edgeau wrote:Mate, just a heads up on your radius. I had a 600mm on the front of mine and 6mm marine ply only just bent around it with a few stress cracks I had to sand back. That said I also had 480 for a portion of the hatch and that worked OK. If you can source 4mm that would be better.
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Thanks mate. Making the decision on the radius has been a major impediment to my progress. I read about your adventure with surface checking, and it gave me pause.
My local choices are 4mm marine ply or 2.7mm luaun ply.
The 2.7mm luaun ply is so flexible (local joint uses the alternative spelling) but is "interior bond" so a bit unappealing.
The 4mm was recommended by a local bloke who built a beautiful semi-displacement boat that he used for commercial fishing.
He followed that with a replica of a 1950's model bondwood caravan to tow behind his restored FJ Holden.
He's a control room operator at work, and when I got seconded over to his plant to assist with the metallurgy for a while, we found time for a decent discussion one quiet-ish night shift.
Anyway, he reckoned 4mm marine ply is plenty strong enough to clad a tear drop and bends OK.
I looked it over at the store, and I could pick up the top sheet and flex the full 8 feet sheet a little just by hand, hanging onto the long edge. This made me think it doable.
The Benroy drawings show a 19 inch front radius, 600mm is a touch over 23.5inches. So I said bugger it, time to "piss or get off the pot".
I calculated that, if you wanted to leave 25mm at each end of the curve for fastening the sheet, max radius is 732 mm.
If I absolutely have to, I'll put little tiny kerfs through the surface veneer on the inside of the curve. That can be hidden and will effectively turn it into 3mm 2 ply. I have a pointed bit that will fit one of the routers, and I could easily set it for say 1mm, if soaking the sheets in hot water doesn't do the business. Of course at 600mm radius, and say 10mm spacing, it'd be something like 90 cuts.
I was feeling a little hang dog about all this. Clearly, materials selection is very important, freight cost is a killer here in South Oz, and choices are limited.
Then I thought of the words of a previous General Manager when he was asking me to go sort out a an area that had been left with no technical support for years, and was looking somewhat disorganised. "I know I'm giving you an elephant and a spoon, Michael. Just a spoonful at a time, mate, you'll be right."
