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View Full Version : pros and cons of various glues for balsa?


oscillator
01-22-2007, 07:20 AM
Got a great deal on some laser cut balsa kits and am re discovering how much I enjoy building balsa airplanes.

Back in the day I only knew about "airplane" glue. These days people seem to use anything but airplane glue: CA, PVA, PU, Epoxies (thinned and straight), and probably a few others.

I recently built a kit up with CA. Very fast, but brittle joints and they don't sand well. I'll probably use a PVA glue for my next kit as it is very strong, odor free, sands well, and more pleasant to work with.

Sow how do the weights, strengths, flexibility, and other characteristics of these glues compare when used in small to medium balsa models?

Thanks!

Sky Sharkster
01-22-2007, 02:26 PM
Hello Oscillator, Here's a couple of links to "Adhesives", these are from the "Builders Links" Sticky at the top of this Forum. The gremlins ate the first two versions but I'm slowly replacing it, apparently the software has a glitch, it's being worked on.
http://www.airfieldmodels.com/information_source/construction_materials_for_model_building/adhesives.htm
http://pldaniels.com/flying/balsa/glues-guide.html
Generally I like to use Titebond aliphatic resin (carpenters glue) for wood-to-wood or wood-to-foam but it is slow drying, like overnight. It sands well, is fairly light and strong.
CA has it's uses, I like to use it instead of pins, for "right-away" joints and areas where the wicking properties are helpful. But it's heavy, even in small amounts, hard to sand and the fumes are nasty.
Expoxy is mainly for extremely high-stress joints (motor mounts, landing gear, wing joiners) and when attaching dissimilar materials like wood-to-metal. It is also good for non-porous materials, since it forms a pool and everything covered is stuck! But it is very heavy and hard to sand.
Those are the main types, there's specialty adhesives like canopy glue, contact cement, covering film adhesive, etc. For balsa and plywood, the first 3 types should see you through.
Good Luck and welcome back!
Ron

oscillator
01-22-2007, 07:16 PM
Thanks Ron. Sounds like the wood glue (PVA) is the way to go for most balsa/balsa joints. Certainly much more pleasant to work with.

-Mark

gsk11740
01-22-2007, 07:27 PM
Ok, I'm new to the Balsa thing here. What is "PVA"? What do I look for at the LHS? I've tried using epoxy (too messy) and the only thing I seem to glue together with CA is myself. It never seems to hold anything else.

oscillator
01-22-2007, 10:13 PM
Hi Gary,

PVA (Polyvinyl acetates) is basically carpenters wood glue. Most people use PVA to refer to the yellow varieties, but I think some of the white glues are also PVA.

No need to go to the LHS for PVA - get it at the hardware store.

CA does a decent job with balsa, but it is heavy, brittle, and fumes like crazy. Oh, and as you point out it does a great job attaching your fingers to the model!

gsk11740
01-23-2007, 12:45 AM
Hi Gary,

PVA (Polyvinyl acetates) is basically carpenters wood glue. Most people use PVA to refer to the yellow varieties, but I think some of the white glues are also PVA.

No need to go to the LHS for PVA - get it at the hardware store.

CA does a decent job with balsa, but it is heavy, brittle, and fumes like crazy. Oh, and as you point out it does a great job attaching your fingers to the model!

Thanks Mark! Is there any particular brand or anything I should look for? I have a trip to Home Depot coming up so I'll add it to the "shopping list".

oscillator
01-23-2007, 03:51 AM
Elmers Pro Bond, Titebond II, etc. Anything that says carpenters wood glue should be fine.

gsk11740
01-23-2007, 01:06 PM
Elmers Pro Bond, Titebond II, etc. Anything that says carpenters wood glue should be fine.

Great! Thanks! I did go to the LHS yesterday and bought some more epoxy but this time I got it in separate bottles instead of that "easy" syringe thing that never seems to work right. I remember seeing the Pro Bond so I'll pick up a bottle on the next hardware store trip.

slipstick
01-23-2007, 02:17 PM
Generally the white stuff is plain old-fashioned PVA. The yellow wood glue (Titebond II etc) is aliphatic. Aliphatics are basically modified versions of PVA with various improved characteristics....the most typical improvements are faster grab and set (an hour or so vs 12-24 hours for plain PVA) and improved water resistance (though don't believe them if they tell you it's fully waterproof ;)).

BTW Elmers ProBond isn't either of those. It's actually a polyurethane glue with completely different characteristics, mainly that it will only set in the presence of water (but there's enough damp in most wood to set it off) and it expands/foams while it is setting. You can get a nasty shock if you use Probond when you think you're using PVA.....e.g. when it foams up and forces all your joints apart (don't ask how I know :().

Steve

gsk11740
01-23-2007, 03:20 PM
Generally the white stuff is plain old-fashioned PVA. The yellow wood glue (Titebond II etc) is aliphatic. Aliphatics are basically modified versions of PVA with various improved characteristics....the most typical improvements are faster grab and set (an hour or so vs 12-24 hours for plain PVA) and improved water resistance (though don't believe them if they tell you it's fully waterproof ;)).

BTW Elmers ProBond isn't either of those. It's actually a polyurethane glue with completely different characteristics, mainly that it will only set in the presence of water (but there's enough damp in most wood to set it off) and it expands/foams while it is setting. You can get a nasty shock if you use Probond when you think you're using PVA.....e.g. when it foams up and forces all your joints apart (don't ask how I know :().

Steve

Thanks for the tip on the ProBond. I'll have to remember that one! Sounds like Titebond (and similar) is what I'm after then.

oscillator
01-23-2007, 05:21 PM
Hey Gary,

Just noticing your avitar. I love the Aviat Husky, great airplane. I own a Mooney 231 which I have taken to some dirt strips in Alaska (you should have seen the looks on their faces). I also have an Alaskan Malamute - and she loves to fly!
http://www.epicsunlimited.com/flying/Mooney%20231_files/image001.jpg

gsk11740
01-23-2007, 05:34 PM
Nice plane Mark! I got to fly a Mooney M20J many years ago. Quite a change from the Cessna 150/152's I was training in! I was working towards my private pilot's license but life (and the rising expense of flying) got in the way. Too bad I couldn't win the lottery. I'd get my license and then be at Aviat's door to order a new Husky for myself! :D Since that isn't likely to happen though, I fly the little ones. I have a Goldberg Husky 400 in the works, hence the avatar. Ever since I rode in a real J-3 Cub, I've always had this thing for Cubs and anything that even remotely resembles them but since it seems everyone in R/C has a Cub, I had to be just a little bit different. :rolleyes:

oscillator
01-23-2007, 05:41 PM
And here is the dog, with my son:
http://1stclass.mylargescale.com/MarkScrivener/haley/haley_caelan.jpg

gsk11740
01-23-2007, 05:45 PM
Nice! I had a neighbor that had a dog that looked a lot like yours. Felt sorry for the poor thing though during the summers we get around here! By the way, it snows in CA? I lived in Seattle for a year and saw only one frost during the winter I was there.

oscillator
01-23-2007, 05:47 PM
Yep, know all about the expense of flying. I could have paid off my mortgage by now if I didn't purchase the Mooney several years back. But then I wouldn't have had all those great times flying to all those wonderful places. Still, it will have to go one day. Hopefully when that day comes I can pick up an old J-3 cub. Of course a Husky would be even better.

Since you like cubs, have you seen this kit?
http://www.houseofbalsa.com/store/store-type-tem.html?item=products:k-61&sid=0001Rygc9iDThxEpV4696s0

I picked up a stack of these for $20 each! Let me know if you want one.

gsk11740
01-23-2007, 05:59 PM
Yep, know all about the expense of flying. I could have paid off my mortgage by now if I didn't purchase the Mooney several years back. But then I wouldn't have had all those great times flying to all those wonderful places. Still, it will have to go one day. Hopefully when that day comes I can pick up an old J-3 cub. Of course a Husky would be even better.

Since you like cubs, have you seen this kit?
http://www.houseofbalsa.com/store/store-type-tem.html?item=products:k-61&sid=0001Rygc9iDThxEpV4696s0

I picked up a stack of these for $20 each! Let me know if you want one.

Yeah, if it weren't for the wife and kids, the house and car payments and all those other things that seem to get in the way of our fun.... :D

Sure, I'd love to have one of the kits. I haven't built a plane totally from a kit yet but I want to try. So far I've just done ARFs but the Soareasy I just finished seemed to take a lot more building than I thought it would for an ARF and the Husky apparently takes a lot of little modifications to make it right. Let me know what I need to do.

oscillator
01-23-2007, 06:18 PM
PM sent.

oscillator
01-23-2007, 08:38 PM
...BTW Elmers ProBond isn't either of those. It's actually a polyurethane glue with completely different characteristics, mainly that it will only set in the presence of water (but there's enough damp in most wood to set it off) and it expands/foams while it is setting. You can get a nasty shock if you use Probond when you think you're using PVA.....e.g. when it foams up and forces all your joints apart (don't ask how I know :().

Steve

Hey Steve,

I think Elmers must sell more than one type of glue labeled "Probond". I have a bottle of Elmers "Probond" Carpenters Wood Glue. It is your basic yellow wood glue, not polyurethane, and doesn't foam.

gsk11740
01-23-2007, 09:31 PM
PM sent.

And hopefully, I did everything right and you should have what you need. :)

slipstick
01-24-2007, 12:17 AM
Hey Steve,

I think Elmers must sell more than one type of glue labeled "Probond". I have a bottle of Elmers "Probond" Carpenters Wood Glue. It is your basic yellow wood glue, not polyurethane, and doesn't foam.
Could well be, how confusing. Oh well, I'm relying on failing memory here cus Elmer's doesn't exist as a brand over here and it's a good few years since I lived on your side of the pond ;).

Steve

Sky Sharkster
01-24-2007, 01:37 AM
Hello Mark, I think you're right about the "Elmers", my local "Home Builders" store has about 5 kinds of the stuff, white, yellow, tan.
A good replacement for Titebond is made by SIG Mfg, called Sig-Bond. It's exactly like Titebond, same ingredients, color, drying time, characteristics, etc. It's sold in most hobby shops. I bought one little bottle (2 oz) to use, then re-fill the little one from big ones, it's cheaper!
SIG also makes a couple of formulas of good epoxy, I believe it's "10 minute" and another, "2 hour". Both work well.
Ron

olmod
01-24-2007, 02:25 AM
Hey Steve,

I think Elmers must sell more than one type of glue labeled "Probond". I have a bottle of Elmers "Probond" Carpenters Wood Glue. It is your basic yellow wood glue, not polyurethane, and doesn't foam.

In Oz the foaming PU is branded Selleys probond it comes in a 750Ml bottle and i decant it into a concertina topped bottle that cartridge ink comes in fitted with a piece of 2''x 3/32 brass tube ,wich is great for the small amounts needed ,after use i squeeze the air out and use a rubber cap to seal,if you dont a hard crust will form after a prolonged period,
i have found the glue itself takes a little getting used to and find myself using about a quarter the amount compared with PVA,it sticks to anything and it can be used to make foamed in place nests for servo's and alike just wrap with saron wrap ;) if you dont like the colour there is a new "Sumo" brand by loctite on the market wich dries clear.

weathervane
01-25-2007, 01:08 AM
Hello,
There is a lot of good info in here. I have just started my first kit build. I like the idea of using the Elmers over the CA. CA probably is not the best with the kids, it might make the wife happy no oders. My question is, on my bottle of Elmers, it says Probond Interior/Exterior wood glue, weatherproof fast tack.
Is this the same stuff you guys are using??? Can I use this every where?? Aside from motor mounts, landing gear blocks, wing joints.
Thanks,
-Andrew

raptor-9
01-25-2007, 01:25 AM
Hello Oscillator, Here's a couple of links to "Adhesives", these are from the "Builders Links" Sticky at the top of this Forum. The gremlins ate the first two versions but I'm slowly replacing it, apparently the software has a glitch, it's being worked on.
http://www.airfieldmodels.com/information_source/construction_materials_for_model_building/adhesives.htm
http://pldaniels.com/flying/balsa/glues-guide.html
Generally I like to use Titebond aliphatic resin (carpenters glue) for wood-to-wood or wood-to-foam but it is slow drying, like overnight. It sands well, is fairly light and strong.
CA has it's uses, I like to use it instead of pins, for "right-away" joints and areas where the wicking properties are helpful. But it's heavy, even in small amounts, hard to sand and the fumes are nasty.
Expoxy is mainly for extremely high-stress joints (motor mounts, landing gear, wing joiners) and when attaching dissimilar materials like wood-to-metal. It is also good for non-porous materials, since it forms a pool and everything covered is stuck! But it is very heavy and hard to sand.
Those are the main types, there's specialty adhesives like canopy glue, contact cement, covering film adhesive, etc. For balsa and plywood, the first 3 types should see you through.
Good Luck and welcome back!
Ron

Hello, SkySharkster-Do you know any good adhesive for Lithoplate to balsa is there a (loctite) product that does the job?

Marcellus
01-26-2007, 03:11 PM
I have always been under the impression that CA was very light but two of you here say the opposite. I'm surprised. The bottles weigh next to nothing. Is it because the wood soaks it up?

Sky Sharkster
01-27-2007, 05:38 PM
Hello Raptor, I've never tried using Lithoplate, don't really know how to attach it. For metal-to wood, epoxy usually works, but if the metal is smooth, it's better to scuff or scratch it beforehand, to give the adhesive a better grip. I'd imagine there's a "Loctite" product that would work, maybe the blue or green formula. All I've ever used that for, was pinion gears-to-drive shafts on gearboxes. Sorry I can't be more help!
To Marcellus, I think the reason CA seems light is because the bottles are so tiny! Seriously, they're usually 1/4 ounce (7 grams) or so, most glue tubes or bottles are 2 ounces. If you notice, a 1/4 ounce CA bottle doesn't last too long. And, you're right about the soaking up factor, one of the great advantages of CA is it's ability to "wick" or soak into the smallest spaces, even defy gravity to do so. Normal glue won't do this nearly as well. While it makes for a great bond, there's two drawbacks; One, it will soak in farther than conventional adhesive, thereby more adhesive is used, more weight, even after evaporation. Two, it makes a hard, brittle "shell" area around the area, increasing the chance of shock or impact failure. One of the great qualities of balsa (or foam, for that matter) is it's ability to soak up vibrations, shocks, etc, without transmitting them locally. It's "soft" or absorbent, in other words. If the joint is substantially stronger and harder than the material around it, that's where it will break, every time. Right at the end of the glue joint. So, it's usually better to have a joint that has a slight amount of flex, and dried CA has none. There are exceptions to this, usually high-stress areas.
Which doesn't mean that CA isn't useful. It is, in the proper places and amounts. Using the thin "applicator tips" and only one drop per joint will cut down on the weight and shock-transmitting factor, but it takes discipline.
Hope this helps!
Ron

raptor-9
01-28-2007, 08:08 PM
Hello Raptor, I've never tried using Lithoplate, don't really know how to attach it. For metal-to wood, epoxy usually works, but if the metal is smooth, it's better to scuff or scratch it beforehand, to give the adhesive a better grip. I'd imagine there's a "Loctite" product that would work, maybe the blue or green formula. All I've ever used that for, was pinion gears-to-drive shafts on gearboxes. Sorry I can't be more help!
To Marcellus, I think the reason CA seems light is because the bottles are so tiny! Seriously, they're usually 1/4 ounce (7 grams) or so, most glue tubes or bottles are 2 ounces. If you notice, a 1/4 ounce CA bottle doesn't last too long. And, you're right about the soaking up factor, one of the great advantages of CA is it's ability to "wick" or soak into the smallest spaces, even defy gravity to do so. Normal glue won't do this nearly as well. While it makes for a great bond, there's two drawbacks; One, it will soak in farther than conventional adhesive, thereby more adhesive is used, more weight, even after evaporation. Two, it makes a hard, brittle "shell" area around the area, increasing the chance of shock or impact failure. One of the great qualities of balsa (or foam, for that matter) is it's ability to soak up vibrations, shocks, etc, without transmitting them locally. It's "soft" or absorbent, in other words. If the joint is substantially stronger and harder than the material around it, that's where it will break, every time. Right at the end of the glue joint. So, it's usually better to have a joint that has a slight amount of flex, and dried CA has none. There are exceptions to this, usually high-stress areas.
Which doesn't mean that CA isn't useful. It is, in the proper places and amounts. Using the thin "applicator tips" and only one drop per joint will cut down on the weight and shock-transmitting factor, but it takes discipline.
Hope this helps!
Ron

Cheers Ron no problem,-I appreciate in your interest replying the thread-If you need help,feel free to ask!-R9

olmod
01-28-2007, 09:31 PM
Hello, SkySharkster-Do you know any good adhesive for Lithoplate to balsa is there a (loctite) product that does the job?
I have not tried loctite 480 black max but ill bet it will work ,i use it for magnets ,gluing all sorts of metal together and its the best thing i've come accross to use on fibre glass circuit board ,it has a very strong peel strength and is a high strength ,high temp',high impact product.
cheers Lez.

raptor-9
01-29-2007, 10:12 AM
Cheers Lez.-thanks!..i'll check it out-.I appreciate in the info & your interest replying the thread-If you need help,feel free to ask!-R9.

R.C.Pilot
02-14-2007, 03:58 AM
Several brands of contact-adhesive have worked well with thin metal skin laminations, Wilhold and 3M in small metal cans were the best way to go a few years back.

Consider also that that in certain areas automotive RTV / Silicone works well, although it is heavier than most other glues / sealants

Generally I build with medium Ca using small tip applicators, Yellow Carpenters glue (int/ext) and 15 and 30 Min epoxies.

Formers and main structural components that don't require epoxy are glued with Yellow glue, but I often dab a spot of ca to hold joint tight if clamping is not conveinant.

Yellow and white glues will brittle-out after a few years, but I have found it to be easier to pick-out and re-glue as well.

Sky Sharkster
What plane is in your avitar??

Ed Emmons
02-14-2007, 04:19 AM
Has anyone tried GORILLA glue? It's an water activated adhesive which foams after activation and while curing.. Slow drying, but very strong bond. Two years ago I had to bond 2 pieces of 2 x 6 x 10 foot long cedar planks. After 2 winters of exposure to rain, snow, ice, and below zero temps, planks show no signs of separting along the glue joint.

Ed Emmons

Balsa Shavings
02-15-2007, 03:13 PM
Hello Fella's. Heres my 2 cents worth. If you are building from a laser cut kit, and want to use CA, use medium. Thin CA doesn't wick into the joints like diecut kits. The laser makes a extreamly fine cut, where a diecut kit is ragged where it is cut, this makes the thin CA wick into the joint.



Keep The Faith: Johnny

50+AirYears
02-25-2007, 05:25 PM
A thing about the relative weight of CA, the glue doesn't harden by evaporation of solvents or retardants like regular PVA, aliphatic, or household/model cements, which loose a fair amount of weight through the drying process. CAs, like epoxies and polyurethanes, set by forming long linked molecules through a chemical reaction, therefore no weight is lost. They don't "Dry".

Saucerguy2
07-09-2007, 01:18 AM
I destroyed a couple of ARF's and a kit build recently, I intentionally tore them apart and was alarmed as to how many of the bonds between the joints just fell away, they were CA'ed together, and in fact, only 60% of the elaborate lazer cut componentry was actually held together by glue, the rest was simply floating around. I'm going back to using PVA, yeah, I like being able to build quickly with CA, it's only advantage, but the bond simply is not there since the glue is too thin and doesn't really soak into the balsa, just rests on the surface, and what does soak in, it doesn't go very deep since it kicks off too quickly.

I can run this same analogy with commercial surfacing material, ie. laminate, common name brand formica. I've had vendors in the past insist they have something new I should try out and it's main advantage being that it kicks off more quickly then what I'm currently using. The problem is, with the tests, I ran into the same conclusion as I am now with CA compared to PVA, that extra time is necessary to soak into the material to form a stronger bond.

Also, I totally agree with the other posters stating CA doesn't sand well at all, it's simply more dense then the balsa it's next to, so you end up having to use a small nail file to sand the CA'ed piece alone and hopefully you don't go to far, then alternate with the sanding block on the softer balsa areas, any overrun from the CA, especially on the sheeting, you can never truely blend away.

50+AirYears
07-09-2007, 04:42 PM
I also ruined several lighter rubber powered models trying to use CA on 1/16" balsa. The CA wicks so far into the wood, it becomes inflexible and brittle.

Saucerguy2
07-09-2007, 08:54 PM
I guess you and I are coming from two different build styles, I don't want anything going anywhere, flexibility should remain in the stock itself, but kept to a minimum, which is why I lean towards making everything rigid rather then flexible, PVA is not flexible at all, but I suppose it's going to give a little compared to CA which forms more of a brittle final form once set up.

Rodneh
07-09-2007, 09:25 PM
Most carpenters glue is NOT PVA, they are an aliphatic resin. PVA's are usually white while the aliphatics (Titebond, Elmers carpenter Glue, etc. ) are off white or tan or brown in color and generally stronger than the PVA's. Also the aliphatics can be waterproof and most are water resistant. Both can be cleaned up before curing with water. Titebond II is very resistant to water and I believe that Titebond III is totally water resistant.

50+AirYears
07-09-2007, 10:51 PM
Saucer guy, what I meant about inflexibility is that when you double glue well fitted uprights to longerons with a cellulose based glue like thinned Duco, Ambroid, or Sig, allow to dry adequately, then try to glue the crosspieces between the fuselage side, the sides bend easily and form nice curves. Because of the evaporation of solvents, there is a weight reduction that really helps to keep the airframe weight down especially with Peanut and No-cal scale rubber models. When using CA, the longerons and uprights sometimes soak up enough CA that forming a smooth contour when joining the sides is difficult. The balsa has lost a large amount of the softness and flexibility that allowed smooth bending. I have even had longerons crack rather than bend. And even when I did manage to complete one of these small models using CA, they were generally so heavy they couldn't be competitive.

After ruining several small scale models for FAC competion, and a fair amount of contest grade balsa, I went back to thinned cellulose cement (traditional Model Airplane Glue).

The weight gain isn't anywhere near as critical with larger RC and Contol line planes as it is with competition free flight.

With the lightweight competion rubber FF models, especially indoor models, or when working with 1/64" to 3/32" or even 1/8", it's best to stay away from CA. With larger models, if the joint is properly made, any glue, including thin CA works well. In any model, all glues work well with a properly made, gapless, close fitting joint that has a minimum of compression or tension stress on it. I competed in SAM antique and Texaco contests with a 4.5 pound 6' Spook 72 for 7 years. I also flew it as a recreational and club fun fly plane just by switching from a non-throttled to a throttled engine. The plane was built using thin and medium CA for everything except for some Epoxy on the firewall and LG mount.