Bedding in a new windshield - what to use?

[missinginaction]

Hi Folks,

I'm getting ready to have the windshield glass made up for my old Silverton. I've got the new frame in place. I've been doing some research on the best way to bed the glass into the frame. Below is a link to a photo of the frame. It's designed to give the glass a substantial shelf to rest on. You'll get the idea from the photo.

http://www.boatdesign.net/forums/att...s-img_0281.jpg

My question is: What do you recommend for bedding material? I want to do this once and once only. The frame is made of Phillipine Mahogany and has been thoroughly epoxied and painted with white Interlux Perfection over a coat of Interlux Epoxy Primecoat.

I'm reading about silicone, butyl, Sikaflex, 3M 4200, 3M 5200.....and more. I'm used to using 5200 but think that it might be a little overkill in this application. On the other hand I never want to have to pull this glass anyway.

What do you say guys?

As always thanks for any suggestions you might have.

MIA

[CDK]

Prime with Sika 206, then use Sikaflex 292 as a bedding compound.

It will satisfy your requirements, you won't be able to remove the glass no matter how hard you try!

Originally Posted by CDK

Prime with Sika 206, then use Sikaflex 292 as a bedding compound.

It will satisfy your requirements, you won't be able to remove the glass no matter how hard you try!

Concur!

[missinginaction]

Thank you gentleman!

MIA

[baeckmo]

Had exactly this setup accepted according to the DNV 15 m rule for two aluminium fifi catamarans. But: you should use four small distance pads of neoprene rubber, say 3 to 4 mm thick, to ensure that the Sika bed has the correct thickness all around. I may be wrong, but I feel the black one is better than grey or white?

Originally Posted by baeckmo

Had exactly this setup accepted according to the DNV 15 m rule for two aluminium fifi catamarans. But: you should use four small distance pads of neoprene rubber, say 3 to 4 mm thick, to ensure that the Sika bed has the correct thickness all around. I may be wrong, but I feel the black one is better than grey or white?

The neo is a helpful contributor but should not be over 1 - 1,5 mm.
The black has the higher density, you are right.

Regards
Richard

[missinginaction]

I think have the idea and thank you all for the suggestion on the sikaflex. I didn't know about the 206 primer.

I'm using 1/4" laminated glass for the windshield. Each panel weighs about 30 lbs. The perimeter of each panel is roughly 140" and the "shelf" that each windshield rests on is 1" wide. I'm looking at the 206 and see that it's sold in a 250ml container. It looks as though this will be plenty to prep the area.

I can buy 1/16" neoprene here in the US, which comes in at a bit under 2mm. This is as close to 1.5mm as I can get apex.

Here is my plan.......

1. Prep with 206.
2. install neoprene pads to shelf (will tack them in with 5 minute epoxy so they won't move).
3. Apply generous bead of 292 to shelf and around edge of glass.
4. Place glass panel.
5. Install small 3/16" wooden dowels to center glass in frame while sikaflex cures.
6. After sikaflex cures trim excess that has squeezed out with a razor knife.
7. Trim exterior of windshield........done.

Thanks again guys for the advise.

MIA

I am completely ignorant of the Sika brand so just perused their site. I now question the differences of 292, 295, and 296. Is 292 equal to 3M 5200 or superior in this application? Would it help at all to etch the glass where it will be bonded? Thanks

Originally Posted by mark775

I am completely ignorant of the Sika brand so just perused their site. I now question the differences of 292, 295, and 296. Is 292 equal to 3M 5200 or superior in this application? Would it help at all to etch the glass where it will be bonded? Thanks

3M 5200 is uncommon in Europe so, I do´nt know much about it, but as far as I understand it is a glue rather than a bedding compound?
Sikaflex remains flexible even after 25 years, thats the main advantage.
One must not etch the glass, Sika sticks perfect on the clean surface. But of course it should be degreased.

The different formulations are just for different applications Mark (different elasticity, different hardness, etc.)

Regards
Richard

[CDK]

Mark, I will not say anything negative about 3M, in my company we used dozens of their products with great satisfaction, and I think 3M 5200 is more or less similar, but not quite the same.

Sika 206 is a different story.
I doubt there is anything from another brand that could replace it.
It is a very volatile liquid which adheres to any surface, dries quickly and leave a thin, hardly visible film with incredible adhesion for any bedding compound. Even silicone compound adheres better than to any other material I know of.

[missinginaction]

It's interesting that you mention silicone CDK. My glazier isn't familiar with Sika 206. He's suggesting that I bed the glass in pure silicone. His procedure is as follows......

1. Immaculate mounting area for the glass and clean windshield.
2. Apply very generous bead of silicone to frame. Allow silicone to set for 15 to 20 minutes (allows silicone to skin over somewhat).
3. Install windshield and set glass into silicone allowing excess silicone to squeeze out of bed. Do not touch anything at this point.
4. Return the next day and trim off excess silicone after it has cured.

The glazier swears that he's never had a comeback using this technique. He does residential,commercial and auto/boat work and I've used this guy for three other (non-boat) projects with great results.

I'm curious what you think CDK and Apex about using the 206 and silicone?

Still think I'll go with the 292 and 206 though.......

MIA

Originally Posted by missinginaction

It's interesting that you mention silicone CDK. My glazier isn't familiar with Sika 206. He's suggesting that I bed the glass in pure silicone. His procedure is as follows......

1. Immaculate mounting area for the glass and clean windshield.
2. Apply very generous bead of silicone to frame. Allow silicone to set for 15 to 20 minutes (allows silicone to skin over somewhat).
3. Install windshield and set glass into silicone allowing excess silicone to squeeze out of bed. Do not touch anything at this point.
4. Return the next day and trim off excess silicone after it has cured.

The glazier swears that he's never had a comeback using this technique. He does residential,commercial and auto/boat work and I've used this guy for three other (non-boat) projects with great results.

I'm curious what you think CDK and Apex about using the 206 and silicone?

Still think I'll go with the 292 and 206 though.......

MIA

That is a good method, no doubt. But silicone is not as strong as sika.

Stick to your plan posted above.

Regards
Richard

[baeckmo]

Forgot to mention: DON'T USE ANY KIND OF ALCOHOL FOR CLEANING IF YOU GO FOR THE SICA SOLUTION!!!!! The Sika will not cure.

Apex1: I think 1-1.5 mm is on the lean side for bond thickness if you have a big difference in thermal expansion ratio between the glass and superstructure; we were recommended ~3 mm (hardened glass to Al) from Sika lab guys. What is the argument for a thinner layer?

Originally Posted by baeckmo

Apex1: I think 1-1.5 mm is on the lean side for bond thickness if you have a big difference in thermal expansion ratio between the glass and superstructure; we were recommended ~3 mm (hardened glass to Al) from Sika lab guys. What is the argument for a thinner layer?

I was talking about the neoprene foam thickness Bodo, not the compound!!!

Cheers
Richard

Thank you. I learn every day still.