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Author Topic: .75 vs 1.4 fiberglass - finished weight  (Read 381 times)

Online Brent Williams

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.75 vs 1.4 fiberglass - finished weight
« on: February 07, 2019, 11:27:52 PM »
I have been curious if there are any advantages to using 1.4 oz/yd cloth vs .75oz/yd cloth when glassing the nose/fuselage of a plane or on sheeted wing panels.  The weave of the .75 seems looser compared to 1.4.  Obviously the weight of the cloth is nearly double.  Is the finished weight also similarly higher, or does the tighter weave of the 1.4 prevent some resin pooling, ect.  I would think that the 1.4 would be stronger/stiffer overall.

Any thoughts or experiences on this topic?
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Online Istvan Travnik

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Re: .75 vs 1.4 fiberglass - finished weight
« Reply #1 on: February 08, 2019, 08:39:52 AM »
If you use glass as a covering material, always the lighter is better. If you feel that it won't be strong or stiff enough, you can double it at the next step, after a slight sanding the first cote.
Furthermore, if the warp/weft is not 1/1, you can play with the strength too, by positioning the different coats...
Istvan


Online Brent Williams

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Re: .75 vs 1.4 fiberglass - finished weight
« Reply #2 on: February 08, 2019, 10:38:32 AM »
Thanks for your comments Istvan.  Glad to hear your thoughts, as coincidentally, this is actually for a blue foam fuselage I am experimenting with.  So, I would surmise that in this application, .75oz cloth would be appropriate as the exoskeleton material?
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Online Istvan Travnik

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Re: .75 vs 1.4 fiberglass - finished weight
« Reply #3 on: February 08, 2019, 04:05:46 PM »
Dear Brent,
For the sake of accuracy, do you count the specific weight of your glas in ounce / sqyard?
How wide is an usual roll of glas by you?
Istvan
« Last Edit: February 08, 2019, 04:36:00 PM by Istvan Travnik »

Online Brent Williams

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Re: .75 vs 1.4 fiberglass - finished weight
« Reply #4 on: February 08, 2019, 06:08:44 PM »
Dear Brent,
For the sake of accuracy, do you count the specific weight of your glas in ounce / sqyard?
How wide is an usual roll of glas by you?
Istvan

Most of the cloth sold in the USA is measured in oz/yd. 

Using several of the online conversion calculators shows these weight figures:
.75oz/yd = 25 gm2 (gsm)  (though some charts show this as 17 gsm) ???
1.4oz/yd = 47.47 gm2   (33gsm on some charts)

https://www.easycalculation.com/unit-conversion/fabric-weight-converter.php

0.75 ounce(s) = 21.26 grams
1 square yard = 0.836 square meter
1 square meter of .75oz material = 25.43g
« Last Edit: February 08, 2019, 06:33:10 PM by Brent Williams »
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Online Istvan Travnik

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Re: .75 vs 1.4 fiberglass - finished weight
« Reply #5 on: February 09, 2019, 04:06:43 PM »
Dear Brent,
I see now. The problem is with my poor English: the right expression is "yard squared", and not "square yard", as I thought at the analogy of "cubic centimeter", or "cubic inch" :) :)
Well, the .75 oz. glas is absolute a good basement, practically everything can be coated with it. Most components made of mid density (34 ozs / cu.ft) Bluefoam  (flaps, wing, elevator, fin-rudder) will be strong and stiff enough by single coat.
Naturally, the surface of foam must be stabilized by thin resin and sanded to be perfect before coating, because no way to correction: it is forbidden to sand the glas into half or less: the strength comes from the fibres, not the resin.   
When you think to reinforce a spot somewhere (typical is fuselage  sides right before the horizontal stab), I suggest plus coats put on at first, and next day sand the contours gradually down to the base. ( 280 grade wet paper).
Where more pieces of glass meet and overlap, do the same.
When I encountered how many portions of resin I used on the entire plane, came out 25-30 portions (most of them were 10+4 or 20+8 ccms, no more). It means different 25-30 days certainly.
Istvan


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