Best Glue for wood

Discussion in 'Wood Construction' started by Pietenpolflyer, Apr 28, 2003.

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  1. Jul 20, 2004 #21

    orion

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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.
     
  2. Jul 21, 2004 #22

    Falco Rob

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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
     
  3. Jul 21, 2004 #23

    Jman

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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.
     
  4. Jul 22, 2004 #24

    wally

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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.
     
  5. Jul 22, 2004 #25

    Jman

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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 :D .
     
  6. Jul 22, 2004 #26

    Jman

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    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 didn’t 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.
     
  7. Jul 22, 2004 #27

    Falco Rob

    Falco Rob

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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
     
  8. Jul 22, 2004 #28

    Jman

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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.
     
  9. Jul 22, 2004 #29

    Falco Rob

    Falco Rob

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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
     
  10. Jul 22, 2004 #30

    StRaNgEdAyS

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    Very informative thread indeed guys!:D
    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! :D
    Now I can get on with setting up my workshop :p:
    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. :angry:
    I'm looking at getting my spruce from a place in Townsville called Rosshaven marine, they sell rough cut 2"x6" (I think :confused: ) 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.
     
  11. Jul 22, 2004 #31

    Jman

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    Strangedays,

    Congrats on the house, sounds great. Let us know what you hear from your local builders.

    Rob,

    Ha! I guess I should have been a little more descriptive :D. The mountain flying I expect to do is with helicopters - OH-58Ds to be exact. One of my dream jobs would to be a Bush pilot up in Alaska and getting stationed in Colorado at least gives me a litte taste and experience. I have no illusions about trying to back-country fly with the Piet. I'm hoping the 110 HP of the Corvair will be enough to crawl around the local field in a respectable fashion. Actually, now that I think about it, I doubt I will even finish the Piet in Colorado (if that's where I go). Usually it's around a 3 year tour; however, the Army is coming out with this new stabilization concept where an individual may be in the same location for around 6 or 7 years. If that's the case, there is a chance it will be done...Maybe.

    Thanks for all the help with and interest in my new project. It means a lot. Anyone else out there have some wisdom or experience with glue they would like to share?
     
  12. Dec 12, 2004 #32

    Greyeagle44f

    Greyeagle44f

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    Wood Glues

    First post, new member...West Systems epoxy is as good or better than any of the others...very convemient to measure and use. I also used it as the "varnish" during construction.

    A good number of Falcos have been built with it, including mine (N644F). I had discussed the use of this product with my friend the late Tony Bingelis and he supported my decision (came to visit and inspect a few times during construction).

    As with all epoxies, the recommended final finish should be of a lighter color, mine is silver (waterbased polyeurathane). Found some charts at one point comparing colors with respect to expected "heating".

    As I recall (some years ago, first flew it in 1995) I made tests heating joints up to 150F or so; wood broke, not the glue.

    The Ancient Aviator
     
  13. Dec 13, 2004 #33

    Johnny luvs Biplanes

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    Greyeagle44f
    Did you varnish outside or inside the aeroplane?
    I was thinking of using West only for water protection outdoors of wooden structures.
    Cheers,
    John.
     
  14. Dec 14, 2004 #34

    Greyeagle44f

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    All wood was "varnished" with West Systems, inside and out. Exterior was then covered with a 2-4 oz layer of fiberglass, filled with a mixture of West Systems and micro, sanded, primed, painted.
     
  15. Dec 16, 2004 #35

    Johnny luvs Biplanes

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    I had considered using 1oz cloth from big modelling to keep the weight down (over Polyfiber) if I went for a painted finish, why did you need so heavy? Does covering the wood with fiberglass totally prevent moisture ingress along with coating everywhere else? What problems did you face applying the covering, also does it sit in sun much?
    Cheers,
    John
     
  16. Dec 16, 2004 #36

    Greyeagle44f

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    Greetings John...

    I found no problem with the application, used a plastic squeegee. The combination of the pre-varnished birch plywood skin and the 'glass before the paint gives it a great deal of protection it would seem, yet adding little weight (I may have used 2 Oz, can't quite recall).

    My Falco is hangared, does sit in the sun from time to time...but do not understand the significance of that question. Clarification? The fiberglass contributes nothing to strength.

    Check Six
     
  17. Dec 17, 2004 #37

    George Sychrovsky

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    error
     
    Last edited: Dec 17, 2004
  18. Dec 18, 2004 #38

    Johnny luvs Biplanes

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    Greyeagle44f
    The reason I ask if it sits in the sun is I may have to consider a tie down outside once I build my project. England suffers with rain and high temps as well as cold so moisture and UV protection is what I am aiming at. Hope that clears up where I am coming from with my questions?
    I am surprised you say the fiberglass adds nothing to the strength, why not?
    Cheers,
    John
     
  19. Dec 18, 2004 #39

    Greyeagle44f

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    Greetings John...I would expect there are paints that could provide UV protection, never gave it much thought myself.

    With respect to my comment about the 'glass not providing strength...it was not my intent and given the weight used I believe it provides little...the Falco will take 9+ positive Gs by design, no glass covering mentioned!

    I did it for Wx protection in the event I was unable to hangar it.
     
  20. Dec 18, 2004 #40

    org

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    According to those who engineer such things, the failure modes of wood and fiberglass differ enough that the fiberglass will carry the entire load until it fails...at which time the load is transferred to the wood structure, which may also fail. Apparently the fiberglass doesn't elongate as much as the wood structure, so it doesn't share the load until it fails. In order for the glass to add strength, the fiberglass must be adequate to carry the entire load by itself, which is not very efficient considering you're hauling the wood structure around and it's not doing anything:)

    At least that's the way I understand it.

    One area I think the fiberglass might be more useful is in adding stiffness to skin areas that might benefit from rigidity, such as control surfaces or wing skins....assuming too much weight isn't added.

    Another area is protection of the wood from the elements. Paint will crack and allow moisture to enter the wood, and fiberglass adds a reinforced layer of protection and allows for filling of small irregularities in shape without worry about damaging plywood when sanding the filler smooth.

    the last two paragraphs are IMHO, and I'm receptive to being corrected if someone disagrees and can talk me out of it.

    UV protection can come from a primer that completely blocks UV rays from the fiberglass. I think Rutan used to recommend black primer, but I think any high solid primer would be fine. I'm using Stits UV Smoothprime. (see the Stits website, ACS sells it and it's really good to work with)
     
    Last edited: Dec 18, 2004

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