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[Gil]

Hello Leif and Paul,

First thanks for the positive feedback. I have been thinking about this method for awhile now and wanted to get it off the "list". Actually this method came from the work of early aircraft builders of such beautiful specimens as the Albatros and Vegas. The use of a fuselage mold to layup strips of glued veneer produced extremely clean fuselages. The advent of all metal construction was the end of this technique till the advent of fiberglass and carbon fiber composites appeared. Going back to the Albatros and Vega it occurs that cutting out the patterns isn't really required. 5 or 6 mm wide strips laid diagonally into the mold at 45 degree angles between layers will work beautifully just as it did for those ancient builders. So in essence this eliminates those carefully cut pieces, just straight edged strips. Coating the mold with beeswax or paraffin will make it "stick" proof. 1:16 scale Albatros built up using the technique would have an extremely unique look to it.

Leif's comment about "half baked" is a good point. How and where to apply this in a card model that uses standard building techniques is a more formal rephrasing of the question. Most card models that contain compound surfaces in full view comes to mind. Many subjects suffer from a visual syndrome that I've come to call "segmentia". Making a slightly undersized plug of the affected area can be accomplished by building the affected area "inside out". Think of how canopy molds are made for vacuum forming and you have the method for making the plaster cast plug (need to make formers that externally contain the skin to allow a cast to be made). The plug, in turn, is used to make the female mold halves. Thickness of the paper is problematic but can be augmented by coating the interior of the original paper mold by a building up a layer or two of PVA before casting. The thickness should be just slightly less than the dry thickness of the chip board being used to layup the intended part. From here the laid up parts can be prepared for attachment to the regular model. The normal model skins can now be burnished down over the curved structure quite effectively. Very similar to the PVA moistened wing tip procedure. The whole idea is to provide a backing surface for the print surface to be formed over. Note that the print paper surface has to be sealed or "plasticized" with acrylic sealer before attempting to burnish it down. This process also assumes that there are enough segments to allow the burnishing method to work. I don't think anyone will try this as it is fairly complicated and requires a lot of patience to make it work. From some of the recent work I've seen it's possible to "burnish form" the pieces "freehand" to achieve similar results and doesn't require any of the overhead preparation work. But still I think it's worth the time to speculate on how it could be done.

The next phase of the project will be interesting as it doesn't have any real precedent in the full sized construction methods but shares many aspects of a well established commercial technology used in hobby model manufacturing...,

+Gil

[CharlieC]

Originally Posted by Gil

The use of a fuselage mold to layup strips of glued veneer produced extremely clean fuselages. The advent of all metal construction was the end of this technique till the advent of fiberglass and carbon fiber composites appeared. Going back to the Albatros and Vega it occurs that cutting out the patterns isn't really required. 5 or 6 mm wide strips laid diagonally into the mold at 45 degree angles between layers will work beautifully just as it did for those ancient builders.

+Gil

This technique survived in Russia until the 1940s - the Polikarpov I-16 fighter's fuselage was constructed in exactly this way. When the NZFPM restored their I-16s from wrecks they found that the Russians had no problems rebuilding the fuselages using the original techniques. (http://www.nzfpm.co.nz/article.asp?id=aircraft).

Regards,

Charlie

[Gil]

Chip board pulp blended with hot water and calcium carbonate was used to make the test shell shown in the image below. The pulp was laid into the mold and packed down with a sponge to remove water from the pulp and to work it down against the mold. Cotton towels were then used to remove the remaining moisture from the pulp before putting the mold lay up in front of a muffin fan to dry.

Chip board isn't recommended for casting smooth surfaces as evidenced by the "lumpiness" or paper egg carton "crinkle" exhibited in the image. The next shell will be cast from 100% cotton linters with calcium carbonate added to control acidity and kaolin clay added to reduce shrinkage and improve surface smoothness.

+Gil

[boosed]

Very interesting.

I have an anthology of flying model articles from the WWII era, on of which deals with making a fuselage out of brown gummed paper wrapped wet around a mold. I also recall toy cars made out of a material much like this material.

Don

[Gil]

The title sums up the digital images below. Acrylic gesso was applied, sanded and repeated three times prior to applying acrylic silver paint to the exterior of the shell. Some areas needed filling with automotive spot and glazing putty before a second coat was applied. The inside was simply coated with acrylic gesso (it looks exactly like a fiberglass lay up).

This particular method is much easier than the piece lay up but still requires a lot of prep to obtain a surface that's half way decent for a gloss spray coat.

The next go will be with the right stuff and shouldn't require as much surface prep (hopefully none at all). Have to refit the supplies before that happens...,

+Gil

[Gil]

Discovered a small amount of clear acrylic gesso left over from earlier castings and decided to try using it as an adjunct in the casting process. Some leftover dryer lint pulp was drained and mixed with the gesso (dryer lint trap cotton fibers that had been previously prepared for paper making) . An old Guillows Dr.I vacuum molded styrene sheet was used as a mold and into which the prepared pulp was laid. Excess moisture was pulled out with a sponge followed by tamping with a one inch wide stencil brush while covered with a cotton towel to remove the last bit of moisture and to push the pulp firmly against the mold. It was then put in a drying oven at 95 degrees Fahrenheit and allowed to dry.

The mold wasn't prepped before molding (it will be next time) resulting in a small amount of the paper being pulled off. Other than that it turned out surprisingly well with shrinkage almost nil and with little or no warping....,

+Gil

[Leif Ohlsson]

That is rather nice, isn't it? Better than the original plastic parts, as I remember them. I had one of those Guillows sets, long time ago.

On the wish list: Something that is really difficult, well nigh impossible in fact, to achieve by "ordinary" paper modeling, namely realistic pilot figures. Several scales preferably; over time also several postures: Sitting in the cockpit, flying position, one hand one the stick (or wheel), the other on the throttle. Sitting, one armed raised to signal for pulling the prop (vintage). Standing beside the aircraft.

I could go on, but for starters, I think there would be a real market for a generic pilot figure (or interchangeable parts thereof) in 1/33. Me, of course, would want one in 1/16, but that's me.

As I remember it, there was a pilot figure in that Guillows kit. Just the upper torso and head, but still. Perhaps an investment in a really good plastic pilot figure would be worth your while in the long run...

Leif

[Gil]

That first pilot figure may look like a petite Brazilian popular in Paris during the Belle Epoque...,

He'll be about 2 inches tall at 1:32.

+Gil

[jmueller]

Hi Gil,
just stumbled upon this very interesting topic. I have the pilots idea on my mind, too, for quite a few years now. One question: The machine gun parts, do they still have the feel of paper when it comes down to cutting and glueing? Or is the glue the major part?

Cheers
Jan

[Gil]

Hi Jan,

The molded piece preserves the look, feel and working qualities of paper.

+Gil