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themongoose

1/32 T-38A Talon

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I decided to start this concept in my spare time as it may take awhile. I could wait forever for someone to inject one  <_<  An initial look at the lines tells me that the back of the canopy is the reference point and everything moves forward from there. I picked up the Belcher Bits get to transform the F-5E to an A. I also have 3 canopies, 3 front fuselage sections, and 2 complete kits to work from...my version of mistake proofing  :coolio:  The big question mark will be whether I can get a canopy formed or not. I dropped a note over in tips and techniques but if anyone knows someone that can help me out with a vacuum formed canaopy let me know.

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Here's my 1st test, I wanted to see if there was any way to combine 2 canopies to make it work out. No dice unfortunately. The stock canopy drops too far in the front. Thought I might be able to make one shorter and the other taller by building up the frame but it's just too far off. If nothing else I wanted to try out these new ultrafine saws I got.

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I was doing a couple things at once here; finding the marks on top for relocating the coaming (not sure if this is the right term but the cover over the instruments).

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I found a great straight on shot of the plane with the canopies raised so I took the ratio of the canopy length to the overall length of the opening and mocked up the two cockpits.

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And here's where I left things today. Canopies in place just to see how it looks in profile. 

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If you've looked into doing something similar let me know your thoughts on the design. Any advice from you guys that scratch build alot let me know how you'd proceed. I'm just working off the 1st set of practice parts so I can do some experimenting here for sure.

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Cool project! I love the T-38. I have also been and still AM waiting for someone to kit one.

 

Does the F-5E/A have the same underbelly curve up from aft to the tip of the nose like the T-28 does?

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T-38 is so cool. Good luck with this. Everything I think of doing something like this the same old problem rears it's ugly head ...the canopy. You will probably need to vac a new canopy, good luck with that. I have crashed and burned several times in he past.

 

Dan

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Cool project! I love the T-38. I have also been and still AM waiting for someone to kit one.

Does the F-5E/A have the same underbelly curve up from aft to the tip of the nose like the T-28 does?

The Belcher kit includes a nosecone with a modified arch to it. Then everything behind the cockpit is also in the Belcher kit so it looks like all the curves are matched up now. The IP coaming moved forward nicely without having to narrow it or widen the fuselage so that makes for a clean look without worrying about any of the lines looking wrong. I’m excited about this now that I kicked it off and it feels possible to accomplish.

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Back on this baby today. I'm working on the form so I can make a mold for the vacuum formed canopy. 

1st I traced the outline of the canopy from the sections I had made earlier. Then I determined where to make the cuts to keep the profile smooth. I read on here that using clay give support to the clear plastic and minimizes the chances of cracking it while sawing.

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Next I notched the canopy out. The frame along the bottom is pretty straight. I think it will take some filing and filling once the mold is done but it matched up real well between the halves. Where as the curved portions of the canopy weren't even close.

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Next I used some T beam evergreen strip to set the profile and stiffen the pieces up.

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Then last I placed flat sections of evergreen over the entire outside. That will keep the molding material inside the canopy until it dries. More next weekend as I'm traveling through Wednesday and then the kids have school activities. I'm going to have to get out of my cave this week  :)

F87BE4BC-09B7-4E69-9E34-B37E3F5D821D-L.j

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Wow, ambitious project. Though F-5 is similar to T-38 but far from it's beauty. So, you have your hands full but a great journey ahead. ;)

 

If you don't it have it already I strongly suggest you get the Daco T-38 book. It will be a strong reference point for your build. Just a thought.

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Tonight I made my first impression of the canopy mold. Since this is new I figure to try 2 different techniques. From this I’ll make a clay overmold that i can pour bondo into for the first method. For the second method Tomorrow I’ll pick up some plaster and make a form that i can directly place the hot PETG over. One of the guys in the Cincinnati scale modelers club iffered to help with the forming if I could do the molding.

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Lots of fun this project! So the clay was interesting. Because the canopy is sooo long shrinkage was actually a consideration. It ended up 1/8†short. Lesson learned use clay right away for the mold.

My plaster mold and casting came out ok. Almost messed it up. Apparently the mold moved when i poured the castable around it. I’m going to use it but as a spare. Tomorrow I’m going to do another set now that I’ve experimented once. The rest of it seems to be good. While the castable is still drying, about an hour after pour, i was able to sand the lip of the canopy to a uniform angle all the way down the length. This has been the hardest part to recreate because it’s rather thin.

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If I may, you are on the right track, but your molds, whether positive or negative, look a bit rough to achieve a smooth result.

 

If you use a female mold to form the clear plastic (PETG is the one to use, with plenty of stock for failures, because it is extremely sensitive to temperature - too hot and bubbles will form inside the plastic, too cold and it will not form ), create a small hole for the air, and hence the plastic sheet, in the mold to be sucked.

Use monofilament to create this hole. Stick it in the male master, pour your mold, and when the mold has set, remove the monofilament with pliers : a neat, smooth small diameter hole will result. To avoid the « dimple Â» created by the hot plastic being sucked in the hole, the diameter of the hole should 1/2 of the plastic sheet thickness, i.e. 0.5 mm for 1 mm sheet, or 0.375 / 0.4 mm for 0.75 sheet. This is why monofilament is the best way to get this small diameter hole in the female mold.

 

Keep going. You’re learning a new trade, and scratchbuilding is sometimes (often ;) ? ) frustrating, but I know no more satisfying modelling.

 

Hubert

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Thanks for the observations Hubert! It just wasn’t working that way for sure. I think it’s somewhat more complicated because I’m starting with a female mold...at least I’m telling myself that 😣🙈🙉🙊 so next time I may use foam and start with the male mold though it’s probably got its own set of complications.

I went back to the original canopy pieces I glued together and finished the inside as smooth as possible. Had a small crack in the bondo from all the handling but i filled it with clay and the put vaseline on it so the clay would come out. Ruined one because I forgot the vaseline.

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When i put the mold on the bottom of the tuperware it kept moving around and material got under it in places and made it uneven.

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The solution I thought was to press the mold in from the top. Now i just needed a way to keep it from settling to the bottom. 🤔 So i made it a lifejacket 🤣

I cut slits in the side so no air would be trapped. I put the screws through the platic sheet and into the clay while it was still inside the canopy so the clay wouldn’t distort. This also made it easy to remove the clay without messing up any corners. I mixed up the perfect cast and poured it in the tuperware, sprayed the clay with a windex type product to minimize air bubbles, and then angled it into the casting material so the slanted rear of canopy was filled first. And presto it floated!

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Here’s my finished product.

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It has to dry for 24+ hours so I’ll wait till Monday to try a mold from it that i can use to form petg over. Tomorrow I’ll probably make another one so I have a spare. I will probably have to make several molds anyway So I don’t get caught short in the forming stage. One of the guys from the local club is goingg to help me with that as he does them all the time for his paper models.

 

Any upfront advive on this next molding step would be appreciated for sure.

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Now that I know I have a good copy of my canopy mock-up I felt safe pouring a mold right from the original. The bag says this perfect cast gets hot so i was worried about distorting the pep canopy plastic and bondo i made it from. After a few molds though I recognized it was just getting warm, not hot. I applied a light coat of vaseline, capped the ends (left a small hole for air to escape), and then hit it with the hairdryer so the vaseline would flow out smoothly eliminating any chunkiiness or streaking. Hopefully I can finish this nicely and use it for my mold.

 

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