CNC Plans not Included

Seems like you'd need two hoist systems, not big problem. The tender cant remain on the platform as it swings down. Of course, I could be failing to see your idea in full.
Question. How wide is the clear space under the transom and what is length of the tender?

 

Yeah, the tender would be under the platform actually. So you would drop it till the boat hits, release the davit drops and then lower it the rest of the way to act as a swim platform, not very elegant.

The other way, I think might work. You just lower - by cable - one big platform. Then you don't need swinging davits to accommodate different sized tenders. The platform would have to be stayed to keep it from swinging back and forth but that is not a big deal. If you plan on scuba diving, I would load the tanks on the platform first. If I went that route I would remove the sidewalls on the transom steps so you could just use those to get back up.

On my boat the platform would be 20' long. Good for a couple of lounges and an umbrella )) ... here is where those super lightweight carbon trusses would come in handy )) ... however there would be other issues such as the darn cable being in the way etc...

I am going to keep browsing and see who has the nicest solution. Fountain Pajot solution ... I guess they put the tender on the roof?

 

Something that looks like this?

 

That is what I was thinking at first. How would you do that while keeping it light? I couldn't figure out the lines

Meanwhile I went further on my simple hoisted platform. The wings on the end could be a tank rack. Makes it easier and safer to place the tanks on the platform in the up position while leaning against the rear bulkhead. There is about 6 foot 3 inches of headroom. Maximum tender width would be 5 feet.

 

We provide CAD files, also for our stock designs: Launched Boats and Catamarans Designed by AM Design, Thailand http://amdesign.co.th/Stock_designs.html

 

I'l have a look Alik.

 

jorge, please, keep the tanks in the middle of platform since the main strength should be to support the tender
loading one end heavily is not good. Anything is possible, but efficient?

 

I think that would work once when going down. As soon as you reverse direction on the arm and then try to lift, it's going to bind.

I could move the lines closer to center but 4 lines and a truss platform would be pretty robust. I could put the tanks in the tender actually, just make a hatch in the top platform, that would let me make a smaller platform but I think the idea was to be able to access the steps as well.

it's just under 14' span between lines. Once up it could be locked in place.

 

Too busy for graphics but you want scuba racks. Good, as these will need to be strongly constructed.
They sit between the tender and the aft beam and their tops take the pivots for a pair of parallelogram arms that
keep the platform level as it swings. Binding can be avoided by moving the top hoist point aft slightly.

 

Not scuba racks for storage, they are way too out in the open back there. Just a good way to lower them down instead of carrying down the steps.

I have the helm up front next to galley, would it be better as an elevated helm aft center. Trying to omit that long run of steering and get better view of sails though I doubt anyone would be at the helm for most the time. Seems like you could still get a decent view of what's around you under the sails.

 

to secure the bottles as you lower the platform I think you would still need some robust rack system.
Here is one image. The platform has been lowered by about 10 degrees just so the arms are clear.
The lift lines attached to the main strength beam that carries the tender. This centers the load and balances the platform so loads on the arms are lower.
One problem is that get enough "drop" to reach the water the platform basically is flush with the top of the aft beam.
Steering by wired remote from the fwd station and all the hydraulics and emergency manual steering kept aft?
With the price of HQ video cameras/systems falling you could provide any station you want with good views.
Ah, rotating masts means you'll need mounting systems for radar, GPS etc.

 

Where will you sheet the sails from, ie control and trim the sails?

 

UOS that system might work. Want to see how high that puts the tender on my design, though it might be strapped to the bottom. I think radar etc... would have to be off the rear of roof.

To control sails, it seems there needs to be a line run down the sides of the roof in which case it could lead back to the position I highlighted.

 

Good idea. slinging the tender under the platform means the lifting points can directly fall in line with the loads and the tender can launched with the platform up.
Much much lighter platform seems possible.

 

If the benefits exist (and you agree they do), then surely a production company would build one and charge accordingly? People will pay way over the odds for anything they think will give them an edge in "performance and ease of use, safety etc". That no production company offers these obvious advantages implies that there is more to it than simply cost.
Perhaps when you cost your boat, record the cost and time to do everything associated with the stayed rig. We can then work out the cost of doing it unstayed and compare.

Why have a line across the bow? The "entire crew" would be what? 8 people ? They could easily fit on 2 triangular tramps with a gap in the middle for the anchor. ie, the support lines go from the bow to next to the anchor roller on the front of the bridge deck, which from weight, ease of access, safety and communication with the helm points of view is the sensible place to put it with a bridle from the bows.. A bit of sag in the tramp makes it more comfortable to lie on and the view while sailing is better than leaning over a forebeam. Holding a rig up with strings, but putting a 50 kg + forebeam plus anchor and chain on the bow to support a tramp seems a bit illogical.

The logical way to hit the beach is stern first so you can pull yourself off with the anchor, the bows meet any waves and access is up the stern steps into the cockpit rather than around the cabin. If you do need beach access from the bow, use the gangplank, rather than the heavy structure required to support a forestay and prodder.

One other thing to think about.
If you have a biplane rig do you agree that both masts have to be strong enough to capsize the boat?
And that if you are hit by a squall and dump one sail, can't be stuffed hoisting them both or something breaks on one of them the boat will sail perfectly well on one rig, the same way a daggerboard boat will sail equally well with either board down?
If so, why not make one mast higher and the boom longer and dump the other one with all it's cost, weight and space?