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TheThunderbird · 16-02-2016, 15:49

I examined several Jongert designs over the last four decades, noticing that the transom or lazarette are getting larger, unobstructed, recreational, also giving better protection to the helm position, not any longer placed two foot away from stern ( if Mr.C.Archer allows..).

Jongerts, originally pure centerboard motorsailers, may have pioneered the concept, also adopted to a measure by the Swans in the last decade, as Wally Yachts first dictated the "sleek" lineage ,(that which I deeply dislike, BTW).
Beyond the 60' LOA, a large stern platform, maybe stowing water toys or other, is a given now.
...
Well...

I reasoned whether it could make sense , any change in That direction, on a more traditional design like the one I am using (a S&S-derived design from the mid 80s).

The artifact would be a continuum with present bulkhead/hull lines, some 6-8 foot long (for a Nauta54'), with a flush deck and water tight portholes with the closing from outside, sub-like.
No structural function for Rigging or sheeting would interfere on that add-on, structurally-wise, apart for the mooring lines, and maybe a fixed stern anchor line.

Advantages?
1. Extra space, on deck, and for stowage,
2. Extra buoyancy, if/when needed
3. Additional water-tight bulkhead
4. Possibly, the artifact can be made unsinkable (double layer with closed foam inside)
5. Remarkably, unobstructed Solar panels, and a rigid Dinghy, are the most valuable pros upon deck (plus sun-bathing beauties..).

Transoms nowadays are the most looked after section of any boat, bar a deck saloon...

Cons ?
1. Cost ☺
2. Any implications with papers and insurance !?!? I have no idea...
3. Finding the right execution (yard!)

Conceptual Structure

The U shape of the stern section would be matched with a Vented Flange trimmed (by welding) along the bulkheads, being fixed with alternate high-tensile ss bolts acting on inner counter-plates of similar size and thickness.
Where available, the longitudinal ribs or any reinforcing plates already in place could be equally matched and engaged.
Structure would be after glued with fibers and modelled externally for smooth seamless appearance.

The artifact would remain substantially Above the floating line, as being a Sugar-scope indeed (yet closed on deck), with no extra drag, Yet..providing

1. Longer lines when heeling, adding to floating and to Critical Speed
2. Extra buoyancy with high seas from stern
3. Possibly, less hiving (if weight is kept low).

Concern... Which Material??
1. SS AISI 304 for flanges, ribs, maybe bulkhead sheets too?
2. Expensive, and difficult to weld (?) ERGAL (aeronautic.. Structural Alu) ..ensuing complication in corrosion control...afterwards
3. Carbon fibers!? I feel ignorant on matter, structural design seems to be largely empirical to me....
4. GRP built around a SS, or ERGAL backbone!?

At present, my helm is less than 3' off the edge of deck, and my stowage area is my major concern/criticism about an otherwise splendid design.

Nauta had already designed a longer scoop for racing purposes.... and if i well remember... The immortal Sir Francis Chichister stopped in NZ to get a longer bow line
I am just stretching the concept for an equally noble project.

TheThunderbird · 16-02-2016, 16:36

I find it unhelpful that the draconian limit of 30' for editing may apply to the very first post. Reason dictates differently...

Thus, please, let me integrate:

Errata corrige: Sir Francis Chichester ! He changed the hull design to increase the bow grip on the short waves he faced

IF the add-on is not much weighted up (consider a light inflatable, or a little skiff, fenders, ropes, deck pillows, wintertime's duvets...) Overall the boat will result even more mid-centered than originally aimed for, only with positive results

Execution and material must respect the present make. Maybe carbon fiber could involve heat processes not applicable on a dry boat... (Wild guess..)

The boat I sail on, originally rated at 20tonnes, is now 27tonnes with wet tanks and a torpedo ballast (say 3+tonnes added by the Jezequel design team). Thus, some longer body would not harm, by improving the displacement ratio, and the length/beam ratio.

Boats had fine, well tapered lines, before bubbling up after the full-beam stern sections of the " surfing generation "

Orion Jim · 16-02-2016, 17:51

A qualified naval architect would have to design the "artifact" while taking into account the stress the "artifact" would place upon an existing hull structure for which no consideration had been originally factored. You might, at the very least, require a rudder modification and adjacent hull strengthening. It might just make sense, in the long run, to purchase a more suitable boat. Professional architectural design services and qualified builders are very expensive commodities.

UNCIVILIZED · 16-02-2016, 18:19

Firstly, use language below the Porofessorial, English major level. And Secondly, compose your post using MS Word, or similar, & then do a smiple cut & paste.

I'd have been happy to help, but couldn't concieve of what you're really trying to say, other than that you want a boat extension.
Which, sans Naval Architect involvement, isn't wise. But it's something which Nautor has done plenty of times in the past.

cruisersfarm · 16-02-2016, 18:30

The "artifact" (addition) will add weight astern without any change of the hull shape to compensate for this additional weight.

This means the boat will definitely squat to a degree if the addition follows the fairness of the hull, acting as a new, extended transom.

Putting toys in the new transom locker will make this more pronounced.

As to the choice of materials to do a stern extension, it matters first what your hull is made out of. It's usually best to stick with the same material.

Lizzy Belle · 16-02-2016, 18:40

Quote:

Originally Posted by TheThunderbird

The artifact would be a continuum with present bulkhead/hull lines

Either 'artifact' has a meaning in English I am unaware of or you want to add a few feet to your hull using an actual artifact?
Or you used the word artifact wrong and made your post (even more) confusing

Pls consider posting a TL;DR version of what exactly it is your wanting?

TheThunderbird · 16-02-2016, 19:42

Artifact is a combination of two Latin words, arte, meaning "by skill" and factum which means "to make."

Intuitively, I suggest it being a carefully designed, stress-checked, and properly executed piece of manufacturing, mostly made up by hands, by a craftsman.

Therefore, "artifact" conveys the meaning of something thought after and manually put in place, surely not the application of the remain of any old and forlorn ship from a dilapidated yard.

That said..
1. I expect the boat to tilt a bit upwards, adding up 2 to 3% of actual displacement {good downwind) and actually less than Half of my tanks content...
2. Apart from its very weight and some upward push due to floating (i.e.a few tons) there is no structural stress from ballast or rigging (tens of tons, which is a different magnitude)

Of course, calculation is required. I remind anyone that long masts (beyond 60') are made up of two pieces joined together, and that is an area of stronger stiffness indeed.

The profile below water and the centers of push/reaction remain the same,... So, I don't expect any change in rudder/ballast shape, or adverse change in the directional stability under sail.

My concern rests with the material of choice. Adding GRP to GRP may work well for finishing on surface, but not for structural rigidity and stress distribution

Nauta54' is built by Nauta (italy) which is not Nautor Oy (Finland) maker of the Swan line

socaldmax · 16-02-2016, 20:03

How about buying a bigger boat?

TheThunderbird · 16-02-2016, 20:39

Quote:

Originally Posted by socaldmax

How about buying a bigger boat?

I asked it myself

I need more stowage, not a 900sqft Mainsail instead of a 700sqft one, nor a larger engine...

Commercial ships in steel are easily cut out and made longer...
Yards usually upgrades models simply stretching appendixes.
Nauta has designed a longer Sugar-scope for this model, though for a minor purpose.

I truly believe that an ingenious design can outperform the costs when compared to other options.
I laid out 80sqm of insulation on this boat... I nail to it ��

Note: in changing ordinary specs, laymen tend to think of things as Fixed, Untouchable, the way they must be.

Herreshoff designed and calculated by intuition , experience and hand drawing.... In real life I have seen America's Cup gurus proceed by intuition, gut feeling, test&try.
As example, radiators, carburettors, carters of engines are Not designed, but built up, prototyped, and tested....

Again, my sole concern is about materials of choice, and suggestions about better than standard execution. Thanks

**atoll** · 16-02-2016, 21:17

if steel,a better bet would be to cut the boat in half in the middle,and add your exstention there

TheThunderbird · 16-02-2016, 21:36

This way, even an atoll can become an island! ��

Indeed, that's the way they do. By having the most of it under waterline, flexional rigidity is not compromised.
Any super-tanker on dry would collapse...

**atoll** · 16-02-2016, 22:00

Quote:

Originally Posted by TheThunderbird

This way, even an atoll can become an island! ��

Indeed, that's the way they do. By having the most of it under waterline, flexional rigidity is not compromised.
Any super-tanker on dry would collapse...

I have a friend that did this with his 50 footer to convert it to a fishing vessel,he added 25 feet in the center which became a freezer compartment,the front section became the crew quarters.

the aft section became the galley and his quarters.
he also added a second larger engine with the 2nd prop shaft running under the existing shaft!
extra fuel water and ballast were built into the extention.

he also added a second longer mast forward and moved the old mast aft!

Celestialsailor · 16-02-2016, 22:52

Sorry...but I have to wonder...who the hell are you trying to impress?

svGenesis · 16-02-2016, 23:40

Just buy a plywood size piece of 1/2" thick pvc and a few door hinges, mount on the aft of your boat about a foot above the waterline fold it up when under sail, fold it down when anchored!