windscreens

Hi guys, anyone have much success in building a boat winsheild.i have a 21' superboat & i am not impressed with my efforts so far. i am using 1/4 inch plexiglass & am having alot of trouble getting the pattern right as well as the bends. any help would be greatly appreciated

 

Without knowing what kind of windshield you are building, it is not possible to help much. If it is a curved and raked affair, one way would be to fit a thin piece of scrap plywood in the chosen position and mark out the dimensions on the plywood with a tic-stick. The accurate shape can then be transferred to the plexiglass blank.

If you don't know what the tic-stick method is, I expect it needs an illustration to show it. I don't have scanning ability right now so maybe someone else can do that. Anyway, it is far, far better than the cut and try method and has saved my sanity many times.

Plexiglass is a fairly brittle material and could even cause injury in a windshield application. Lexan polycarbonate would probably be a better choice since it bends easily and is almost shatterproof at normal temperatures.

 

Tom is correct in that Plex (acrylic) is brittle compared to Lexan (Polycarbonate), but Lexan does not thermoform as easily as acrylic. Lexan, generally, has a higher melt / softening point and is a real bear to thermoform. The only way bends can be formed for a windshield is either in a well monitored (for temp - if over heated you get lots of bubbles from the H2O in the PC) pizza oven type oven or (easiest) is to use a torpedo heater, and heat both sides and use a form for each method - even if using acrylic. Try Implex or Duraplex if you need to use acrylic - more durable than regular plex. - JB

 

Have you considered toughened glass. There a a few guys out there that can do custom radii. Might be expensive though...

 

Is toughened glass really that superior to Lexan to justify the cost? Is glass superior to Lexan In longevity only, or would it be noticably better even in initial quality? What is the shortcoming of using Lexan for a windshield?

 

BTW, what is the tic-stick method?

 

The downfall of Lexan is its poor resistance to UV weathering, although there is a new formula out that has a ten year guarantee against yellowing. With this new formula and with the new formable, scratch resistant hardcoat available now on MR-10 Lexan sheet, it is superior to glass in many ways for its price and ease of fabrication (it planes like butter). The only real disadvantage is that it is not quite as scratch resistant as glass, but pretty good. No solvent will touch it like acetone, MEK, not even methylene chloride. I use it for glass bottoms in my boats and it holds up well enough. - JB

 

BTW, toughened glass is kindof a confusing adjective when there are really these types only (in increasing order of toughness):
- Laminated annealed glass - not tougher at all, just safer if broken
- heat - strengthened glass - halfway between annealed and tempered, with twice the impact resistance of regular (annealed) glass
- Tempered glass - (more heat applied before air cool quenching) four times stronger than annealed. You can almost take a hammer to it, just not on the edge.
- Tempered, laminated glass - you get the picture.
A Lexan shield is still way better (impact resistant) than tempered, just don't wipe it down with the towel you use to wipe sandy feet. - JB

 

Thanks for the Lexan lesson JB!

 

Lexan is extremely sensitve to chemicals. If you should get any on it kiss it goodbye! www.updplastics.com has many stock windshields at reasonable prices. They aslo do starboard doors, and hatches as well.

 

Forming polycarbonate (Lexan)

Check out this article about forming polycarbonate
[SIZE=-1]www.thermoforming.com/Articles/IAPD-Polycarbonate/Thermoforming.pdf [/SIZE]

 

Tick - Strip

http://www.thedaysailor.com/sidebars/tickstrip.htm


-also worth taking a look at this fellow's impressive finished product at

http://www.thedaysailor.com/

 

http://www.trendmarine.com/

 

Generally, any windshield that is taken from a auto is fantastic. Now that was easy, what is next? How to fabricate the frame? Go to a good tubing fabricating shop. Non tubing desired? Go to a metal fabricating shop. Boy, that was almost as easy to do.