Inspired

There are just too many reasons why a double moth won't work.
cost ie for 2 new identical boats = about £12,000, + extra for combining.
If you go for cheap old boats, then the weight will be more like 2 x 40kg = 80 kg.
Twin rigs are much less efficient than one big rig - maybe only 50 % more drive than single rig.
Single rig would need big mast, sail, crossbeam etc etc = £££ or kgs.
The drag is doubled, but only 150% drive = goes slower.
More righting moment - but only if the windward hull flies out of the water - ie with leeward heel. And we all know how slow leeward heel is in a moth.
The displacement taken by the lee hull is increased by the extra weight added ie 140 kg instead of 100kg.
The hulls are tuned for 100kg displacement, as any fat person, or 2-up sailor will have noticed.
Any extra righting moment and the larger pitch down force resulting has to be balanced by more T foil angle. or different bow shape, = more drag.

For foiling the same applies, but worse - the windward heel ( that gives low drag ) won't work in the cat format, so more than double drag, much less than double force = slow.
Also problems with keeping all the foils under the surface.

If you want a light cat - the A-class would seem to have all the right stuff!

But maybe you could build a (moth)² and prove me wrong!

cost ie for 2 new identical boats = about £12,000, + extra for combining If you go for cheap old boats, then the weight will be more like 2 x 40kg = 80 kg.

I'm only going to be using the bare hulls of older moths, and there's no
way they're gonna weigh 40kg, more like 20kg

Twin rigs are much less efficient than one big rig - maybe only 50 % more drive than single rig.

There was never any plans to use a double rig

Single rig would need big mast, sail, crossbeam etc etc = £££ or kgs.

I have a Cherub rig, part of a 49er rig, and part of an Int.14 rig already.

The drag is doubled, but only 150% drive = goes slower.

True speed isn't the issue, it's the perception of speed. Granted it's never
going to win any races!

More righting moment - but only if the windward hull flies out of the water - ie with leeward heel. And we all know how slow leeward heel is in a moth.

As above

The displacement taken by the lee hull is increased by the extra weight added ie 140 kg instead of 100kg. The hulls are tuned for 100kg displacement, as any fat person, or 2-up sailor will have noticed.

You seem to have forgotten to factor in the dynamic lift from the hull
when moving at speed. ie. windsurf boards

Any extra righting moment and the larger pitch down force resulting has to be balanced by more T foil angle. or different bow shape, = more drag.

The risk of going down the mine is half the fun!

The whole point was:
- it would be great fun to build
- it would be really interesting to see what happened
- a bit of a laugh to sail

Buying a cat just seems to destroy the whole object!

Edited by Strawberry

Isis and shotgun, you seem to have the right idea!

Andy, I'm sure your technically right, but speed isn't the issue here. If I
wanted to go fast I would buy a powerboat!

To quote a convo with Ben Isis:
"if you want to feel like your going fast, get the shortest boat you can lay
your mits on and cram it with rag"

But I may adopt the (moth)² thing

I'm quite up for designing/building a 6ft skiff. They say your 1st design/
build is always crap/overweight. So might aswell get the first crap one out
the way on something not too serious/expensive.

a six foot skiff would be cool but would you put foilers on it?