Epoxy vs Gorilla glue - filling in a gap

[Jerry Bittner]

Building a rocking chair and screwed up on one of the cuts to attach the rocker to the leg -- an angle cut -- a gap showing about a sixteenth or less. I'd rather avoid recutting all for four angles (so I'm looking for ways to fill in that gap.

The plans call for the rockers to be attached to the legs with screws but I was also going to glue the joints prior to inserting the screw. One suggestion was glue it with an epoxy glue that has gap filling capabilities. Another was using Gorilla glue whih I would like to avoid -- never able to stay ahead of the foaming characteristic.

Another suggestion was glue it and then after attaching the screw, glue up some thin veneer like strips and insert them into the gap and after drying, sand the rough edges.

What's the recommendation of you experts? And if it is using an epoxy glue, what type/brand am I looking for.

Thanks.

[Art Mann]

I'm sorry I can't claim the title of "expert", but I will tell you what I know. Polyurethane glues do not have good gap filling properties. Epoxy has good gap filling properties when mixed with wood flour, which is nothing more than fine sanding dust. Mix it together until you have the consistency of peanut butter. I learned this from boat building, where it is used extensively. I have experience with "System Three" brand epoxy, but I am not sure where you can buy it in less than gallon quantities. I have heard that RAKA brand epoxy is also good and it can be bought in smaller quantities. Retail Marina supply stores often carry "West System" brand, which is also good. Do a Google search on those brands and you will easily find those sources. I would not trust the "5 minute" epoxies available at Wal Mart type stores.

I can't say whether this stuff will be strong enough for your application because I can't visualize your problem very well.

[Don Abele]

Jerry, I just finished reading the August issue of FWW. There is a really good article in there on glues.

For your specific question:

Polurethane glue (Gorilla glue) was the poorest performer all around. I'll add that I'll agree to that based on my use of it (and I hate the foaming and extreme caution you must use to keep it off your skin).

For gap-filling, Epoxy (System Three) was only tops when used with Maple. In Oak and Ipe, Type I PVA glue (Titebond III) came out on top. The only gaps I fill with epoxy are non-joints (knots mainly).

Oddly enough, I just started using Titebond III this year and have absolutely fallen in love with the stuff.

While I've never made a rocker myself, I personally would recut. Any amount of filling/shimming is still going to degrade the strength of the joint somewhat. And a rocker just screams of the need for tight/secure joints or it turns into a fall-apart-er. :D

Be well,

Doc

[Art Mann]

Don,

I don't believe FWW used epoxy mixed with wood flour, which is standard practice in the boat building world. If they really wanted to discover the best gap filling properties, they should have done that. I have other technicalissues with that study as well.

[Don Abele]

Art, you are correct. It was solely based on the product alone. I've used PVA mixed with wood dust in the past with excellent results, but not in a joint that needs to be as strong as one found in a rocker.

Be well,

Doc

[Jim Becker]

Don, I'll agree that I'm very, very pleased with the Titebond III product...I even like the color better!

[Art Mann]

For normal woodworking, I have gone over to TB III exclusively. I see three advantages. It provides a little longer working time, it is nearly waterproof and is suitable for building outdoor furniture. The color is not as conspicuous.

[Montgomery Scott]

Don,

I don't believe FWW used epoxy mixed with wood flour, which is standard practice in the boat building world. If they really wanted to discover the best gap filling properties, they should have done that.

That question was dealt with in the current issue. System Three instructions make no statement regarding using wood flour, ergo it was not used. Outside of the boat building world how many wood workers are familiar with this practice?

[Victor Stearns]

Greetings. I would not suggest Gorilla glue. It sort of looks like the insulating foam and doesn't hold. I would use epoxy as it will fill the gap and dry transparent. Plus hold much better.

[Don Abele]

Art that's a good point with the open time. I have found that since I have started using TBIII, I still switch back to TBII when I'm doing quick shop projects. With TBII it's nice to set it in clamps and "let it cook" for 30 minutes then remove the clamps and move on. With TBIII I usually leave it alone for 3-4 hours before I even think about removing the clamps.

I also agree with both Art and Jim...there's something about that color - it's between the original color and the "dark wood" glue color - it just disappears in all the woods I've used it on (pine, poplar, maple, oak, mahogany, walnut).

Be well,

Doc

[Cliff Rohrabacher]

Everything I know from my own experience to articles and reviews says do not ever use any of those urethane glues on anything that will be stressed- ever. And don't use it at all unless you have either: a lot of surface area on which to rely or have composite components like plastic to wood joints that nothing else will touch. Gorilla can adhere to plastic better than most other things. but it's just not strong stuff and doesn't rip wood out when it fails. The glue just fails.

You are better making an epoxy with a little bit of sawdust up or making some wood dust and titebond putty.

[Cliff Rohrabacher]

Outside of the boat building world how many wood workers are familiar with this practice?


Oh I dunno know 'bout that. It seemed a logical thing to try with plain old yellow glue to me way back about 36 years or so ago and I've done it ever since with various adhesives with pretty good results most all the time.
It's really a pretty obvious connection to make.

[Mike Cutler]

Jerry

System Three Epoxies has a product marketed as T-88. Its a two part epoxy that is mixed 50/50. It already contains the thixotropic(sp.) agent, so no microballoons,or wood flour need to be added. It will dry to a clear appearance.

[John Bailey]

My preference is almost always epoxy when needing gap filling. West System, System Three, and my favourite, MAS are all good choices. I used to buy fillers, but now I use bandsaw sawdust. It works just as well and is free. Mixing with sawdust or wood flour isn't too good if you are going to sand later. It is harder than the wood and tough to sand without gouging the wood.

John

[Art Mann]

That question was dealt with in the current issue. System Three instructions make no statement regarding using wood flour, ergo it was not used. Outside of the boat building world how many wood workers are familiar with this practice?

Actually, System Three gives away an excellent book on how to use their product that has several pages on using the wood flour mix. I would not expect the average woodworker to have read it since it is specific to boat building. At this point, I would hope that at least a few more woodworkers know about it since I just mentioned it on Sawmill Creek.:)

[Mike Cutler]

Actually, System Three gives away an excellent book on how to use their product that has several pages on using the wood flour mix. I would not expect the average woodworker to have read it since it is specific to boat building. At this point, I would hope that at least a few more woodworkers know about it since I just mentioned it on Sawmill Creek.:)


System Three epoxy is pretty much my standard, and you are correct, that book is a great primer on epoxy application and use.
I'm certain that West Systems products are just as good. System Three was the first product line I tried, so I've stuck with it.

The dust that collects in a palm sander makes a nice wood flour. I just found it easier to use T-88. It's already mixed and ready to go. The ratio, being 50/50 ,s easier than the 2:1 of their normal epoxy line. It can be mixed in very small quanities also. I usually mix it in a jar lid.
If I need to add some color I'll add wood dust to the regular resin/ hardner mix.
One more product for consideration are the epoxy sticks from Mohawk Finishes of Connecticut. They come in a zillion colors and they have coloring pens to match the grain. Working time is very short though, minutes.

[John Bailey]

Even though I use MAS now, System Three is a very good company to deal with. I once had a Sea Kayak Club for at risk high school students. We had a group make their own paddles. System Three sent us 20 copies of their book for free for the kids to use. We also had to call them a few times and the advice was great. Great to work with.

John

[Mark Singer]

Epoxy is the way to go! I hate poly glue!

[Greg Jurrens]

The best and strongest way to get this joint tight is to get a good fit.
The easiest way is to slide 120 grit sandpaper backed with packing tape through the joint making sure not to round the corners. This doesn't take as long as you would think.
Greg Jurrens

[David DeCristoforo]

A gap of 1/16" on a joint that is going to have as much stress on it as a rocker/leg connection is too much to try and fill with any glue. You would be much better off to shim (with pieces of veneer) or wedge the joint tight.

[Bob Swenson]

I agree with Mark. The only foam I want to see is in a beer glass.

[Rob Blaustein]

Quick question about the System Three T-88—is it meant to be used only if you need to fill a gap, or will it work fine as a general epoxy? One nice thing is that it seems to come in smaller quantities than the standard 2:1 resin:hardener system.

Also, what about PL Premium construction adhesive? It had some favorable properties in Bob Smalser's tests, detailed in his excellent thread "Are your glue joints repairable?". (http://sawmillcreek.org/showthread.php?t=21822) Here is an extract from his summary of several different glues:

PL Premium Construction Adhesive: This polyurethane goo shows promise as a marine glue with further testing and use. Works like 3M 5200 but cures and behaves like liquid poly. Appears to bond well to everything epoxy does, and more where epoxy and liquid poly won’t, perhaps because of a higher isocyanate content…it bonds to difficult surfaces only cyanoacrylate super glues will bond to. The only general-use glue I’ve found that will bond difficult aliphatic-contaminated surfaces. Appears flexible to temperature and moisture content with gap-filling ability, but as a construction adhesive, its open time is shorter than liquid poly. Appeared to like high clamping pressure, and unlike other glues, wouldn’t bond at all without at least some. Repairable with itself and epoxy. Glue line as in liquid poly.

[J.R. Rutter]

That question was dealt with in the current issue. System Three instructions make no statement regarding using wood flour, ergo it was not used. Outside of the boat building world how many wood workers are familiar with this practice?

If you use epoxy professionally, odds are you know about fillers. If you don't then the knowledge isn't obvoius. West System sells several types, but the only reference to gap filling is in the use column for the thickest "peanut butter" filler mix:

http://www.westsystem.com/webpages/userinfo/manual/

I use wood dust from my sander vac with epoxy.

[Kyle Stiefel]

The best and strongest way to get this joint tight is to get a good fit.
The easiest way is to slide 120 grit sandpaper backed with packing tape through the joint making sure not to round the corners. This doesn't take as long as you would think.
Greg Jurrens



Building a rocking chair and screwed up on one of the cuts to attach the rocker to the leg -- an angle cut -- a gap showing about a sixteenth or less. I'd rather avoid recutting all for four angles (so I'm looking for ways to fill in that gap.
Thanks.

Jerry,

Take a look at what Greg wrote, you will get a flawless joint this way. You can take the rocker securing either the front or back leg to the table and then put another clamp over the joint in question. Take a half sheet of your sandpaper and slightly open the joint placing the paper in. Now hold down the seat over the joint sliding the sandpaper out "with the nonabrasive curving out from the joint so you don't round over the corners on the portion you are sanding down." A good 10 passes usually and they will be mirror images of each other. I was actually using this technique last night and will again for another arm joint. Hope that helps.