light and strong seat base

[jfm]

Personally I'd use an aluminium skin http://www.metals4u.co.uk/aluminium...showvat=true&gclid=CNjE7Of2hbwCFQsCwwodJ34AIw
and egde it with anodised channel to make it look nice http://www.aluminiumwarehouse.co.uk/Aluminium-Silver_Anodized_Channel/c120_133/index.html

But each to their own

The spec called for lightweight. Ally is about 4x the density of plywood, so 2mm ally sheet is 1.5x heavier than 5mm ply for a given area

Quick lookup here http://www.makeitfrom.com/compare-m...0-AlSi10Mg-Die-Cast-Aluminum&B=Bamboo-Plywood

 

[vas]

slight thread drift:

I wonder if I could built a bathing platform from this honeycomb material (and glue teak on top that is )
doing some rough calculations on a proper (a'la MM boat) bathing platform brings up some impressively large weights (all hung at the worst possibly place for a boat designed without a platform at all)

 

[prof pat pending]

The spec called for lightweight. Ally is about 4x the density of plywood, so 2mm ally sheet is 1.5x heavier than 5mm ply for a given area

Quick lookup here http://www.makeitfrom.com/compare-m...0-AlSi10Mg-Die-Cast-Aluminum&B=Bamboo-Plywood

Don't forget the GRP

I could calculate the difference based on type of resin and number of plys, but I spend all day doing that sort of stuff

Oh, and you have the wrong materials in your comparator. I'd imagine marine ply would be the material of choice here

 

[jfm]

Don't forget the GRP

I could calculate the difference based on type of resin and number of plys, but I spend all day doing that sort of stuff

Oh, and you have the wrong materials in your comparator. I'd imagine marine ply would be the material of choice here

There's no GRP in my proposal of a 5-20-5 sandwich with 20x10 battens as the filling. The thing would just be painted or varnished. Nick was suggesting covering it all in GRP; I was discouraging him from it!
I know about the comparator thing. I wasn't suggesting that Nick actually make the thing from bamboo ply (ffs!). The comparator didn't have marine ply in its database but bamboo has a pretty normal density in the world of wood and therefore the result is broadly same as marine ply. I said "about" 4x denser and that is correct

 

[prof pat pending]

Yeah alright mate, no need to swear.

Bamboo is quite light iirc

"about" ... and that is correct

I don't have much experience constructing structures from wood, but I suspect that the weekness in your idea is stiffness, the weight saved in the seat is likely to be gained in the frame.

 

[jimmy_the_builder]

Yeah alright mate, no need to swear.

 

[prof pat pending]

Sorry Bob, didn't realise this was the lounge

 

[PCUK]

The spec called for lightweight. Ally is about 4x the density of plywood, so 2mm ally sheet is 1.5x heavier than 5mm ply for a given area

Quick lookup here http://www.makeitfrom.com/compare-m...0-AlSi10Mg-Die-Cast-Aluminum&B=Bamboo-Plywood

An ali' frame - not sheets of it for fecks sake.

 

[prof pat pending]

An ali' frame - not sheets of it for fecks sake.

To be fair, I spec'd sheets

 

[jfm]

To be fair, I spec'd sheets

. This is hilarious Prof! Best wishes

 

[prof pat pending]

 

[Nick_H]

If anyone was following this, I spoke to a very helpful company called easycomposites about the aluminium honeycomb for this application, and they reccomended a PVC closed cell foam instead. Similar weight, similar strength, but easier to work with. They think 25mm foam + 1.5mm GRP each side will be plenty strong enough.

http://www.easycomposites.co.uk/products/core-materials/EasyCell75-Closed-Cell-PVC-Foam-Core.aspx

 

[Assassin]

Closed ce3ll foam, carbon fibre and epoxy resin laminate, easy to make, incredibly strong, and totally waterproof unlike GRP.

If you can work with GRP you can work with carbon fibre.

 

[jfm]

Thanks Nick. Good to know, and all logged for future projects

 

[prof pat pending]

and totally waterproof unlike GRP.

That really depends on the resin system used, and the foams can be quite heavy compared to honeycomb

 

[Assassin]

Clearly states epoxy and not polyester resin.

 

[prof pat pending]

You can use epoxy on GRP, so why go to the extra expense of CFRP unless you intend to have a black seat base and want the bling