Laser cutting.

[Torchy]

Fantastic...you must be very proud

Quack!

[Torchy]

Trouble is that you add a fair bit of work and weight on the shell with all the stitching together and so on.

Stitch with carbon thread like they use to strengthen sails, epoxy inside...then cut off from the outside like they do on Mirror Dinghy.

I think it could be done down to weight but I'm no expert...the 12 foot lugsail dinghy we have has a single line of epoxy on the inside and no tape holding it together (9mm epoxy ply) that I can see. It was pinned (screwed) during construction, then the screws removed prior to finishing off. I think strength is achieved by overlapping the ply.

Our 16 footer is similar (I think) but using thinner ply. I don't see why carbon would be much different

[john_hamilton]

then think of the rig tension used on the osprey and compare it to a cherubs.... and also ospreys don't tend to jump (and subsequently land) off waves hugely often

[Torchy]

I'm no expert but rig tension is in the tubes

Falling off a wave?...Osprey weighs half a tonne and pirouettes quite nicely in a Solent chop

I think it could be done but:
a. Could it be built light?
b. How much would it cost?

The attraction of a kit for DIY duffers like me is major and even I could make a Mirror Dinghy.

[Phil Alderson]

The thing is that building the shell on the mould is not the most expensive or difficult part of a boat. The tricky parts are getting all the ancillary bits on, and getting the strength in the right place, which you would still need to do with a flat pack.

[Andrew Whapshott]

Whatever you buy as a kit will obviously need putting together in some way, surely less parts the better, as there are less things to get wrong.   

If you want to try it, design a simple cherub shape and try and build it using balsa sheet, (you could probably get a Cad program to export all the right shapes for you then laser-cut them?) . 

I've just designed and built a strip-planked balsa model by hand, I can assure you, I would have appreciated a mould!    If the planks were pre-cut they would still be a pig, as they need to be super thin to bend round the shape, which has chines, I only just managed it.  The thought of trying to build a cherub hull from panels like that is not a punishment I would wish on anyone..   

[Torchy]

Yes...it would only work really well (in giving DIY duffers like me a not-too-daunting project) if someone took upon themselves to make a kit with all the bits and instructions...not that likely.

The bow is where the tricky bending is...there's probably a way around this

I think the saving could be £1500 on a boat. I did a 'beer mat' calculation and I think such a boat done entirely DIY would be £6000+ incl sails and all gear ('sticky weekend mast?).

Add £1500 to that and you have the cost of assembling pre-moulded hull and deck and completing yourself = £8k approx

You could sell a kit for £6000+ ex-sails

Might be a business model in this for someone? Not very like maybe but an Arup Skiff kit for £6k??? This might have takers.

[phil_kirk]

We chose to get the hull and deck shell for E-numbers made professionally and do everything else ourselves.  This still involved a lot of work because we had to make, cut and sand and then fit all the other components.

This approach is acheivable by someone with limited initial experience.

It would have been a lot quicker if all the other components had been made and cut to shape.

One way around the hull and deck shell building is to make it with someone who has done the same before using the mould.  if you were determined and with 2 people these two components could be made over 3-4 days.  Over another similar period of time you could make the bulkhead panels, tubes and gantry depending on how that specific boat went together.

The ARUP Skiff concept focusses on reducing the number of components and including reinforcements into the main mouldings.

To put together a method of asisted building as above someone would have to create the templates for the all the other components.  obviously this is of greatest benifit if several boats were going to be built.  A scheme is more possible now that the rules have stabilised and the designs and boat layouts are becoming more similar.

[daryl_wilkinson]

I have just been reading up on some Farr 3.7 build blogs. The thought that I was having was... can you laser cut pre laminated foam/carbon sheets? Anyone got any ideas?

Just in case you were thinking of building a Farr 3.7 with the same techniques as the ply boats that are currently being built, but out of foam / carbon. To avoid the up keep associated with wood boats and make a very light boat. My recommendation would be to build the hull in ply from laser cut ply and the decks (edit: and floor) in foam carbon. This removes most of the wood upkeep issues. Is cheap and reduces the weight of the boat. And as the decks are hand fitted there is no need to get water jet cut carbon foam. It also removes the issue of altering the files  to accommodate the increased skin thickness needed for a foam hull.