Attaching strut to acrylic

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Neeves

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I had a thread on drilling acrylic = this is a bit of a continuation.

We have a 38' cat and the designer had the idea that we would love to sail this yacht fully exposed to whatever elements were thrown at us - so they expected we would invest in top of the range foul weather gear.

This is not an uncommon assumption of cat boatbuilders/designers.

We built an enclosed helm station with a 'lift out ' windscreen. This is fine except we, and the instruments, get wet in the rain (not that we have had much, or any, rain in Sydney for months).

So to keep out the future rain and the ash from the fires we have dispensed with, or are dispensing with, the lift out windscreen and have a split screen with the bottom half lifting up. The idea is to support the screen with struts but the strut ends have 'flanges' and need to be attached to the screen. My idea was to simply rivet the flanges to the screen - but as I later surmised when you apply the rivets the acrylic cracks (I tried it on an offset (I'm not that daft). I did try using small washers under the rivets, waste of washers.

What are the alternatives. So far I'm leaning toward tapping the screen and using small bolts, M4, M5 which I would secure with adhesive.

Any suggestions

Drilling acrylic turned out to be a breeze. I just used my normal drill bits, which may have lost their edge anyway. My concerns were unfounded - but thanks for the advise - I was at least cautious until I gained a bit of confidence.

Jonathan
 
Thanks Vyv,
I did wonder about that, hence the washers (which were unsuccessful) but I would need to make backing plate (9which is what I think you are suggesting) and before I did that I thought I would canvas for ideas. I confess to being discouraged from making the backing plate - because the washers did not work (twice)

Jonathan
 
Small washers would barely be an improvement, still point loading that acrylic does not like. Backing plate the same size as the flange is a well established method. With glass there is also a soft layer e.g. rubber sheet, between metal and glass to give slight elasticity. Probably worthwhile with acrylic.
 
vyv_cox said:
Small washers would barely be an improvement, still point loading that acrylic does not like. Backing plate the same size as the flange is a well established method. With glass there is also a soft layer e.g. rubber sheet, between metal and glass to give slight elasticity. Probably worthwhile with acrylic.
Click to expand...

As usual - good advice, I had not thought of the soften layer. And I had noted - you said bolted.

Thanks
 
Try and line the hole with metal tube or similar to prevent 'compression'. Another alternative is use polycarb which I think could be welded!
 
I've drilled and tapped to fit hinges to a piece of acrylic to cover the engine start panel - from memory M5 and that worked fine but maybe not for your application.
 
I made up some perspex washboards and glued a thickening section also perspex to stiffen the edges.

If attaching to a metal frame use a backing strips and make the holes in the perspex about 1mm bigger to allow for the differential expansion of the perspex and metal frame.

I am in the progress of making some deck hatches from a stainless steel frames with 12 mm perspex between the outer frame of the hatch and an inner frame to support the perspex.
 
vyv_cox said:
I think you would need some additional support. It is common to put a metal plate on the outside with the acrylic sandwiched between it and the flange. Bolted of course!
Click to expand...
Not sure that would help as expansion properties are all different and would promote "starring" around holes.

I would drill and tap and maybe use plastic washers to aid compression.

Donald
 
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