The 202gf seems to be cheaper than titebond III and Gorilla glue. If it is also waterproof why bother with the others?
Len
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c>>The Garrett -Wade catalog has a PVA glue that it claims:
I don't want to be seen as a pedantic jerk by you chaps even though my students often called me one but:
Glass sheets are held together by water between them because the water has driven out the air and occupies the space between the two sheets. The sheets themselves are then forced together (and against the water lamina) by the air pressure that pushes them together at about 14 lb/sq in. The only mediating pressure is the very slight air pressure on the thin lamina of water between the sheets of glass that forces the water to push outward against the sheets by pushing inward on the water. Surface tension has not much to do with it unless there is an interactive attractive force in the glass (or whatever) that pulls the water molecules toward the sheet but this would be very slight in almost all cases of materials. Air pressure is the force both holding the sheets together and, to an extremely small degree, pushing them apart by pushing on the water lamina. If the glass sheets are uniformly flat and measure, say 10"x10", each sheet is 100 sq in. The air pressure produces 14 lb/sq in on each sheet so the total is [14 lb/sq in x
100 sq in/sheet x 2 sheets] - [the pressure on the water from the sides], or 2800 lb. (I ignored the very very slight pressure on the water lamina because it close to zero). 2800 pounds is the amount of force needed to separate the sheets if there's no other factor. We don't need that much because when we slide the sheets over each other we reduce the amount of air pressure push against them at the places where they are together. Finally, by sliding the sheets enough, the holding pressure is reduced to an easy force to apply.Glues work differently and don't depend on air pressure to hold things together. There are essentially two aspects, the adhesion of the glue to the surfaces and the internal bonding strength between the molecules that make up the glue itself. The solvent for the glue (water, alcohol, whatever) is just a carrier. The glue dries by losing its carrier and (in some cases) the chemical nature of the glue itself changes when that happens. When it dries, it bonds to the things being glued and internally inside the dab of glue between them. In the old days, both these bonds were relatively weak and either the glue's internal bonds broke or the bond with the material broke. Some glues produce bonds to materials that are stronger than the material itself is internally AND the internal glue intermolecular strength is also stronger.
Spaces in glued up joints produce weakness because theres no glue in the spaces to form a bond.
Agkistrodon
They may be the same formula because they all kinds look alike and are in the same price range. The Lee Valley 2002GF is about USD 11.00/liter and the GW 202GF is about USD 12.00/quart.
I've never seen it sold here in Durham or Raleigh, NC, CSA but I'm going to order some of each. Maybe some experiments and a report?
Agkistrodon
intermolecular
Yea, that's just what I was gonna say. :-)
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******** Bill Pounds
What? The part about being a pedantic jerk??? Hell, I know it! And I don't give a flip, either.
Agkistrodon
Yeah, the history if some of the designs they had for future planes would have made Wernher von Braun proud. One Messerschmitt design was captured by the Americans and became the F-86 Saberjet used a lot in Korea. I'm not sure about the designer but there was also a design (Focke-Wulf?) captured by the Russians that became the MiG -8(?) that fought the F-86s. So, the Luftwaffe kept on flying!!
Agkistrodon
Now you are beginning to show signs that you understand the point that I was trying to make. You stated,
Now you are showing signs that you might understand the point that I was trying to make.
You said,
"A roughed up surface holds better than a smooth one because there's more glue in the between pieces volume, ain't it?"
Roughed up surfaces often cause spaces in the glued up joint. A smooth surface is Ideal for glue.
That is really debatable, mein Herr. It depends. If the glue can get into the roughed up spaces, it will be stronger because there will be more glue in the joint as a result of the increased surface area caused by the roughening up. The gap causes a weakened area of the joint relative to the rest of it because there's no glue there. This calls for scientific investigation!! Roughed up vs. smooth glued surfaces. Aha, something I know about.
If I do some sexperiments, would anyone want the results? How would you design the set of experiments? I'll do them this weekend.
Agkistrodon
I believe the glue companies already have this data. IIRC their recommendation is a smooth surface. Hence there are rip blades made for glue line ripping that produce smooth surfaces. Jointers straighten a board and produce smooth surfaces for gluing. Thick glue in a joint is not desirable. It is usually an indicator of a poor joint that does not fit well. Roughing up a surface has little value for gluing as the surface produced from roughing up leaves loose and weak fibers of wood.
First step - glue together two end-joint pieces. The ends are always rougher than the sides. So the glue should hold better according to the theory you are testing.
Some of you may have already done this... :-)
The German "mosquito clone" aircraft was the Ta-154, designed by Kurt Tank and so it's also referred to as a Focke Wulf. As I thought, it was also named "Moskito"
I don't know what Tego-Film replacement was, but my sources describe it as a cold glue that had problems with residual acid. Maybe it was an early PVA ?
I doubt it - he just did rockets ("That's not my department", says Wernher von Braun)
No, this was the P.1101. It was captured almost complete in Oberammergau, generally ignored for years and NASA later flew it as the Bell (sic) X-5. The original version had a variable sweep wing that was ground adjustable, but Bell developed this to allow in-flight sweep changes. Last person to fly it was some guy called Neil Armstrong.
The F-86 almost entirely ignored the German swept wing research. What the Americans learned about sweep, they mainly picked up from the British.
The first supersonic jet to fly was the DH108 Swallow, a swept wing tailless development of the 1943 Spider Crab - both with short and tubby wooden fuselage sections, built by the Mosquito laminated wood sheet production technique. However the Swallow was a bit of a widow maker and all three prototypes killed their pilots. Not before however, almost certainly becoming the first supersonic jet, albeit unrecorded and in a near-fatal dive.
Germany's tailless Gothas and Hortens would probably have suffered similar problems, had they ever been flown under real power.
The first supersonic aircraft was of course the Miles M.52. Cancelled by a short-sighted British government in 1946, the first real test wasn't until a model flight in 1948 - when it promptly achieved M1.38 in level flight, with no fuss at all.
The Russians weren't so daft. They copied everything Messerschmitt did with swept wings and produced the Mig-15 and Mig-17 on the basis of them. However, given what the British did by giving them Nene engines to power them, no doubt we'd have given them wing designs too, if they'd asked.
The Me328 (twin pulse jets) was a dismal failure. The wooden fuselage was destroyed by the intense acoustic noise from the pulse jets, so they were moved off the fuselage and under the wings. Here they became uncontrollable, as pulsejets aren't easily throttled to balance their thrust. Unbalanced thrusts such a long way from the centre line gave it a tendency to yaw wildly - and the fuselage still fell apart.
Not quite. A lot of German data on swept wings was used in the design of the F-86, but it was not a German design or a copy of one. The US did capture the P.1101 prototype, of which the Bell X-5 was a partial clone. Other than being a swept-wing jet it bore little resemblance to the F-86.
TA-183. The Mig-15 looks a little bit like it but a long way from being a clone.
So, the
Forget the physics... wood fibers are held together by lignin and xylan, woodworking glues mimic natural glues by bonding the wood fibers together. That's why it isn't necessary for the glue to soak in and why a smoother (planed) wood surface holds better than a rough (sawed/sanded) surface.
Hmmm. I don't think you have this quite right. According to your description, why wouldn't the water just be forced out of the gap?
The sheets are held together because of the surface tension of the laminar fluid layer. Pulling the sheets apart would seriously increase the free surface area of the fluid which surface tension seeks to minimize. I think it is pretty clear that this has nothing to do with the bonding in glue joints, since, after all, the glue in short order ceases to be a fluid. Cohesion (-> surface tension) is important, but adhesion is the key. Roughing the surfaces, as most glue manufacturers recommend, exploits this aspect. However, glue films should be thin, just not too thin. Have you ever been impressed by the strength of a cured gob of glue?
However, it is far to easy to over-generalize when speaking of glue.
-mw
In the course of learning to work wood, I suppose it would do me good to learn about adhesives. Any recommended tomes on the subject? I don't need "all" the science, but I would like to see coverage similar to that presented in Flexner or Jewitt's finishing books.
kiitos JP
You don't really need a book if you read Chapter 9 of the Forest Products Lab Handbook (link below). It outlines the properties of a properly prepared surface and discusses, in detail, the fact that glue bonding is almost entirely a mechanical process rather than a chemical one. It sounds like several people in this thread may benefit from reading Chapter 9. You can download it - FOR FREE (the best part)- right here:
When fresh glue is directly applied to a surface it has maximum ability to 'wet out' the surface and achieve optimum adhesion. Adhesion will normally be a combination of chemical and mechanical properties.
Squeeze-out will never yield optimum wetting and therefore adhesion. The fact that squeeze-out doesn't penetrate the wood and easily chips off when dried doesn't really tell you much about the adhesives properties where properly applied. Wally Goffeney
Do any wood glue manufacturers recommend roughing the wood? The wood should be planed smooth to achieve the strongest joint.
Depends on the glue and the wood. Actually, I was thinking of non-porous materials when I wrote the quoted text--forgetting the context of the thread. Most wood glues work through 'wetting'-- the glue penetrates several cells deeply in the porous wood, forming mechanical (interlocking) (and also chemical) bonds. Thus smooth well mating surfaces are optimal as clamping then very effectively helps force the glue into the wood. A uniform thin layer is desirable. Machine and tool marks obviously diminish this and create distinct pockets.
With very dense, oily wood, porosity is minimal. The story is different. Epoxies do not depend on deep penetration and require different preparation. Slightly roughing the surface is sometimes desirable; see for example, .
I think I will say no more having already fallen into the generalization trap. Mr Ruttan's suggested reference, is a good one indeed.
-mw
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