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-   -   #27 Model Airplane Building Clinic >> Mimi DLG 1 meter polyhedral<< (http://www.Wattflyer.com/forums/showthread.php?t=67866)

aeroknot 09-01-2012 03:11 AM

#27 Model Airplane Building Clinic >> Mimi DLG 1 meter polyhedral<<
 
This thread intended as a discussion of building the 1 meter polyhedral DLG Mimi. Any tips, hints, and good humor is sincerely appreciated. Please also refer to Murocflyer's building clinic thread.

I plan to build the Mimi over the next few months...building on scattered days now and then....I've built foamies, but this will be my first balsa build.

I also have no experience with sailplanes or DLG....:D

Mimi
span - 1000mm
length 780mm
weight 160-170grams

The Mimi is designed by Frans Bal, who has on request freely emailed many people his Mimi plans. There are several links to various build threads and also his email on his web page.

His web pages also have many detailed photos of his build. His build photos are a good guide.

There are several Mimi versions including a dihedral solid balsa wing and a polyhedral semisolid wing.

I will build the polyhedral semisolid wing version.

When finished, I'll update this post with some photos, etc.

eidt - 2012 09 08 - edited the first sentence a little.

aeroknot 09-01-2012 03:21 AM

plans
 
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I "poster" tiled printed the semi-solid plan using Abdobe reader 10 (X) and taped them together. Printing at Kinkos would have been quicker and better.

I checked the one-half wingspan of the taped plan and it was 50.5cm. After sanding the angles for the polyhedral panels, the final wingspan should be 100cm.

If necessary, I'll reprint any critical parts of the plan - some of the rib templates are bridged by two pieces of paper.

The wing panels are first glued with non-shaped balsa parts, and then sanded to the wingform shape using the root and 'tip' templates and a long sanding block.

Stevephoon 09-01-2012 03:05 PM

Good start! I have always had issues with aligning "tiled" plans. I have spent more time fiddling with the plans than the actual build on some of my foam planes!

I have never built or flown a DLG plane, so I will not be much help there… I am hoping to learn some tips from you for my Chrysalis build.

Good luck! I’ll be watching.

Steve

kenh3497 09-01-2012 03:32 PM

FWIW, my local Staples store quoted me $1 per square foot to print plans on their plotter. I don't know how this compairs to Kinkos, but that is the only choice I have besides a private print shop that is very expencive.

Ken

aeroknot 09-01-2012 11:28 PM

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kenh3497 - you get an 'official wattflyer' 'thanks' !

Stevephoon - and also thanks for your encouragement.

Kinkos was somewhere around $0.74 per square foot or $4.01 for the black and white printed plan.

I'll keep the whole page plane pristine and cut out sections from the tiled plan. I'll spot copy the sanding templates from the whole page plan.

The whole page plan measurements are identical to the tiled plan.

aeroknot 09-01-2012 11:36 PM

Music
 
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Decent music is conducive to an enjoyable build!!

I'm listening to various genres in 'Pandora' via my roku player - tv - stereo.

The genres are on 'shuffle' - here are a few samples

aeroknot 09-01-2012 11:47 PM

shopping
 
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In order to best cut the balsa, I had to buy a razor saw - found at Hobby-Lobby. I'm currently using the one with 54 teeth per inch 1.25 inch deep with a number five handle.

I also bought a aluminum Task Force 16 x 3-1/2" Aluminum Float which I plan to use as a long sanding bar - I don't have the long Great Planes sanding bar.

There's also a balsa tool page at f3k.nl - mimi - tools, as well as a Mimi bill of materials, etc.

aeroknot 09-01-2012 11:59 PM

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Lastly for today, I cut out the outside panel leading edge balsa blanks.

I used the heavier denser balsa.

Weights:

12 x 100 x 1000mm 130.3 grams
12 x 76 x 1000mm 152.7 grams

I still don't have a building board to pin things to....particle board felt hard, and cork looked not quite flat. Maybe I'll use painters tape for now - not really a lot of balsa piece stabilization need, just a really true flat surface.

That's all for now...:)

pd1 09-02-2012 12:41 AM

If you have to pin something down, you can use a Celotex ceiling tile laid flat on the table.

Or you can do like I do, I use a hammer to drive my pins into the board. Sounds worse than it is. You just need a pair of pliers to remove the pins.

I always wanted to see what was in a DLG.

aeroknot 09-02-2012 03:05 PM

thanks pd1. After thinking about it, I'll probably try magnets and a metal plate. The wing panels are relatively small so there's a lot of options.

edit -

Oh yeah, I like your byline - just noticed! Now I might have to change mine, since you have forum seniority.

aeroknot 09-02-2012 08:11 PM

magnetic "pinning" board
 
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magnetic "pinning" board -
This will work well. I bought two 22 G steel sheets and a bunch of whatever magnets were available. Can always use more magnets.

I will sand the rib length for the leading edge and trailing edge for a tight fit.

Edit - on the tip panel outside tip, cut all outer edge parts straight with the straight outer tip edge of the plan, and round off later, just before gluing the panels together.

aeroknot 09-02-2012 08:14 PM

Note the balsa grain when cutting
 
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The plans are marked to indicate the grain direction of the balsa.

aeroknot 09-02-2012 08:22 PM

Switching the leading edge to lighter balsa
 
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I recut all the leading edge balsa blanks, after asking my self "Self, why are you using the denser balsa instead of the lighter less dense balsa?"

Four leading edge lighter balsa blanks - 47.8 grams
Four leading edge denser balsa blanks - 80.9 grams.

The weight savings will be less than that after shaping the wings, but still a large weight savings. I'll leave the thin trailing edge blanks as the heavier balsa.

Total wing wood weight except ribs - 75.8 grams.

kenh3497 09-03-2012 02:08 AM

Quote:

Originally Posted by pd1 (Post 881158)

I always wanted to see what was in a DLG.

Actually it is... "what's not in a DLG".

60 inch plane ready to fly and some are only 8 ounces, Maybe even a tad less. Mine is a beginner model, to fit my skills, and it weighs in at a "portly" 10 ounces.

The technology is pretty astounding. Foam core, (some are hollow) wings and tail parts. Strings to actuate the control surfaces with a spring for return motion, extensive use of carbon and Kevlar to build an 8 once plane that is relatively rugged. Entry lever 1.5 meter planes are considered full size. Mine can be bought for about $230 plus the radio gear. Some are $1000. Yup, that is the right number of zeros:eek: I can just see my wife now if I came home with a $1000 DLG. I don't think I can afford the divorce:eek::eek::eek: :D:D:D:D

Ken

pd1 09-03-2012 12:44 PM

I've only seen DLGs fly a few times, but I thought they were fascinating.
Maybe some day I'll try one, for now I'll just watch and learn.

aeroknot, maybe we should start a still learning group. All welcomed.

JetPlaneFlyer 09-03-2012 01:12 PM

The MiMi is a great little design. I did the drawing of the built up wing for Frans, though I never got around to actually building one. I do have a set of parts cut out and one day I'll get around to it:oops:

Regarding weight, I'd call 160-170g rather 'porky' for a 1M DLG. If it were me I'd be aiming for as close to 100g as possible. I'm pretty sure 120g could be done without too much trouble if you pick your wood carefully and use lightweight finish and RC gear. I've got the Elf 1M DLG which weighs 95g ready to fly. When weight is added to the Elf it has a very noticable negative impact on performance. I guess if you are flying just for fun then ultimate performance is possibly not the main issue but nonetheless you do want to keep it as light as reasonably possible, especuially at the tail as any weight added there is likely to be multiplied several fold with added nose weight.

Steve

aeroknot 09-03-2012 03:03 PM

Saving weight
 
Good info, jetplaneflyer. Although I'm building according to the plans, I've considered using depron for the tail feathers - I'll have to compare weights and see which is lighter, versus what looks better.

I'll use the lighter balsa for the ribs, but will keep the trailing edge heavy balsa.

I planned on covering the wings with 1.5mil laminate, which I think will cost about 3grams heavier than the So-Lite. But I already have a bunch of the laminate.

(Solarfilm lite (So-Lite) weighs about 20-25 g.s.m, and 1.5 laminate (Doculam) about 41.5 gram per square meter. I'm estimating a wing area of 0.13 square meter (130mm * 1000mm). So, about 21.5*0.13 = 3 grams difference weight penalty.) We'll see what the actual weight change with the laminate is.)

aeroknot 09-03-2012 08:20 PM

a larger 'balsa stripper'
 
5 Attachment(s)
a larger 'balsa stripper' - clamping table, razor saw etc. The razor saw is clamped at an angle, with the left side on the photo even with the table.

For larger pieces, the aluminum flat acts as a slide, and moves relative to the table, with the balsa stationary on the aluminum flat. For less wide pieces and just shaving off that last thin strip, I did not use the aluminum flat.

The clamped wood acts to keep the balsa strip perpendicular to the razor saw, as well as the guide and determining cut thickness.

For pieces where the two cuts do not meet, a #11 blade completes the cut by hand.

aeroknot 09-03-2012 08:34 PM

gusset grain detail and cutting the rib blanks
 
3 Attachment(s)
Note the grain when cutting the gussets. The apex angle is not quite 90* and the gusset was sanded to fit.

Ribs -
The leading edge and trailing edges of the wing were clamped, and the rib blanks custom cut and sanded to fit.

Need to buy some original Titebond wood glue. I read that it sanded better than the Titebond II wood glue....don't want to use CA, just personal preference.

I'll use some weights on top when gluing.

I need to remember to weigh the wing panel before and after gluing.

edit - I used Titebond II (which is water resistent - the balsa fails first) and Titebond II sands great.

Frans Bal 09-03-2012 09:55 PM

Hi Steve,
Shame on you for not having build a MiMi yet :):)
Have been a while since we had "contact", hope your doing fine.

Weight isn't that critical with the MiMi. The biggest difference with a Elf is it wing area. The MiMi has quite a bit more. In light wind a Elf will outperform a MiMi. The biggest advantage of a MiMi is it's ability to carry a fairly amount of ballast. Empty the Solid wing version will weigh 150-160 gram. But you need really light balsa for this weight. A semi solid wing version will weigh the same but the wing can be build from heavier balsa. The build-up wing is the lightest with 140 gram. With this weight the wing loading is almost the same as an Elf.
It is possible to ballast the MiMi up to 220-230 gram in high winds without losing to much of performance and that's a plus.

Hello Aeroknot,
Wow, great step by step building log / clinic. [popcorn]

have fun Frans

aeroknot 09-03-2012 10:30 PM

I'm really excited to be building the Mimi - it's been fun and I've learned some for my first balsa build. Glad you pointed out the wing loading, but will still watch the weight - I have to resist adding just a little more glue or a little thicker rib. All my foamie builds have been at or above the upper end of the weight bracket, so I'll be extremely proud if I hit a good weight target!

JetPlaneFlyer 09-03-2012 10:31 PM

Yes Frans, I hang my head in shame:( I just cant find time to build these days.

Good to see you hear, maybe this thread might inspire me to dig out that kit of parts i cut years ago from my lightest contest balsa;) I've done a rough calculation and I think the Mimi has about 14dm^2 of wing area compared to the elf's 11.7dm^2 .. So that's about 20% more area.

So my target of 120g would bring it in on similar wing loading to the Elf. I'm think it could be done with the built up wing and very light wood selection and a small lipo in place of the Nimh battery. But you are right in that the Elf is a fair weather flyer, it cant really cope with anything more than a gentle breeze. Ballast helps the performance in wind but duration does seem to take a hit.

aeroknot 09-05-2012 02:25 AM

If you build your Mimi and get a chance, please post some photos!!!

I'll be building off and on - I won't get a chance to do anything probably for a few days.

aeroknot 09-08-2012 07:05 PM

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I mirror imaged the left wing panels for the right side - could have traced the back. I just scanned in the panel part of the printed plan, mirror flipped it with irfanview, then printed to a pdf file using bullzip pdf virtual printer.

While the panel glue is drying (used Titebond II), I cut and sanded the sanding templates. I'll post some photos 1-2 days, gluing the tip panels in stages and I want to weigh when dry.

Scanned the sanding template part of the printed plan, so I could print one page, instead of tiling. I ended up printing three tip templates.

The tip sanding template took me three tries to get one I liked!
I overbuilt the sanding templates with 6mm ply (I had to overbuild something!!)

Frans Bal 09-08-2012 08:29 PM

Hi Aeroknot,

I think you need to take out your sanding block load up some fine paper and give the wing templates a whee extra sanding. ;-)
Sand the templates accurate on the line.
http://www.f3k.nl/tl_files/Mimi/mimi%20vleugel/V7.JPG

Good progress.

Frans


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