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Old Aug 30, 2014, 11:43 PM
The Junk Man
Jacksonville, Florida
Joined Jul 2006
1,333 Posts
Discussion
Guillow's FW-190

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" which looked and felt more like Oak veneer than balsa. Sigh.

Here are a couple of photos.

Tom
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Old Aug 31, 2014, 03:10 PM
The Junk Man
Jacksonville, Florida
Joined Jul 2006
1,333 Posts
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
The Junk Man
Jacksonville, Florida
Joined Jul 2006
1,333 Posts
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
Registered User
United States, FL, North Port
Joined Mar 2004
3,168 Posts
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
The Junk Man
Jacksonville, Florida
Joined Jul 2006
1,333 Posts
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 Yesterday, 12:06 PM
The Junk Man
Jacksonville, Florida
Joined Jul 2006
1,333 Posts
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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