Texas GIS

[SimonLew]

MIK - It's my fault for not reading the note on the drawings which makes it obvious that the sides are not reflections. I get frustrated when a machine shop does not read a note I place on my drawings so this is nothing new

If I had seen the note, a solution is to flip the cut side when using it as a template so the two sides are mirrored. I think there is enough ply margin to make this work but have not checked for sure. Worst case the butt joint on one side would be off by a few mm but as long as the two hull sides are cut the same that should not matter.

[MiddleAgesMan]

The parts won't fit if the sides are mirrored without an additional sheet of ply.

My concern when cutting my parts out was that the ply might bend easier one way than the other. As it turned out there didn't seem to be a detectable difference.

[john goodman]

The 2 layers of glass went down nicely. However on the next coats of epoxy we are getting lots of bubbles. We changes to a different foam roller and that helped some, but they will come back after about 10 minutes.

What is happening?

[CCBB]

My two guesses:

That is actually the epoxy picking up the texture of the glass below it.

or

the resin is kicking and you get outgassing, the products of the reaction, and the gasses get stuck in the resin and when they escape, you get the pock marks. Are you using fast hardener?

[john goodman]

I am using System 3 with slow hardener on western red cedar.

In a small area I tried using a hot air gun (industrial hair dryer) to heat the epoxy just enough to break the bubbles. It works on the tiny ones, you can see them pop, but if the area gets too warm, bubbles seem to come up from between the glass fibers as if the wood is off gassing. It creates a lot of pock marks.

I smoothed the epoxy down a couple of times. It looks better each time, but there are still bubbles that show up after I leave. The epoxy started to kick so I am left with pock marks.

I have only done one side of the foil, so I would like to do the other side with a better outcome.

Temperatures are around 60 degrees today, a humidity of 75%.

[BobWes]

John,

I am no expert and have never played one on television, so what I am about to share may have no relevance to what is happening with your foil.

A friend is trying to educate me on the basics of varnishing. She is a patient woman.

One of the things she told me to be aware of when varnishing is to varnish when the wood is cooling rather than heating. Apparently, wood in a heating cycle is more likely to release gases and cause bubbles in the varnish. I have no idea what the temperature range is for a wood's heating cycle or cooling cycle. Quite frankly, I have no idea how to tell what the wood is doing. I have questions for my friend. As I said, she is a patient woman.

I have no idea if this has application to what you're seeing with the epoxy, but it may. Perhaps others can comment on the heating/cooling cycles. I will share whatever other information I get.

[woodeneye]

The 2 layers of glass went down nicely. However on the next coats of epoxy we are getting lots of bubbles. We changes to a different foam roller and that helped some, but they will come back after about 10 minutes.

What is happening?

Hi John

This happens with epoxy when it's quite warm, ie. "kicking" as Compass Project puts it. I've noticed that even when you tip off the epoxy, the bubbles return. At first I thought it was the timber out-gassing, but this happens on the 3rd coat too, when the first coat has cured already, so I don't think that's the reason. Epoxy cures by exothermic reaction and my guess is that some gas from that reaction is being given off. It's a royal PITA, as it creates so much work (and unhealthy epoxy dust!) to sand smooth, despite our best efforts to prevent it.

Although the epoxy phenomenon is unrelated to varnish which cures very slowly by comparison, what BobWes said is true. Best to varnish late in the afternoon/evening when the timber is cooling to prevent bubbles from the timber out-gassing.

Edit: Another reason quoted by West System, and I'm probably guilty of this, is vigorous application with a foam roller. This aerates the epoxy too much and even though the layer applied is quite thin, the bubbles keep popping out as the cure progresses. This is only remedied by wet on wet, or in the case of the final coat, tipping off every 10 minutes until the gel point is reached. Even so, some pin head bubbles may still appear.

[Boatmik]

Howdy - if the ambient temperature is rising it is almost certainly outgassing even with the previous coats cured or part cured.

I really dislike the term outgassing as it implies that there is a special gas that appears from somewhere. But I haven't got any good alternative!

From vigorous rolling you sometimes end up with a foggy appearance to the epoxy - but it is not likely that those will appear as visible bubbles on the surface - they are just too small.

The epoxy film from three coats or less is not going to generate much heat. The only place in normal epoxy work that much heat appears is in either very thick layups or if epoxy is left in a tin or a bag for too long.

There are no solvents in epoxy to evaporate suddenly and make a bubble either.

So ... would always assume outgassing if the temp was going up.

MIK

[woodeneye]

Howdy - if the ambient temperature is rising it is almost certainly outgassing even with the previous coats cured or part cured.

I really dislike the term outgassing as it implies that there is a special gas that appears from somewhere. But I haven't got any good alternative!

From vigorous rolling you sometimes end up with a foggy appearance to the epoxy - but it is not likely that those will appear as visible bubbles on the surface - they are just too small.

The epoxy film from three coats or less is not going to generate much heat. The only place in normal epoxy work that much heat appears is in either very thick layups or if epoxy is left in a tin or a bag for too long.

There are no solvents in epoxy to evaporate suddenly and make a bubble either.

So ... would always assume outgassing if the temp was going up.

MIK

Hi Mick
The bubbles appear even when the temp is falling. This happened to me late yesterday afternoon, so I can only assume then that it was not outgassing from the ply, but fine bubbles from the roller action. West mentions this possibility, but the funny thing is they still recommend their 800 foam roller. When you're trying to get an even, level coat, it's hard not to be vigorous. I am using the recommended West System 800 rollers too. (They have a hard cardboard core)

On page 15 of their manual, West also attribute pinholes to surface tension of the epoxy film pulling away as from bubbles before it gels. Their solution is to force epoxy into the pinholes with a stiff plastic or metal spreader and to recoat/tip off the coating after the pinholes all filled. So maybe there is nothing that can be done to prevent them in the first place, we can only minimise them

Other tips mentioned in the West Manual:
http://westsystem.com/ss/assets/Uplo...lver-2008-.pdf

[MiddleAgesMan]

Application of heat from the hot air gun is aggravating the problem. As Bob W pointed out it's best to be laying down resins on warm surfaces that are now going through a cooling cycle. That was Robb White's technique for building his strip planked boats--warm up the shop to 120-130F, turn off the heaters and start laying down the resin.

[john goodman]

I have been curious as to how others have been finishing the trailing edge of the foils.

I have covered some thin planks with packing tape and clamped one plank on the bottom and one on the top on the trailing edge fiberglass. The fiberglass has been trimmed down to about ¾” while green so there is something to clamp too. Using the small wood stick between the clamp handles I can align the trailing edge with the centerline of the board by moving the stick towards or away from the foils to adjust the angle of the clamp which in turn adjusts the fiberglass. The clamping is done after the epoxy has cured but still a little flexible so not to disturb the fiberglass on the foil. I did not hang the boards and let gravity help with the alignment because I was putting the extra coats of epoxy on at the same time.

Results will be posted tonight.

[SimonLew]

John - your trailing edge clamps look like a good idea. You might end up with a little ridge in the epoxy where they end. I'm not suggesting this is necessary, but I vacuum bagged the glass onto the blanks precisely so that it would conform to the trailing edges, and it's fun to do.

As to the bubbles. I'm finding that there is an optimum amount of epoxy spreading. Just enough to spread it evenly but not aerate.

One big factor for me has been working temperature. If it's 70 or above the epoxy is runny enough that it levels beautifully and all of the bubbles pop by themselves due to the lower viscosity. When I'm epoxying in mid 60s and lower I get significantly poorer results. I'm using MAS and they advertise that they have designed the surface tension properties to minimize bubble trapping. Don't know if that's true or just marketing hype but I'm not having much bubble trouble with it.

Oh and if I apply the epoxy in a rising temperature it guarantees bubbles.

[Boatmik]

Hi Mick
The bubbles appear even when the temp is falling.

That is good and bad. Wanted to make sure the obvious was not being missed.

The foils look really good!

MIK

[woodeneye]

It's interesting too that West System recommend 207 hardener for coating. Better finish and compatibility with other finishes, and no blush as it does not react with moisture. I wish I'd known that!

[john goodman]

"That was Robb White's technique for building his strip planked boats--warm up the shop to 120-130F, turn off the heaters and start laying down the resin."

Read the article and tried it on a small scale. Built a small plastic enclosure around the foils stands. Put in bulkhead 1& 2, rudder and daggerboard. Daggerboard was just there to cook a while. Got it up to 106 degrees Fahrenheit for a couple of hours all wood surfaces were warm to the touch. I had warmed the epoxy too, but just to room temp in the house before bringing it out to the garage. In the pouring rain of course. (note to self build next house with attached garage)

Used the bulkhead sides that are not seen to try this with. Of course there were bubbles, but not too bad and they could be tipped out with a foam brush. Worked the surfaces and bubbles out until epoxy started to kick.

Tomorrow will tell how the final results are.

PS. Rudder is a disaster. I am going to blame it on the new kitten, because she had a pretty good amount of epoxy on her head this morning. Rudder had been knocked off it's stand and was found on the floor laying on the plastic. The new surface epoxy looks like the plastic sheeting, wrinkles and all. Kat has been banished from the garage.