installing hatch vent w/out damaging acrylic

[matts997]

I’m about to install a Lewmar passive hatch vent and I’m getting a little nervous about cutting the required 3” hole in the acrylic of my relatively new v-berth hatch. I just bought a bimetal 3” hole saw & pilot drill bit, and I have a variable speed drill. But from what I’ve read and watched online, a hole saw can easily cause acrylic to crack, split, melt, etc.

The Lewmar instructions for the vent suggest cutting in the pilot and 3” holes from both sides of the acrylic. West Marine suggests first applying masking tape over the area to be cut. Someone on a previous thread several years ago said it was absolutely necessary to first get scrape pieces of acrylic to practice on!

Wondering if any of you who have actually done this could lend some advice. Is it really this much of a challenge?

Thanks,

Matt

 

[Ralph Johnstone]

I would remove the hatch from its frame and submerge the hatch under a half inch of water while cutting. Hole saws generate a large amount of heat because the teeth are not that precise. A table saw will handle acrylic (no problem with 1/2") very nicely because of the high speed, light touch, and wide kerf.

If you're a little more adventurous, go with the vent manufacturer's instructions of cutting from both sides and go VERY slowly alternating from side to side. Kep the work cool. The quality of the hole saw will determine the outcome of this adventure.

And definitely, use scrap pieces to practice on first to see what happens before you find out it doesn't work all that good ON THE HATCH !

 

[thinwater]

Submerging it is probably over kill, but using a spray bottle and stopping frequently is smart. And definitely drill from both sides. I would do it in place. It's not that big a deal. Just drill the inside first, and then go slow from the outside.. Very light pressure, solid grip on the saw.

Yes, a test hole is smart, mostly to get used to the feel. The saw can grab. You will learn about heating. And most importantly... it will relax you! It's not difficult at all, but practice is always good.

 

[matts997]

Thanks, just what I needed. I ordered an acrylic sheet from Amazon to practice on and desensitize myself. Think I'm going to be adventuresome and try the cutting from both sides method. It might be better to begin on the outside where I’m drilling downward, at least to get a small pilot hole started, and then going inside the v-berth to drill upwards, which will probably be a bit more challenging.

I'll let you know what happens.

 

[thinwater]

Thanks, just what I needed. I ordered an acrylic sheet from Amazon to practice on and desensitize myself. Think I'm going to be adventuresome and try the cutting from both sides method. It might be better to begin on the outside where I’m drilling downward, at least to get a small pilot hole started, and then going inside the v-berth to drill upwards, which will probably be a bit more challenging.

I'll let you know what happens.

You really want to do most of the drilling from outside for a number of reasons. A minor one, not mentioned, is that the pressure is DOWN on the hatch, pushing the glazing into the hatch, rather than pushing it out. Same with the latches. You only want to do enough from the inside to score the circle.

 

[matts997]

Only “scoring the circle” from the inside seems much more doable—thanks.

 

[Ralph Johnstone]

How about opening the hatch to a vertical position and have someone hold it vertical while you drill from the underside face. Holding the drill in an upwards position can be a challenge.

it's all overkill until something breaks . Replacing the lens would be a real bugger. Mind you, you'd then be able to drill both sides in a downward direction with the new lens laying on a bench .

 

[b.needalman]

I usually put painter’s tape on the cut line when working with plexiglass

 

[Galind]

I installed a Marinco Solar Vent in the front hatch. I taped both sides of the hatch where the cut was to be.

I tried removing the hatch cover but it was too much work. I used the same 3” hole saw you are using. Just let the saw do the work and do not apply any pressure on the pilot drill or on the cutter. As was recommended, only cut from the top but make sure you have taped both sides of the cut to avoid any rough edges. I had to enlarge the hole a little because the opening was a little shy for the vent.

Good luck just take it slow and you will be fine.

 

[Caspurr]

I purchased this hole saw from ebay (~$13). Practiced on a spare piece of plexiglass. Took me 2 days to get up the nerve to actually make the cut in my forward hatch (2007 H33). I went slow as the heat can melt the material. I drilled a small hole on center before using the bit in the kit.
Once the hole is finished sand with a file or sandpaper. Also use a heat source to slightly heat up the inside edge of the hole. This will help prevent any splitting of the cut under stress. Follow the instructions for setting up the blades as they cut at different points to prevent melting.

 

[thinwater]

I purchased this hole saw from ebay (~$13). Practiced on a spare piece of plexiglass. Took me 2 days to get up the nerve to actually make the cut in my forward hatch (2007 H33). I went slow as the heat can melt the material. I drilled a small hole on center before using the bit in the kit.
Once the hole is finished sand with a file or sandpaper. Also use a heat source to slightly heat up the inside edge of the hole. This will help prevent any splitting of the cut under stress. Follow the instructions for setting up the blades as they cut at different points to prevent melting.

A fly cutter (illustrated above) is really only safe in a drill press IMO. They can really catch if the work is not securly mounted or the drill gets tilted. They are deffinatly handy, though because they will cut any size.

 

[tfox2069]

Following...have been putting this off for a year.

 

[MikeHoncho]

Use a drill press if available. If you worry about heat you could drill the pilot, ring it with butyl tape and also the outer diameter of the hole and fill will water then drill. Go slow and limit the “bit” of the bit especially at the start.

 

[Tricia]

I opened my hatch and clamped a piece of plywood to the underside, then , with the hatch resting ajar on the clamps, drilled slowly with a hole saw. The plywood fit inside the frame with about an inch to spare, so was clamped directly to the plexi. When I was part way through, I moved the clamped plywood to the top, opened the hatch fully and drilled from the bottom. I used very little pressure so as not to stress the hinges. I bought special drill bits for plastics to drill the screw holes. It worked well.