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Dec 18, 2014, 02:01 AM
Res Ipsa Aviatur
Longhorne's Avatar
Thread OP
Build Log

SBO 4: 45" Miles M.20 (the sequel)--free downloadable plan

Update, 8/14/2015: this design became the subject of the Construction Series in Model Aviation magazine. The M.20 first appeared in the series in June, and was released by MA as a free downloadable plan in July.

MA thoughtfully posted the plan in two formats. The plan can be downloaded in its original E-sized format for printing on a plotter at a blueprint or copy shop, or in tiled format for desk top printers.

The plan includes a second sheet with parts outlines for hand cutters. A laser cut short kit is available from Manzano Laser Works.

The custom spinner for this project can be printed from the STL file found here:

For printing, I have used to locate local 3D printers in my area. Cost normally runs less than$20 for the spinner and backing plate combined.

The graphics file that I used is attached as a Word doc. It can be used to print your own decals or vinyl. Alternatively, Callie has this file and can make a set for a very reasonable price. The prototype shown in this thread has Callie's vinyl graphics on it.

RCDan and I entered last year's SBO3 with a fresh design. Life got in the way when we got to the building phase, but I'm going to dust this project off and take another run at it for SBO4.

Here is some recycled info from the previous thread describing this aircraft:

"[T]he Miles M.20. Only two copies of this odd little airplane were built, one for the RAF and one for the Royal Navy. Responding to fighter losses during the Battle of Britain, the original design challenge presented to Miles was to produce a simple, wooden light fighter that could be churned out in larger numbers than the Spits and Hurris.

The performance of the M.20 was respectable, but interest in the type wained with the conclusion off the Battle of Britain.

I stumbled across a photo online and thought that it was a prototype of the Tempest. After looking more closely, the proportions appeared to be perfect for RC. Dan and I were both interested in a warbird with fixed gear. Lastly, it just seems weird enough to grab some attention at the field."
Last edited by Longhorne; Dec 31, 2018 at 03:47 AM. Reason: Added graphics source and file
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Dec 18, 2014, 09:14 AM
Summit Model Aeronautics
Steve85's Avatar
Hey Paul,

Great to see this one resurrected.

Dec 18, 2014, 10:24 AM
Registered User
JIMA's Avatar
I am back for another go round. This was one of my favs from SBO3

Dec 18, 2014, 01:49 PM
Registered User
D-Rock's Avatar
Count me as subscribed

Dec 18, 2014, 11:38 PM
Registered User
raipe's Avatar
So glad she gets another chance Definitely following!

Dec 19, 2014, 08:10 AM
Oh no, not again!
jhspring's Avatar

Dec 19, 2014, 11:48 AM
Res Ipsa Aviatur
Longhorne's Avatar
Thread OP
Thanks very much, all! Happy to be a part of this SBO with so many cool projects underway.

Bear with me for just a little more review from the previous thread. That one covered the CAD design work in detail. If interested, that thread can be found here:

In this thread, I'll just offer the finished CAD project so that we can see where we are heading.

Next stop: gluing stuff!
Dec 19, 2014, 12:23 PM
Or current resident
glewis's Avatar
Signing on to see round two of this one!
Where is ole dan-o anyway?
Dec 19, 2014, 12:38 PM
Registered User
Yoyocafe's Avatar
Subscribed! This looks like a sweet build.

Dec 19, 2014, 03:28 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Dec 19, 2014, 05:02 PM
roscoedude's Avatar
Hey Paul,

Good to see this one getting built, I was really looking forward to it last time around.
Definitely a cool bird, and different..... just how I like them.

Dec 20, 2014, 01:50 AM
Res Ipsa Aviatur
Longhorne's Avatar
Thread OP
Well, I suspect that ol' Dan will show up sooner or later

As promised, here is some new progress. Not much new here, but for the uninitiated here is the process.

The laminations for the tail group outlines were done a couple of weeks ago.

The forms were made from a sheet of foam core posterboard that was laying around. Copies of the the tail parts were mounted with 3M spray adhesive. After the outlines were cut out, a little tape around the edge kept glue from sticking to the form.

Balsa strips were soaked in water with a splash of ammonia for a day or two. After they softened a bit, they were wrapped around the forms with a little wood glue. After sitting pinned to the forms for a couple of weeks, they didn't spring off of the forms even a little bit.

The proto shortkit arrived from Charlie earlier this week. Been a year since my shop had the happy smell of burnt balsa!

Dec 20, 2014, 09:21 AM
Registered User
JIMA's Avatar
Hey Paul. Last time I tried to laminate some balsa wet everytime I tried to apply glue it just beaded up and turned into a rubbery mess. The glue I was using IIRC was Elmers Carpenter glue. Ended up applying the wood around the forms and letting them dry first. Then took them off, added the glue, and put them back on. Worked just fine. Could I have had too much ammonia in the brew that caused this?

Dec 20, 2014, 11:19 AM
Res Ipsa Aviatur
Longhorne's Avatar
Thread OP
Hi Jim,

Yes--you hit it right on the head!

Ammonia and aliphatic glues don't play well together. I found this out the hard way, too. Not a problem at the couple of percent range, but when I threw a little ammonia in and didn't mix well I got the rubbery blobs at one end of the strips and the tame result at the other.

I've heard mixed reports regarding whether the ammonia is needed. I spent some time thinking about that, and my theory is that the ammonia is not softening the wood through chemical action. I think that what it does do is work as a surfactant that allows water to soak into the wood more quickly. It also smells better at low levels than soggy balsa

Curious to hear other opinions.

Dec 20, 2014, 11:34 AM
Slip the surly bonds...
Sopwith Mike's Avatar
I'm following this build with interest. There are so few WWII monoplane fighters with fixed UC (some Japanese, Martin-Baker MB2 & 3 etc.)

I've made lots of laminated tips using both 1/32 and 1/16th balsa (often with a 0.4mm ply strip in the mix) and never used ammonia, just hot water. You do get the odd breakage or two, but I find it helps greatly to pre-bend each strip round a suitable thing like a baked bean tin (choose your own vegetable). If you hold one end on the tin and use your thumb to force the wet balsa strip round the curve of the tin it hardly ever breaks, for some reason!


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