How Thick?

[Stemar]

I'm building a spray top for Jazzcat. Here's a photo of the first trial fit. I haven't done the cutout for the port window, but it'll be the same as the starboard one.



The long, top edge is about 90cm, allowing 3cm for fixing, and it's around 52cm high. They shouldn't need to contribute much to the strength of the side, but I don't want them too feeble either. What thickness of perspex should I use?

I'm also thinking about putting four windows in the roof, to allow light in; they'll be around 40cm square, again, allowing 3cm all round for mounting. I presume they could be thinner, but how thick should they be?

Thanks in advance

 

[RunAgroundHard]

I changed from 3mm to 5mm perspex for my greenhous. The large panels are flexible, the shorter square ones are stiff, and a bigger area than yours. I would suggest 5mm would be fine. The stuff is low cost, you you could get buy a 3mm thick x 40cm square panel and see if it is flexible or stiff enough.

 

[johnalison]

It may be a bit late for your design but the screen on our HR turned into a tropical hothouse in bright sun and the saving grace was an opening section towards the bow that would let air through.

 

[Boathook]

I would go for 5 or 6mm. The perspex windows on the wheel house of my 9m are about 12mm thick !

 

[Minerva]

That looks pretty good! Well done! Looking forward to seeing the final product!

 

[rotrax]

I'm building a spray top for Jazzcat. Here's a photo of the first trial fit. I haven't done the cutout for the port window, but it'll be the same as the starboard one.

View attachment 209799

The long, top edge is about 90cm, allowing 3cm for fixing, and it's around 52cm high. They shouldn't need to contribute much to the strength of the side, but I don't want them too feeble either. What thickness of perspex should I use?

I'm also thinking about putting four windows in the roof, to allow light in; they'll be around 40cm square, again, allowing 3cm all round for mounting. I presume they could be thinner, but how thick should they be?

Thanks in advance

I saw the post title and could not help wondering what forumite we were going to discuss......................................

 

[Tranona]

6mm polycarbonate will be more than strong enough.

 

[oldmanofthehills]

If it’s a permanent doghouse then it should be strong enough to resist bad weather and folk leaning on it while attending to reefing. A spray hood can be taken away for restitching but a solid structure cannot. I would be inclined to go for 9 or 10mm

 

[Stemar]

I saw the post title and could not help wondering what forumite we were going to discuss......................................

Well, I wouldn't dare discuss US - or UK, for that matter - politics

 

[Stemar]

It may be a bit late for your design but the screen on our HR turned into a tropical hothouse in bright sun and the saving grace was an opening section towards the bow that would let air through.

It's going to be completely open to the cockpit, so that shouldn't be any more of an issue than the old canvas one was.

 

[PetiteFleur]

I would use 6mmm perspex, fixed with m6 ss coach screws and a ss washer between the perspex & plywood to prevent sealent being squeezed out. Use Butyl tape for sealant.

 

[Mister E]

Interesting that your ply design is almost identical to to the manufactures rfibre glass one on our Catalac 8 and our windows are 5 mil thick.

 

[C08]

Have you thought about solar panels on the roof? From my experience 5mm polycarbonate windows are a bit floppy so I would go for 6mm perspex as this tends to stay clearer for longer.
I like that you have gone longer at the rear than the original factory sprayhood. I think there is real advantage in being even longer at the rear and giving better protection at the helm.

 

[Neeves]

You need to ensure that the boom can never be lowered such that the boom touches the God Pod. So make the topping lift the correct length.

I built something similar but used 12mm foam, glassed both sides. My windows were 6mm acrylic, the one at the front had a hinge allowing the window to be lifted up, piano hinge (it meant you could have the window open even in the rain). I had flexible solar panels on the roof. Its very easy to make the roof, gently, curved (if you wanted). I embedded 4mm aluminium strip into the design and was then able to tap the aluminium and bolt on hand holds/rails. I made each panel in turn at home, took two panels to the yacht and ensured I had everything correct, glassed each panel in turn, at home. By the time is was finished it was surprisingly heavy and large. But I was not controlled by the weather.

Foam is easy to bend. Cut a piece over size, bend on a flat bit of ply and fit the centre on an appropriately sized batten. Screw down the edges by screwing a batten on either side. Add a layer of glass, when set off the ply will retain the curve you induced. Cut to size.

To get the curve of the deck right

I covered the location of the device with packing tape. Made up filled and viscous resin mix, peanut butter consistency. Plonked the device onto the viscous resin/filler mix and left to set. When set it lifted cleanly off the packing tape (much to my surprise) and I just had to grind back where it had squeezed out. The interface was perfect. I glassed the resin because I had designed the filler to become a flange I could secure with screws into the underlying structure supplemented with Sika.

By having parts curved makes it look original and professional rather than something bought from IKEA. With the curved roof and rounded edges (its easy to grind the curves) - it looked streamlined.

I made a plastic tent in my workshop encasing the god pod. I then spray painted from gaps in the tent meaning I did not contaminate every thing surrounding nor afiixiate myself.

Jonathan



Jonathan

 

[Stemar]

Thanks for all the helpful advice and encouragement!

Catalacs are pretty angular, but I am putting a curve in the roof to add rigidity and match the curve of the top of the windscreen, basically using your technique, Jonathan.

As for solar panels, they'd be too close to the boom for comfort and, in any case, I've made a frame that holds my panels mounted between the backstays.

I like the idea of the plastic tent for spray-painting. It might be the excuse I need to get a spray gun. What paint did you use? Jonathan?