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Old 06-09-2019, 08:12 AM
rewalston rewalston is offline
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Pulling my hair out over card stock

I'm attempting to build a model that calls out specific card/paper. I've tried four times to build this thing and I keep getting fit errors ie rolling cylinders for axles etc. The model calls out the following 67lb/147gsm/7.5mil paper and 20lb/75gsm/4mil paper.

Now I've found 20lb but it isn't 4 mil it's thicker and I've also found 67lb but it's thicker than 7.5 mil. I went to a print shop and found 4 mil and 7.5 mil stock but they are not the correct weights and still having fit issues. This is driving me NUTS and don't have much hair left to pull out. Any suggestions?
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  #2  
Old 06-09-2019, 08:33 AM
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Rubenandres77 Rubenandres77 is online now
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Problem is that "mil" is a thickness measure, while "gsm" and "lb" are weight measures.
So they are not necessarily related.

That is: you can have a thick cardstock with little weight if it is porous, and a much thinner paper that is a lot heavier if it is much denser or has a special finish.

If your issue is fitting problems, I'd recommend to go after the proposed thickness by the designer, instead of the weight.


Thickness, even if it is just a couple of "mils" different, can cause issues in certain kits that have been designed taking that into account.

Make sure you use a caliper to measure the thickness. Some paper shop employees don't even know the details of what the shop sells, and may well make mistakes selling you a different product. A good way of measuring is to take 10 sheets of cardstok, measure their overall thickness, and divide in 10 to get the individual sheet thickness.

If, after getting the correct thickness suggested by the designer you still have fitting problems, check the following:

* Cutting inside or outside the line / this can alter the dimensions of the parts.


* Printer is set to "do not adjust" / This avoids distortions.

* Check your printer distortion: You can make some tests before by drawing 1, 2, 3, 4 and 5 inches (or centimeters) squares on the graphic software of your choice, and printing the test page. Measure carefully. Some printers can cause vertical distortion depending on how they handle the paper feeder, and the 5X5 inches that you draw in the computer magically distorts (even if by some hundredths of an inch) when the paper leaves the printer. If that's happening, that may be the cause of your parts not fitting correctly.

If all of this fails, I would try to contact the designer reporting the problem and asking for support.

Regards,
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Old 06-09-2019, 09:54 AM
rewalston rewalston is offline
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I've contacted the designer but haven't gotten a response. Thanks for the suggestions, I'll have to check it out.
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Old 06-09-2019, 11:09 AM
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airdave airdave is offline
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Forget paper thickness.
(I've never seen mil thickness used in paper kits anyway)

If a part needs to be a certain thickness (eg 1.2mm) then that will be specified, regardless of paper type/weight.

Obviously a standard paper weight, somewhere around 67lb cardstock is recommended for building.
67lb is specifically "cover" stock or similar...
I use 65lb cardstock (which is a bit cheaper).
Its close enough to the same thing, and the same thickness (about .23mm).

The reason 20lb paper is recommend for other parts, is because they are smaller parts.
Or they may be harder to roll or form...and thinner paper will work better.

But again, the actual thickness of the paper isn't the issue.
..24lb premium paper is often used,
and its basically the same thickness as 20lb, just a smoother finish.
So anything is that range will work.

So, I'm not sure why a kit would be confusing us with "mil" thicknesses.
Its pointless...unless I am missing something here?

Card thickness will also not affect how well a cylinder rolls to the desired diameter.
It might be harder to roll small tubes smoothly, but whether or not you roll it to a certain diameter, is totally up to you.

If parts are not properly matched...ie the kit specifies a 3mm tube, and the hole drawn is only 2mm...then thats designer error.
Just adjust the tube or the hole to match.
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Old 06-09-2019, 07:10 PM
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Jim Nunn Jim Nunn is offline
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The most common fit issue I see is on tubes, and the fit of the skin over the forming bulkheads on ship hulls and aircraft fuselage. As a rule cut the forming bulkheads on the inside of the line and the skins on the outside of the line. In most cases you will need to sand the forming bulkheads to get the best fit.

Why this is so is that most us builders do not take into consideration the thickness of the paper. Lets say we are making a 0.200 in tube with a round inside former. The designer uses the circumference of the former as the dimension for the skin. In this example .200 * 3.1415 = .628 inch. In reality the length should be .200 + (2* the thickness of the paper skin) * 3.1415. The thickness of 67 lb paper will range from .0075 to .009 inch. Using the 0.009 dimension the length should be 0.684 so you would end up with a .056 gap. This is of course the worst case example most designers do take into consideration the thickness of the paper, but even a small difference in the paper thickness will make a difference and create seam issues. Note this error is constant it does not vary with the diameter of the inside former.

Back to the beginning check the fit, recheck the fit and its better to under size on bulkhead formers.

Start building simple models too get the “feel’ of working with paper. There are several good models in our down load section and of course there are free models on the net.

Jim Nunn
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Old 06-10-2019, 10:43 AM
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a380 a380 is offline
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i agree with jim. i am about to start working on the mba card model zaporozhets tractor. while the designer specifies 170 gsm and 80 gsm paper, he also lists 3 cardstocks of 1mm, .5mm and .2mm that the paper needs to to be glued on. i went looking for supplies at an art store with my calipers to check the thickness of the paper/card stock available. i chose a couple of different types that i could then stack to achieve the thickness required.
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Old 06-10-2019, 11:15 AM
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rickstef rickstef is offline
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which kit is it that you are building?

maybe those who have built it can provide some detailed assistance
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Old 06-11-2019, 06:24 AM
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My approach to building: believe in the best, be prepared for the worst. Sometimes it's just not your fault...
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Old 06-11-2019, 06:29 AM
rewalston rewalston is offline
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Quote:
Originally Posted by rickstef View Post
which kit is it that you are building?

maybe those who have built it can provide some detailed assistance
I highly doubt anyone on here has built it. It's one I bought off the net of a v12 engine. I know that there is another one of a different design on the forum here. But I wanted to build this one first since I have already paid for it.
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Old 06-11-2019, 06:41 AM
Falco Falco is offline
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You need more hair to pull out... that's your problem! I have been fighting this same losing fight for some time now; I can never seen to find the correct "paper" it's always an experiment 99.9993% of the time. Don't get me started on models that demand to be printed on A4 format, I live in the US and I can't find that anywhere.
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