Print Page - Curare 20

Title: Curare 20
Post by: sanjayrai55 on January 26, 2019, 04:32:49 AM

Thanks to a gentleman in Bangalore, Mr. Lingaraj, I have got hold of an incomplete MK Models ( Kato) kit of Hanno Prettner's legendary Curare, in a 20 size

It's a very old kit, and a fair number of parts are missing - fortunately mostly balsa/ply which can be replicated

About Prettner - http://www.rcindia.org/rc-general-topics/hanno-prettner-living-legend-of-rc/msg297475/#new

Title: Re: Curare 20
Post by: sanjayrai55 on January 26, 2019, 05:16:59 AM

(https://i.postimg.cc/qMK63vKT/IMG-1299.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on January 26, 2019, 05:18:47 AM

Plans from Outer Zone

(https://i.postimg.cc/W39gXYpc/IMG-20190125-185947169.jpg)

(https://i.postimg.cc/PqjWx8V9/IMG-20190125-185956042.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on January 26, 2019, 05:20:07 AM

Will be using an ASP 25 Glow Engine

(https://i.postimg.cc/cCrYj76g/IMG-20190125-190003860.jpg)

(https://i.postimg.cc/j5qy6Ybh/IMG-20190125-185933821.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on January 26, 2019, 05:23:34 AM

The plans only have the right wing, so, after 44 years I did some GT (Glass Tracing). Last done to copy Engineering Drawing Assignments in 1974-5

(https://i.postimg.cc/brWbjG26/IMG-20190125-184652942.jpg)

(https://i.postimg.cc/59R8zrkw/IMG-20190125-184709470.jpg)

Now I've traced and pencilled a left wing on the reverse side of the plans ( a mirror image, so to speak)

Title: Re: Curare 20
Post by: sanjayrai55 on February 01, 2019, 05:53:37 PM

(https://i.postimg.cc/43DBxyr0/IMG-20190201-164719835.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 01, 2019, 05:54:14 PM

(https://i.postimg.cc/MT1tMxwp/IMG-20190201-164723749.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 01, 2019, 05:54:58 PM

(https://i.postimg.cc/x8Y5L7jy/IMG-20190201-164731878.jpg)

Title: Re: Curare 20
Post by: K K Iyer on February 01, 2019, 06:38:29 PM

@sanjayrai55,
Sir,
Guess the dark wood is from the kit and the whiter pieces are new, right?

Is the original material balsa?
Regards

Title: Re: Curare 20
Post by: sanjayrai55 on February 01, 2019, 07:13:15 PM

Quote from: K K Iyer on February 01, 2019, 06:38:29 PM
@sanjayrai55,
Sir,
Guess the dark wood is from the kit and the whiter pieces are new, right?

Is the original material balsa?
Regards

Correct on both counts sir

Title: Re: Curare 20
Post by: sanjayrai55 on February 02, 2019, 04:50:51 AM

I have had very limited exposure to quality kits. In the late 80's, I had 2 OK Model (Pilot) kits, and a few years ago a Great Planes kit. This is my first MK Kato kit

I must say the balsa quality is exceptional! I have encountered 4 different grades of balsa, selected for the application. Even the ply, while being light, is extraordinarily hard. Brilliant kit maker, Kato

Title: Re: Curare 20
Post by: sanjayrai55 on February 02, 2019, 07:08:50 PM

(https://i.postimg.cc/PxSfQxB5/IMG-20190202-165027146.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 02, 2019, 07:09:39 PM

(https://i.postimg.cc/ZRbKN3sQ/IMG-20190202-165051810.jpg)

(https://i.postimg.cc/YCF9Btmd/IMG-20190202-165102042.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 05, 2019, 11:00:12 AM

Wing ready for covering

(https://i.postimg.cc/CLWK7nHh/IMG-20190205-103015861-BURST000-COVER-TOP.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 05, 2019, 11:01:46 AM

Since I didn't have 15 mm thick balsa, made the wingtips from 3 different sheets glued together ;)

(https://i.postimg.cc/PrLx1QDV/IMG-20190205-103030310.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 07, 2019, 04:35:42 PM

The horizontal stab has an anhedral! 8-) ???

(https://i.postimg.cc/ZRX3ZZDP/IMG-20190207-103838906.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 07, 2019, 04:36:43 PM

Started the fuselage

(https://i.postimg.cc/TYMm4dbf/IMG-20190207-094353085.jpg)

Title: Re: Curare 20
Post by: Mehul Anand on February 07, 2019, 06:29:12 PM

just another awesome build by Sanjay sir!!
By the way how would anhedral stab affect how the plane flies??

Title: Re: Curare 20
Post by: sanjayrai55 on February 07, 2019, 07:18:54 PM

I myself am not too sure :rofl: Looks cool, and Hanno Prettner said to use it

The most logical explanation I found was in RC Universe:

RE: anhedral on horizontal stab
An engineer once told me that the anhedral on the F-4 tail was to help with low-speed yaw stability. The tail of the F-4, like most airplanes, generates negative lift, so anhedral on the horizontal tail would actually work like dihedral for a wing (it's stabilizing). This seems to imply there is a tradeoff with yaw stability while inverted, which of course wouldn't be a problem for the F-4.

As for RC aerobatic airplanes, especially so-called 3D, I doubt it has any benefit. The anhedral adds effective side area to the tail, which is the same as adding more fin area. It does add it down low, however, which might help knife-edge tracking if it is done properly, but that's only theory, and I believe that was the thinking behind the Curare tail. I remember some discussion about it in the '70s (or was it the '80s?). It seemed to work, but then so do many other designs without anhedral. You would probably have to be an aerodynamicist or an avid experimenter to design it so there is any discernible benefit.

If you think it looks cool, a little bit probably will not hurt. Or if you think you need to redistribute the vertical stabilization area lower, it might help.

As for adding maximim side lift capbility, there would be no benefit at all, since adding tail area is stabilizing. Good knife-edge lift has a lot to do with the proper balance between area ahead of the CG and area behind the CG. All else equal, adding effective fin area, without changing anything else, will make it harder for the rudder to yaw the airplane and generate side-lift. Also, the length of each horizontal stabilizer/elevator would have to be multiplied by the secant of the anhedral angle to keep the same pitch effectiveness, which would of course increase weight slightly.

Title: Re: Curare 20
Post by: sanjayrai55 on February 07, 2019, 07:19:47 PM

However for my (very limited) flying skills, I don't think I'll be testing, or valuating it's use ;)

Title: Re: Curare 20
Post by: K K Iyer on February 07, 2019, 08:55:52 PM

Quote from: sanjayrai55 on February 07, 2019, 04:35:42 PM
The horizontal stab has an anhedral! 8-) ???

(https://i.postimg.cc/ZRX3ZZDP/IMG-20190207-103838906.jpg)

Sir that anhedral stab is the signature of the Curare.
With a flat stab it'd no longer be a Curare!

I'm glad you had one of the other unique elements - the thick fin leading edge.
Hope you have the chin block too...
Regards

Title: Re: Curare 20
Post by: manojswizera on February 07, 2019, 09:31:13 PM

great going sanjay sir.

Title: Re: Curare 20
Post by: sanjayrai55 on February 08, 2019, 04:28:50 AM

Thanks Iyer sir; yes, the chin block and thick fin LE will soon make their appearance

Thanks Manoj. You are always encouraging

Right now I'm in an intense struggle: the design called for an oval fuel tank of 150 cc capacity, with the larger axis horizontal. Can get no such tank, nearest is a rectangular 180 cc. To fit that, there is fouling with the wooden engine bearers. So I've decided to use a Glass Filled Nylon mount. Which brings it's own complications in installing - tight space. I also want to use a steerable nose wheel against the fixed one supplied

Title: Re: Curare 20
Post by: K K Iyer on February 08, 2019, 08:15:47 PM

Sir,
A few suggestions
1. If you think 90cc will suffice, check out MD rum ka bachcha. I've been considering one for a 10 size model. It's quite oval.
2. If you omit EM1 and EM2, there should be enough space for a round or square section tank. Without printing the plan, I'm not able to estimate the available space. Pl let me know. Then I'll see if I have something suitable.
3. If possible, skip the steerable nosewheel. On such a small streamlined model it's not worth the effort
4. If going radial, please finalise the holes in the firewall and mount the flanged nuts before starting the fuselage. The nose is complete on mine, and the flanged nuts epoxied to the back of the firewall. No way to make matching holes in the radial mount. I'm not able to bring myself to cut the cowl free! See pic.
5. If you don't have 4 flanged nuts and matching bolts, let me know. I think I got some in 2006!

Title: Re: Re: Curare 20
Post by: sanjayrai55 on February 08, 2019, 08:23:50 PM

Quote from: sanjayrai55 on February 07, 2019, 04:36:43 PM
Started the fuselage

(https://i.postimg.cc/TYMm4dbf/IMG-20190207-094353085.jpg)

Iyer sir, the picture doesn't tell the whole story, but the FW is already glued in place, with blind nuts fitted. The Engine mount is also fitted, and the Sullivan flex 180 cc tank fits fine. 90 cc is too small for a 25 Engine. Just that everything is very cramped.

The cowl blocks will need multiple holes for tightening the Engine and mount bolts, and the exhaust bolts. Also, I'll be keeping the Engine upright, not at 90 degrees.

Regarding the nose gear, I'm still deciding.

Sent from my Moto G (4) using Tapatalk

Title: Re: Curare 20
Post by: sanjayrai55 on February 09, 2019, 04:43:59 AM

Engine ( ASP 25) mounted with GFN mount: the wooden engine bearers are not used to accommodate the tank

(https://i.postimg.cc/G23ZtcWD/IMG-20190209-040911222.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 09, 2019, 04:45:00 AM

Tank position

(https://i.postimg.cc/bJ6427PB/IMG-20190209-041041917.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 09, 2019, 04:46:14 AM

Firewall with blind nuts. I will be putting some triangular stock to reinforce

(https://i.postimg.cc/brsW0mNN/IMG-20190209-041053598.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 09, 2019, 07:16:40 AM

Tank fitment, 16 mm hole in firewall(https://uploads.tapatalk-cdn.com/20190209/f223852fb9c9916fec42f88ad16302e4.jpg)

Sent from my Moto G (4) using Tapatalk

Title: Re: Curare 20
Post by: sanjayrai55 on February 09, 2019, 06:38:44 PM

Pressure test the tank for leaks

(https://i.postimg.cc/4y0TMBfn/IMG-20190209-182337114.jpg)

Title: Re: Curare 20
Post by: K K Iyer on February 09, 2019, 07:52:48 PM

Sirji,
I see that you're doing this test in your kitchen (Don't think you have a microwave in the workshop)
Hence this tip.
"Do not try to warm epoxy in a microwave after it is mixed."

But its ok to warm them in separate cupsbefore mixing
Regards

Title: Re: Curare 20
Post by: Rooster on February 09, 2019, 10:05:37 PM

Quote from: K K Iyer on February 09, 2019, 07:52:48 PM
Sirji,
I see that you're doing this test in your kitchen (Don't think you have a microwave in the workshop)
Hence this tip.
"Do not try to warm epoxy in a microwave after it is mixed."

But its ok to warm them in separate cupsbefore mixing
Regards

Sir pardon my ignorance on this but what is heated epoxy used for

Title: Re: Curare 20
Post by: K K Iyer on February 09, 2019, 10:52:54 PM

Quote from: Rooster on February 09, 2019, 10:05:37 PM

Sir pardon my ignorance on this but what is heated epoxy used for

There may be occasions when 5 minute epoxy is too quick and regular Araldite is too thick/ too slow.
And you don't have the thin Bob Smith 20 min Finish Cure epoxy.

That's when you have to put some Araldite epoxy in a small plastic cup, and hardener in another small plastic cup, and give them a little time in the microwave (like 10 seconds, not more)

Result - a thinner and quicker setting epoxy.
If you microwave it after mixing, it'll become a lump before you can use it.
Hope this helps...
Regards

Edit
Rai saheb,
Hope you don't mind this slight diversion from the main topic...
Regards

Title: Re: Curare 20
Post by: sanjayrai55 on February 10, 2019, 04:24:51 AM

Not at all Iyer sir. Gyan is always good :)

Title: Re: Curare 20
Post by: Rooster on February 10, 2019, 10:32:16 PM

Thank you Sir for this insight. Never tried this before. Will try this method on next build

Title: Re: Curare 20
Post by: sanjayrai55 on February 14, 2019, 08:45:55 AM

Fuse(https://uploads.tapatalk-cdn.com/20190214/7fa43e5576cf8f85ea153ef27a01704f.jpg)(https://uploads.tapatalk-cdn.com/20190214/05384bd4efdca4b5d31b3f019ef227e6.jpg)

Sent from my Moto G (4) using Tapatalk

Title: Re: Curare 20
Post by: sanjayrai55 on February 14, 2019, 08:46:35 AM

Stab(https://uploads.tapatalk-cdn.com/20190214/81679af88f4ab0d05ea53a8769b88355.jpg)

Sent from my Moto G (4) using Tapatalk

Title: Re: Curare 20
Post by: sanjayrai55 on February 14, 2019, 11:35:24 AM

Stab done(https://uploads.tapatalk-cdn.com/20190214/48e4c3b5d9fefe0148280784d2dc529a.jpg)

Sent from my Moto G (4) using Tapatalk

Title: Re: Curare 20
Post by: gaurang.1972 on February 14, 2019, 12:34:04 PM

Rai sir another good build from you i always like balsa and play construction

Title: Re: Curare 20
Post by: sanjayrai55 on February 14, 2019, 12:45:25 PM

Thanks Gaurang

Title: Re: Curare 20
Post by: sanjayrai55 on February 17, 2019, 07:05:22 PM

Some progress: the tail

(https://i.postimg.cc/rwC9ZQ1j/IMG-20190217-171852202.jpg)

(https://i.postimg.cc/5tdSt8nT/IMG-20190217-175915969.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 17, 2019, 07:08:33 PM

Landing Gear installed

Wing mounting arrangement done. Could not use the original because the fuel tank fouls. In fact, because of the tank, I had to change the engine mounting from wooden bearers to a GFN mount, and this had a cascading effect in changes really extending this build

(https://i.postimg.cc/0Nk0TDZs/IMG-20190217-175904108.jpg)

(https://i.postimg.cc/N0dFnc9D/IMG-20190217-175926948.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 17, 2019, 07:20:49 PM

The original tank is 190 cc, oval, with the larger axis horizontal

(https://i.postimg.cc/FRFCVww0/DSC02310.jpg)

Title: Re: Curare 20
Post by: K K Iyer on February 17, 2019, 09:27:25 PM

@sanjayrai55
Sir, I rememberreading somewhere in Hanno Prettner's writing that even that thick fin leading edge has an experimentally found aerodynamic reason, like in the case of the anhedral stab...

Title: Re: Curare 20
Post by: sanjayrai55 on February 18, 2019, 10:07:04 AM

Quote from: K K Iyer on February 17, 2019, 09:27:25 PM
@sanjayrai55
Sir, I rememberreading somewhere in Hanno Prettner's writing that even that thick fin leading edge has an experimentally found aerodynamic reason, like in the case of the anhedral stab...

No idea really. Just a very complicated build ;)

Title: Re: Curare 20
Post by: sanjayrai55 on February 20, 2019, 04:43:23 AM

Fitted in the Servos and pushrods

(https://i.postimg.cc/1XJtTBhN/IMG-20190220-040850997.jpg)

(https://i.postimg.cc/C5F5mttg/IMG-20190220-040855647.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 20, 2019, 04:45:16 AM

There are twin elevators, so 2 pushrods into one servo. Bound with copper wire and soldered

(https://i.postimg.cc/j5YLJC4C/IMG-20190220-040900749.jpg)

(https://i.postimg.cc/MT0X0x95/IMG-20190220-040910954.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on February 21, 2019, 07:36:42 AM

Made the wing fillets(https://uploads.tapatalk-cdn.com/20190221/a7f361afbe42fead580f09a904e93ad9.jpg)

Sent from my Moto G (4) using Tapatalk

Title: Re: Curare 20
Post by: sanjayrai55 on February 21, 2019, 07:38:47 AM

Test fit of the control surfaces(https://uploads.tapatalk-cdn.com/20190221/f5a720ca20558bc8f1fe18de3d641c3f.jpg)(https://uploads.tapatalk-cdn.com/20190221/94b200efcf390a398d970edddf85984c.jpg)

Sent from my Moto G (4) using Tapatalk

Title: Re: Curare 20
Post by: sanjayrai55 on February 21, 2019, 06:09:03 PM

Turtle Deck fitted

(https://i.postimg.cc/QxzfmRPv/IMG-20190221-180009487.jpg)

Title: Re: Curare 20
Post by: unidrakeshrc on February 21, 2019, 06:55:41 PM

Sir your craftsmanship is extraordinary. :hatsoff:. I think you have a full fledged workshop around.

Regards!!!

Title: Re: Curare 20
Post by: sanjayrai55 on February 21, 2019, 06:57:48 PM

Quote from: unidrakeshrc on February 21, 2019, 06:55:41 PM
Sir your craftsmanship is extraordinary. :hatsoff:. I think you have a full fledged workshop around.

Regards!!!

Thank you, You are kind, I'm not that good :)

Title: Re: Curare 20
Post by: sanjayrai55 on July 28, 2019, 05:13:31 AM

No, the project was not abandoned! My house is being redeveloped, so I have temporarily shifted to a rented accommodation. What with the vicissitudes of shifting, and lots of other work, I had to temporarily put the build on hold, but have now restarted

Title: Re: Curare 20
Post by: sanjayrai55 on July 28, 2019, 05:48:49 AM

New workshop till about 2020 Diwali

https://youtu.be/A5H1lYV7KeY

Title: Re: Curare 20
Post by: sanjayrai55 on July 28, 2019, 05:59:09 AM

Started covering

(https://i.postimg.cc/JhJ8jgv1/IMG-20190706-115603478.jpg)

(https://i.postimg.cc/Cx9YBYvP/IMG-20190706-115606686.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on July 28, 2019, 05:59:52 AM

Complicated covering - too many compound curves

Title: Re: Curare 20
Post by: sanjayrai55 on July 28, 2019, 06:08:33 AM

(https://i.postimg.cc/rsZ3BC3n/IMG-20190727-192019.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on July 28, 2019, 01:40:35 PM

(https://i.postimg.cc/4Nbtv6mt/IMG-20190728-130839-LL.jpg)

(https://i.postimg.cc/fyMWM9Dn/IMG-20190728-130853.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on July 28, 2019, 01:41:09 PM

(https://i.postimg.cc/kgJST2bH/IMG-20190728-130843-LL.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on July 31, 2019, 09:41:17 AM

Started on the wing

(https://i.postimg.cc/MZ5qGfNd/IMG-20190730-184940.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on August 01, 2019, 08:29:17 PM

Airframe nearing completion(https://uploads.tapatalk-cdn.com/20190801/98a7ae88eae8ec74ae0eaabce8d4f892.jpg)

Sent from my motorola one power using Tapatalk

Title: Re: Curare 20
Post by: sanjayrai55 on August 01, 2019, 08:30:06 PM

.(https://uploads.tapatalk-cdn.com/20190801/c9af47146db7c0f54aef661ab8699c41.jpg)

Sent from my motorola one power using Tapatalk

Title: Re: Curare 20
Post by: manu on August 02, 2019, 10:04:50 AM

wonderful sir.

Title: Re: Curare 20
Post by: sanjayrai55 on August 02, 2019, 10:52:31 AM

Thanks Manu

Title: Re: Curare 20
Post by: prabal276 on August 03, 2019, 10:08:45 PM

It's a hottie sir!
😋😋😋

Title: Re: Curare 20
Post by: sanjayrai55 on August 04, 2019, 04:35:49 PM

Thanks Prabal :thumbsup:

Title: Re: Curare 20
Post by: sanjayrai55 on August 06, 2019, 11:10:51 AM

Construction complete

(https://i.postimg.cc/6qhTPxhn/IMG-20190806-102744.jpg)

(https://i.postimg.cc/h48JvVqv/IMG-20190806-102753.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on August 06, 2019, 04:05:51 PM

Some details

(https://i.postimg.cc/SNK5Hc63/IMG-20190806-102807.jpg)

(https://i.postimg.cc/ZKDgm0jR/IMG-20190806-102817.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on August 06, 2019, 04:09:20 PM

(https://i.postimg.cc/ZR2cgyJt/IMG-20190806-102835.jpg)

(https://i.postimg.cc/BbFgGQv8/IMG-20190806-102840.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on August 06, 2019, 04:14:38 PM

(https://i.postimg.cc/Wbjr47WY/IMG-20190806-102843.jpg)

(https://i.postimg.cc/057Dx4fJ/IMG-20190806-102850.jpg)

Title: Re: Curare 20
Post by: sanjayrai55 on August 06, 2019, 04:18:36 PM

(https://i.postimg.cc/nhXLVjJw/IMG-20190806-161132.jpg)

Title: Re: Curare 20
Post by: Aeroresurrect on August 07, 2019, 01:31:07 PM

Superb build ! Excellent finish....

Title: Re: Curare 20
Post by: sanjayrai55 on August 07, 2019, 04:31:10 PM

Quote from: Aeroresurrect on August 07, 2019, 01:31:07 PM
Superb build ! Excellent finish....

Thanks :)

Title: Re: Curare 20
Post by: manojswizera on August 07, 2019, 06:14:42 PM

Sanjay sir, the final product looks superb

Title: Re: Curare 20
Post by: sanjayrai55 on August 07, 2019, 06:31:06 PM

Thanks Manoj! Hope she flies well :giggle:

Title: Re: Curare 20
Post by: R C on August 08, 2019, 05:47:01 AM

Sir,
Awesome build and very neat covering. {:)}
Colour scheme makes it look like an ARF :salute:

She will definitely fly well Sir.
All the best for the Maiden flight Sir.

Title: Re: Curare 20
Post by: sanjayrai55 on August 08, 2019, 06:03:01 AM

Thanks R C :salute:

Title: Re: Curare 20
Post by: Rooster on August 08, 2019, 10:25:23 AM

Awesome build Sanjayji. As always it is perfect build.
Awaiting the maiden video.

Title: Re: Curare 20
Post by: sanjayrai55 on August 08, 2019, 11:19:26 AM

Quote from: Rooster on August 08, 2019, 10:25:23 AM
Awesome build Sanjayji. As always it is perfect build.
Awaiting the maiden video.

Thank so much :D

RC India

RC Models => Gas/Glow/Nitro Planes => Topic started by: sanjayrai55 on January 26, 2019, 04:32:49 AM