fastening windshield

[bob lico]

i am not sure on the best method of sealing the holmsey composite winshield.i am joining the bottom of the windshield to the raised area of the fordeck.i did not raised to bridge just suported it and the windshield has a gap of at least 1/2" faily evenly along the top.the bottom is a irregular gap with a twist thrown in.the windshield is very strong and i had bill put in 2" fir along the bottom edge.what i have done is put in a ss 1/4" hanger bolt every 6" and when it is finally in place i will use 1/4" ss lag bolts and washers in between every hanger bolt.alot of explanation because i wanted to pin point the problem.is the best and stongest method to lay down two beads of epoxy thicken with 50/50 milled fiber and colloidal silica on a sanded surface or sand and clean and use sikaflex 292 with beads around the bolt holes and two beads along the surface?? either way i still have to feather the outside seam with epoxy fairing which bring up another question: the sikaflex remains somwhat flexible by fairing i have eliminated that feature.the top will be solid built up epoxy unless someone says otherwise.

[bob lico]

capt patrick what your input.not many people can answer this but you are familar with the convex shape on the top of the boat combing and the concave shape of the bottom of windshield.this is the joint i am refering to.thank you

[CaptPatrick]

Bob,

I start with the top joint, get it dry fitted with seven 1 1/2" x #10 screws, then check the bottom to see how it's going to fit. Once I see that I will be in the ball park, I make a few registration marks, remove the top screws, raise the house top enough to get the epoxy in and srew it back down.

I know that you think that you can get away without screws inside, but believe me, it ain't gonna' be easy. I later recess the top screws and fair them over. If you use Plexus, you can worry less about leaving the screws and just touch up the 3/16" holes. You can do that with just gelcoat and nobody's gonna' notice.

There are, as you're already aware, going to be gaps that have to be filled no matter how close you're able to get the windshield fitted. In my book that means fairing and paint...

I use epoxy also for the bottom joint and 1" x #10 screws through the coaming. At least as many as bertram did and usually a few more at the outside corner areas. Again, gaps and inside fairing...

Here's a brief pictorial of the B31 I'm working on:

Br,

Patrick

[Whaler1777]

Capt Pat, The time and effort that you put into every single project is simply incredible, you really do some beautiful work...

[CaptPatrick]

Thanks for the kind words, John!

the Sikaflex remains somewhat flexible by fairing i have eliminated that feature.the top will be solid built up epoxy unless someone says otherwise.

Bob,

I wouldn't use any urethane type of bedding in the installation at all. If you're more familiar with epoxy than most, you'll know that you can get somewhat creative with the mixing ratio in order to modify the final cure characteristics.

By adding a bit more hardener than the ratio dictates, the final cure will remain more flexible, as opposed to more resin, that causes a more brittle cure. How far off ratio you can go depends on the recommended ratio. Lower ratios, 1:1 & 2:1, are more tolerant of off ratio mixing. Higher ratios, 3:1 & 5:1, are less tolerant.

Mix in too much hardener and the epoxy will never set up and remain rubbery. I use a 3:1, (3 parts resin:1 part hardener), medium speed epoxy and when I need more resilience in the cured product, I mix at around a 3:1.25 ratio. 3:1.5 would be the limit of my off ratio mix for this epoxy.

Mixing off ratio by adding more hardener doesn't adversely affect the bond strength and helps greatly the ability of the cured epoxy to flex with the boat in rough sea conditions without cracking.

However, in the instance of the windshield replacement, there is very little flexing that can take place in that area and between the screws and epoxy, all flexing will be distributed throughout the windshield itself, not in the joints.

The bottom exterior joint is my main worry point in regards to cracks showing up eventually. For this reason, I prefer to glass up the entire joint and fair it out.

The image below shows the windshield epoxied in and the lower joint ready to be ground down and glassed over.



Br,

Patrick

[bob lico]

i don`t know what to say.i will start with thanks a million ,you really went out of your way showing us a step by step procedure for this pretty intricate installation.other then a change to larger screws using 1/4" lag instead of #10 self tapping mainly because there is no chance of stripping them.i will follow this procedure to a tee.------thanks again

[bob lico]

incidently i assume you are making referance to west system when changing mix ratio from the normal 5 to 1 mixture to a 3 to 1 for more flexibility.

[CaptPatrick]

incidently i assume you are making reference to west system when changing mix ratio from the normal 5 to 1 mixture to a 3 to 1 for more flexibility.

ABSOLUTELY NOT!

I'm talking about a slight increase in hardener volume for any given system's ratio, be it 1:1, 2:1, 3:1, 4:1, or 5:1... It's far trickier to play off ratio games with a 5:1 ratio than it is with a 1:1 ratio system.

The system that I use is a manufacture's stated 3:1 system. (Generic brand, but identical to the "System-3" brand)

However, here's a little known fact: In almost all cases, one system's hardener will work fine with another system's resin, as long as the ratio of the system's hardener being used is kept at the ratio for the HARDENER. For example you can use a 3:1 hardener with a 5:1 resin mixing at 3:1. You can use a 5:1 hardener with a 2:1 resin mixing at 5:1. Basically, epoxy resin is pretty much all the same, it's the hardener supplied that dictates the mixing ratio.

Br,

Patrick