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Old Aug 30, 2014, 11:43 PM
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The Junk Man
Jacksonville, Florida
Joined Jul 2006
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Build Log
Guillow's FW-190 Foam Conversion

I started the write-up a week or two ago and it changed in mid-stream. But I thought I would post what I had and show where it lead.

I thought I would start another build. I put aside the Monocoupe a bit ago because of a distraction with a bit of furniture building and a couple of modifications to my bike (2008 Harley Road king Classic) Not much time to devote to building. I'll get back to it soon but this came up.

I picked up a couple of Guillow's kits on eBay. A FW-190 kit #406 and a P-40, kit #405

These are the larger Guillow's kits and should be easier for me to rig up as my experience with electrics is nil.

This FW-190 is not going to be a detailed scale build... more of a "Stand Off And Squint" type.

There are a great many actual FW-190 variants and scores of minor modifications even among each variant. So this will be a generic Butcher Bird... perhaps in the colors of Josef "Pips" Priller in his FW-190 "Black 13" flown on D-Day. Priller had more Spitfire kills than any other German ace in WWII, 68 confirmed kills. He survived the war but died at the age of 45 from a heart attack.

The kit was complete and in great shape with the exception of the canopy which looked like it had be subject to some heat damage.

The wood was old-time "Guillow's Wood".

Here are a couple of photos.

Tom
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Last edited by T_om; Nov 02, 2014 at 10:53 AM. Reason: Changed title to reflect foam build
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Old Aug 31, 2014, 03:10 PM
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The Junk Man
Jacksonville, Florida
Joined Jul 2006
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Parts

I wanted to go with solid tail structures for a number of reasons so I decided to do an experiment here... one set of horizontal and vertical stabilizers out of foam, one out of balsa

I had some VERY light balsa and made the other set out of Owens-Corning Foamular.

Both sets were covered with .75 Oz. cloth and vacuum bagged. Finished thickness I was looking for is about 3mm.

Having the plans scanned made it very simple to cut out patterns. My old Wil-Kro razor plane made shaping the balsa a pleasure. 80 grit paper on a sanding block did the same for the foam.

Tom
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Old Sep 01, 2014, 09:48 AM
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The Junk Man
Jacksonville, Florida
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Next up is glassing the parts of the tail I cut out.

But first, here are some weights, in grams, as the process continues.

----------
Balsa Elevator/Stabilizer: Balsa Rudder/Stabilizer

2.85 as cut------------------ 1.07 as cut
2.45 After planning------- .86 After planning
------------------------------------------------------------------------
Foam Elevator/Stabilizer: Foam Rudder/Stabilizer

1.23 as cut----------------- .53 as cut
1.15 After shaping------- .48 After shaping
----------

To get a good finish on a bagged part requires a smooth release material in contact with the surface. Most of the composite guys use a BoPET plastic that goes by the trade name of "Mylar". The normal thickness used is about .014".

I have some but it is too thick to wrap around these tight leading edges. So I am using a paper product. It is "release paper" (almost nothing sticks to it) and can be purchased by itself commercially. This is very thick paper, not like copy paper. At my office we use a lot of plastic laminate with release paper backing and the release paper is thrown away after the laminate is peeled off. So I have an endless free supply.

The release paper was trimmed to fit the parts with just a bit of overhang. The idea is to make a release paper "taco" just bigger than the part so that when pressure is applied in the bag, the paper wraps around the curved bits and conforms well to the part. The tacos are taped together at the trailing edge to keep things aligned and make handling easier.

The best tool to apply epoxy is a roller. There is no contest. I have posted my Pool Noodle roller covers before. Very cheap, does not soak up resin, and best of all, applies just the right amount of resin. It requires a bit more rolling because the noodle surface does not soak up resin, but that is a good thing. The layer is very uniform and never too thick. Extra resin just adds weight, not strength.

The .75 Ounce glass is cut to the shape of the release paper "mylars" with a bit of overhang to wick out excess epoxy. The glass is then rolled onto the surface of the release paper, not the part. The part is then given just enough epoxy to produce a sheen on the surface. Do not put on too much. If you have more than just a bare sheen, use a paper towel to blot it off.. Stick the part in the release paper/glass taco, then bag it.

Tom
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Old Sep 01, 2014, 04:21 PM
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The release paper trick is GOLD Tom! I have been wanting to do some painted mylars on a small airframe for months (wing is airfoil sanded from 1/8" balsa) and havent done so yet because i havent been able to figure out how to do it because of the thickness of the mylars..

Now to fine some release paper.
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Old Sep 01, 2014, 09:19 PM
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The Junk Man
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Glad it might help. Release paper comes in various thicknesses. I will mic the thickness tomorrow at my office shop for you. The thick variety is best. Even the thickest release paper is thinner than the .014" Mylar I have.

Tom

EDIT: This morning I re-checked the thickness of my Mylar (.014" like I thought) and the release paper... exactly half of that, .007"
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Old Sep 02, 2014, 12:06 PM
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The Junk Man
Jacksonville, Florida
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Out of the bag

Time to open the bag.

The parts came out just fine. The flashing around the edges is where the excess epoxy was squeezed out and is easily removed. The fairly thin release paper conformed to the shaped edges just fine.

Take a look at the surface finish straight out of the bag... no filler, no sanding, no nothing. Ready for paint. I can live with that.

The edges are trimmed and sanded. After that, they are somewhat rough as all sanded surfaces are. So, for the balsa parts, I coated the edges where needed with Randolph dope. I have used Randolph products for years and years. I can't even remember the last time I bought dope in a hobby shop. I get mine from Aircraft Spruce and Specialty. Go here: http://www.aircraftspruce.com/search...h+dope&x=0&y=0

For the foam parts I used MinWax acrylic. Sometimes erroneously referred to in RCGroups posts as "WBPU", which it is not... it is an acrylic.

Last photos show a somewhat surprising strength test. With a 223 gram load, the balsa and the foam horizontal stabilizers had almost the exact same deflection. I expected the balsa to be somewhat stiffer than the foam. Both have the exact same glass, .75 ounce, both had the glass applied and were bagged at the same time. Both parts were WAY strong enough to use and if I do them again it will be with .5 ounce cloth.

Also surprising at this point is how close the weights turned out. The foam was 6.0 grams and the balsa was 6.88 grams. the only explanation I can offer is that the foam soaked up a bit more epoxy than the balsa, narrowing the weight gap somewhat.

Tom
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Old Sep 03, 2014, 07:35 PM
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The Junk Man
Jacksonville, Florida
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Plan B

At about this time I took another look at the balsa in the kit and became a bit concerned. If it was going to be heavy, I might as well think about other material options.

So I figured I would put the wood away, return to the plans, and do it differently.

Plan B.

There are a lot of detractors speaking out against even having to have a Plan B. But I prefer this quote by James A. Yorke "The most successful people are those who are good at plan B". Of course, he is also the guy that coined the mathematical term "chaos", which typically describes my though processes so I am particularly attracted to the way he thinks.

But I digress.

After bringing in the plans in SketchUp, I pulled the necessary profiles and former shapes spaced every 2 inches because that is the thickness of the foam I have on hand. These segments can be any thickness you like but make it easy on yourself. I took section shapes from the plan on 2 inch intervals. See the screen shot below.

After that, I hotwire cut a bunch of 100mm x 100mm blocks out of the 2" foam. I put centerlines on EVERYTHING, it makes it sooooo much easier to align stuff later.

All the formers were cut out of a heavy, adhesive backed paper we use here at my office. You can, of course, use anything you like... the craft paper that manila file folders are made from is fine. It does have to be stiff enough to lightly guide a hot wire so regular old copy paper is too light but you do not have to go as heavy as Formica or phenolic sheet (which I use for wing templates sometimes).

Make sure the datum line and the top and bottom centerlines are placed on the blocks VERY accurately as errors here are multiplied down the line. Did you know the first three levels of the Leaning Tower Of Pisa were level for a while? When it started to settle, they tried to start compensating for the tilt on the 4th level and you see how that turned out.

The photo shows the first segment cut out from F1 to F2. The outer rim was cut with a very small hand-held hotwire bow and the insides removed with a neat little tool I picked up at our local Michael's craft store called a "Styro Cutter Plus" . That little hot "wand" was perfect for the job.

I cut out two different types of formers for the different segments. One with the wing root and the cockpit included in the formers and the other one (shown as already cut segments below it) with just block spacers where the root and cockpit intersect the formers. The second set is the way to go. It is much more accurate cutting out the wing root and cockpit later. And it gives a more uniform wall thickness to the fuselage.

More to come.

Tom
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Old Sep 04, 2014, 03:37 PM
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The Junk Man
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Wing it time.

Fuselage segments, except for the solid one at the very tail, are done and shown. The third photo below shows both of the fuselage trials. The one on the left is just stacked, not yet glued, and is the one I will be using.

The first shots show blocking out the wing for hot wiring. These segments are very small and not worth setting up my drop bar cutter (a home-made Feather Cut), so I just pulled the wire through by hand. I got some very nice cores... first try.

I debated whether or not to sand in the break in the leading edge close to the wing root or make a separate segment. I decided to make it separately would be best and it turned out fine. It is a really defining part of the overall 'look' of a FW-190. Some standoff scale models omit it for simplicity sake but it just does not look right without it. I just had to make a few more templates is the only thing.

I wanted 2 degrees of washout in the wingtips and that was very easy to calculate and diagram in SketchUp. It turned out a 3mm shim on the tip template did the trick. Please note the height of the shim is determined by the length of the template. If the template had been longer, the shim would have had to be a bit higher. I like cored wings so much more than built-up because of stuff like this. So much easier to build accurately and with precise washout not dependant upon twisting some wood and covering and hoping it will stay where you put it.

The 7th. photo shows all six wing panels cut and resting in their shucks with the next photo of just the outer wing panels. It is really important to keep those shucks as they will be what supports the wing panels in the vacuum bag.

Tom

PS: Editorial comment follows. Can someone PLEASE invent a foam adhesive that can be sanded? I would pay a LOT of money for such an adhesive. Everything I have tried so far leaves a ridge at the joint because the glue is so rubbery it won't sand. UHU POR, Foam Tac, Bob Smith Foam bond, everything. An adhesive is needed that cures hard. Harder than the foam is not really a problem because with a flat sanding block the ridge will still go away. With all these rubbery adhesives, the rubber just does not sand.
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Old Sep 05, 2014, 11:59 AM
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The Junk Man
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The first photo shows my favorite foam-working tool (next to the absolutely necessary hot-wire setup of course).

The company, MicroPlane, makes several of these great tools as "zesters" for chefs. They are perfect for shaping foam during the stage prior to sandpaper finishing. This one is sized perfectly: http://www.amazon.com/Microplane-400...rds=microplane

The rough wing saddle/root cut was made using heavy paper templates. It is easy to align provided you kept the datum line intact on the fuselage. If not, it is a PITA.

My next shot shows cutting out the cockpit... but this ended up being a mistake. Fix shown later.

The entire fuselage, minus the small tail segment, came in under 8 grams. This is before filling and finishing, and before being covered with .5 ounce cloth and epoxy.

The filler I use is a combination of Durham's Water Putty and DAP ultralight spackle comound. The Durham's adds a bit more strength and adhesion as well as a bt of color to see where you are with the sanding procedure. In these photos it just makes the surface look dirty. You can also see where seams have to be dug out when the *&^%()$# adhesive breaks through the surface. Those have to be dug out and filled which is a chore I hate doing.

Last shot shows the canopy edge that was damaged, apparently by heat but who knows. It is just not useable as-is, so I ditched it. Solution will be shown later.

Tom

[EDIT]: Well, maybe not later. Since this build thread is generating zero interest, and the time to take and annotate all these build shots take up time I could be doing something useful, I am just setting this thread aside for now. I will continue the build though. May be back with the completed model if it seems worthwhile to do so.
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Old Sep 12, 2014, 05:54 PM
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Any updates?

This build really has me thinking about build some foam models.
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Old Sep 12, 2014, 08:23 PM
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The Junk Man
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Quote:
Originally Posted by Dave K View Post
Any updates?

This build really has me thinking about build some foam models.
Updates will come as people ask I guess. Otherwise there is not enough interest in the thread to spend the time to take, and annotate, the photos.

Tom
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Old Sep 13, 2014, 12:00 AM
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Tom,
Im lurking!
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Old Sep 13, 2014, 04:29 AM
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So am I

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Old Sep 14, 2014, 11:20 AM
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Me too!
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Old Sep 14, 2014, 03:59 PM
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