Deck fittings with a new twist

I love those deck fittings. They are strong and easy to make. I am a bit leery of using polyester-based binders, like Bondo, to make them. Polyester resin has poor adhesion to epoxy. I make mine like Petrus and use chopped fiberglass in epoxy resin with a layer of glass over to smooth it. Using a fast hardener, they can be de-molded in less than 4 hours. Plus epoxy doesn't stink...

"Petrus i Tranås gör på liknande sätt: packar in slangen i förtjockad epoxy (microfiber, slipdamm eller liknande) och avslutar med ett lager väv i epoxy."

Det gjorde jeg også til mit byggeri. Troede at det var min egen opfindelse. Brugte to lag væv, men ellers inge forskel. Der kan man bare se. ;-)

Bortset fra det blev det klaret i en arbejdsgang, med lidt efterslibning. Og det er tæt.

Ett litet förtydligande om antal lager väv, jag brukar lägga 6 lager 160 g väv över slangen och fyller bara förtjockad epoxy under och runt slangens genomgång i däcket. mvh Petrus

@Petrus: You do it a little differently then I do. For reinforcement I rely mostly on the chopped fiberglass. The outer layer of glass smooths the resulting fitting.

On my next commercial build I'm going to try something even more different: I'm going to laminate the tubes using woven carbon biaxial sleeving. They should be even lighter and stronger.

Dan

While I can understand the issue one may have with the strength of the adhesion between the epoxy and the poly, is it really that much a concern? The filler is really there to make a waterproof seal and to provde something to stop the deck line from pulling through the hull. As long as it is solid and not moving, isn't that enough? The only way you could break the adhesion is with a lateral or sideways movement of the fitting (I tried this with a hammer). There is absolutely no lateral force on thes fittings- the deck line can only pull vertically through the holes. Granted, this is my first time building these fittings, so I may be way out to lunch (I've been so before)

The Bondo is waterproof, so that should not be a concern. It also fills in like an epoxy so there should not be an leakage.

I think the use of the thick walled windshield washer tubing /wire/teflon tape combo is probably more intriguing than the use of the Bondo. I was amazed at how well the tubing/wire held the tight radius without collapsing. The teflon tape made the removal very easy.

Cheers all,

Sean

Sorry for second posting but I just found an interesting article on the West System's website. Assuming that a polyester gel coat is similar in properties to a polyester filler (like Bondo Hair), I should be safe.

http://www.westsystem.com/ss/assets/Uploads/Ew22Polyester.pdf

According to the article "Applying gelcoat to a cured laminate relies on a mechanical bond. Because of the difference in curing chemistry, it is not possible to achieve a chemical bond between epoxy and polyester gelcoat. We developed some tests, to determine whether or not the mechanical bonds achieved between gelcoat and properly prepared, cured epoxy were strong enough to achieve a durable repair."

In a nutshell, the test concluded that the mechanical bond between the poly gelcoat and the epoxy was quite acceptable - even in below waterline applications. That polyester gelcoat will bond to a properly prepared WEST SYSTEM® epoxy as well as to a cured polyester laminate. That polyester gelcoats can be applied over cured WEST SYSTEM epoxy on repairs below the waterline.

So, I guess the concern with poly over epoxy is based on the fact that there is no chemical bond but rather it must rely entirely on mechanical. Given the rigour of the tests by West Systems, I think it's OK to use the poly filler with the fittings.

Once caveat - I am not a chemist, so I can't attest to whether the poly gel coat is the same as the poly filler. I'm just thinking that they are basically the same chemcial composition.

Sean

My experience also. It is a mechanical bond and as such it depends on a clean surface, sufficiently scratched by sanding – but that is also the case when epoxy is applied over old cured epoxy...

I wouldn't lose any sleep over adhesion in this case.

On the other hand all 16 fittings on my latest kayak took a little more than a three hours (plus a little sanding the morning after), done the traditional way with epoxy and fiberglass. That makes approx 12 minutes per fitting – and it did not smell...