Converting 9 metre wharram to bridgedeck cabin

[Innes Hutton]

Hello All,

I know this may horrify some of you but I'm thinking of building a bridgedeck and cabin with 6 ft headheight on to  uncompleted 9m wharram hulls. I realise this will affect windward ability but intended use is as a coastal cruiser  and will fit big outboard. Has anybody else done this and what do you think ? Also what would one pay for two old hulls poss 6 to 8 years old (no rigging). 

Thanks

Innes

ps the cabin roof would be attached to the extreme port and starboard sides of the existing

hulls and rise up to 6 feet in the middle - a sort of half circle shape at the stern end and sloping down to a front beam at the bow end.

[Rogerio Martin]

[Shaun]

Eh, not horrified exactly, but being one of the puritanical simplicated barbarically bent types, eh WTF?
It could be done,... anything can be done, but it would cease to be a Wharram, they're not designed for BIG outboard engines, they're designed to be handled and lived with,not bulked up and driven.
These cats are weight sensitive, especially in the pointy bits and changing the weight bias plus the wind affected profile simply changes the design parameters without due regard to the physical dynamics of the boat, not a great combination.
Consider dropping a v8 in a t model ford or Morris minor, outside the design parameters and the physical ability to cope well, it can be done but the beast created may not perform to expectations.
Under nice gentle circumstances, it may well be quite OK, but if Mother Nature springs a surprise and says, alright laddy let's see what you've got, it may be a situation not easily escaped from!
Not saying don't or can't, just suggesting great caution and understanding, it seems the desire and the platform on which to lay that desire don't quite match.
Please take no offence, opinions were asked for and this is just one.
With respect and Cheers,
Shaun

[wakataitea]

why you don't get a houseboat.... ?

for sure, i will be a pretty ugly boat later... have fun living in it... pore James and Hanneke. if they read this, they will probable give up....

[Wolf]

Hi,

this has been done before (i.e. by Steve Turner, a professional builder in the UK). The attached pictures show a Tanenui monocoque: no flexible beamconnections, no longer transportable, 9m long, 6ft headroom in the hulls, a nice double berth and sitting headroom in the central cabin. Certainly not a Wharram anymore, but the owner reports good sailing ability. I think this is the most you could probably do with 9m hulls. But be aware, that example was built by a very experienced professional, who kept a close eye on weight...

How big is the outboard you want to mount? For some (me) 10-15hp would be already big.

Cheers,

Wolf

[Andy Best-Dunkley]

Hi - think VERY carefully before going any further!! First, if you are thinking of buying uncompleted hulls, you should be very careful to check their condition. If they have been standing outside they may have fresh water inside = potential rot. If you buy an old, completed boat, at least you know it works as a whole to some extent! Secondly, to your question, 6ft headroom on the bridge deck on 9m hulls? This means you either will have a caravan sitting on the deck level, or the bottom of the bridgedeck will be only just above water level - neither of these are a good idea IMO! If you really want this type of cat, look for another designer's boat. As mentioned by others above, some Wharrams have been successfully built or converted to having bridge decks, but even these are much lower profile than what you are talking about. If you are considering this type of project, you might save yourself a lot of trouble to build from scratch - Shuttleworth has some designs this size, but they may not be suitable for home-builders.

Good luck anyway!

[Raf]

1.8 meter height cabin the the full length and width of  the hulls? It will not longer be a sailing catamaran. Will look like a humpy and the reselling value will be next to nothing. Might as well build a raft with 44 gallon drums and build a hat on it. Cheaper and will perform just the same way.

[Innes Hutton]

Hey I like this, but I want a bigger cabin.

Rogerio Martin said:

[Innes Hutton]

Raf said:

1.8 meter height cabin the the full length and width of  the hulls? It will not longer be a sailing catamaran. Will look like a humpy and the reselling value will be next to nothing. Might as well build a raft with 44 gallon drums and build a hat on it. Cheaper and will perform just the same way.

LOL liked your comment Not the full length Raf just length of the existing roofs of the hulls.

[Innes Hutton]

Hi Yes your correct it may be quite ugly...

wakataitea said:

why you don't get a houseboat.... ?

for sure, i will be a pretty ugly boat later... have fun living in it... pore James and Hanneke. if they read this, they will probable give up....

[Innes Hutton]

Hi Shaun,

No offence taken mate, and you are correct re windage not intending on adding too much extra weight.

Two layers of 4mm ply/ windows/  also will keep weight down in the hulls. Thinking of two 15hp outboards.

Shaun said:

Eh, not horrified exactly, but being one of the puritanical simplicated barbarically bent types, eh WTF?
It could be done,... anything can be done, but it would cease to be a Wharram, they're not designed for BIG outboard engines, they're designed to be handled and lived with,not bulked up and driven.
These cats are weight sensitive, especially in the pointy bits and changing the weight bias plus the wind affected profile simply changes the design parameters without due regard to the physical dynamics of the boat, not a great combination.
Consider dropping a v8 in a t model ford or Morris minor, outside the design parameters and the physical ability to cope well, it can be done but the beast created may not perform to expectations.
Under nice gentle circumstances, it may well be quite OK, but if Mother Nature springs a surprise and says, alright laddy let's see what you've got, it may be a situation not easily escaped from!
Not saying don't or can't, just suggesting great caution and understanding, it seems the desire and the platform on which to lay that desire don't quite match.
Please take no offence, opinions were asked for and this is just one.
With respect and Cheers,
Shaun

[Innes Hutton]

If we all worried about reselling stuff why would we buy it in the first place. 

Raf said:

1.8 meter height cabin the the full length and width of  the hulls? It will not longer be a sailing catamaran. Will look like a humpy and the reselling value will be next to nothing. Might as well build a raft with 44 gallon drums and build a hat on it. Cheaper and will perform just the same way.

[Innes Hutton]

Andy Best-Dunkley said:

Hi - think VERY carefully before going any further!! First, if you are thinking of buying uncompleted hulls, you should be very careful to check their condition. If they have been standing outside they may have fresh water inside = potential rot. If you buy an old, completed boat, at least you know it works as a whole to some extent! Secondly, to your question, 6ft headroom on the bridge deck on 9m hulls? This means you either will have a caravan sitting on the deck level, or the bottom of the bridgedeck will be only just above water level - neither of these are a good idea IMO! If you really want this type of cat, look for another designer's boat. As mentioned by others above, some Wharrams have been successfully built or converted to having bridge decks, but even these are much lower profile than what you are talking about. If you are considering this type of project, you might save yourself a lot of trouble to build from scratch - Shuttleworth has some designs this size, but they may not be suitable for home-builders.

Good luck anyway!

Hi Andy,

Good point the hulls I looked at are old but seem reasonably well built and rot free. Its going to be a sort of squashed bubble shape on deck . I'm also thinking of building an A-frame rig using fibre glass flagpoles for the masts. I have already chosen another design to build at a later date - this wharram is a kinda fun project. If it does'nt work I can butcher  it back as per purist plan.