Tender garages

If you imagine the entire vessel from the side as one flat plane, the size of the door is relatively small, probably not much bigger than the gear door, or a couple of access panels on the underside of the wing of a Mooney M20. There are also multiple parallel layers on that plane that do not have corresponding holes.

Darn, it's tough trying to explain some things without having an analogue inscription instrument (pencil) and paper

Actually the LG doors was an excellent example. Hadn't thought of that one. Another would be bomb bay doors. Is this thread drifting yet?

Kelly

Drifting...Not really The engineering and how these vessels are put together are valid points of interest.
Does my attempt at an explanation of the structural integrity answer your concern?

I am not a structural engineer at all,

but forget about the doors offering any structural support, open or closed. Best they can and will offer is watertight fit and at that I am sure a certain about of leakage is factored in. Telling me that when the doors are closed they offer an increase in haul support is like telling me if I use a thicker glass in the windows of my home I can use a smaller header beam.

The first time you would rely on that door for support will be the last time it ever gets opened.

Just my take on it, maybe I am wrong.

Cheers all

Codger, I do understand you explanation (my father was an Air Force pilot). However I don't think the aircraft analogy "flies" in a hull design problem. The loads and environments are to different, in my view. So we will have to just agree to disagree.

Kelly

I can't think of a problem that a Garage door would pose, after all this is not a new idea, and it's been well thought out and no doubt perfected by naval architects the world over. Here is a site that is not case specific, but gives one an overview nevertheless...
http://en.wikipedia.org/wiki/Strength_of_ships

wannabeeYhtsman is right.

The side hatches don't contribute to the longitudinal strenght of the boat. It would be different if they were bolted every 10 cm or so, but that would be rather unpractical when you want to open the door . There are just a few locking pins to keep the door in place, but they don't connect the side shell to the door plating.

However, the area where these hatches are located is not very stressed (it's in the middle of the "beam" near the neutral axis, not at the top or the bottom). The builder or N.A. would also carry out a proper study (Finite Element Analysis) to make sure they don't impair the structural integrity. So I wouldn't be concerned about that.

Waves rolling in could be a concern, but these tender garages are seperated from the rest from the boat as a watertight compartement, so as long as the watertight door inside is kept shut when it should be, it's not a big problem.

The main problem I see with side launching doors is that it becomes difficult/dangerous to launch the tender when the boat is rolling. When the cable is alternatingly under tension and loose, it can jump off it's roller. One way to deal with that is cranes with built-in "wave-compensation". The hook is automatically winched in and out to keep the boat near the water's surface. I don't know if there are any yachts fitted with this system, but it's common on military vessels.

My vote would go for the stern garage.

Bruno

Naval Architect

Question I have been reading the posts and do like them. But on beam doors could you have a sliding dor? Tink of the doors of a minnie fan? You would have the same amount of seamage unless you want to split it down the middle, and you would not risck hitting the door with a wave rolling the ship. I was thinking this could be used for tenders that would be in more calm waters, but if the boat and crew could take it, maybe ruffer water would not be a problum?

I hope I do not sound to uneducated, but this door system sounds like it might have promise

Really not a bad idea mp-willow. Just a little more technically difficult. Other alternative would be a multipanel door that accordian folds. Or one that rolls down into a slot in the floor.

Kelly

Hi,

Orion, If you read back though this thread you will see where these typical side doors have been discussed at length.

They have a number of shortfalls. The ship rolling and tender rising and falling has been known to cause contact between the two. The wires tend to snatch very badly when any sort of sea condition is present, this can be caused by the boat rolling and or the tender dropping away at a speed greater than the winch cablecan be retrieved.

I like this idea for certain applications. I can see it getting in the way in certain situations, though (portholes, other hatches, etc.). It'd be handy though for opening the hatches while docked with limited space between you and other vessels/docks. Sure, you still couldn't get the tender out, but for maintenance and whatnot it'd be nice to be able to open it. Aside from this though, what advantages would it offer? One aesthetic (and engineering?) downside would be having to have a track along the hull for the door to sit on.

I never thought so much could fill a thread about tender garages!

But, having read Kelly's comments and Codger's points, I think I can add something here.

Take your basic automobile. The part that provides the majority of torsion resistance is the roof.
So, we build a convertible model of that same automobile. This thing's gonna twist like a wet noodle, right?
By strengthening the "box" that makes up the drivetrain tunnel ( plus a few other tweaks), that ragtop will not exhibit any cowl shake-- at least by the car companies who do it correctly.

So, I'm with Codger on the "Limitless". Boats utilize lots of longitudnals, transverse frames, bulkheads, web frames, subframes, and so on, to where the car guys probably have a tougher time engineering around a "hole".

My humble opinion.

Must add structure when you subtract

Loren is on the right track and the analogy is correct.

Whenever you make a hole in a structure, there must be additional framing and girders inserted to support what the removed wall section previously supported.

On the 63 meter Oceanco Lady Lola, we designed both a side opening door (top hinged) for the tenders to be launched by a double overhead beam crane on the starboard side as well as a huge hydraulic stern opening door (bottom hinged) on the transom to provide the tender embarkation point and swim platform.

In order to support the remaining structure around the two huge openings in the hull, we had to add three tons (3 MT) of steel in the hull, overheads and starboard aft corner consisting of headers, girders and framing.

Launching tenders from any crane from any location in rolling seas is a difficult and dangerous operation. The main ship is usually maneuvered to put the tenders being launched or recovered in the lee to mitigate these conditions, or simply move into a protected anchorage or harbor area. Tenders are not usually operated in the open seas.

Also, from a practical perspective, owners and guests don't normally play when the water is rough.

Guys,

Giving this thread a bump. Can't think of anything intelligent to post 'cause I've already reached the limit of my cerebral capacity. How about this... if your tender garage is broken, do you call Genie or EDL?

Dunno about who ya call. But I have the background music -

http://www.poemhunter.com/lyrics/songs/lyric.asp?artist=2773&song=19908

I love this tender!!!