question about the order of fiberglass layup repairs

[jlroberts280]

Hello,

My wife and I purchased a 'new to us' 1969 Pearson Coaster last winter. This is our first 'big' boat and I have not done a lot of sailing since High School when a friend of mine bought a Triton for almost nothing and we spent our summers sailing around Block Island. The engine on Orion never really worked and we had no money to fix things but the boat never let us down. So Pearson was on the top of my list when we started shoping.
I had a great summer sailing in Casco Bay out of South Portland. I did a lot of work on the boat while it was in the water but this spring I need to address a few deck repairs. I have read a lot about this topic on this site as well as in several books. I admire Tim's work and have been following his daily entries on his other site for a long time. You all have taught me a lot already and I thank you sincerely for taking the time to post all the detailed photos and descriptions. I finally joined the fourm. So...

My question is: In Casey's book, This Old Boat, he goes into great detail about the order of the layup pieces used to fill a hole after grinding. He swears you should use the smallest piece first, getting larger as you go, unitl your final piece is almost the size of the entire area you have beveled. He gives several reasons why this makes sense (at least it sounds good).
I have read numerous people on this site, including Tim, say you should do the opposite, starting with the largest piece and pushing it into the bevel, then filling in with the next largest unitl you use the smallest piece last. Am I just confusing the issue or is there a real debate about the topic? If you support the "biggest piece first" can you explian why.

Thanks in advance. PS- I know this has been talked about before but I am looking to make sure I understand.

[Rachel]

I go by the following:

If a repair is going to see much sanding/grinding/fairing after it's laid up then go largest piece first. That way you're not removing part of your "best" piece (i.e. the large piece) and ending up with just a bunch of rings. Usually you do some reasonably extensive fairing on a hole patch, so, largest first.

For something like tabbing in a bulkhead, where you normally aren't going to remove much material after you lay it up, then smallest to largest works.

At least that's how I understand it.

As an aside, on a round hole (like an ex-seacock hole), the patch is really there to keep the water out, not to "mend" the structure.

Welcome to the forum! And feel obligated... err, I mean free, to start a thread showing us your Coaster ;)

[Tim]

Repairing a hole: largest first, smallest last. Why? Because the largest piece ensures the largest possible bond between the new repair and the existing laminate, and, as Rachel says, less chance of grinding away the most critical bonding area when smoothing the repair. It makes a lot of sense once you think about it.

Tabbing: smallest first, largest last. Why? This is how I learned it. I respect those who taught me, and besides this approach makes logical sense for bulkheads or other similar tabbing.

Remember that properly applied laminates work less as multiple, distinct layers stacked on each other, and more as a cohesive mass that becomes one during the curing process. The strength of any repair or tabbing requires good bonding area, but also relies upon the overall thickness of the layers working as one. This is why largest-->smallest works.

[Quetzalsailor]

I've seen writeups espousing that replicating the original layup is appropriate, particularly when working with exotic reinforcements, larger areas, and wanting to maintain the original appearance inside and out of some hot raceboat.

Most of us have boats that are not pushing the technology by today's standards and not very much in their day, either. So Tim's explanation makes lots of sense. It's the mass of reinforcement and the density. When building back up at closed throughhulls or even some repairs, I'm likely to use up my scrap 'glass collection and see to bedding them densely and randomly.

I don't know how much embedment it takes to develop the full strength of a collection of fiber. In concrete with steel reinforcement it's so many diameters for specified strength of concrete and position (all neatly set out with formulae in the ACI Code). It can't be very far with ordinary 'glass fibers.

As for tabbing starting with the smallest, narrowest strips, you're building up the reentrant corner first and working to the wider pieces that might actually lay into the corner. And the appearance is neater. NA PEs will tell you that the most highly stressed place in that tabbed joint is at the corner next to the join, though.

[jlroberts280]

Thanks again. Great site. Happy Holidays! I'll try to get some pictures up.

By the way, I noticed a thread while browsing the site talking about Norhteast Sailboat Rescue out of Freeport ME. This happens to be where we bought the Coaster. Michael, the owner, was very helpful. He took our Compac 16 in as a trade and we sealed the deal with a handshake. We bought the boat during the winter and he promised the boat in the water and ready to go. He delivered on the date we needed it and had the old A4 engine ready for our first motor from Freeport to South Portland. The deal depended a lot on trust since we did not see the sails and several other items before the purchase. I would recommend the company and think it's a great idea. The one thing I found funny was the brightwork was in really rough shape. He suggested painting it "to be done with it". I'm glad I didn't take that advice, although I did paint the spreaders and from the dock it's really hard to tell.

Sorry to get off topic and thanks again.