How would you cut this out?

[Safire6]

I'm building a MPC  1/16 '82 Trans Am. I'm building the kit with the optional T-top so I need to cut a section of the roof out. There are recessed grooves in the underside of the body to show approximately where to cut. What is the best way to cut this section out? Xacto knife? I'm afraid if I put too much stress on it when cutting that I'll damage one or both A posts. Anyone have any tips for cutting this section out?

 

 

[STYRENE-SURFER]

Hard to believe any kit manufacture would think this was doable.

All I can think of is try to put some kind of strengthening into the body(like they do on 1-1 cars) something

that will brace/hold it together while working on it, but later removed. In other words sacrificial cross braces to keep it

held in place for that work. Perhaps the kit chassis would suffice. 

[Ace-Garageguy]

Cutting panels open may seem daunting, but it's really quite easy...but PATIENCE is the key.

Repeatedly scoring the lines you want to open with a dedicated scibing tool or the back side of an X-Acto blade will do it.

Work GENTLY. Do NOT rush it.

If you can't get a good straight line started, or if the grooves in the plastic body shell aren't very deep, you can lay a guide of Dymo tape (if you can find any) or strips cut from real aluminum dict tape (not the fabric stuff).

Once again...PATIENCE IS KEY. Work SLOWLY and CAREFULLY.

This is a great opportunity to learn precise tool control, and thinking modifications through...like determining exactly how much material needs to be removed by comparing the optional parts with the existing top panel.

You CAN do it.

 

Edited October 24, 2019 by Ace-Garageguy

[Casey]

Since the sacrificial door opening filler pieces have been removed, you're risking even more body flex, but it can be done.

Trace around the H-shaped piece, on both the top and bottom of the roof. It's clear where the rear edge should be cut, but the front edge is less clear. I would mark your marks, then scribe (back side of an X-acto knife blade, scribing tool, etc.) the front edge first, from the underside (inside of car) of the roof. Go slowly and let the blade remove a thin curl of material instead of trying to cut the two sides apart-- that induces too much stress. When you have almost cut through the front, do the same at the rear, leaving enough material to remove with a handful of passes. Scribe all the way through the front, use medium tack tape (Scotch clear tape would be a good choice) to hold the windshield header and soon-to-be-removed roof section in place, then scribe the rear joint again until it's free. Use files and fine sandpaper until the H-shaped piece fits correctly.

[Plowboy]

Since you don't need to save the top, I would use a Dremel and cut off wheel. Leave plenty to trim and sand. Sounds brutal. But, it puts much less stress on the body. I've cut down very delicate pieces with a Dremel and cut off wheel. Even glass on rare kits. 

[STYRENE-SURFER]

Looks like a fairly fragile body, I would take the advise from Bill and Casey although think it would be a good idea to stabilize the

body so things don't go south. 

[DukeE]

Fine line sharpie on inside cut lines. Probably keep upside down on hard surface and use something firm under hood and rear window area so it doesn't flex or move around. 

Like everyone said, take your time. Either back edge of new 11 blade, or scribing tool. Agree front line hard to see. Maybe do 1/2 side at time, from middle to window, do front first then back to keep stress off windshield frame.That way, last cut is along C post which is way stronger than windshield side. Maybe go most of way thru, then finish with little saw blade in xacto knife.

Dremel good idea if you're used to it. Could use it on front edge, and on back with a bit of margin to clean up. But if you're not used to a Dremel, scribe away

Edited October 24, 2019 by DukeE

[BigTallDad]

19 minutes ago, Plowboy said:

Since you don't need to save the top, I would use a Dremel and cut off wheel. Leave plenty to trim and sand. Sounds brutal. But, it puts much less stress on the body. I've cut down very delicate pieces with a Dremel and cut off wheel. Even glass on rare kits. 

Sounds like a plan to me!

[Ace-Garageguy]

Only problem with using a Dremel if you're not really used to it...it's easy to get the blade just a little cocked in the cut. Then it bites. Then you have two halves of a body, because when the cutting blade bites, it snaps the body out of your hands, and breaks it.

[STYRENE-SURFER]

Well. As you can see There are as many ways to do this as there are members here.

Myself, I wouldn't start butchering until I had a good fit between the chassis and body.

Only then would I start on this modification. For reasons I've already gone through.

To each there own.? Build it !

[StevenGuthmiller]

47 minutes ago, Plowboy said:

Since you don't need to save the top, I would use a Dremel and cut off wheel. Leave plenty to trim and sand. Sounds brutal. But, it puts much less stress on the body. I've cut down very delicate pieces with a Dremel and cut off wheel. Even glass on rare kits. 

I would do it the same way.

I believe in the neanderthal approach to modeling.

 

A mini, multi-speed Dremel  is a miracle modeling tool.

 

 

23 minutes ago, Ace-Garageguy said:

Only problem with using a Dremel if you're not really used to it...it's easy to get the blade just a little cocked in the cut. Then it bites. Then you have two halves of a body, because when the cutting blade bites, it snaps the body out of your hands, and breaks it.

That's where a cutting wheel comes in.

Just lightly grind a line at low speed until you are nearly through the plastic. (When the cut is nearly transparent)

Then finish the cut with a sharp X-acto blade.

 

 

Steve

[Bucky]

It would be sorta difficult to work on the inside of the roof with the chassis in place, in my opinion.

[Bucky]

Being a 1/16 scale kit body, I would most likely use the Dremel approach.

[STYRENE-SURFER]

8 minutes ago, Bucky said:

It would be sorta difficult to work on the inside of the roof with the chassis in place, in my opinion.

Well DUH!

You do want the parts to match up in the end without any undo flexing or whatever.

Is this really that hard for you to understand

[ScottH454]

Get yourself a straight saw so it will have a good chance of being straight. Plus tape lines can be helpful guidelines.

[StevenGuthmiller]

36 minutes ago, ScottH454 said:

Get yourself a straight saw so it will have a good chance of being straight. Plus tape lines can be helpful guidelines.

The nice thing about a cut like this, where the center part of the roof will be discarded, is that you really don't need to worry about the initial cuts being straight.

They can be refined with some shaving and sanding later.

This way, there's no need to worry about possible mistakes.

 

On the razor saw note, this particular task might be difficult to do with a saw.

A saw puts a lot of back and forth stress on the surrounding fragile body parts.

This one looks particularly fragile.

There will be nothing holding the body together at the end of the cutting except the rocker panels.

 

 

Steve

[ScottH454]

Then it would depend on how you saw plastic, Steve. I for one would rather make the cut once. Trying to refine the windshield side after is cut will be harder. I had to make three cuts to chop that beetle roof with fragile pillars and that that's a IMC kit with open doors. If he holds the center portion as he cuts there won't be any stress.

[Matt Bacon]

+1 for the slow, gentle and steady with a scriber. I’d do the windshield cut right through first, upside down with the roof taped firmly onto a tile or bench so the only stress on the A-pillars is the (slight) drag of the scriber. Then do the back, and once you’re nearly through, snap the roof up and away...

best,

M.

[James2]

For what it's worth, I would mark the exterior roof line with tape. But just shy of the finish attachment points. I would use a razor saw and cut through both lines leaving a 1/16" uncut at the drip rail. This allows you to do most of the work without breaking anything. Then gently make the last four cuts and sand the edges until the T top part fits perfectly. I wouldn't trust the mold line to be accurate. And as mentioned take your time, be patient and don't drink any caffeine before starting. 

[Ace-Garageguy]

A method I've actually used successfully multiple times while doing similar work is to reinforce the body shell while cutting by simply taping the door shells in place.

After cutting, you will also want them firmly in place to guarantee correct alignment while you position the new roof insert.

This is a job, again, where paying close attention, thinking through every move, and working carefully and slowly will make a nice job instead of an ill fitting mess.

I recommend you use good tape, like 3M Green or the heavy aluminum tape from 3M.

I also recommend you re-tape everything after cutting and double check your alignment before gluing your new roof center in place.

[Safire6]

Lots of good ideas, thanks for all of the input! Not sure yet which way I'll proceed but I'll be sure to let you all know what I did and how things turn out.

 

 

[Slick Shifter]

Instead of using the doors, i'd first glue in some heavy stock to join the front fender and rear quarter panel along the imaginary line where the top of the door would be.

You can make the ends of this bridge conform to the inside of the fender and quarter by heating it and then pressing it into place. Or glue it with a blob of epoxy if you dare.

Then i'd hot-knife the roof out, windshield edge first, finesse the cutlines along the W/S frame with the Dremel while holding the top of the W/S frame firmly. Do the same with the other cutline.

Then glue in the H piece after reinforcing it with steel wire, probably 2 large 'C' shaped pieces to make it very stiff.

 

 

 

 

 

[Safire6]

So what I did was buy a small dremel tool called a "Stylo" ($49). My big dremel tool was to big and bulky to comfortably do the job. Made the back cut first and then the front, leaving about 1/16" material on both. Then I used aluminum tape and a couple of wood sticks to reinforce the body.  Then used the Stylo on low speed with some small sanding discs to remove most of the leftover plastic and finished it off with sanding sticks. I used a dial caliper to measure the cross section at the top of the windshield frame and the front edges of the T-tops to show me where to sand. I think it worked out pretty well but the proof will be when it's all done. Thanks everyone for the great ideas!

 

[Plowboy]

Looks like it worked fine. You'll find lots of uses for that new Dremel.

[Greg Wann]

I have not read any of the above suggestions.  You might mark the lines on the inside with a black fine tip marker and then you might hold it up to a bright light and see them from the top.  You could drill a tiny hole in a spot and saw it with thread.  This is the way one of our club members cuts bodies open.  Not certain what kind of thread, but I have seen it work.