20 engine, at this weight the .07 engines will be a huge disappointment. 18 to 25 oz would be my target weight with a .07 engine.

rrragman

RE: Tiny Curare
 

Nice link. Thanks a lot.

RE: Tiny Curare
 

rrragman,

You are right a norvel .074 might be a good substitute for this plane. I never forgive my self because of 2 things. first because of the norvel I had and sold it with its plane ( a piper J-3) and then because of a Cox TD .051 with RC carb and muffler with its plane ( again a piper J-3) I didn't buy it.

Ehsan

RE: Tiny Curare
 

unfotunatelly there is not much progress on the wing pannel skin today. only one half has been completed. I continued procedur using the old wood glue and the result was really good. When using wood glue I'm not worried about the short setting&amp; working time butam always concerned with the time when I use epoxy. the only point which must be considered during using wood glue is not to use it on a big surface specially a big surface of thin balsa. If so ,balsa sheet will be deformated.
Note the the butt joint edges of the skin parts attached to each other with no step shown in the image.

Ehsan

RE: Tiny Curare
 

I have been using Tite Bond for years for building wings. Only place I use epoxy in a wing is for the gear mounts and to join the wing sections together. I have never had a failure, and I am flying a Super Kaos that was built in 1985 with no wing repairs to date.

John

RE: Tiny Curare
 

Hi again guys

I was really busy in the past few days. last night I got enough time to complete the wing skin but There was something wrong with the server, thus I couldn't upload any photo.
any way as you see L.E. is now ready to be carved, I usually defer attaching the balsa strips to the ribs after L.E. is completed, it's because of the fragile characteristic of the balsa strips.

Ehsan,