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Newbie glue/bonding broken windshield support ?


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All:

This is my first post on this forum.  I did follow the instructions specifically on searching for this answer but to be honest I'm not exactly sure how to describe it.

I used to be into models heavily when I was a kid (about 40 years ago) long before the internet, forums, etc.  I still have some old tools, glue and kits from back then.  I recently decided to get back into modeling for a number of reasons.  I'm basically starting all over and there is a lot to learn and a lot of different resources for info.

I've started by starting to learn how to properly prep, prime and paint.  I always used spray cans but the results were not great.  I bought about 15 years ago an aztek 4907 and small hobby compressor I never took out of the box until about 3 weeks ago.  My plan is to use and buy some old bodies some of which I have and some of which I have been buying on eBay.  I like the larger scale stuff, 1:16, 1:18, etc.  

My first question I have is how to I "fix" or "weld" these pieces back together.  Both of these cars I bought used and I'm intrigued how do one go about fixing this problem.  Any help, advise, techniques would be appreciated.

I know I need to glue these pieces together but what is the best glue for the job?  I also have to remove some old glue from previous fix.  I also need to have a tool to keep the two pieces inline and tight against each other.  I'm sure there is also some type of "putty" work as well to smooth/fill the two pieces into one again. 

One body is a testers 959 1:16 and the other is a 1:8 Mercedes Gullwing..both of these are projects and learning experience rebuilds.

TIA.

 

 

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Edited by 428street
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Welcome back! Like you, I took a break of about 50+ years. A lot has changed.

To get things perfectly lined up, you can try a couple of things. These are going to take 3 hands or some sort of tool to hold the parts together. You could try gluing the pieces by applying CA glue (Super Glue) and while you or someone holds it in "perfect alignment", hit it with some accelerator. It'll bond instantly. I use this brand. 

https://www.hobbylinc.com/hobbylinc-insta-set-cyanoacrylate-accelator-2oz-hobby-ca-super-glue-accelerator-151

You can also try the stuff they're selling on TV (can't remember the name) that cures instantly when you shine the light they provide on it. I've also heard that it is good for filling voids. I don't know if it will work on your problems. 

If there's space without it being too noticeable, I'd cut a piece of thin sheet plastic and glue it to the back side for added strength. 

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My first question I have is how to I "fix" or "weld" these pieces back together.  Both of these cars I bought used and I'm intrigued how do one go about fixing this problem.  Any help, advise, techniques would be appreciated.

I know I need to glue these pieces together but what is the best glue for the job?  I also have to remove some old glue from previous fix.  I also need to have a tool to keep the two pieces inline and tight against each other.  I'm sure there is also some type of "putty" work as well to smooth/fill the two pieces into one again. 

I'd probably start with cleaning up the repair areas first. Maybe use fine grained sandpaper, or files to clean out all the old glue without tearing up too much of the surface.If the breaks are otherwise clean, and the parts in question are styrene, then I'd glue back together using model cement. Once that is set, then do any filling and sanding, and restoring of body detail, like trim, drip channel, etc.

The above assumes the repair is moderately simple. If the repair areas will be hidden in the final build, then you may want to back up the repair with some sheet styrene cut to bridge the break, on the side that will be hidden. If the plastic is thick enough to drill edge on, adding styrene or metal pins would add stability and strength to the repair.

As for tools to keep things aligned, alligator clips, clothespins, rubberbands, other types of clamp are all available. One neat way to custom clamp something without over- or under-stressing it is to use a rubber band with a shoelace keeper (a little spring loaded device) you put the band around the body, slide the keeper over the band until it applies enough force to hold the repair without exerting extra force. (Props to the board member who shared that tip!)

Again, once you have a solid repair, then you can continue on with the putty/filler, and body line restoration.

Oh, and definitely search the forum for repair examples. There are some excellent resources here.

Hope this helps.

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Thanks Allen and Tom.  Allen, any idea what the search would be for the repair examples.  Thats where I get stuck, trying to figure out the proper name or string describing my problem.  I know I'm not the first, last or only one that has had this issue and I don't want to clog the system up with redundant posts.  Thanks.

 

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You can also consider backing the break with a very thin sheet of brass. You can get it as thin as a sheet of paper and it will hold the joint. If you make it as long as the windshield support, the kit's windshield post wont need to have any strength itself. 

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You can also try the stuff they're selling on TV (can't remember the name) that cures instantly when you shine the light they provide on it. I've also heard that it is good for filling voids. I don't know if it will work on your problems.

It's called "Bondic" or "Laser Bond" & while it has many great uses, this isn't one of them.

There's just not enough bonding strength to withstand the rigors of the build itself.

You wouldn't want to get the body all beautifully painted up & polished out & then have one or more of these joints fail.

I would go with either a super type glue or an epoxy with some backing plastic anywhere that it's possible.

Your best bet might be to replace the body.

If it's not a rare kit you may want to consider just scrapping it & starting fresh.

After all, as I said, You'd hate to waste a bunch of time & materials just to have it come apart on you before you can finish it.

 

Steve

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There are several problems with most of the repair procedures available to fix this, and I've tried them all and know what works from experience.

Bondic, CA (superglue) and straight epoxy actually have very little structural strength. You can't just stick two ends of a small piece of plastic together and really expect it to stay fixed. The world just doesn't work that way.

If you'll follow my directions here and really think the procedure through, you CAN achieve a permanent, stable repair.

The first thing you need to do is to get the parts aligned correctly and hold them there. Do this by putting the "glass" in place and taping the broken parts securely in position, so that they actually FIT the window "glass".

Next, you need to fixture the parts in place so you can do a good repair, and the parts will still be aligned correctly AFTERWARDS. This is where most people skip steps, and why so many tend to say "start with a fresh body because you can't fix it".

You do this by very carefully gluing styrene "splints" to the outside of the broken areas with liquid cement. DO NOT let it get on the "glass". 

When it's completely hard, overnight, remove the taped-in window "glass. What you want to do now is "vee" out the broken ends on the backside, tapering the break gently from almost nothing to the unbroken thickness, and roughen up the surface with somewhere around 100-180 grit sandpaper.

You're going to fill the "vee" with epoxy (30-minute epoxy at a minimum...5 minute just won't hold here), or CA, and some kind of fiber reinforcement. Read Snake's "fauxberglass" remarks, or use dryer sheets, very fine fiberglass (made for RC aircraft) etc. It's best if most of your fibers run in the long axis of the post, and you need to soak your  reinforcement fibers thoroughly in whatever adhesive matrix you choose, and make it thicker than it looks like it needs to be.

When your goo is completely hard or cured, you'll file it to correct shape, then remove your temporary "fixtures" and do the outside of the break the same way.

If you do this CORRECTLY, it WILL work.

Lots of effort? Yeah, but if you want good results, sometimes you just have to go the extra mile.

Any other method is almost guaranteed to at least crack when you're handling the model after paint, during sanding and polishing. Non-fiber fillers like talc and baking soda that folks recommend also have NO structural strength.

One good thing to use is "cotton flock". Mixed with a high-strength epoxy, we use it routinely in the sport aviation industry to assemble and repair plastic aircraft that can exceed 7 or 8 G.

 

 

Edited by Ace-Garageguy
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