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Old Jul 26, 2012, 03:07 PM
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Freddie B's Avatar
Omaha Nebraska
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Winds of change.

So after seeing Walt doing some hot wire work on his MiG-15, I thought why not give a quick try on this mini size build. After all I can use the same templates I made for making the folded Depron fuselage. That is right, the poster board templates should be good enough to do something like this.

I also just brought home some 1 1/2" Pink foam, to compliment my supply of 1/2" stuff. I do want to get some 3/4", 1", and 2" now! Guess it is making my day, as they say. White EPS, Pink, Blue, etc could all be used here. I think something is available anywhere around the World if one searches. I do like pink for it is firm enough, sands easy, and doesn't pop little beads all over when working with it. Use what you like I say.

I was worried about weight at first. A solid (more or less) fuselage, instead of built-up? Well so far I am finding this just may be the ticket. So I am confident enough to move forward. I also think this may be the new wave for me to do some builds I may have put off before because they wer too complex. I did some nacelles this way once, and just didn't go further. So now is the time, and I am liking it. Hope you do too.

I do have some hot wire stuff I built, and it is as simple as using a 10 amp or so Brushed ESC, batteries, wire, and a servo tester to drive the hot wire. But for now, sometime ago I did buy a ready made hot wire cutting wand from Woodland Scenes, the Rail Road area in the LHS carries these (on line, I think Hobby Lobby Craft stores does too).

So here first is the cheapest way to get a hot wire cutter if you don't want to put one together yourself. However the home made kind is more versitle, and If you already have the Brushed ESC (2 wire, DC), probably cheaper too!

Fred
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Old Jul 26, 2012, 05:06 PM
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Omaha Nebraska
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Originally Posted by sudovod View Post
Hallo Freddie B.
i`m watching your threads with interest, both this one and F-84, great job, i like much your relation to micro size and the way you applying "big" technologies to small models. Few years ago i flew my yak-15 scratched around EDF-40, link to my blog to see building progress, maybe you`l found something useful .
Best regards
Evgen
Evgen,

Thank you. I too like your Yak 15 in the 40mm size. Sure came out looking great. I need mine to be much lighter with only a 30mm EDF in it. Some of you building styles are also very interesting and helpful to me with some great ideas. You did a very detailed build and detailing. I too fear the thrust angle issues with the exhaust so far below the CG, but we will be ready for that! Thanks again!

Fred
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Old Jul 26, 2012, 05:21 PM
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I cut 2 pieces of pink foam, and placed them together so that in essence the fuselage parts will be split down the middle. I spot glued the blocks well outside the area that will make up the final part (near edges)These were trimmed to a final length fore and aft, of the station section I am working on, based upon the template set I made.

I first started with using the two 1/8" holes in my formers (from the Depron build) to locate the templates onto my foam. A few straight sewing pins made a secure way to keep them in place and hold the two block halves together. A line was drawn around the perimeter to get my formers the right height (station lines) and I used the slit in the foam blocks as alignment of the center of the templates. Hope that makes sense.

I used a brass tube to drill an access hole to feed my wire through, and promptly cut out the duct hole in the foam. Nice and precise actually. Very impressed. You can see the results here of my SECOND attempt, because the first one was a learning curve. There is also a need for some post sanding and shaping by hand with the sanding block, but this went very quick and easy.

Fred



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Last edited by Freddie B; Jul 26, 2012 at 05:30 PM.
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Old Jul 26, 2012, 05:30 PM
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What the heck.................

So that first attempt that didn't go so well. If you twist the wire, like in not keeping it parallel with the edges as you cut, it will stretch and pul into some convelouted wierd shapes and take some major shply turns inside the template edges.

1st rule, keep wire fairly parallel to the edges as you are cutting.

If you just cut across both exterior templates, you get a very straight line. OK for some fuselage sections, but not on the nose section (noting the very small front, and much wider aft section). This is like a camber line in an airfoil, undercutting the true countoured shape we are after. Needed to cut against the template edge on each side, but leave a fat center section in-between. Sort of like a 'V' shape cut.

2nd rule, cut exterior of the nose section from both ends, leaving the center section wide, finish sanding to final shape.

See what I mean?

Fred



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Old Jul 26, 2012, 05:45 PM
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Let's talk about templates.

Before you walk away thinking this is too much trouble. Do note nose section was cut using a simple card stock template, no problem. I used a poster board, but manilla file folders or cardboard would work well too.

I also will state right now, 90% of my fuselage was completed in one day. Try to do that bending and forming Depron or other sheet foam. Probably faster if you don't take breaks for chores, posting, and yard work.

But I found that a roll of aluminum roof flashing is ideal. It is so thin you simply cut it with standard scissors. They will never burn even if you had too hot a wire. They also make good templates to repeat a build, draw you plans after the fact, and are just too easy not to give a try. I also found it is easier to get a final edge the exact size you want (no raised edges from sanding), and also no nicks for the wire to catch.

For holes you can drill and trim, using a Dremel and sanding drum to smooth things out. I have a hand held sheet metal punch that I really like, but not needed unless you like to collect cool tools.

So either way, cardboard, or aluminum was just as quick for me. Some guys use formica, plywood, wire glued to ply or card stock. So many ways. Everyone has threir favorite. This was just fast and easy for me. I would make templates anyway, so why not use them as tools too!

Fred
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Old Jul 26, 2012, 05:54 PM
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Just another notation on templates.

Note yellow cardboard (poster board templates). And shiny Aluminum templates. Both work. The aluminum are just a quick, so I actually re-made all my cardbaord ones out of aluminum. They are stiffer, more durable, and how else is a guy going to do a Yak -15, and a Yak-17, and then probably a Yak-21 and do it quickly?

Fred
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Old Jul 26, 2012, 06:03 PM
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So section number two was next. Note template shape makes for the final duct section and the exit hole in the nacelle shaped bottom. Trim foam blocks to length, draw alignment lines. pin templates, cut with hot wire. I finish up with the sanding block (we are artists right?) but only rough for now, We will final sand when everything is glued together.

Fred
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Old Jul 26, 2012, 06:13 PM
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Once the templates are removed, the blocks will split where the seam was, so we need to be able to re-align them right. So before removing the template I decided to make some very tiny, 2mm location dowels and matching holes in the sections. This will allow seperation, and re alignment multiple times before I am ready to glue everything together. After all we need to sand, shape, fit, and goof around making airplane noises as we go.....

So since things can get might thin sectioned here, how do I do this accurately? Well I took a long sraight pin, and poked it through one half of the foam, until I was sure it went into the opposite foam block in my sandwich. Now I have tiny pin holes that touch exactly aligned in each center section.

Split the blocks apart, and poke/twist a 2mm sharp toothpick into the pin marks, each side. I then cut tiny 2mm dowels from toothpicks, and glued them into one side only. Now both sides can be put back together and be matched perfectly. See photos.

Fred
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Old Jul 26, 2012, 06:30 PM
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Quote:
Originally Posted by Freddie B View Post
and how else is a guy going to do a Yak -15, and a Yak-17, and then probably a Yak-21 and do it quickly?

Fred
So which one are you making for me???......

Where do you get the pink foam in thick blocks like you have???

Kevin
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Old Jul 26, 2012, 07:28 PM
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Originally Posted by Kevin Greene View Post
So which one are you making for me???......

You didn't get it yet? Too much work to re-make that one, darn....

Quote:
Where do you get the pink foam in thick blocks like you have???

Kevin
Here we get it at Home Cheapo, or Menard's. 1/2", 3/4", 1", 1 1/2" and 2". Home Cheapo also has Pink fff, but I think Menard's is Blue fff. The large thick 4'x8' sheets are like $10, $17, $19, $23, and $29 respective. Quite a bargin.

Lowes only has Blue, but it is soft and squishy. I do not like handling soft and squishy anything because it is so tender you look at it and it gets damage. The pink weighs slightly more but will not show squish marks from heavy handling, and does not tear when you go to sand it with course paper..

We all know anbout white foam. But it is the lightest I think. I just wish they carried 2lb density around here and then I just migh build with that!

Fred
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Old Jul 26, 2012, 07:41 PM
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So here we go. I figured that the first two sections should be joined. I would probably take and remove some more foam in section #2 before joining, but this is all a prototype anyway.

Using the 1/8" dowel holes and short dowels (no glue on dowels) I can plug the sections together. The dowels are on the split, so they will fall away later when we seperate the parts.

5 minute epoxy was used to glue Section #1 to section #2, and as the dowels held alignment, I just held everything together while the glue set. i kept glue away from the edges that will need final sandng so as not to create hard spots, or get everything stuck premature. The seams will all be good to go with further processes as we will see later.

Some photos show the parts glued together., then seperated at the split centers, like an ARF (cough, cough). I also have section #3 in the photo, waiting to have it's core removed in a bit. Look close and you can see the little dowels, holes, and how this all works. I tried Walt's Filler Receipe in the duct, just to make sure my transition of the two sections is smooth and nice.

I didn't mention these three sections as they sit, with more foam to be removed weigh in at 18g so far. That is pretty light considering how much foam is still in these blocks.

Fred


I will link to Walt's filler recipe later, unless he steps in and re-states the process here.


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Old Jul 26, 2012, 07:41 PM
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Old Jul 26, 2012, 07:54 PM
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Thanks Dave! Always like to see you following along. I can always count on some good advice and great friends from 'down under'. I love your threads too BTW. Always something to learn and motivate.

Fred
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Old Jul 26, 2012, 07:58 PM
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Crystal River Fl.
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Man!! I take one day and take the wife to the beach for the day(a big sacrifice! Time away from the Mig build and now I'm sunburnt!!!) and while I'm gone for the day you just go completely foam crazy on me here!!!! Fred,, looking great! Post some pics of the pieces laying together, each half? On the work bench s I can get a better idea on how your splitting the fuse? Or am I even close to what is goin on here, I'm overwhelmed by all this work and pics,,, I haven't even visited my own Mig thread yet!!! I swear, ive had some totally irrational thoughts of buying a teeny fan/motor setup now!!! And it's all your fault!!. Man I gotta get up north and get me a load of PINK foam!! Can't get it here!!! Anyways wow Fred coming along fantastic,,oh yeah, I forgot to tell you about keeping the wire parallel to the templates or you get something nasty looking ... Gotta go look at my Mig, maybe post a pic or two later... Mig or sunburnt me!W
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Old Jul 26, 2012, 07:59 PM
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Man, another post!!, I can't keep up here!
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