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Old 05-02-2008, 15:58   #1
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New Bi-Rig Performance Cruiser

I have been working on a new design for a 47 ft performance cruiser, that ticked as many of my specified boxes as possible. Beam is 8,20 m/27 ft. Beam centreline is 6.3 m/20'8". Max hull beam is 98 cm/3'2". This gives around 1:13.5 beam/length ratio
I have chosen to use 2 unstayed masts that can rotate 360 degrees. Masts are 19 meters (62 ft) off the waterline and will be teardrop shaped profiles with a chord of 10% of the mast/sail length. Sail area on each mast around 62 m2 and each mast around 5 m2. Gennaker on the lee side for light winds. No forward beam. Mainsail sheets can be released/adjusted from either cockpit.
Displacement for lightship is around 7 tons, with a 3 ton load. Fully loaded bridgedeck clearance is 100 cm (39") lightship is 15cm/6" higher.
Draught is 52cm/20" lightship. 2 asymmetric daggerboards.
Forward cockpit with steering, also steering from the aft cockpit and maybe steering from the saloon, otherwise via autopilot.
Construction will be corecell/epoxy vacuum bagged, with kevlar on the inside to about 1m/3' above the waterline.
Aft bimini folds into the targa, fwd bimini and a dodger fold into a recess in the fwd cockpit/deck area.
Despite all the hype for diesel electric propulsion, I have chosen 2 40hp Yanmars with the new 3/6 kVA generators on the flywheel. 700 Watts of solar panels on the coachroof.
The "eyebrow" over the saloon windows is to cut down on heat, and is a separate mould that is attached to the actual roof, with a 50 mm gap, so airflow can cool the windows. The recess on the eyebrow also functions as a handhold.
All winches are recessed to minimise windage, and ensure straight line runs.
Layout is 2 aft doubles with acess to the bunks from 2 sides. I double fwd in port hull, as well as separate shower and toilet. Stbd is the owner side,so a large bathroom fwd, and a workshop area midships.
Nav station is forward facing in the saloon, stbd side. All tanks are midships under the soles. Each hull has 3 waterproof bulkheads, as well as 8 contained spaces under the midships sections. 2 watertanks each side, so water can be pumped aft/fwd or side to side for trimming. Engine rooms fully separated from the accomodation.
The forward 4metre/13' section of each hull is foam filled to about 60cm/2' above the waterline. The area above is for stowing fenders and sails only.

I would much appreciate comments and ideas from the great pool of knowledge here, as I am reaching the final design stages, and expect to start building within a few months.
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Old 05-02-2008, 17:29   #2
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I think it looks great!! I am not a boat builder so I can't really give you exact schematics for anything, but as a 3rd party observer, I love it so far!!

Keep us posted and what is the price range and possible first fully functioning demo be available??
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Old 05-02-2008, 18:15   #3
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Wow! Whos says cats aren't beautifull. I particularly like the dual cockpit/steering stations and the large galley with forward facing dinette and nav station. I would love to see drawing with the rig included. Congratulations!

Mike
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Old 05-02-2008, 18:19   #4
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Hi Mike,

I haven't got a full rendering with the rig, but attached is a preliminary sketch

Alan
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Old 05-02-2008, 18:42   #5
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Quote:
Originally Posted by Nordic cat View Post
I have been working on a new design for a 47 ft performance cruiser, that ticked as many of my specified boxes as possible. Beam is 8,20 m/27 ft. Beam centreline is 6.3 m/20'8". Max hull beam is 98 cm/3'2". This gives around 1:13.5 beam/length ratio
I have chosen to use 2 unstayed masts that can rotate 360 degrees. Masts are 19 meters (62 ft) off the waterline and will be teardrop shaped profiles with a chord of 10% of the mast/sail length. Sail area on each mast around 62 m2 and each mast around 5 m2. Gennaker on the lee side for light winds. No forward beam. Mainsail sheets can be released/adjusted from either cockpit.
Displacement for lightship is around 7 tons, with a 3 ton load. Fully loaded bridgedeck clearance is 100 cm (39") lightship is 15cm/6" higher.
Draught is 52cm/20" lightship. 2 asymmetric daggerboards.
Forward cockpit with steering, also steering from the aft cockpit and maybe steering from the saloon, otherwise via autopilot.
Construction will be corecell/epoxy vacuum bagged, with kevlar on the inside to about 1m/3' above the waterline.
Aft bimini folds into the targa, fwd bimini and a dodger fold into a recess in the fwd cockpit/deck area.
Despite all the hype for diesel electric propulsion, I have chosen 2 40hp Yanmars with the new 3/6 kVA generators on the flywheel. 700 Watts of solar panels on the coachroof.
The "eyebrow" over the saloon windows is to cut down on heat, and is a separate mould that is attached to the actual roof, with a 50 mm gap, so airflow can cool the windows. The recess on the eyebrow also functions as a handhold.
All winches are recessed to minimise windage, and ensure straight line runs.
Layout is 2 aft doubles with acess to the bunks from 2 sides. I double fwd in port hull, as well as separate shower and toilet. Stbd is the owner side,so a large bathroom fwd, and a workshop area midships.
Nav station is forward facing in the saloon, stbd side. All tanks are midships under the soles. Each hull has 3 waterproof bulkheads, as well as 8 contained spaces under the midships sections. 2 watertanks each side, so water can be pumped aft/fwd or side to side for trimming. Engine rooms fully separated from the accomodation.
The forward 4metre/13' section of each hull is foam filled to about 60cm/2' above the waterline. The area above is for stowing fenders and sails only.

I would much appreciate comments and ideas from the great pool of knowledge here, as I am reaching the final design stages, and expect to start building within a few months.
That will be a georgeous boat. Curious about where you will step the masts and how you'll engineer the lateral loads. I'm guessing you have to step them in the bottom of each hull in the plane of the main forward bridgedeck bulkhead. I assume they will be composite?

Just some first reactions:

The room being taken up by the forward helm area makes the bows look shorter than they want to be. Holding this thought for a moment, the sterns look a bit short creating shorter extensions and a steeper set of steps. So, I wanna say the length look like it "wants" to be extended at both ends.

"Gennaker on the lee side for light winds." I can't picture what you mean by this.

"All winches are recessed to minimise windage..." Splitting hairs here? Winches probably contribute minimally to windage. Don't put them where they can't be easily used. Electric for the main halyards?

"2 watertanks each side, so water can be pumped aft/fwd or side to side for trimming." Splitting hairs again? Is this a cruising boat or a racing boat? Unless the tanks are really large, I suggest you keep it simple. Install a single, smaller tank on each side and give 'em a watermaker.

I've never sailed a Chris White or Gunboat so I may not appreciate forward cockpits. Perhaps you need it for the dual rig? Otherwise, this may not be worth the extra weight and expense. I hear they're wet going to weather.

Good luck - it looks beautiful so far!

Dave
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Old 06-02-2008, 02:19   #6
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Great looking design I love it a lot, but I do agree with 2hulls on some of his comments. Also without the forward crossbeam, wont it be difficult to have any form of trampoline with decent tension ( I understand that maybe you dont want a trampoline) but as a cruiser having that extra area up forward for relaxing etc is I think very important, mind you that's only my opinion. Looking forward to seeing one built.
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Old 06-02-2008, 03:01   #7
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Originally Posted by 2Hulls View Post
That will be a georgeous boat. Curious about where you will step the masts and how you'll engineer the lateral loads. I'm guessing you have to step them in the bottom of each hull in the plane of the main forward bridgedeck bulkhead. I assume they will be composite?


Just some first reactions:

The room being taken up by the forward helm area makes the bows look shorter than they want to be. Holding this thought for a moment, the sterns look a bit short creating shorter extensions and a steeper set of steps. So, I wanna say the length look like it "wants" to be extended at both ends.

"Gennaker on the lee side for light winds." I can't picture what you mean by this.

"All winches are recessed to minimise windage..." Splitting hairs here? Winches probably contribute minimally to windage. Don't put them where they can't be easily used. Electric for the main halyards?

"2 watertanks each side, so water can be pumped aft/fwd or side to side for trimming." Splitting hairs again? Is this a cruising boat or a racing boat? Unless the tanks are really large, I suggest you keep it simple. Install a single, smaller tank on each side and give 'em a watermaker.

I've never sailed a Chris White or Gunboat so I may not appreciate forward cockpits. Perhaps you need it for the dual rig? Otherwise, this may not be worth the extra weight and expense. I hear they're wet going to weather.

Good luck - it looks beautiful so far!

Dave
The masts will be up against the forward bulkhead - slightly further forward than on my sketch. The lateral loads are easy to define and engineer for. The masts will be carbon fibre and engineered to flex about a metre in 25 knots, to dump power in gusts.

The bow length also looks shorter, due to the "flat platform" at the rear of the tramp, this is designed to give a nice stable surface to stand on when acessing the hatches there, also a place to sit. The extended area in the corners is to minimise spray, as well as to cover a hatch on each side in the hulls. This will provide rain protection when anchored, enabling good ventilation through the hulls.
I have decided to make the transom steps in 2 segments, with a nice large platform to stand on between them. This platform is for fishing, working on the dinghy/handling the outboard, as well as acess to the aft cockpit. It will also be used as a platform to tie the dinghy to, so it doesn't hang in the davits that are recessed into the targa. There will be a couple of pipes under tyhe brisgedeck that extend oot to support the dinghy, so the windage from the dinghy is also eliminated.
I am considering extending the transom by a couple of feet, but will wait to see the results of the hull resistance calculations in different trim modes/speeds.

"Gennaker on the lee side for light winds." I can't picture what you mean by this.

There will be provision for a masthead furling gennaker/Code 0 type sail that can be attached to the bow. For downwind work I expect to use a Kitesail attached to the decks. I have used one for 3 years on my curent boat, and its great if used correctly.

All winches are recessed to minimise windage..." Splitting hairs here? Ergonomics are key here, but by recessing them a bit, I can get a straighter run to the winch drum. Main halyards will be run to an electric winch.

2 watertanks each side

The main reason for smaller tanks is to enable cleaning through a smaller opening, otherwise I need several openings in each tank or a large opening that is heavy and difficult to seal. Once rigged, pumping around is simple, and can offer advantages in trimming the boat. There will be a watermaker, so will probaly only use 2 of the tanks at a given time.

The gunboat has more of a "workpit", and is deeper than mine, the Chris White designs have more of a "monohullstyle" cockpit with a longer/narrower shape. Yes, I have heard they can be wet, but then I can just go to the aft steering position, or go inside. I reckon that on a nice hot day in the tropics, or at anchor, the forward cockpit will offer the coolest place on the boat.

Thanks for the encouragement!

Alan
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Old 06-02-2008, 03:05   #8
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Great looking design I love it a lot, but I do agree with 2hulls on some of his comments. Also without the forward crossbeam, wont it be difficult to have any form of trampoline with decent tension ( I understand that maybe you dont want a trampoline) but as a cruiser having that extra area up forward for relaxing etc is I think very important, mind you that's only my opinion. Looking forward to seeing one built.
There will be a trampoline with a wire across the front. The tramp will be of spectra, so non stretch. I don't think tension will be a problem. The bows will be very stiff from side to side to handle anchor bridle loads and para anchor loads. No crossbeam saves nearly 200 kgs/ 440 lbs out at the ends.

Alan
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Old 06-02-2008, 03:09   #9
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Unique, and not unattractive lines.
Why so many steering stations?
You seem to be cramming a lot of accommodation into a couple of 3'2" hulls. Id be interested to see the layout drawing.
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Old 06-02-2008, 03:23   #10
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Unique, and not unattractive lines.
Why so many steering stations?
You seem to be cramming a lot of accommodation into a couple of 3'2" hulls. Id be interested to see the layout drawing.
The layout is not yet fully drawn up in CAD - I work on paper and have a guy do it in CAD, otherwise I would still be learning to use CAD efficiently.

Each steering station has a certain set of conditions where it is best. Forward cockpit is great until the spray starts coming, then move aft. In lousy weather, inside is best, as there is a window in the coackroof to see both sails from the inside helm. Aft helm is best for docking so you can see all 4 corners.

The drawing below gives you an idea of the asymmetric hulls. The bridgedeck/hull join will of course be rounded, the "triangular" section created, will be used for conduit runs, as I will be using a bus based electrical system, that will save me alot of cabling and weight.
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Old 06-02-2008, 07:17   #11
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Alan, Thanks for answering my question, I thought you would have the appropriate answer, keep us all posted on this. Thanks
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Old 06-02-2008, 10:38   #12
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Looks like bi-plane rigs are in vogue in 2008!
I think they make a lot of sense in many ways. However, they do seem to obviate the need for a forward cockpit. This design still requires a 'climb' to the aft helm station. Mainecat and Gunboat keep the bridgedeck accom. and helm on a single level. This is a more important feature than is given credit for.

Lose the fwd cockpit, it's a fad, not an enduring feature. Especially so, as you simplify the rig into a bi type rig. Additionally, multiple steering stations are expensive and complex. The fwd cockpit takes up potential ability to, if not outright increase more accommodations etc, it will enable more 'loosened' up dimensions on the current layout. I also suspect that owners will tend to favor one station over another and will use the other more infrequently than the space/complication equation justifies.
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Old 06-02-2008, 12:13   #13
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Looks like bi-plane rigs are in vogue in 2008!
I think they make a lot of sense in many ways. However, they do seem to obviate the need for a forward cockpit. This design still requires a 'climb' to the aft helm station. Mainecat and Gunboat keep the bridgedeck accom. and helm on a single level. This is a more important feature than is given credit for.

Lose the fwd cockpit, it's a fad, not an enduring feature. Especially so, as you simplify the rig into a bi type rig. Additionally, multiple steering stations are expensive and complex. The fwd cockpit takes up potential ability to, if not outright increase more accommodations etc, it will enable more 'loosened' up dimensions on the current layout. I also suspect that owners will tend to favor one station over another and will use the other more infrequently than the space/complication equation justifies.
Thanks for the comments, I agree with the idea of having the helms at the same level as the bridgedeck accomodation where possible, but boat design is the art of attempting to master compromise
The saloon and cockpits are all on the same level, so the inside and fwd helm are on the same level. The aft helm is 2 steps up. Gives redundancy as each of the outside helms run to their own quadrant, with a rod between the 2 rudders. Anything happens to one, I can just disconnect it and continue.

The forward cockpit, in its true sense is at present only offered by Chris White as far as I know. Whether it is a fad or not, only time will tell, alot of fads have come to stay - like multihulls, flat top mains, unstayed masts, chartplotters etc. It does limit accomodations a bit, but I hate bunks on the bridgedeck, they are only any good at anchor or in harbour, even with more than 3 feet of bridgedeck clearance, the odd wave is sure to hit, and at least disrupt your beauty sleep.

Having 2 really nice aft cabins, and a smaller forward cabin on a 47 foot boat clearly signals that this is not a condomoran. Stringent weight saving and weight control, without compromising strength, as well as meeting CE regulations, that adds unneccesary weight without the strength, will have the boat at around 6 tons, start adding luxuries we get up to over 7. (this is for light ship, i.e. all equipment onboard including safety equipment, but no liquids and personal items). This is a performance cruiser, if I define the weight like most marketing people do, then I could bring it down below 6 tons, let everything else be an option. Small standard engines, minimum safety equipment, minimum instrumentation, thin matresses, no solar panels, no water cooling of the refrigeration - lots of stuff to make it look good!
I have chosen to design top down,i.e. starting with a really luxurious fitout, and then remove what I don't want, instead of the normal way, which always leads to an overloaded and under performing boat. But with this approach I hope to be able sell a few boats, to the kind of people who would love a Gunboat but are sensible enough to look for better value for money. I also think the boat looks nicer than a Gunboat - but now we are getting subjective methinks...

Regards

Alan
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Old 06-02-2008, 13:16   #14
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Is it just my failing eyes (not sarcastic, they are), or is there no appreciable seating/lounging space in the cockpit?

One shouldn't discount features, only useful at anchor - most cruisers spend 3/4 of their time there.
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Old 06-02-2008, 13:42   #15
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Is it just my failing eyes (not sarcastic, they are), or is there no appreciable seating/lounging space in the cockpit?

One shouldn't discount features, only useful at anchor - most cruisers spend 3/4 of their time there.
Thanks for the comment Gord, this is an issue that is not finally sorted, but I have used the cockpit of my 35' cat as a yardstick, I don't want to have a cockpit for 15 people, they are terrible to cross in bad weather as they normall lack handholds, and are downright dangerous
The forward cockpit benches are 120 x 160 cms or 4' x 5'3" each, the side stairs design will be changed to a more open, givein an extra 30 cm/1' to the 120 cms in the for/aft direction

The aft cockpit bench is 150 x 400 cms or 5' x 13', there is plenty of room on the aft sidedecks for sunbathing...

The saloon has a 200 x 200 cm sette, or 6'6" x 6'6".

I am enclosing an slightly clearer rendering I hope...

Anchoring time is probably even higher on average, I know mine is..

Regards

Alan
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