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Old Apr 09, 2012, 09:11 AM
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United States, MA, Boston
Joined Oct 2010
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How much weight can glue add/save on a build

I constantly hear modelers talking about building light, and I was curious if anyone had actually evaluated how much weight glue added to a plane, and looked at ways of reducing that number... without having the plane fall apart.

I tend to build with CA, because I don't have a ton of time so faster drying is better, but it is brittle, and particularly at key joints I never want to skimp too much. However, the other night I weighed my glue when I started working, and after a few hours of work, and realized I had added a few grams to the plane.

What is the lightest glue option? Is there a way to use less CA?

Just thought it might be a subject of interest.
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Old Apr 09, 2012, 10:07 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,390 Posts
The weight of glues like CA, even most of the others, is probably still negligible compared to say the potential for reducing the weight of many of the other components of a plane.

Cutting holes on foam, using lighter balsa, reducing all the wires that we end up trying to stuff into a fuselage, smaller connectors, using smaller batteries, servos, motors, lighter props. Less add-on 'strengtheners', such as extra bits of carbon, tape, epoxy and glass cloth, fillers, paints, decals, etc etc etc.

When you consider all the other bits and pieces that could be reduced in weight, personally I think adhesive weight is such a small part of the overall weight of a plane as to be not even worth considering its actual weight.

But that wouldn't stop me being cautious with the amount used.
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Old Apr 09, 2012, 11:27 AM
aka: A.Roger Wilfong
gnofliwr's Avatar
Novi, Michigan, United States
Joined Jan 2001
2,531 Posts
Glue can add significant weight. There are multiple factors that contribute to weight and to strength.

- Solivent based glues that evaporate tend to be lighter than glues that cure. Based on making a proper joint with the right amount of glue, old cellulose glues like Ambroid and Sigment are lighter, Superphatic and alaphatic glues like Titebond are next, CA is probably next and epoxies are the heaviest.

- The strongest joints use the least glue. Actually "the right amount of glue". Glue on the surface around a joint only adds weight, not strength - if glue squeezes out of the joint when you clamp it, wipe it off..

- You can add more strength to a joint per weight with a 1/64" plywood gusset than a glue fillet.

- If you have to use glue to fill a gap, recut the piece(s) - you'll get a stronger joint and lighter structure.

As to cutting holes in foam and balsa. Unless you're need to save every gram or you're dealing with really thick stock, you won't save all that much weight for the effort. But if you're that concerned with weight, you're probably flyin in-door microfilm and you'll be using a hypodermic to apply the glue (and staying away from CA).

Sheeted foam wings have a reputation for being heavy, but it's not because of the foam, usually it's because of the amount of glue (usually epoxy) that's used to bond the skins and edges to the foam. When you're sheeting a built-up wing, there's really only a few square inches of surface area that gets glue - even if you're sloppy, you just can't add that much weight - compare that to the hundreds of square inches of foam and you can see where glueing technique and glue selection can signifficantly affect the weight.

- Roger
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Old Apr 09, 2012, 10:18 PM
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Keremeos, BC Canada
Joined Mar 2004
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I knew a guy who used a hot glue gun for his construction, and THAT is heavy!!
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Old Apr 10, 2012, 12:38 AM
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United States, CA, Bear Valley Springs
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Just add more power.

mw (easy peazy)
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Old Apr 10, 2012, 03:32 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,390 Posts
Quote:
Originally Posted by TLyttle View Post
I knew a guy who used a hot glue gun for his construction, and THAT is heavy!!
How many ounces of glue did he use ?
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Old Apr 10, 2012, 06:23 AM
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flypaper 2's Avatar
Kingston, Canada
Joined Jun 2004
12,901 Posts
Hot glue is only heavy if you put it on heavy. No heavier than epoxy. I use it on my smallest 1.5 oz foamys. Put the gun nose perpendicular to the surface to be glued and use a thin film. Don't know how many of those little indoor Cubs and Champs I've glued up to keep the guys flying. Works great if used discreetly.

Gord.
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Old Apr 10, 2012, 08:36 AM
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United States, MA, Boston
Joined Oct 2010
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That is about what I suspected: it can make a difference, but big picture there are easier ways to cut weight. That being said, if you can cut half an ounce off a park flyer through conservative glue use, that means you have more wiggle room for MORE POWER as well. Win/win.

I us a hypodermic to apply CA most of the time. It allows you to get right into the joint, and apply a very controlled amount of glue. I bought a case of 100 pet syringes off amazon for something like $15.
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