Chad Veich

My Feedback: (60)

Luke, please let me know how the Bondo works in a plastic mold. I've been wanting to try this for some time but just have not had opportunity. I will gladly learn from your mistakes!! The plugs I'm working on are for the 83" Taylor designed airplane. They have not progressed much in the last couple of months but I will be returning to them in October.

PS- I know the Bondo would work in a Silicon mold. Silicon is just so danged expensive.

SCALECRAFT

My Feedback: (13)

Hi Guys

On the bondo thing, It will distort the plastic you wish to mold. But if you must try it, the way to get a flawless surface is to mix polyester resin in with the bondo to thin it and minimize bubbles. Again you must control curing heat, it will distort. Plan on a slow cure. Or even cool with water bath.

One of the best ways to reproduce a canopy for us is, to layup glass /epoxy in the "plug" canopy. Remeber to wax and PVA first for easy release. The heat will not be a problem fir the mold. Controled heat ofcourse.

Pourstone works also. But sets in about 2 minutes, move quickly.

Good luck.

Steve

RCFlyer55

My Feedback: (28)

I need to make 8 Boat Canopies. The boat is made from balsa and so is my first canopy, but I do not want to go through he work of making 8 more wood ones. I figured that making a plug out of a solid balsa block and vacuum forming the canopies would be the way to go. The origional balsa canopy is just over 13" long.

Any suggestions?

Will a balsa block work?

Where can I purchase the plastic material for forming the canopies?

Here are some pics so you can see what I mean.

Goggles

My Feedback: (4)

Taken from the second paragraph of the 1st post: Only I had to pay $25 for mine, oh well it's still pretty cheap and I should be able to get about 25 canopies from it.

BTW, I have the plug made from fiberglass, now I just need to sand smooth, prime, make a vac box and see what happens.

Good luck with your boat.

RCFlyer55

My Feedback: (28)

What does "PETG" stand for?

Goggles

My Feedback: (4)

Polyethleneterephtalate Glycol (PETG) copolyester sheet

LesUyeda

"P E T G" does not stand for anything; it is the name of the plastic, and you would ask for it just like that.

Les

antonio104

put "Spectar" in your search engine or check this site:
http://www.boedeker.com/spectar.htm

dionysusbacchus

My Feedback: (25)

If I was going to use balsa as a form I would harden it with some thin CA and then give it a coat of finishing resin. Sand it smooth and then spray on some primer. I would also use the .030 PETG for the boat, good luck!

Good Luck Goggles, let us know how you do and post any questions you may have.

I'm going to stay with Plaster of Paris coated with resin and primer as my main way of making plugs, cheap and easy for me just the way I like it![8D] Not to mention the canopies come out perfectly clear! Your plug sounds great, post some pictures!

Dion

LesUyeda

I stand corrected. Just goes to show when I repeat what my plastics shop people told me.

Les

Goggles

My Feedback: (4)

I'm trying to make the canopies now, but I have a stupid question: Do you take the plastic cover sheet off before or after you make the canopy?

I just did one and it didn't turn out and I wanted to see how clear it was, well, I had left the protecting covering on and it doesn't want to come off. I'll try one with it off and see what happens.

hnesitd1

Goggles........you take the plastic cover sheet off before you heat the plastic. Here is some pics of a canopy I just made. The first 7 pics or so are the successful fabrications. The last (5) pics are previous trial and error (failures).

http://members.allstream.net/~machten/vacuum/

One word of wisom ............ don't heat the plastic too much......Good luck

Goggles

My Feedback: (4)

Thanks for the pics.

How do you keep the static from the plastic from picking up everything in the air?

After the first try with covering on, I removed it for the next 3 pulls. 2 didn't turn out but the last one did actually get pulled tight. I found out I need to have the plug a lot smoother than I have it now. For the covering, I took it off just before I placed it in the oven, but even at that I still had crap show up on the plastic. I even wiped it with a tack cloth before I placed it in there.

dionysusbacchus

My Feedback: (25)

Static is the enemy, I haven't tried it but I am going to wipe the plastic down with a dryer sheet and see if that works. You should never form clear over unsealed plaster or wood. If you have plaster you should spray it with a few coats of auto primer and sand it smooth, just make sure you let it dry completely before forming.

Dion

hnesitd1

Yeah, static is the enemy............I use windex just before I put the sheet in the oven.........just wipe with paper towel. My suggestion is to perfect the technique first, then concentrate on fine tuning. Hopefully you're buying the PET-G in 8X4 sheets...........makes trial and error very economical, eh? I'm not sure what problems you're having (static, etc, notwithstanding). I can tell you that if you have a good vacuum pull down and you're experiencing problems it is probably related to allowing the plastic to get too hot, ie, too much droop. If you're getting a lot of wrinkling, that is most likely the culprit. Thousands of modelers use this technique, it's not rocket science! If they can do it............you can do it.

Goggles

My Feedback: (4)

What happens if it gets to hot? (too much droop)

hnesitd1

[X(]When you experience problems you'll probably suspect that the plastic is not getting soft enough and, you'll let it droop more before removing it from the oven. I went through this learning curve only to discover that I was letting the plastic droop too much before placing it over the plug and activating the vacuum. Too much heat caused severe wrinkling when the vacuum was activated........the plastic was too soft. Hope this helps.

Chad Veich

My Feedback: (60)

An easy method of finishing your plug is to simply vac form over it and leave the plastic on the plug. Sand it with progressive grades of sandpaper (finishing with about 320) until ALL the gloss is removed from the plastic. Then pull another canopy over the top of the first. As long as you don' t leave any gloss on the plastic over the plug it will not stick to subsequent pulls. I just tried this method a few days ago on a 1/5 scale teardrop style canopy for a Spitfire. I am satisfied that with a few minor changes to my system it will produce a really nice, crystal clear canopy. I need to pick up some thicker PETG and I will continue to expirament. Good luck to all, Chad Veich.

PS - I did not even attach the first layer of plastic to the plug, simply set it in place. I had no problems at all with the plastic sticking together, they would generally fall apart after being removed from the plug.

Goggles

My Feedback: (4)

I'll have to try that method. Thanks Chad.

Kelsey_B

I need some advice.

I have been trying to form a canopy. Many pcs of plastic have yielded bad results. Here are a few pics showing the problems I'm running into. I cant' seem to form the plastic without wrinkles.

Also notice the plastic did not pull up to the bottom of the plug. I'm guessing i did not heat it sufficiently.

How quickly do you push the plastic over the plug?

Any suggestions would be appreciated.

YAT-28E

Looks like you did not get a good seal and maybe the plastic was heated to much and has too much "droop".

Kelsey_B

I think your thoughts about the plastic not sealing is exactly the problem. The 1/4 pegboard is very slick, which lets the plastic slide around and wad up against itself.

I was getting pretty aggravated. Thanks for the help.

Grumpy Monkey

My Feedback: (7)

Kelsey,
Another trick is to place a spacer under the plug to raise it above the pegboard. 1/4" should work. This way the vacumm can pull the plastic past the bottom edge of the plug allowing a clean bottom edge.

Warren

drcrash

Judging by the curvature of one edge of the plastic, I'm wondering if the plastic pulled out of the clamping frame there. You may want to make a sandpaper-like gripping face on the top face using J B Weld (high-temp epoxy) and tamping sand into it.

You might also need a gasket around the edge of your platen, or some other way of making it seal.

"Webbing" is a common problem if the plastic has stretched too much, and folds in on itself when sucked against the mold. Unfortunately, in a simple vacuum former, there's no way to heat the plastic sufficiently for forming without a certain amount of sag, and that may be "too much" in this sense.

It can usually be reduced by putting the buck (mold) up on a riser. One that flares out may help. If the webbing is only problematic on one side or end, it may help to tilt the buck upward on that side/end. (But it looks like you have fairly symmetrical webbing on both ends.)

Is this webbing actually a problem? It looks to me like what you're actually trying to make curves up on the ends, and your buck has a built-in riser there.

funkworks

help!... I have a canopy I'd like to start making but it might be too big for a homemade rig. It is about 16 inches long and about 4 inches wide. I've attached a photo of the model to give you guys an idea. I had someone else make this one for me but I'd like to start making my own. I tried making a rig but it really didnt work well. I made a box and made a small platform (basically a few blocks under the plug to hold it level) to hold the plug just below the edges of my box. The platform was glued to the bottom of my box and I secured my plug to it with double sided tape. I used marbles to fill the box and allow air to escape (it helped to keep the box stable too). I could never get the plastic to suck down all the way. It seemed like it was cooling too fast for my vacuum to draw it around my form. I was using a cheap upright vacuum cleaner (possibly one of my problems) as the only vacuum source.

I would be happy if I could just find someone who could make my canopies for a fair price. I dont mind making my own plug.