Layup schedule question

[galleywench]

I'm interested in everyone's opinion regarding the layup schedule when doing a recore. Last night I finished the first small layup on my cabintop (there were 6 areas +/- 1 square foot). In each of the 6 areas I set the balsa core, filled it flush (including any hardware cutouts) and waited about an hour for it to kick. At this point it was still sticky, so I laid down both layers of biax glass (wet each one out as I went), flattened them out with a laminate roller and then weighted everything down. When I came back this morning everything looked good, no voids, seemed strong (although it was still green) and everything was in place (see http://www.alberg35.com for details). Zach had suggested this technique when I asked another question last week, but I think he actually put on fairing compound as well.

I have read a bunch of writeups on the subject and have followed many of Tim's restorations over the years and it seems like many people will set the core in place, fills any voids and then lets it cure. At this point they remove the blush, take down any high spots and then apply the cloth.

Should I be following this schedule where I let the core cure before proceeding to layup the glass? It seems to me that a lot of time can be saved by applying the glass along with the core. Granted I have not done a large layup yet, so it may become way too cumbersome to try and apply a much larger piece of glass to a sticky mass of epoxy, but I would like to save time where it makes sense.

[Tim]

I like to ensure the core is thoroughly bonded before applying the new top laminate. To this end, I prefer to leave the core clamped/weighted overnight to allow the epoxy to cure sufficiently. Epoxy doesn't reach full adhesive strength for many hours. Core needs to be well bonded, or else one runs the risk of the same debonding and other situations reoccurring that led to the need to recore in the first place. Rushing the unclamping of the core runs the risk of a partial release that you might not even know about. The larger the area in question, the more this risk exists.

There's a time and place for combining steps, and this often can work to streamline the process. I've not found core application to be one of these based on how I approach things, but of course techniques and opinions vary. I only know what works from my standpoint.

Speed and efficiency come naturally with experience, but each individual has to get there in their own way. I'd rather preach caution and a methodical approach as a general rule, particularly to those who've not done the work before. The end result is far more important than the speed with which you complete the work. Do what you're comfortable with, but be aware of what you're trying to accomplish, and what might go wrong if you take alternate approaches. The first step to avoiding typical issues is being aware of their potential beforehand.

[triton318]

Tim, you should write a book. I'm serious -- you have the knowledge, experience, and an excellent command of the English language. When you describe a process or outline the steps involved in accomplishing a specific task, they are very clear and easy to follow. In addition to that, you have many useful insights into the business of working on old fiberglass boats.

I'm serious; if you wrote a book on different aspects of restoring plastic classics, I'm sure it would be a best-seller.

I like to ensure the core is thoroughly bonded before applying the new top laminate. To this end, I prefer to leave the core clamped/weighted overnight to allow the epoxy to cure sufficiently. Epoxy doesn't reach full adhesive strength for many hours. Core needs to be well bonded, or else one runs the risk of the same debonding and other situations reoccurring that led to the need to recore in the first place. Rushing the unclamping of the core runs the risk of a partial release that you might not even know about. The larger the area in question, the more this risk exists.

There's a time and place for combining steps, and this often can work to streamline the process. I've not found core application to be one of these based on how I approach things, but of course techniques and opinions vary. I only know what works from my standpoint.

Speed and efficiency come naturally with experience, but each individual has to get there in their own way. I'd rather preach caution and a methodical approach as a general rule, particularly to those who've not done the work before. The end result is far more important than the speed with which you complete the work. Do what you're comfortable with, but be aware of what you're trying to accomplish, and what might go wrong if you take alternate approaches. The first step to avoiding typical issues is being aware of their potential beforehand.

[galleywench]

Thanks Tim, I knew you must have had good reasons for your methodology. I certainly don't want to jeopardize all this work for the sake of a few hours. The small areas I did made it easy to do that, and to be honest, I'm not sure I could pull it off with a piece of cloth 4 feet long because once the cloth goes into that partially setup goop, its not going anywhere. There are no second chances.

I'm not going to sweat the pieces I did that way though, the core was small enough to hopefully ensure a good bond with the bottom skin.

[galleywench]

Tim, you should write a book. I'm serious -- you have the knowledge, experience, and an excellent command of the English language. When you describe a process or outline the steps involved in accomplishing a specific task, they are very clear and easy to follow. In addition to that, you have many useful insights into the business of working on old fiberglass boats.

I'm serious; if you wrote a book on different aspects of restoring plastic classics, I'm sure it would be a best-seller.

Without a doubt, your ability to explain a topic with a well thought answer is second to none, and I have no doubt your book would be more informative than Casey's 'This Old Boat'.... I used to turn to that for project info, now I look to one of your well documented restorations and all questions are answered, and in the rare occasion where it is not (like this thread), I can count on a solid answer from you right here.

[Rachel]

I wasn't sure whether to put this in your "Finally moving forward" thread or this one, but since the title of this one sounded more appropos, I chose this one.

I was perusing your blog (which is great, by the way - thanks!) and reading about your re-coring, and as I looked at the photos a question came to mind. What I'm wondering is if the ground down areas on the old skin (where you are overlapping with the new skin) are wide enough (?). They just looked a little narrow to my eye, but then, my eye is amateurish and may easily be all wrong. The other thing is that I can't tell if it is just the white "ring" around the repair areas that is your ground-back taper, or if the adjoining tan areas are also fiberglass that has been tapered or core material (if the latter is the case then they look plenty wide).



I'd like to have a better feel for how much taper is right, is one reason why I'm asking.

Rachel

[galleywench]

Looking at the picture, it does look a little thin and it may be but most of the tapers I cut are roughly 1.5 inches (I think that should be adequate). The picture makes it hard to see where the taper ends, it appears that the white area is the taper, but that is just the gelcoat (or whatever the top finish was). Attached is a better picture to show the entire taper (the red delineates the taper).

[Quetzalsailor]

Serious repairer sources (PBB, for example) say match the original layup. The taper varies with the fiber and the resin. I recall as little as 1:8 for ordinary polyester/glass, on up to 1:30(and more?) for scrimped epoxy/carbon parts - beyond most of our capabilities or needs. I meet or exceed the amount (total thickness) of original glass fiber, since I'm not usually doing 'serious' repairs, and I don't normally have the original weights of cloth or roving on hand.

I'd call most of your deck repairs not serious, structurally, and it's going to be easy enough to do that cabin top. Read Chris Campbell's and many other's strings on this subject for encouragement. And, I'll read your blog and string for encouragement, as soon as I get up the nerve/energy/tme to do my deck work.

[Rachel]

Aha, so some of the "tan" is part of the taper too. Do you ever look at something and see it one way and then it's hard to make your eyes see it another way? That's what happened to me with your tapers. I first saw them as just the grey and white layers, which would have been really minimal, and then I just couldn't decide if the tan areas were part of the taper too, or if they were balsa, or...

Thanks for the annotated photo - that makes it perfectly clear and....... never mind!

Rachel