Scale Build Off 4, Monocoupe 90A - RC Groups
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Mar 02, 2015, 07:27 AM
Jim Young's Avatar
Build Log

Scale Build Off 4, Monocoupe 90A

Not like I don't have enough on my plate already, so I'm throwing in another new design into the build off, a Monocoupe 90A.

A friend (who should be posting here too) got me interested in this, and I need a high wing plane in my fleet so what the heck. Wing span is 55" and I'm targeting a TBD 30mm outrunner on 3S 3300mAhr pack.

Features of the design include plug in wings (ala my WW44 and LTR-14), operational flaps, working cabin doors (for battery access), laser cut balsa and plywood self aligning construction.

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Mar 02, 2015, 07:37 AM
Jim Young's Avatar
I ordered 3 sets of prototype parts, two friends will be building (and debugging) along with me. It is great help to have some fresh eyes on the plans. I've been starring at my monitor for several months, so I know how it should go together but can others figure it out or find something I've missed.

With the parts sorted, I started on the tail feathers. The tail outlines and wing tips are laminated from 4 layers of 1/16" balsa. I like this method and it produces strong, light structures. I got the fin and rudder framed up Saturday morning. The outline and internal structure are 1/8" thick with a laser cut piece to help with the fin alignment. The internal structure will be faced both sides with 1/32" balsa and sanded to bring it to 3/16: thick and allow for easy shaping.

Mar 02, 2015, 07:54 AM
Wanted for breaking Ohm's Law
Dennis Sumner's Avatar
Hi Jim,

Watching until I get my kit.....
Mar 02, 2015, 12:02 PM
Registered User
Sub'd. Always liked the lines of the Monocoupe 90A. If there is a kit, I'll surely consider.
Mar 02, 2015, 12:35 PM
There are some who call me....
campbelltf's Avatar
Great looking subject and color scheme. Sub'd
Mar 02, 2015, 04:27 PM
Registered User
Dave Grife's Avatar

Great Subject Jim !

I'm really looking forward to seeing your Monocoupe.

I had an old friend in the Ann Arbor Falcons who did one in the early 90's.

I'll have a pleasant flashback when I get to see yours.

Toledo project ?????

Mar 02, 2015, 04:51 PM
Registered User
Yoyocafe's Avatar

Mar 03, 2015, 07:28 AM
Registered User
Martin Irvine's Avatar
I like it!


Mar 03, 2015, 08:36 AM
Jim Young's Avatar
Hi Dave,

Don't know if I'll finish it by Toledo, I'm getting a pretty late start and I've got too many other things going (High School Musical set construction and 3 Science Olympiad teams), but it should definitely fly this Summer.

Here are the prototype parts and plans, there are 5 sheets of 1/16" plywood, a couple 1/8" balsa, and a couple 1/16" balsa. The first screw up on my part was the wheel pants, I only have enough for one so I'll be tracing them before I laminate them up.

Mar 03, 2015, 08:46 AM
Jim Young's Avatar

Stab Construction

I'm going to try and get a little done each night on this model. I had an hour last night and framed up the stab.

Pretty straight forward, 1/8" center and outline with 1/8" square balsa internal structure. The T.E. and ribs are faced with 1/32" balsa on both sides. While this may be a little more complex than necessary, I always seem to sand the ribs concave. This way I can just round off the fronts of the ribs and have a mild airfoil shape to the stab and fin.

Mar 03, 2015, 09:17 AM
Gravity sucks.
mrittinger's Avatar
Looks good. I would laminate stab center or run grain spanwise though, but that me.
I have plans for the same ship from a 1970's MAN mag, free flight ship...very pretty bird.
Mar 03, 2015, 12:16 PM
Jim Young's Avatar
Hi Mark,

Good idea. I still need to add the 1/32" to the center piece, and cross grain will strengthen it. Also, I forgot that there is span wise sheeting along the L.E. of the stab (I should look at my own plans!) that will also add some strength.

Mar 03, 2015, 02:25 PM
R Throne
Robert Throne's Avatar
Looking good so far Jim! I'm just a little bit behind you. The Laminations are finished! I should have the tail assemblies ready in a day or so.
Mar 03, 2015, 02:42 PM
Wanted for breaking Ohm's Law
Dennis Sumner's Avatar
Hi Robert,

Welcome to RC Groups!

Looking forward to watching yours and Jim's builds.

Mar 03, 2015, 02:54 PM
dusty bible = dirty life
Majortomski's Avatar
Looks like you've got your plans already but if you need more data, I know that Tom Stark designed the SIG rubber powered monocoupe by measuring a 90AL owned by a family friend.

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