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Old Jul 15, 2012, 03:29 PM
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Waltjg's Avatar
Crystal River Fl.
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Originally Posted by J Morgan View Post
Nope. Palmer drew this out with a 1/8" balsa skin. I just went with the regular sized formers for templates. Therefore my fuse is a little over 1/16" undersize all around. We're not going to TopGun or Scale Masters so no worry.

Thanks Doug


J
The scale masters I went to,,, you would have no problem competing with some of your planes!!!!!! w.
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Old Jul 15, 2012, 09:34 PM
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J Morgan's Avatar
Chapel Hill, TN USA
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Thanks Walt but I'm not so sure about that.

I thought I would relate my canopy vac forming attempts and failure. This canopy is big. No it's huge because I included the cutout all the way back to where the horizontal windows end .Used 3M tape for the framework. Remember the canopy was cut off the plug so it has 4 layers of 3 oz cloth, very stout and should stand up nicely to hot plastic and vac pressure.
But here's the problem. It is about 11" wide, long I can't remember but at least that long too. It has a 5" depth to further compound the difficulty of vac forming.
I have built 3 vac boxes and the largest one is 12" x24". Great for a canopy on a 1/8th scale F-86, F-18, etc. And when I order plastic I get it in with the proper dimensions to fit my vac boxes. I could have built a bigger box but then would have to order plastic too. But you don't pull an 11" wide canopy on a 12" wide vac box. Just not enough mat'l to make the stretch and give a good pull.
I hated to but I cut it in half with a Zona saw. Very clean precise cut. Tried 5 times to pull with .040 or.030 Vivak and just can't get the job done. Best pull I had was the second try but it came out with a wrinkle right across the pilot's windscreen.
Finally had enough, no sense in wasting plastic.
So I will glue the canopy halves back together, repair the seam and send it off to my vac forming hero Sparky. He does great work and I can get back to fiber glassing.

J
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Old Jul 16, 2012, 05:44 AM
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rawy's Avatar
swiss watch makers area
Joined Dec 2002
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Very nice work with the frame J,
The Vac forming is actually what delays three of my builds for some months now, I went to check your tutorial in your blog and have some questions.
When you write you give a coat of epoxy it was'nt clear for me if you glass it or just brush epoxy on it.
After having trouble with blue foam structure showing thru the first pulls, I decided to make the molds with Balsa, actually I'm still not happy with the shape (F14) what do I have to do when the shape is right ? epoxy, glass/epoxy or is there another method to avoid the wood structure to show in the pull ?

sorry for the noob question but watching to your builds I'll always feel like a beginner

Walter
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Old Jul 16, 2012, 09:10 AM
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Hey Walter,
I always use foam for the plugs only because I have a lot of it and it is so easy and fast to shape. Balsa is better by far, it will stand up to the heat unlike foam which needs a protective barrier. If it is a small plug I usually give the foam a coat of epoxy and then bondo. The bondo eats foam hence the epoxy coating first. Then I sand it smooth and do a pull. If I have a large plug then I will usually give it a couple of layers of 3 oz glass( to help withstand the heat) and then a finish coat of epoxy sanded smooth.
If you have a balsa plug, I would glass it with lite cloth just to cover the balsa grain. Then a finish coat of epoxy sanded smooth and you should be ready to pull.
Hope you have better luck with it than I did with the 119 canopy section.

J
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Old Jul 16, 2012, 10:18 AM
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Chapel Hill, TN USA
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Parting planes........
I've discussed this with my friend thinking there should be an easier way to make a pattern for parting planes but we can't come up with anything. Sort of labor intensive but works. I taped a right triangle to the nose and door plugs. It was all set p on top of a file folder taped the the table. The use another triangle to go all around the perimeter making pencil points the whole way around. Finally connect the dots and you have a close pattern. I cut that out and after checking that it was close enough I cut one out of lite ply. Used hot glue to tack it on the centerline of the plugs. Clay squeezed into the small spaces and leveled off and it was ready for wax.
If anyone has a better way of making parting plane pattern, please post it. Always looking for easier ways to do things.

J
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Old Jul 16, 2012, 02:36 PM
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United States, WI, Fond du Lac
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Gee, I go away for a few days and you're half done with another plane!

Great subject. The anhedraled center wing section gives an aggressive look to a cargo plane.

Waiting to see how you do the main gear.
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Old Jul 16, 2012, 03:00 PM
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Waiting to see how you do the main gear.
....not with a smile on his face....
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Old Jul 16, 2012, 03:43 PM
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....not with a smile on his face....
Yeah, we all know how John loves retracts......the more complicated the better!
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Old Jul 16, 2012, 04:16 PM
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Ah, but remember, I have help on this one. I have someone that actually knows retracts to help me.
We're going Spring Air 402 series. They will have some mods.
And you're right Pat, I hate retracts.

Been working on the nose cone and door lay ups. Pics show the molds curing.
The wing cores are in transit to me so as soon as the nose and rear doors are done I'm planning on jumping on the wings. I also have 21 lbs of balsa & lite ply in transit.
Did I say this is a big plane?

But I have to leave tomorrow for a few days on family business, will be back on the build at the end of the week. I'll sneak in on the Groups occasionally while I'm out of town.

J
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Old Jul 16, 2012, 04:24 PM
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Canada, NT, Yellowknife
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Originally Posted by J Morgan View Post
If anyone has a better way of making parting plane pattern, please post it. Always looking for easier ways to do things.
Only thing I can think of is instead of file folder use stiff foam set up like you have there then go around your item with vertical hot wire to create the plate instead of another right triangle. however I don't know if the foam would work for this or if the hot wire will kill the item to be molded, I'm trying to learn form you here
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Old Jul 16, 2012, 04:36 PM
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Glad you got a plan for the gear.

I started drawing up plans for a much smaller C-119 a couple years ago. Those pyramid struts on the mains are a signature feature of the 119. Never came up with a simple way to do retracts that would look credible and lost interest.

There are a few videos on the web of things that folks have build that duplicate the scale mechanism; pretty impressive!
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Old Jul 16, 2012, 04:42 PM
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Baltimore MD USA
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J when making the mold this way(a two part mold) do you do it the same way as the plaster (one off molds) and use light 3/4oz glass first as your base layer?

Bruce
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Old Jul 16, 2012, 05:45 PM
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upland CA
Joined Dec 2004
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Hi John, for parting boards I use a lite bulb (not floresent) high above the work to cast a shadow on the barting boad material...for big parts you may need more than one bulb or you have to move it along a straight line...but your way seems very easy to me.
S.
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Old Jul 16, 2012, 08:45 PM
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Once again superb work!!!
Subbed without a doubt
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Old Jul 16, 2012, 09:26 PM
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Pat,
I think my buddy has a plan for the gear, some ideas anyway. I try not to think about it, it hurts my brain. And then every now and then this thought flashes through my mind....... GEAR DOORS! Really not looking forward to those.

Bruce,
When I made the door and nose molds I shaped, spacked, sanded, and then gave them 2 layers of 3/4 oz glass/resin. Then if you are careful with them they will stand up to very small amounts of hot glue to tack the parting plane on. Too much hot glue can melt the foam under the glass though so you need to be careful.
Then work the corners with microfibers/resin mix because you'll never get that sharp corner with glass. The I put small patches of 3/4 glass over the corners and then small patches of 3 oz glass over them too, build up the corners. One layer of 3/4 cloth over the entire piece for a smooth inside finish and you are ready for heavy cloth for the rest of the layup. It takes a lot of heavy glass to build up the strength to be able to pull pieces from the molds. My molds ar about 1/8" thick.

Scott,
I thought about a light bulb but figured it may be harder than this way. May try it next time.

Thanks Doush

J
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