Segmented Turners Question

Epoxy

Richard Allen

>Hi John

I find that epoxy joints will not creep.

Epoxy has it's own set if "issues".

Thanks

Richard

Re: Epoxy

newbie

>Can you elaborate on the epoxy issues?

Re: Segmented Turners Question

Mark Kauder

>John,

When I went through this same thing a few years ago, Michael Dresdner advised me that short of an Poly, epoxy or CA (all of which have their own problems), Hide glue was one of the few adhesives that does not exhibit this problem.

This lead me to using Hot Hide Glue for several years for my segemented work. This worked well for me, as long as I was using the segmenting process where I glued two segments to each other, etc until a full ring was achieved. However, recently I have change to a process where I assemble whole rings at one time with band/hose clamps. This process could be done with hide glue, but I decided it was too much trouble, and have opted to go back to Titebond (I ro II). On at least one piece, using this process, I have used Gorilla Glue. It works, should not creep, but is terribly messy (and relatively expensive). Everytime I clamped up a ring, I would have to wipe squeeze out off everything with an Acetone soaked rag.

I have not tried Liquid Hide Glue, mostly because of the long tack time. I suppose it would work.

Just my .02 worth.

Mark

Large Ray Allen Piece....

Wally Dickerman at Green Valley, Az.

>Ray Allen, who was the segmenter's guru, used original titebond. Here's a shot of one of his large pieces, around 36 inches in dia. I examined this piece, years after it was made, and saw no sign of creep.

Wally

Re: Epoxy

Richard Allen

>Epoxy is messy.

Epoxy migrates into the wood which can "stain" the wood.

Different Epoxies have different tints. I like West System epoxy with the "slow" hardener because it is the most clear of the commonly available epoxies.

You can clamp an epoxy joint to tight weakening the bond

Heating the wood before applying epoxy will draw the epoxy deeper into the wood and can make a stronger bond or starve the joint of epoxy.

Endgrain will absorb more epoxy than side grain so care must be take to insure there is epoxy left in the joint when the epoxy cures.

If you tint epoxy be sure to "wet" the joint first to prevent the tint from migrating into the wood beside the joint.

Filler should be used in the joint to prevent light from being able to shine through a less than perfect joint. Epoxy will hold a less than perfect joint a lot better most other glues but the un filled joint will be clear, letting light pass through. This will look like a bad joint to someone looking inside a segmented hollow form because they will see light in the otherwise dark exterior. A little filler will block any light.

Epoxy cures by heat, not air or water... It creates it's own heat by the catalytic reaction of the resin and hardener. If the environment is to cold the epoxy will not fully cure. If the environment is to warm the epoxy will cure quickly and you make not have enough time to set the pieces to your liking. If you heat the glue-up towards the end of it's curing cycle (usually a couple of hours after the epoxy has started to cure) you will achieve a more fully cured joint.

Good Luck

Richard

Re: Epoxy

adrien

>Rich that's a very helpful summary

Re: Epoxy

Richard Allen

>Don't get me wrong, I like and use epoxy all the time. It works great for glueing wood together, filling voids, filling open grain woods. I am learning more about using epoxy all the time.

Re: Segmented Turners Question

Keith Tompkins

>Hi John, it may be helpful if you post a photo of the piece.

You cannot stop wood from moving.....so it is a fact that we must work with. Without seeing your piece, I can only guess, but I bet the bowl is segmented in the same manner EXCEPT the base.

This is the usual culprit, since the base is moving in a different direction from the rest of the piece. The rest of the assembly is attempting to limit the amount the base can expand and contract....eventually it may pull the piece apart or even cause a crack up the side. NO glue can stop a design problem such as the one I described.

My solution to this problem is to segment the base in the same way as the rest of the piece. That way, the whole piece moves together, with less strain on the glue joints. Sometimes what appears to be glue creep is actually the result of uneven wood movement. Hope this helps.

Re: Epoxy

Fog Tanner

>I have used epoxies for over twenty-eight years in woodworking building high performance model aircraft. These range from the older ones that left a waxy film as part of the endothermic process to the current formulas. On most of these specialized projects I would use five differnt epoxies. These would include the typical ones you normally find to some that you can't buy (friends at one of the large chemical companies). As part of this excercise we had to learn a lot about epoxies.

One of the misconceptions is that the "cure time" is what is stated on the package (i.e. 30 min cures in 30 min or 1 hour in 60 min). They all say can be used in 4 hr or 8 hr or some other number. Other than five minute, which is a special case and never really cures, all the normal epoxies you will buy take seven days to cure. You can handle then within a day, but you can also move the joint if too much stress is placed on it. There are some speicalized epoxies for pattern making that can be oven cured and have a pot life up to eight hours, but these are nor typical to woodworking (other than model race planes).

The most common problem that people make when the pot life is too short (i.e. they mixed up some 30 min epoxy and it starts setting in 15), is they mixed up too much. As the process is endothemic, as the mix starts to warm up it generates heat, which in turn speeds up the process, generating more heat and so on. You can either mix a smaller amount, spread that, mix some more, and repeat. You will still be in the working time of the first batch. You can also place your mixing cup in another cup filled with ice to slow the process down. I have done both, and prefer the first method. The key is not to waste any time - just get on with the program.

Some of the epoxies can be thinned up to 10% with 90% isopropal alcohol - you can't use 70% or more than 10% by volume. More than 10% can affect the cureing process. You can also add tint to the mix if you are concerned about any gaps in your joints or want to accent the fine glue line. You can get these from a marine supply shop nex to the epoxies or from an art supply in the paint area.

Of all the glues you are typically going to use, epoxy is the only one that has any strength when you have a less than perfect joint. For the yellow glues to really work, you have to have a perfect surface. And CA is just too brittle. But, if you are going to use epoxy in an appication where you will/may have a gap, it is stronger if you have some sort of binding agent. There are a number of these avalable from the sandable to unsandable variety. What I have used in some areas where the joint would be seen, was sawdust of the wood I was glueing. If it wasnt't going to be seen, I use other types of fillers depending on the stress area and whether I needed to sand it.

Some epoxies will shrink more than others when exposed to heat (i.e. sunlight). One solution to this that we have used, was to glue the piece up, sand it to finished shape and down to close to the finished grit. Place it in the sun for a while (doesn't take long in Texas), let the glue seam do what its going to do and then finish sand it. This especially works with the finishing resins.

There are a number of other issues that I am not remembering at the moment, but most of the common problems Richard already stated. Working with epoxy is one of those things you have to learn by doing - noting what you did, and why it did or didn't work. Of course a model race planeplane blowing up at 200mph (due to a bad glue joint) gets your attention a lot more than a bowl having a glue line creep sitting on a table at 0mph, so you are forced into a quicker learning curve. You can also gain additional knowledge by picking up a catalog from a pattern suppy house. They have catalogs containing a variety of epoxies and more information than you will most likely need, but its there if you do.

Re: Epoxy - Thanks and a question

Fred in NC

>Fog, I use epoxy, so I appreciate your explanation very much.

You mentioned that 5 min epoxy never really cures. Is that a problem? Will it fall appart or move with time? Thanks!

Re: Epoxy - Thanks and a question

Fog Tanner

>Five minute will never get as hard as the other epoxies. In some brands it will always have some amount of elasticity. I have used some that was very noticable and some that wasn't. I don't worry about it falling apart. I have some joints that are over 20 years old and no signs of failing and they have had way more stress than you will normally put on a glue joint.

The problem with 5 minute epoxy is the working time and penetration. You have fifteen to twenty seconds of mixing time - no more and in some cases about the same for application. In some cases you can get a whole 45 - 60 seconds. This is for a normal type wood to wood joint where you need to have the glue penterate before its starts setting.

That being said, for some of my joints which are an "external" filling where the glue is totally on the surface and bonding only to the substrate, the times change. If you have ever looked at an airplane around the tail section and noticed the curved faring around the horizontal and vertical stabilizers, these are called fillets. To reproduce these on a model, I use five minute epoxy, a filler called micro ballons, and methanl alcohol. The epoxy is mixed together for no more than 15 seconds, then micro ballons are added until a 70-30 to 60-40 epoxy to micro ballons is achived, mixed another 15 seconds and then trowled into the joint. As the glue starts setting, a finger wetted with methonal is used to scuplt the joint into a nice smooth fillet. Let set for 3-4 minutes and do the other side. This is just a speicalized form of woodworking, although I have used this on items other than airplanes, whete I was going to paint the joint.

Another "fact" that seems to be floating around is the CA glue joints will fall apart in a few years. I have some airframes that were glued up in 1978, totally with CA and are still just as strong as they were back then. The wood will fail before the glue joint. The ting I always try to avoid with CA is the use of accelerators. This will weaken the glue joint, but I have never had one of these fail - its just not as strong as it could be. And I have used all the types and brands. I have used the Cynoacrilic and cynoaphalic, both work. The brand that I finally setteled on is from Bob Smith Industries. Its the one you can find in most of the non-chain woodworking shops or in any model shop. Buy enough and Bob will put your name on it. He used to race airplanes with us and knows what a good glue joint is. CA produces a very strong joint, but does not take shearing action very well. One reason I would never use it to glue a waste block on.

I read a study many years ago comparing the various glue types. The strongest was the apahlic (sp??) resins, followed by epoxys, and then CA which I believe was followed by 5 min epoxy. Each has their application, strengths and weaknesses. There is no one glue that will work the best in all applications, to achive the best results you have to understand the limitations of each and what you are asking of that joint - then select the best glue. As I said in my previous narrative, I use five differnt epoxies on a model raceplane, not counting the two differnt aphalic resin glues (one has filler in it), and the two different CA glues. And I'm not even going into the four different fillers I use in the epoxy. That would really put you to sleep.....

Just be sure to note what you did( how you mixed the glue, how long did you mix it, what type and brand) and why it did or didn't work (what were you asking of the glue joint). The conditions under which you were working (i.e. temp, humidity), type of wood. Then in 20+ years you can pass that on.....

Good luck with your gluing,

Fog

This article was not spelled checked but I still approve its content.

Thank you, Fog !

Fred in NC

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