I have cut my plexiglass for my trolley top

[Ron Dickey]

I cut my plexiglass for my trolley top and am working on drilling the holes for where the brass wood screws will go.

What I want to know is I am planning to put silicone behind the plexiglass to keep water out. around the cut out windows. I also plan to put it around the outside edge but rearly work with silicone.

if I make a mess with it how do I clean it up with out using a substance that will etch the plexiglass?






getting ready to drill for the the holes for the screws.


Ron

[doug hodder]

Ron, before you install the plexi, make sure that the openings into the wood are very well sealed with an epoxy so that you get no water penetration into the window opening grain. Once the plex is installed, it's going to be next to impossible to deal that area as anything used to smooth out the wood opening will scratch up the plex if you get into it. I used an acrylic caulk on mine and was able to smooth out the bond squish with a wet finger, then let it cure. I used glass on my portholes however. Any slopped silicone can also cause painting issues, but an acrylic can take the paint. FWIW Doug

[rowerwet]

isopropyl alchohol is what we use on the plastic windows of airplanes, it will remove uncured silicone caulk

[Ron Dickey]

Ron, before you install the plexi, make sure that the openings into the wood are very well sealed with an epoxy so that you get no water penetration into the window opening grain. Once the plex is installed, it's going to be next to impossible to deal that area as anything used to smooth out the wood opening will scratch up the plex if you get into it. I used an acrylic caulk on mine and was able to smooth out the bond squish with a wet finger, then let it cure. I used glass on my portholes however. Any slopped silicone can also cause painting issues, but an acrylic can take the paint. FWIW Doug

thank you doug and rowerwe for your answers.

As you can see the trolley is painted around the windows and upper side, where the plexi. will be layed.

What I am doing I have never done. so it would seem I do not know what I am doing, but somewhere in my past I have been exposed to it.

So far I have cut out the plexi. drilled holes in it where I would put small brass wood screws.
MY Plan to
I had planned to put the silicone around the window openings screw down the wood screws, then put more silicone along the outer edge of the plexiglass cut out and run a finger or object along the edge to angle it some (wiping up the extra as I went with that isopropyl alchohol, you suggested) put little dabs where the screws or in the screw holes before drilling.

Doug suggests acrylic caulk with the isopropyl alchohol work on that too? Each panel has will have 8 scews.

will my idea work or am I in for a world of hurt.

Ron

[doug hodder]

Water works on the acrylic caulk...with a wet finger you can smooth it...I don't know about using alcohol on the acrylic, haven't tried it since water worked. Like I said, I encapsulated the wood with epoxy, exterior and interior on the flange, prior to porthole install, so my method differs. I did however have up to 8 individual portholes in a trolley top...7 years later, no leakers. Doug

[rowerwet]

having used acrylic caulk and silicone caulk on my house, I only use silicone caulk now, acrylic dries and cracks over time in the outside exposed to sun, I used it to seal my house storm windows and 7 years later it was all cracked and flaking. Most tears don't live outside 24/7, YMMV.

[Woodpecker]

Do not use alcohol on Plexi, especially in a hole or un-sanded edge. Do it sometime (to a scrap piece), pour it in a fresh hole and watch what happens.
At least test a scrap piece. Not all plexi is made alike, some vacuum formed plastics and such can handle it, but when I was building Medical Devices certain types of Plexi weren't allowed because you can't clean them with alcohol.
Alcohol isn't the only thing you should avoid in a cleaner. Several other substances can have an adverse effect on it. Steer clear of anything with solvents. This includes acetone, gasoline, ammonia, and others. Likewise, keep away from anything aromatic, as well as traditional glass cleaner, halogens and ketones.

I'd let the excess silicone dry, trim the edge with a razor knife where needed then peel off the excess. It won't stick well to the plexi. so any extra will peel away easily after it cures.
You can also put masking tape down then caulk. You can goop it all over and get a nice corner then just pull up the tape while it's still wet for clean edges.

Drill the holes over-sized. You don't want screw threads digging into the plexi. as the trailer rolls down the road. That will cause a stress area and cracks. Dab silicone in the hole to seal it and use a rubber or fiber washer on the screw.

[Ron Dickey]

this came to me on my cross bow thread I thought I would add it over here Very interesting!!

Looking Good so far. I was thinking of a similar design before i built mine. Maybe my next build... (nearly finished one and already thinking about my next one)

We do a lot of acrylic bending in work, it's not too hard to do but it does take practice to get it right. First off make sure you are using cast acrylic and not extruded. The cast is usually more expensive. The best way to tell the difference is to cut a scrap piece with some kind of power saw. The cast stuff will have a nice smooth cut, the extruded will be all fuzzy and may even re-weld itself back together before the cut is done.
You can use a blowtorch or a heat gun to heat the plastic , either way you must not spend too much time in one spot or the plastic will bubble and burn. we're talking seconds, 2 seconds with a torch will burn and about 4 with a gun. Just keep moving back and forth until the plastic starts to get shiny and warp, then lose the heat and push the bend by hand. Also make sure you have your hand wrapped in about 4 layers of towel or oven gloves ( but only if you are fond of having skin). hold the shape until the plastic has cooled back down.
You need to have some kind of former made to lay the plastic on so it takes the shape you want. Wood is best but it needs to be sanded smooth or the plastic will pick up any imperfections. also don't press to hard with the cloth or the plastic will pick up the thread pattern from it.
The thicker the sheet you are using the longer you need to heat it. but heat it to long and it will bubble up. Also it's better to use an oversized piece because the edges where it bends usually warp a bit so you cut them off afterwards. Just practice with some scraps first until you figure out how much time you can spend on it with the heat and you should be fine. But once the piece is bent its bent, re-heating a second time will cause bubbles and burning.
One last thing, Make sure the sheet is spotlessly clean before you heat it, any dirt or grease will burn into the plastic.

It's really not that hard to do but it does take a little bit of practice to get to know the how the plastic handles when heated.

Here's a pic of one of our models with lots of bent acrylic going on...



22 years bending plastic and it still take me 2 or 3 tries to get it right

Ron