Koster/Monogram XP-72

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Koster/Monogram XP-72

Postby jeaton01 » Sat Jun 18, 2022 12:18 am

Started on this as a fill in model while others have waiting time. The Koster parts are very good to work with. I followed Bill's directions and sprayed the vac sheets with a good grey primer, then went around the edges with a narrow felt pen. I scored around on the middle of the black line and then put a piece of 220 wet or dry on a glass surface and sanded until things looked right. Since it has been a fill in project I wasn't as good as I should have been about wip photos, but what's not shown is the process of putting together and installing a Black Box/True Details P-47M resin cockpit and Eduard seat belts/instrument panel. I put strips of plastic card in alternating spots on the fuselage halves and glued them together using the Tamiya resin glue in the hexagonal bottle. I am starting to like that glue, though the brush is a bit bigger than I like. There were resin parts for the contra rotating propeller, engine fan, and intercooler below the chin. This airplane was powered with the Pratt and Whitney R-4360 and unlike earlier Thunderbolts it did not have a GE turbocharger. Instead it had a second stage compressor mounted in the back where the turbo was earlier. The compressor was shaft driven from the engine. It had good altitude performance and reached 490mph during the test program. Only two were built, it was too late in the war to be needed.

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I reinforced the cowl seams with .6 ounce fiberglass adhered with thin CA.
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The wing panel lines were scribed. The XP-72 had 6 guns arranged differently so gun ports were filled and the barrels modified. The inner gun port will be re-cut to match the location of the third.
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I backed up the cooling fan with Aves Epoxysculpt, that gave me a lot more time to position the fan correctly. I tried it with gel super glue the first time. but somehow once it was cured I saw that it had deformed to opening of the cowl and I had to take it back out. Some careful Dremel work was successful but I hope I don't ever have to do that again. I put a brass tube in to hold the prop assembly.
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Re: Koster/Monogram XP-72

Postby Stikpusher » Sat Jun 18, 2022 12:41 am

Great subject choice John. Are you going to do a prototype or a what if subject on this one?
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Re: Koster/Monogram XP-72

Postby SteveSki » Sat Jun 18, 2022 3:52 am

Hi John,

This is interesting, I've never seen fiberglass reinforcement. Probably because I don't do many birds, but I learn something new every day, wow. My question would be, is there a noticeable enlargement of the area or does this work like a putty filled seam? I would think this beefs up the cowling and really eliminates the tendency to separate like they often do, but doesn't most of the fiberglass get filed away? I'll have to remember this trick.

Cheers, Ski.
Give Blood, Play Rugby, cause everyone knows football is for wimps!

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Re: Koster/Monogram XP-72

Postby jeaton01 » Sat Jun 18, 2022 1:36 pm

Steve, in this instance there was no need to be concerned about thickness buildup, however the .6 ounce fiberglass is much like a thin gauze and adds little thickness when thin CA is used as an adhesive. It does add a little though. I haven't used it externally on plastic models. I have done a fair amount of fiberglass construction on R/C models and as for thickness in that kind of application resin is a lot of the buildup unless you are careful to use as little as possible. The type of resin used also has a lot to do with the ultimate result with some being stiffer, stronger, and more temperature stable than others. I might use isophthalic resin on a plastic model if I wanted high strength but in the case of the cowl due to it's shape and that it will be reinforced by the attachment to the fuselage CA was fine.
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Re: Koster/Monogram XP-72

Postby BlackSheep214 » Sat Jun 18, 2022 5:16 pm

Interesting subject.
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Re: Koster/Monogram XP-72

Postby jkim » Sat Jun 18, 2022 5:49 pm

Wow, what a cool subject! Hotrodded Jug with contra props! Love what you did with the CA and fiberglass cloth... that should make for a strong bond!
John aka JKim
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Re: Koster/Monogram XP-72

Postby tempestjohnny » Sun Jun 19, 2022 4:37 am

Such a cool subject. If the war had continued Republic had some pretty interesting ideas for the Jug
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Re: Koster/Monogram XP-72

Postby Medicman71 » Mon Jun 20, 2022 1:09 pm

Very cool subject! Gotta love a P-47 on steroids!
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Re: Koster/Monogram XP-72

Postby jeaton01 » Mon Jun 27, 2022 6:18 pm

The basic assembly is done and most of the filling and sanding, though there are a few spots to deal with remaining.

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Re: Koster/Monogram XP-72

Postby LyleW » Tue Jun 28, 2022 6:44 am

That looks good!
To make each build less crappy than the last one. Or, put another way, "Better than the last one, not as good as the next one!"..
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