Working with Resins in Cooler Temps

[drewpster]

Well the major glass work on my old tug is beginning and I am quickly running out of warm days. I was hoping one of you glass guys could give me some advise on working with resins in cooler temps.
In the later winter months the daily temps will be in the 40's. I am anticipating the prep getting finished around February and I was hoping I could start glassing at that time. I own a larger boat and I was thinking of tenting the aft end of the boat inclosing it with a tarp and using some heaters. Will this work, or should I wait till spring?
Part of the work will need epoxy while other parts will be poly. (stringers and some bulkheads, maybe some transom supports and backing for a swim platform)

 

[ondarvr]

Re: Working with Resins in Cooler Temps

Tenting and heating will work. Polyesters will get hard at low temps, but that doesn't mean it's thoroughly cured and using too much catalyst can create problems and weaken the laminate also. To help when you need to work and it's cold, go with thicker laminates if possible, as in building up areas that may need more than one application of glass and doing it all at one time. This will generate more heat and help it cure, don't over do it though. Sometimes retail suppliers carry a winter and summer version of resin, not too many do, but you can at least ask. Heat lamps will work also, just don't get them too close or you can fry the layup, 3 to 4 feet works well, but check to make sure it doesn't get too hot.

If you tent it, remeber you still need to get fesh air in there so you can you can breath.

What areas need epoxy?

 

[drewpster]

Re: Working with Resins in Cooler Temps

I'm still studying the processes involved so I am not sure exactly where I will use the epoxy. I plan to use poly for the majority of the work. Given the price of epoxy, I will only be using it where I think extra bond will be needed. Maybe I will use it where I will be adding support to the transom for the swim platform, maybe. So far I am certain that main stringers/ engine mounts that run the full length of the bilge and under the cabin floor will have to be re-cored. I am of course hoping that I can replace only those portions that are wet, but I have found a loose engine mount lagg bolt at the forward end of the stringers and I used an ice pick to find wet wood through a hole at both aft ends. It is far more likely that the whole shebang will have to go. My biggest fear is that the cabin floor will have to come up. I have not found any soft spots in the deck itself. But I know it is highly unlikely that there is no rot under there.
As I get into it I am sure that some other bulkhead and wing cores will also have to go.
The original glass looks to be heavy roving laminated over wood parts to make up the grid. I know I need to get the surface cleaned and de-greased prior to grinding. Do I need to grind the surfaces smooth removing the pattern in the roving before glassing?
I am also a little intimidated by the possibility of causing problems removing too much support from the hull as I go along. There are pictures of the boat at the link below. She is large and heavy. I plan to post pictures as work progresses so that my mistakes can be made fun of more easily. I am also currently working on stands so that I can lower the boat closer to the ground.

 

[BillP]

Re: Working with Resins in Cooler Temps

Glassing with polyester at 40F is no problem. It's been done for 50+ yrs in all types of glass mfg with zero issues. All you have to do is increase the catalyst to make up for the cold temp...it takes a lot more catalyst to weaken the resin than you will ever need to do poly at 40F. You want the resin to get hard to the touch within an hr or so. Do NOT think or believe longer kick times (overnight, etc) is better for poly at ANY temp...it isn't. Like already said, heat lamps, etc also work but be careful for fires and hot spots which can literally cook the resin...and in turn damage it. IF by chance you have glassed something and it is still "wet" 2-3 hrs later, apply a highly catalyzed batch of resin (say 10cc per qt of resin...btw 40cc is very common in the glassing industry for fill coats) over it. If caught early enough it will start the kicking process and save the job. If you do this too late it will only cure the top layer and leave "rubber" under it.

The same can't be said for epoxy so beware. It has to be mixed to exact ratios and the hardeners selected for certain temps. However, adding heat accelerates the curing time just like polyester.

 

[GiMLit]

Re: Working with Resins in Cooler Temps

Glassing with polyester at 40F is no problem. It's been done for 50+ yrs in all types of glass mfg with zero issues. All you have to do is increase the catalyst to make up for the cold temp...it takes a lot more catalyst to weaken the resin than you will ever need to do poly at 40F. You want the resin to get hard to the touch within an hr or so. Do NOT think or believe longer kick times (overnight, etc) is better for poly at ANY temp...it isn't. Like already said, heat lamps, etc also work but be careful for fires and hot spots which can literally cook the resin...and in turn damage it. IF by chance you have glassed something and it is still "wet" 2-3 hrs later, apply a highly catalyzed batch of resin (say 10cc per qt of resin...btw 40cc is very common in the glassing industry for fill coats) over it. If caught early enough it will start the kicking process and save the job. If you do this too late it will only cure the top layer and leave "rubber" under it.

The same can't be said for epoxy so beware. It has to be mixed to exact ratios and the hardeners selected for certain temps. However, adding heat accelerates the curing time just like polyester.

Thanks for that information.
I am at a stage that I need to add height to my stringers and would like to glass it all in. Your info means I can look for a decent couple weather days and get it done!
Once this is done I can paint up the bilge area and get the power plant in.
I have secured a shop to paint the topside in which is the step after repowering. Guy doesn't want me glassing in the shop due to the smell. Seems reasonable to me.

 

[ondarvr]

Re: Working with Resins in Cooler Temps

What's "commonly done in the glassing industry" doesn't mean it's the correct way to do it.

40cc's of catalyst to 1qrt is about 4%, the maximum amount we recommend for most resins is 2.4% (3% on gel coat) or so, this means it's over catalyzed. Will it get hard? Yes. Will it be as strong as it could be? probably not. Over and under catayzed resin or gel coat is weaker, less water, crack and UV resistent, and none of these are features desired by boaters.

Temperature is also very important to cure and strength, Low temps result in incomplete cures, which result in similar problems as in over and under catalyzed resin. 60F is the normal low end of the recommended range for using polyester resin. Below this temp it can be difficult for the chemical reactions to start and then become complete. Does this mean I've never used it below this temp, no, but as the temps get lower the chance of problems increase (remember you don't see many of these problems right away).

A big problem with polyester chemistry is that its so forgiving you can do many things wrong and still end up with a job that appears to be done right. It may not be as strong as it could be, or it may fail in the near future, but it looks good the day your done. With Epoxy every body knows you need to mix it in the correct ratio's for it work. With polyesters many people think the glug glug method of measuring is close enough, then when it fails, they blame the polyester resin for not holding up.

One reason the quality of boats is getting better is because builders are paying more attention to details, like shop temperatures and catalyst %.

High end boats are typically made in climate controlled shops and the procedures are closely monitored. The people building the boats are not allowed to change catalyst settings without permission and then it's only in a very small range.

If anyone would like to download an application manual just PM me, it's large so you need a high speed connection. It will explain many of the things being discussed in much greater detail.

 

[BillP]

Re: Working with Resins in Cooler Temps

40cc (.0378%) a qt is an extreme mix (will flash fire in the container) and used on only one application that I know of...filling weave in 6oz (or less) cloth to make a base for sanding without hitting the cloth fibers. The resin will kick in under one minute at 80F and drips will freeze in motion before hitting the floor. This layer is purely cosmetic and has zero structural dependency other than bonding for a coat of polyester finishing resin. With hundreds of thousands of products out there done this way and 40+ yrs later there are still no defects. It's an extreme mix with empiracle results that can't be argued with concerning over catalyzing. It does hint however on how hot 4% catalyst really is.

Here's math for more perspective:

20 drops = 1cc.
30cc = 1oz
2% catalyst = 1514 drops or 2.5oz catalyst per gallon.

Going up to 2.4% is a hot batch at anything on the sunny side of 40F (depending on humidity) with most off the shelf resins. Most would never have to use 2.4% under any circumstance. In reality the problem is so small as not to be a concern for most...but my question still remains to what % is resin weakened at 3% catalyst at 77F? Do you have any lab data on even ONE resin that shows this with scientific terms that a normal person can understand?

bp

 

[ondarvr]

Re: Working with Resins in Cooler Temps

As you said, high catalyst %'s like that shouldn't be used, but we frequently find that's exactly what's happening. Instead of buying a resin with a longer or shorter gel time ( they can be from 5 minutes to over an hour), they try to make up for shop conditions by using far too little, or far too much catalyst. Some of the blistering, cracking and poor suface profile on boats is due to cold shop temps and/or incorrect catalyst settings. All of these conditions result it a poorly cured resin, as this resin is exposed to heat and stress it tends to soften and move slightly, also known as post cure. You can frequently see this in darker hull sides, the white area "may" look ok, but the surface of the darker area will start to print or distort, then you can see the glass or core pattern in the surface.