Originally Posted by kjkimball

Karl,

Did ya know the full scale canopy is not made with a plug or a mold? I think this is why modelers have trouble getting the shape right.

Hmmm.... I know they blow mold pop bottles and such. How in the heck could you do it without a mold?

Originally Posted by kjkimball

Karl,

Did ya know the full scale canopy is not made with a plug or a mold? I think this is why modelers have trouble getting the shape right.

Now you have me thinking a female mold and it wouldn't take much air pressure to push it down into it at all judging by how much pressure it takes for me to pre stretch it... A different project of course.

Originally Posted by Krazy Karl

Now you have me thinking a female mold and it wouldn't take much air pressure to push it down into it at all judging by how much pressure it takes for me to pre stretch it... A different project of course.

Is it me or could talk like that be #73

Ha....never liked pre-stretching....but always warmed it up first

Earle

Thats what SHeeeee said>>.....

Originally Posted by 540edge540

Is it me or could talk like that be #73

As soon as she reads it that'll make it #73. Man did I walk into that one or what?

Originally Posted by Krazy Karl

Now you have me thinking a female mold and it wouldn't take much air pressure to push it down into it at all judging by how much pressure it takes for me to pre stretch it... A different project of course.

Karl,

Some FS canopies are made into female molds. A mold for a vans RV9 for example costs about $10,000 to make in high temp tooling and labor). It has to withstand 300 degrees, provide vacuum ports, be stable for many heat cycles, etc. For airplanes like mine and the MX and lots of others, there is no mold. The art in making the part is knowing what shape hole to cut in a 3ft x10ft piece of plywood so that when the plastic is pulled down thru it, the desired shape is made. The plastic is hung on a rack in a vertical oven and heated to the proper temp. It is limber as a dishrag and hot. A vacuum box is used that has the artfully cut plywood top on it. The plastic is placed on top of that and champ sealed to the box. Vacuum is applied and the plastic pulled down into the box. Knowing how fast to pull it down and when to lock off the vacuum is the trick. Then let it cool, remove from the box and cut both ends off that do not look like the desired part.

In the case of the model 12 canopy, the tail end gets about 3ft cut off of it. It extends back that far to near pointed shape to get the desired shape and size of bubble. The front end actually has a squarish look to the plywood hole to get the more blunt windshield shape I wanted. At this point, if you cut the plastic at any section, it will be part of a circle. In most cases, MORE than half the circle. Midway of the canopy is the tallest point and so it is the widest part of the bubble and actually sticks out wider than the fuselage frame there. When we make the canopies here, including the one on Kendal's plane, the skirt along the bottom has to be fitted to the bulge out of the side of the bubble and blend back into the straight line of the fuselage frame and metal skins.

So, if we were to use the bubble just like that, it would not fit the shape of the turtle deck. So, there is a second process done by the canopy maker to reshape the bubble from midway to the rear end. After the tail scrap is cut off, the turtle deck end of the bubble is screwed to a form the shape of the turtle deck. This forces the bubble into a new shape there. The put it in a large oven and let is stay there 8 ors of so at a medium temp. It then takes that new shape without collapsing the entire thing.

So, just about every model 12 RC canopy I have seen is shaped funny, not plump enough midway and wider at the bottom than 1/3 up the side like the real one. Again, take a look at the pics of kendal's and others to see this.

For you, I don't think you can do it with a mold unless female. Actually, if I had spent the $10k for the mold, the real ones would not have the bulge in the either.

Originally Posted by kjkimball

The art in making the part is knowing what shape hole to cut in a 3ft x10ft piece of plywood....

Wow, I never knew that. Sounds like a TON of trial and error to get the shape that you want, that also can withstand all of the stresses.

Very interesting Kevin.

That explains why it cost 100 plus thousand to buy an experimental..
They want to pay for the molds and jigs on the first couple they sale.

Originally Posted by Boomhauer

That explains why it cost 100 plus thousand to buy an experimental..
They want to pay for the molds and jigs on the first couple they sale.

Actually no. The real cost of aviation is litigation.

Originally Posted by justinsebastian

Wow, I never knew that. Sounds like a TON of trial and error to get the shape that you want, that also can withstand all of the stresses.

Depends on where you go. I use the best people in the US for our canopies. I made the drawings, emailed them to him and the first one fit and is still flying today on first model 12 we built. It is an art to know how and what to do with the plastic. He made the windshields for my wooden boat and made the canopy for my Gee Bee Z as well.

Originally Posted by kjkimball

Actually no. The real cost of aviation is litigation.

Agree, kinda like coffee being too hot and burning you. So now I have to pay almost 7 bucks for a big mac meal.

Originally Posted by kjkimball

Actually no. The real cost of aviation is litigation.

Nailed that one.

It is common knowledge to those in the aviation industry that a plane's wings cannot produce lift until the paperwork for said plane weighs as much as the plane itself.

Here's your chance Karl:

https://www.flyinggiants.com/swapsho...ct=27352&cat=2

The BIG Moki! God I wish I had 25 large sittin around!