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FTFC20 Minimoa designed by FoamyDM

FoamyDM

Building Fool-Flying Noob
#1
I really love the Gull-wing style design of the Minimoa which is a German Sailplane. They come in many sizes; 104" 99" 72" 50" 35" and 34".
I will base mine on the Minimoa 50 (plans depicted below.)

The Göppingen-gö-3 "Minimoa" is a the famous 1930s German sailplane designed be the team of Wolf Hirth and Martin Schempp coined thereafter as Schempp-Hirth, made accessible to hobbyist by Keil-Kraft. This version of the Minimoa plan has re-drawn wing ribs. As the original craft moved from flat bottomed foils to Under-cambered to reduce the minimum sink speed. This plan includes both. I would like to see the difference myself.

This is a video of the large one slope soaring:

Based on some paint schemes this was used as a scout plane during WWII by the Nazis.

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History:
Origins of the Minimoa

The Minimoa with its amazing silhouette, it’s probably one of the most reproduced vintage gliders these days, but it still remains a curiosity. Named after a special cloud over Grunau, it symbolizes the 30’s of the German soaring. It was for many of us a technological marvel which helped many pilots quit the slope flying and explore the thermal or even the wave soaring. It was a big step from experimental soaring to pure sport flying.
The Minimoa was one of the first realizations of the young company Sportflugzeugbau Göppingen born in 1935 when Wolf Hirth and Martin Schempp teamed up. Renamed Schempp-Hirth Segelflugzeugbau after the war, they are today one of the most famous and largest glider manufacturer.

It was felt that the "Moazagotl" had been too large for ease of handling on the ground and in the air and the Minimoa was smaller to improve the above defects. To retain the stability and safe handling of the Moazagotl, the new sailplane had the same general features, a swept back wing with pronounced gull dehidral, large ailerons and strong washout, mounted high on the fuselage. Its shorter 17 meter span cut costs while its stronger structure allowed higher speeds.
When seated, the pilot's head was inside the wing, so outward vision was not good. A window in the roof helped a little. Landings would be on a skid. Split flaps were installed beneath the wing to aid landing in small spaces.

Because of his artificial leg, Hirth had the controls set up with an overhanging control column working a torque tube which passed over his right shoulder to bell cranks in the wing root. The entire top front of the fuselage lifted off to allow him to get in and out. This was not to continue with production aircraft however.

This unusual prototype flew in 1935 and was taken to the Rhon meeting. The first Minimoa accompanied Hirth when he visited Japan to demonstrate and promote soaring later in 1935, and was sold there. A second prototype was built, with normal controls. This too went to Japan later. One more of the high winged version was built and sold to a Romanian pilot.





I plan to make a DTFB replica using tongue depressors/craft sticks for wood reinforcement.
Project goals - make a backpack or "throw-this-in-your-passenger-seat" glider, with character
1. Make a 1 sheet version to get the Fuselage skin shape very close ~30".
2. Build it like the plans but using with foam board and tissue.
3. Make the under-cambered wing and test the two wing types.
4. Make a DTFB construction method 50" version.

I'd Like to take a moment here to Thank @rockyboy for his dedication to present these enticing challenges year after year.
Without them, my house would not nearly be as filled with planes. It was the WWII no-service design build challenge that pulled me past following along, and deep into the forums.
 
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FoamyDM

Building Fool-Flying Noob
#2
Build log - Item 1
Objective - Build a 31" version for Fuselage Skin shape and overall chuck glider fun. As always it starts with a plan.
1565646136188.png
Cut out the pieces:

and assemble:

I don't like the Fuse so much. it is too traditional...

There that's better.
I may have mis/taken this fuse shape from other gliders of this type. it works VERY well for DTFB for both construction ease, and strength.

Something is missing... ah ha - a canopy cover. Because of the wing being 1 piece, this attaches to the wing.

OK. I am generally satisfied. with the look, construction and assembly.

It is very heavy however, and need a great deal of speed to stay up. it might be in part to the thick wing. and non-tapered parts.
 

Attachments

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FoamyDM

Building Fool-Flying Noob
#3
The Skinimini Build Log:
This Version of the Minimoa 30 is to build it like the balsa build, just using Foam Board*. The goal is to keep it light, and hope the skin aids in overall model strength.
The original standard build attempt turned out a good build, and a GREAT model, but a TERRIBLY heavy build. This means it needs too much speed to be reasonable to glide at that size.
It is possibly a great Windy day soarer. Time will tell.

*Not exactly DTFB

Step 0 - Power Train/Controls
This will be a 2 channel glider This will need to be small and light. I will be using these:

micro receiver - 2g

1s 300 mAh Batt 14g

Linear 1.5g servos - 3g

AiO Camera - 6g


This brings the total to about 53g AuW. + glue, tissue, Gloss Coating, magnets - I'm hoping 70g. the Camera will be Critical as it's size will make orientation difficult.



Step 1 - Cutting
I have a $2 sheet if the 3/32" thick tri-fold board from Dollar General sitting around. waiting for a project, I feel this Small 30" build might be a good fit.
As always, I take the Plans and print them to mount on the Foam.

I use Super 77 to "soft mount" my plans. It is a contact adhesive so it sticks best to itself. when used on only one surface is sticks, but can easily be removed. I always print an outline for use with a DTFB 29.5"x20" sheet. but in this build I cut the sections out and glued them individually to the thin section of the trifold (7"x22). I weighed the board when I bought it and it came in at 115g - same as the DTFB but half as thick. Based on this. the plane skeleton should be around 28g.

Step 2 - Building
As always, it starts with cutting the pieces out.
IMG_20190926_214830875.jpg IMG_20190926_214839309.jpg
After cutting and reviewing the plans, I realized I needed 16 more "A" formers. I will need to fix that. as you can see all of them were cut from the innards or scrap pieces of the 7"x22" section
IMG_20190926_225051519.jpg
I have never built a balsa model so I don't know how this typically goes, but I noticed my plans didn't include labels.
I will have to correct this over site. Same for the fuse. I have to redo that a bit there too.

IMG_20190927_074422725.jpg
All cutouts are complete and ready for gluing. The lower right piece is scrap, showing where the cutouts came from.
At this point, I notice I have no reference to guide the rib installation. As it will aid in construction if this is indicated on the plans, I will add them.

Debate: I'm also debating on if I should remove the wings individually, per the plan (for the 50" model), or make them a complete wing piece.

NOTE - This is somewhat delicate. Foam this thin isn't crazy strong and creases easy. I'm hoping the skin lends a great deal of rigidity - Like house framing.

Step 2a - Launching and Landing
This plane is set to be a Bungee Launched Glider, with a single Wheel for landings like the full sized craft. This means having the wheel compartment like the plans. and a hardened placement for the hook to launch the plane without ripping it apart.

Step 3 - Electronics Install and controls
My plan is to place the receiver control board under the wing, the battery in a nice slot in the nose, and the servos as close to the CG as possible. aft of the wing bay at worst.
this will need a T-body for mounting. The horizontal for one part, and the Vert for the others.

Step 4 - Skinning this Beast
The original model was a Tissue based covering method. I know almost NOTHING about this.

Step 5 - Falling Style
Reserved for Maiden Glide test, discus launches and banded launches.
 
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FoamyDM

Building Fool-Flying Noob
#6
Reserved for Maidens
Build 1 - Small 31" Skin shape test

Build 2 - FB and tissue

Build 3 - FB and Tissue - Alt wing

Build 4 - FT style build
 

FoamyDM

Building Fool-Flying Noob
#8
Thanks. I have to finish organizing my newly setup shop, so I can really work on this.
Added progress photo to post 2
 

Ketchup

4s mini mustang
#10
I can’t wait to see the finished product! I have been interested in the minimoa for a while and I have always wanted to build one out of foam. Are you planning on adding ailerons or will it just use the rudder to steer?
 

FoamyDM

Building Fool-Flying Noob
#11
I will have options for all of it. But I will fly it with ETR only at first.
I plan to have a removable nose for motor mounting. This should have ailerons and flaps too. Thinking two wings. On with controls, on without.
 

TooJung2Die

Well-known member
#13
I'm following your Bird of Time build. I can't wait to see how both of these birds turn out and fly. You picked two of the most iconic and recognizable gliders of all time.
 

FoamyDM

Building Fool-Flying Noob
#16
I've done an in house glide of the model depicted above... it is lack luster in performance this is likely due to these factors. I didn't iron the trailing edges nor did I sink the spar (I suspect).
also the horiz. Stab may be at an improper pitch While this model weighs in at lite~45g, it has room to go, and base on the flight, it needs it.

No in truer form to original Balsa I will be trying it in foam - I call it the Skinimoa30.
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Also here is the scaled up to 50"
1567803876821.png

I hope to build these this weekend... ah, hopes and dreams.
 

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rockyboy

Skill Collector
Mentor
#20
Do you have any more info on the receiver? The servo connections look pretty obvious on the front, but finding the pads for the battery connection can sometimes be tricky, and binding processes can be odd for some "brand-free" components.