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Old Feb 04, 2013, 08:45 PM
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Macchi MC-72 - Schneider Racer

Hi All,

I’ve pulled down some old plans for a Macchi Castoldi MC-72 from RC Groups and have been busily converting them to CAD so I can resize, adapt them to electric and then get them laser-cut.

The plans I have are very nice and I have found them on several different sites, however there seems to be part of them missing in all copies I've seen. I’ve attached the plans so you can see what I mean. On the right hand side of the page, the horizontal stab spars are cut off, and all of the float formers and some fuse formers are missing.

Does anyone have a whole copy of these plans or know where I might get them. I’ve searched high and low without luck so far.

There are other plans and 3-views out there so I can bodge something up, but it would be nice to have the original if it’s available.

Can anyone help?

-Mat-
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Old Feb 13, 2013, 10:03 PM
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oh man! one of my favorites!! I did a kitbash of a gws formosa to look like the mc-72 years ago... with the twin motor setup, it flew AMAZING!


Macchi MC-72 - Radio controlled Schneider Cup Racer (4 min 39 sec)
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Old Feb 13, 2013, 10:08 PM
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http://www.rcgroups.com/forums/showthread.php?t=934757

here's my build...

I hope yours turns out amazing! one of my motor windings burned up, but now I want to do a rebuild!
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Old Feb 13, 2013, 10:51 PM
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Thanks Rob,

Your kit bash looks pretty nice, well done.

I have pretty much sorted all the float formers now by combining a separate 3-view and scaling it to match the plans I have.

Once I've completed the CAD work I'll start a new build thread and just link back to this thread a bit I think.

I was pretty interested in your CoAx power system. The counter rotating props are one of the things that drew me to this model in the first place.
Unfortunately I am having trouble finding a power system appropriate for my bird .

Preliminary wingloading and power calculations put me in the ballpark of 700-800W combined to get the performance I want out of a 60" racer. The plans weigh the complete model in at 6.6lb, for a loading of about 20oz/sq ft (I think my conversions are right) although I reckon I can build her lighter.

I'm thinking I may have to manufacture some parts to modify a pair of individual brushless into a CoAx pair. fun fun. The idea is easy, making it will be challenging, making it work smoothly.. now there is the hard part
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Old Feb 14, 2013, 03:01 AM
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http://www.hobbyking.com/hobbyking/s...tor_Mount.html

this one big enough???

then I saw SebArt makes a MC72 also.
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Old Feb 14, 2013, 05:26 AM
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Originally Posted by roballoba View Post
http://www.hobbyking.com/hobbyking/s...tor_Mount.html

this one big enough???

then I saw SebArt makes a MC72 also.

hmm, that is just a little large.
It runs on 6-8S at 80A, thats up to 2300W each motor
I think 4.5KW may just send it in to orbit
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Old Feb 14, 2013, 05:51 PM
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oh... you mean you don't want it to be FAST?!?!?!
I think I saw Himax and Axi making them at one time too...
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Old Feb 14, 2013, 09:13 PM
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oh... you mean you don't want it to be FAST?!?!?!
I think I saw Himax and Axi making them at one time too...
Good Call

http://www.maxxprod.com/mpi/mpi-266.html

the CR3516 looks spot on, 800W, 3 cells, 35A.... ouch $200. Thats going to be a fun discussion with the Minister for Home Finance.

I think I may be better sacrificing that scale detail for a saving of $160. Just going for a single direct drive like the Turnigy SK3 3548 - 1050KV. It will still put out the 800w and probably apply them more efficiently than the contras. That allows me to apply the K.I.S.S. principle so there is less moving parts to go wrong.
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Old Feb 17, 2013, 10:43 PM
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Very interesting project! I hope you get the information you need to do the build. I'm looking to start a S.65 build in the near future.

Cheers,
Brian
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Old Feb 18, 2013, 01:29 AM
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Very interesting project! I hope you get the information you need to do the build. I'm looking to start a S.65 build in the near future.

Cheers,
Brian
Thanks Brian, I think I have the info I need, the cut files are almost complete now.

I thought I'd looked through all of the Schneider Trophy Racers but I must have missed the S65 as I would have rememberd such an interesting design. Somewhere between the MC72 and a Dornier 335 with twin booms for good measure. Funny how a lot of the Schneider seaplanes have the same fuse profile, same shape as the V12 motor they carry (or two of in the case of the MC72 and S65).

I'll keep an eye out for your build.
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Old Feb 18, 2013, 09:00 PM
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I cannot stress how amazing the contras are in this plane. HK has a couple to choose from if you scale it down a bit - they sound awesome. they look awesome. they fly ridiculously amazing!! the absence of torque is very enjoyable.
I hear ya on the cost though... but i think the whole thing about the 72 is the contras.

keep us posted on your build!
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Old Feb 19, 2013, 12:33 AM
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Originally Posted by roballoba View Post
I cannot stress how amazing the contras are in this plane. HK has a couple to choose from if you scale it down a bit - they sound awesome. they look awesome. they fly ridiculously amazing!! the absence of torque is very enjoyable.
I hear ya on the cost though... but i think the whole thing about the 72 is the contras.

keep us posted on your build!
I think i'll still stick to the single at least while i work out the kinks and get her flying right. I will build in the capacity to change out the motor mount so can upgrade later.
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Old Mar 04, 2013, 01:02 PM
mcg
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Re the counter rotating drive, you might try sending a pm inquiry to Kuni, here:

http://www.rcgroups.com/forums/member.php?u=19863

He has built several Schneider aircraft and I believe has special expertise in brushless motors. Michael
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Old Mar 04, 2013, 11:33 PM
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Re the counter rotating drive, you might try sending a pm inquiry to Kuni, here:

http://www.rcgroups.com/forums/member.php?u=19863

He has built several Schneider aircraft and I believe has special expertise in brushless motors. Michael
Thanks Michael, I'll vertainly chase up Kuni to see if he has any suggestions for me.

At the end of the day I think there will be a couple of options for for the power system now that I have an idea of the weight, power and loadings. I think I'll concentrate on the aircraft design itself and when I eventually get around to building this one I'll drop Kuni a PM.

I've got 2 builds on the bench almost complete at the moment (Lefish and Limit), and the materials all ready to go for the next one (Mars). The MC 72 is fourth in line
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Old Mar 09, 2013, 06:00 PM
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Here is my Macchi with the contrarotating props:



regards
Andi
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