Fiberglass 101

Roger Long · Feb 10, 2009

Hermit Scott said:
I have vinyl ester to do the repairs. I have no doubts that it will suffice.

The characteristics of resins used in fiberglass boats change charactersitics over time so that new resin sometimes doesn't bond to them well. The issue isn't the strength of the patch itself but whether it stays bonded to the boat under impact. Use epoxy. Sleep better.

Think about eliminating you sink drains. I've found direct sink drains to be a big pain. Everything that floats sits at the water surface inside the pipe. Despite care, this will be a lot of stuff from the galley sink. Other stuff lands on the floating things and you get a clog.

Atwood makes a box with a bilge pump and float switch in it. I suggest running all your grey water drains to one of these (or one you can build yourself) and then eliminating all those separate thru hulls and seacocks. It will even cost less in the end. The 5/8" discharge hose from the sump can be connected to a T or "Y" just before the discharge or to a thru hull just above the waterline. Fewer thru hulls means quicker diagnosis in a flooding situation and fewer seacocks to close when you leave the boat (You do close your seacocks don't you?). You can also avoid pumping soapy water overboard in a marina.

I eventually eliminated my grey water sump and just ran all the sink drains to the bilge. I wouldn't do this with a large shallow bilge where the water can slosh over a large area but I reconfigured mine when I installed the second fuel tank so that there is a small sump about the size of a gallon jug with a small bilge pump in it.

I never noticed any objectionable odor when I took the top off the Atwood grey water sump so I decided to try the direct to bilge arrangement. Never a whiff of odor last season either. Peggie says I wouldn't get away with this in a warm climate but a friend in Charleston SC sends everything to an open bilge sump on a very fancy boat and says there is no odor either. The soap from dishwashing helps keep it sweet.

Full description of my bilge arrangements here:

http://www.rogerlongboats.com/StriderFuelSystem.htm

Here is the Atwood sump which I eliminated.

sailingdog · Feb 10, 2009

HS—

I'd highly recommend using epoxy instead of vinylester/polyester resins mainly due to the much higher secondary bonding characteristics. The adhesive properties of epoxy resins are well known and that makes them far more suitable for many repair jobs, since in many repairs, the main strength of the repair is secondary (adhesive) bonding, rather than primary (Chemical) bonding. This is especially true in cases of older boats, where fewer active styrene sites for the polyester/vinylester resin to chemically bond to will be available.

Grind it out a 12:1 bevel and lay in a proper patch, preferably from both sides if possible.

Ross · Feb 10, 2009

If I have 1/4 inch thick fiberglass with a hole in it I should grind it out to a 6 inch diameter circle. D/2=R so R =3 inches. Area equals 3.14159*R squared or or 9*3.14159 or about 27 square inches. A very conservative adhesive bond strength of 100 psi would indicate that the patch would require more than a ton of force to pull it loose. I suspect that applying a one ton load to a small area of a 1/4 inch thick hull might make a new hole as easily as knocking out the patch.

Maine Sail · Feb 10, 2009

Hermit Scott said:
Maine sail- do you see alot of boats with polyester repairs falling out? I don't know if any one here works in a boat yard or in the industry, do any of you seeing polyester falling off of boats? I don't have enough real world experience here to qualify as someone who knows anything, but some people exsclusivey use vinylester because it has less water intrusion and doesn't shrink and have been doing it 20 years and haven't seen their repairs fall off. What have you guys seen concerning this?

I have seen polyester secondary bonds fail though not specifically a tapered patch. It is quite common to hear of "tabbing" pulling free and I have witnessed this on many boats by all types of builders. Often times the hulls were laid up well ahead of the bulkheads, furniture etc. being installed and when they finally did install them the tabbing became a secondary adhesive bond as opposed to a primary chemical bond. So yeas I have seen secondary polyester resin bonds fail more than once.

Most yards up this way, at least every one I know of, has been using Epoxy for years, as opposed to polyester, so from a yard failure mode perspective it is very rare to see them use polyester.

Vinylester is not polyester and the secondary bonding of vinylester is slightly better than that of polyester but it's still an adhesive bond as opposed to a chemical bond. I mostly use Epoxy (about 85% of the time) but on occasion still use some polyester, especially kitty hair, for areas that don't or won't necessarily require the secondary bond strength but need a mild structural filler.

Provided you've done your tapered patch well I see no reason why vinylester would fail over a 1.5" hole unless you are really cranking down on that seacock.

That being said you can buy Epoxy for not much more than vinylester these days. Vinylester, in small DIY quantities, is NOT easy to find and and neither Jamestown Distributors, Hamilton Marine not Defender even stock it. Vinylesters are capable of forming secondary bonds around 500 PSI, with absolute perfect prep, while epoxies such as West System or MAS Epoxies are capable of upwards of 2000 PSI. If you can find small quantities of Vinylester it might save you a couple of bucks but that's it..

Don't forget that there are two types of polyester resin waxed & un-waxed or finishing & laminating resin. The latter never cures beyond a tacky surface and the former has wax added to force a cure.

Ross · Feb 10, 2009

The other consideration here is the rather small amount of material involved. A square yard of glass will only weigh about 10 ounces and that much resin will be enough. If you must go out and purchase the material then buy the epoxy, it is good for many things, but if you have good ester resin and follow good practice then use that. Either way you will be good. I have used both and like the polyester because I can finish the job the same day I start. I have patched , faired and painted between breakfast and supper.

jibes138 · Feb 11, 2009

Low Cost Construction

Has anyone ever asked Catalina how they could build a boat like this and be able to sleep at night? I had a Catalina 25 for 10 years. Since it was an outboard and a porta-potti I didn't have many through hulls. There were only 2, for the sinks to drain. Both were bonded in pipes and gate valves equivalent to the one for your hose on your house. I bonded the depth transducer to the inside of the hull and it worked fine. But I always wondered how these builders can get away with such poor construction practices. Seems like there should be some minimum standards set by the industry.

Maine Sail · Feb 11, 2009

jibes138 said:
Has anyone ever asked Catalina how they could build a boat like this and be able to sleep at night? I had a Catalina 25 for 10 years. Since it was an outboard and a porta-potti I didn't have many through hulls. There were only 2, for the sinks to drain. Both were bonded in pipes and gate valves equivalent to the one for your hose on your house. I bonded the depth transducer to the inside of the hull and it worked fine. But I always wondered how these builders can get away with such poor construction practices. Seems like there should be some minimum standards set by the industry.

There are industry accepted standards now, ABYC, but back then there were not and many, many boats were built with some pretty scary construction methods..

Catalina now installs Marelon seacocks and their boats, for the most part, are built to meet ABYC standards.. Of course ABYC is a moving target, changes often, and the standards change so that is why I say for the most part. If I remember correctly I believe Catalina stopped glassing in iron pipe in the early eighties..

Roger Long · Feb 12, 2009

Hermit Scott said:
Roger your bilge is immaculant! How deep is your bilge?

It isn't that deep any more but it's even cleaner. The original sump was so deep I could just barely touch the bottom of the grey water sump with my fingers which made cleaning and maintenance difficult.

There is now a fuel tank in that space. Full story here:

http://www.rogerlongboats.com/StriderFuelSystem.htm