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Thread: Best Glue for wood

  1. #16
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    Ah, yes . . ."The Great Glue Debate" this has been going on for literally years as anyone who is building in wood will know. There are lots of choices these days but I took the lazy way out and opted for the easiest to use. That's oversimplifying the process a little, as I did a fair amount of reseach first, but ease of use was high on my list of priorities.

    I'm using West Systems exclusively for my Falco and have found it to be very user friendly and from the tests I've done, also very strong.
    (The usual "three blocks of hardwood whacked with a hammer" type of thing)

    As with all thermosetting resins it is temperature sensitive so it's not a great idea to paint your aeroplane matt black, but to my knowledge no one has yet had a wing fall off on a hot day.

    As some one stated earlier in this thread, Aerolite is not available in Australia so we builders of wooden aeroplanes (Natures composite - you can trust a tree !) are forced to seek alternatives, the most popular appearing to be Resorcinol.

    The downside to it is the need for joints to be quite accurate (ie no gaps) and it also requires high clamping pressures. West System, and I assume other epoxys, has gap filling properties when flox is mixed in and does not need any greater clamping pressure than is required to hold the two pieces in contact with each other.

    In fact high clamping pressures are discouraged as it squeezes the glue out of the joint; advice I received from the technical guru's at Gougeon Brothers Inc. who make the stuff.

    The recommended application method is to mix the resin and hardener (5:1 ratio), brush it onto each surface, then thoroughly mix flox into the remaining glue in the pot to achieve the required consistency. This can range from a creamy texture right up to something like butter, that will stand up on it's own. The more flox, however, the weaker the joint, as the flox is used only to provide gap filling abilities and stop the epoxy dribbling out of the joint all over the floor.

    The epoxy / flox mixture is then applied to only one of the surfaces, and the two pieces joined.

    Aerolite however, is the glue of choice for 90% of Falco builders, probably because it is recommended in the construction manual and also because 90% of Falco builers live in the US or England where you can still get it!

    One final advantage of using expoxy is that the sealing / gluing process can be done in one step. If you use Aerolite, Resorcinol, etc. when fitting a wing skin, for example, you must carefully mask off the areas where the glue will be applied then varnish the remaining interior side of the skin to seal it against moisture.

    With epoxy you can simply brush the mix over the entire surface, apply it to the ribs, etc. that the skin will be attached too, followed by the flox mix, then staple the thing on.

    I do know of one finished and flying Falco that is stuck together with West Systems so this gives me some comfort that mine will be structurally OK, unless of course I do an Icarus and fly too close to the sun !

    Rob

  2. #17
    Site Developer Jman's Avatar
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    Rob,

    I was wondering if you know why Aerolite is not available in Australia. I had heard it put as if it was banned for use. Living in America I don't see how they could ban anything from use but maybe Australia handles their homebuilts differently.

    I had been under the mistaken assumption that the West system was used just for fiberglass work. I guess I was wrong. What made you go with the West system instead of T-88. Don't they have about the same properties?

    Anyone out there use Gorilla Glue?

    Orion: How much more difficult to use are the glues you mentioned?

    Thanks in advance.

  3. #18
    Super Moderator orion's Avatar
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    The two adhesives I mentioned on the previous page are Hysol epoxies and thus generally are no different in their usage than T-88 or the West System products, with the exception that they are thicker and thus may require a bit more attention in their preparation. They are however substantially stronger.

    The Hysol EA 9430 has pretty much become the standard for several industries in secondary bonding and wood bonding applications as it is very strong, can bond disimilar materials, and due to its higher viscosity, can to an extent fill gaps and voids that can be encountered when working with natural materials such as wood. Due to its high viscosity though, I find that it often is necessary to heat the resin before I can even get it out of the can. In a cold environment, the natural state of the 9430 is such that it resembles salt-water-taffy - it can even be difficult to poke a stick into it. Although with a bit of effort it can be mixed at this consistancy, I generally hit the can with a typical electric space heater so that it thins out and I can pour or spoon it out of the can. The catalyst however is more like water so it is easy to work. When the two are mixed, the handling properties are very nice although still a bit thick. The latter however is beneficial since it stays put after application.

    For better working qualities, the alternative is the Hysol EA9412. The formulation is pretty much the same as that of the EA 9430 but the resin is much more liquid and is much easier to handle. The two epoxies have virtually identical properties and to a limited extent, the 9412 can be used for wetting out fabric laminates. The resulting laminate strength and adhesion is great.

    Although I am not initmately familiar with the product, I probably would not recommend the Gorilla product for any primary structure. It is a good adhesive for things like furniture but it still is a urethane and thus has some of the urethane's properties such as sensitivity to shock and vibration.

  4. #19
    Site Developer Jman's Avatar
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    Orion, thanks for the info on the Hysol. Sounds like an ideal to me. I imagine I could easily build an epoxy heater box with pump built in like I see so many composite builders use.

    Do you know its properties after cure when heated to hot summer in Phoenix type temperatures? Does it have a history of being used in aircraft structures? The latter question is not based on scientific reasoning, just piece of mind. Thanks

  5. #20
    Registered User Johnny luvs Biplanes's Avatar
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    Jake, in true English wood building tradition use only Aerodux (not sure of spelling) or Aerolite. They will never let you down, may not be as cheap but they are the best. Aerodux is a slower setting and best used when scarfing, Aerolite is best for the rest of the time. Start saving every plastic food tub you can, even down to yogurt pots, buy packs of cheap disposable plastic knives (like you'd use on picnic's) to apply the stuff and also packs of plastic cups. Keep a diary of the date you mix each batch and number it, then write down what parts you glued with what batch. Make regular test pieces and keep them if space allows correlating them with the other info. Monitor the temperature in your workshop and keep track of this also, if you are really fussy you could measure humidity levels but as long as the building is dry that should be fine.
    Have you the EAA book and video on woodbuilding, they are quite good..
    Cheers
    John
    Do ya thing in a 2 wing

  6. #21
    Super Moderator orion's Avatar
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    Hi Jake;

    As with most room temperature cure epoxies (even West System, T-88, Aeropoxy, as well as others), the service temperature is somewhat lower than the value used for elevated cure systems or resins like Vinylester. Generally you can figure that an average service temperature value for room temperature cure epoxies is between 160 deg. F to about 185 deg. F. At that temperature the strength is still about 80% or so of the room temperature rating.

    But there are two things to keep in mind. First, in a joint, the epoxy is not likely to see that temperture, even in a Scottsdale sun, since the wood (or fiberglass) around it is actually a good insulator and thus it would take a lot of heat soaking to affect the bond significantly.

    Also, the wood surrounding the bond is significantly weaker than the shear strength the epoxy is capable of. The shear strength of the epoxy is probably on the order of 3,500 psi., give or take a bit. The shear strength of the wood parallel to the grain is only several hundred pounds per square inch so, even if the temperature did affect the epoxy, the surrounding wood is still weaker.

  7. #22
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    Jake,

    Some time ago here in Oz (maybe 10 - 15 years, not exactly sure) a gentleman in Queensland took a particular dislike to Aerolite as he believed the high humidity experienced in parts of that State was a problem for the glue.

    He waged a one man war against it and managed to convince CASA, as it was then, that Aerolite was not appropriate for aircraft use. They banned it and to my knowledge I don't think it can even be imported into the country for ANY purpose now, but I may be wrong on that.

    I knew less than nothing about glues until about 5 years ago when I spent a few months helping a guy building a Velocity, who was using West Systems for wet layups of fibreglass work.

    It was very easy to use and when I did some research I found out that Georgon Brothers actually invented it for wooden boat construction, but it had subsequently found it's way into the composite scene.

    It was designed to be fluid enough to penetrate into the grain of the two pieces of wood and once cured, it forms an almost indestructable joint. (That probably describes any wood glue, I guess!)

    As Orion has correctly pointed out, the glue is far stronger that the parent material it is attached to (ie the wood) which is why the "whack it with a hammer test" will always result in the wood failing before the glue. (Assuming you've mixed and applied it correctly.)

    I was interested to read Orion's comments on Hysol, particularly about having to heat it to get it into a workable state. The West Systems resin and hardener are both clear liquids each of about the same consistency in the unmixed state, something similar to house paint.

    The viscosity varies quite a bit with temperature, as does the pot life . . the time you have to work with it before it begins to set - not to be confused with "cure time" which is considrably longer.

    I have used it in the middle of our summer 40 deg C (over 100 deg F)
    and also in winter at about 10 deg C (50 deg F) but not for structural joints, I hasten to add.

    Even at low temperatures both the resin and hardener flow quite easily and don't require any heat input to get them into the mixing pot. Once they come into contact it only gets better, as the chemical reaction is exothermic (it produces heat) thus the viscosity decreases considerably.

    Due to the exothermic reaction care must be taken when mixing larger quantities (more than 200 grams, about 7 ozs) to use a large flat bottom container, a 2 litre ice cream container for example, which gives a shallow level of glue.

    Using a tall slim pot increases the depth of glue, even though the volume may be the same, and can result in a spectacular display of fumes and a rapid rise in temperature beyond the level at which you can comfortably hold the container in your hand!
    The mix will begin to go off in less than a minute and the only solution is to throw it out and start again.

    The hardener comes as "Slow" and "Fast", but don't even think about using the "Fast" unless you're an expert doing it all day for a living.

    Using the "Slow" hardener you have anywhere from 30 minutes to more than an hour of workable pot life before setting begins, dependant on the ambient temperature.

    One final point to note is that if you live in an area of high humidity be prepared to wait several days before the glue sets hard and suitable for sanding. It will normally set to a brittle plastic like state in about 8 hours, less in hot weather, but I have used it a couple of times on wet days only to discover that the next day it is still not hard, it is slightly flexible and you can leave an impression with your fingernail.

    It will eventually go hard and I'm told that it's ultimate strength is unaffected, but I would still caution against it's use in humid conditions and have tried to avoid it myself. Note that this applies only to the humidity at the time you are mixing and applying the glue, once cured it is impervious to just about anything, including water - remember it was originally invented for boats!

    Rob

  8. #23
    Site Developer Jman's Avatar
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    Rob, Orion, and John: Thanks for taking the time to give in depth info on this subject. It really helps to hear how others have tackled the problem. I was hoping to hear about that one special glue that is the obvious choice for all applications. What I'm beginning to realize is that it may just come down to a personal preference between several really good choices. Maybe I'll get a little of each and do some testing just to see which one works for me. It could actually be fun to do a little standardized testing and see who comes out best, if one is better than the other that is.

    Thanks again for the great info.

  9. #24
    Registered User wally's Avatar
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    Here is my .02 worth

    If I were to build a Pietenpol, I would use the T-88. It is 50-50 mix, a little thicker than the West system and not much different in price. It is available in smaller quantities if you want to start small (build a few ribs at a time) The T-88 will cure down to +35F if you want to work in those temps! At normal room temps I found the pot life and cure time to be 'user friendly'.

    When you are ready to build a cowling, use the West System. Shape whatever part you need: wheel pant, fairing, cowling, etc. cover with glass and put the West resin on. It works very nice with glass cloth.

    A Corvair engine will be a nice match for the plane. I have ridden in a 65 hp Contental powered and it was not real zippy but enough climb performance to be very serviceable. The down side is, of course, a nice 65, 85 or 0-200 Cont. will set you back many thousands of money.

    The Ford powered planes are lucky to have a positive rate of climb on a warm day - but that was what was available for the original plane.

  10. #25
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    Wally,

    I just got the chance to check out a very nice Ford powered Piet this weekend. It sure looks nice with that old time engine hanging on the front. This builder also went with the varnished wood landing gear and it looked Awesome. I really like the idea of how the Model A is able to swing a relatively big prop very slowly. A lot more efficient, and it just sort of fits the old time feel of the airplane. Before seeing the Ford in person, I was against it because of the visibility issue, but after seeing it up close, it really does not seem to be a problem. However, the Corvair just seems more practical to me at the moment because it is an easier conversion and will give me a significant power margin. It also has a much higher TBO than 200 hrs!

    I think I'm going to check out a few of these glues and see how it goes. Since Orion mentioned that the glue is unlikely to see temperatures high enough to soften the epoxies, I feel a little better about them. It will probably come down to which glue has the consistency that is easiest for me to work with. Thanks for the two pennies, I'll put them in the bank to save up for some spruce .

  11. #26
    Site Developer Jman's Avatar
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    Have you the EAA book and video on woodbuilding, they are quite good..
    No not yet. I was looking for the EAA woodworking handbook the other day and was not having good luck. Aircraft Spruce had a couple of EAA books but it was not the same one I had seen before. I didnít know the EAA had put out a video on the subject. I think I will give the EAA a call and see if they offer them any more.

    I'm still working the issue of offering books like those here on HBA. I've got the software to do it and once It's installed I will probably start off with about 10 solid homebuilding related books. I Just started a new phase of training and things are a bit hectic (poor excuse!) so it's slow going.

  12. #27
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    Jake,

    I wouldn't stress out too much about building techniques.
    "How to" books are useful for reference but you'll learn more from actually making some saw dust, and a few mistakes no doubt, than by reading about it.

    If you can use basic tools and achieve relatively close fitting joints you'll be fine. As was stated before, the glue failing is the least of your worries, and provided you use aircaft quality spruce the materials will be OK as well.

    The temperature and more importantly, humidity of your shop is the main thing to watch. Avoid doing any structural gluing on wet or humid days unless you have the luxury of a climate controlled workshop.

    On the subject of spruce, I purchased mine from Western Aircraft Supplies in Canada. The guy's name is Marc Septav (aircraft@telus.net) and I highly recommend him.

    Rob

  13. #28
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    Rob,

    I'm hoping to have a climate controlled work area but I won't know until after the move in January. I won't even know the part of the country until around December. I'm hoping for Colorado - Not much of a humidity problem although that's really not the reason I want to go there. I love to ski and I really want some mountain flying experience.

    I was just on the phone with Western Aircraft a couple of days ago. Seems like they really have a great product. They do the Pietenpol wood kits minus the plywood. They pre-shape the wing/tail leading and trailing surfaces and all their pieces are cut to the correct dimensions - just need to cut the length. They are a definitely possibility - thanks.

  14. #29
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    Jake,

    Colorado is a beautiful part of the US, I lived in Denver for about 6 months in 1989 (work related, but great fun!)

    I did a couple of flights in a 172 out over the ranges and it took about half the main runway at Centennial to get off the ground. . . a real shock to me as the elevation of Jandakot, our local GA airfield in Perth, is 99ft !

    If you're planning on mountain flying in a Pietenpol you might want to think about an IO-540 ! Gravity sucks, but high altitude sucks even more !

    cheers,

    Rob

  15. #30
    Registered User StRaNgEdAyS's Avatar
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    Very informative thread indeed guys!
    I've just finished moving my Wife and I to a new place in Kilcoy, about 45 min down the road from where we were. It's great, there is better facilities for my 13 week pregnant wife, and there is an SAAA chapter here along with it's own airfeild!
    Now I can get on with setting up my workshop
    I got a really good place now, 5 Br high set, enclosed under, 2 garages, one 2 car and one 1 car, small workshop area in the 2 car and a rumpus room, on 1/2 acre with 2 small sheds.
    We're stoked with the house, thought we're not so happy with the amount of cleaning we have to do to the place.
    I'm looking at getting my spruce from a place in Townsville called Rosshaven marine, they sell rough cut 2"x6" (I think ) planks of straight grain sitka spruce for $99/metre(yard + a bit). Because I have a wood mill about 1 min stroll down the road who will machine any timber I need for a token sum, it suits me just fine.
    I HAVE however had some difficulty locating suitable glues, I think I'll need to go hunt around the local SAAA chapter and see what info I can shake loose. I now have a gret deal of info with which to work from.
    Life is short,
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