Modern Davits for Landing craft etc

[meeware]

I'm tinkering around with a few projects for phibs, both AU and real, and have started to worry about davits. Specifically it appears that most davits from WWII t the present day have very large height requirements, and further, that a few drawigs are appearing that don't always take these into account.

This started when examining the davits used for LCAs and LCVPs during WWII by the allied forces. This structure lifts the LCA up high, clear of the deck,and for deployment runs the lifting booms down rails outboard, so the boat can be lowered to be level with the deck for embarkation before being launched. A sensible solution, and still to be found on ships to this day for launching lifeboats. However, it's key to note that all this paraphernalia takes up space, specifically vertical space, and in most of my designs it takes at least three decks. See Davits_simple_1944

davits_simple_1944.gif

The second type of davits I looked at are more modern, and I think more flexible, and fairly widely used in SB drawings. These are the systems used to manage the LCAs on the Albion class LPDs as drawn by Kim Werner : download/file.php?id=1285.

However, I think this set up cannot be used as it sometimes is in AU designs, being simply mounted at deck level with no further decks or access below to the waterline. Specifically, I think there needs to be a further open deck below this davit design in order to allow boarding, as indeed Kim has shown on his excellent Albion and Bulwark drawings. In the attached example I show a typical use of modern davits (low to waterline, no boarding deck) next to the excellent representation from the Albion.

Modern Davits.GIF

I do not seek to criticise, I seek to learn. So, is there anyone who can clarify whether these are in fact two totally different deployment systems? Or perhaps the usage is quite different, with the 'compact' configuration used only for launching, and with embarkation carried out elsewhere, in a well deck for instance?

I'll just end by showing some links to decent images of landing craft on davits being deployed, in the hope that we can reach a consensus based on available evidence.
http://www.naval.com.br/blog/wp-content ... cean-2.jpg
http://www.naval.com.br/blog/wp-content ... -Ocean.jpg
https://picasaweb.google.com/1048545293 ... 9332947634 (mind the windsurfer!)
https://picasaweb.google.com/1048545293 ... 3598118514
http://upload.wikimedia.org/wikipedia/c ... ropped.jpg
http://royalnavy.files.wordpress.com/20 ... iew211.jpg
http://img.blog.yahoo.co.kr/ybi/1/24/56 ... 230140.jpg

Hope this is a useful discussion- in an ideal world I can imaging various Davits making it into the parts sheet with indicative minimum clearance represented.

Cheers

[ALVAMA]

impossible @ image? pleace explane.

[acelanceloet]

well, the LCVP drawing at the left (which I made) shows the arrangement on the dutch ships. I cannot answer this for you right now, but I will take a look if I can find out how these are boarded. it is possible (as you suggest) that the loading will be done at the well deck, but I am not certain about that as the JLOS will use these davids without well deck.
please note that the LCVP MK5 can take light vehicles on board, so part of it's load will always be taken from the hull door or dock. so IMO, in that case there is no real need for an special loading deck, which means that the LCVP david's can be placed lower and be more compact.
please note: all of the above is my knowledge/asumptions, I will have to do some research and talk to some people before I can really answer you question.

EDIT: to prove that it works, hereby an picture of the ship were these davids are based on, the HrMs Johan de Witt:

most likely the answer is as following (have to find evidence yet) the david rotates outwards, so the LCVP hangs on level with the deck it rested on before. then it can be boarded. in effect, this works similar as how it does on the HMS Albion, but with an more compact position.

[meeware]

ALVAMA my apologies I meant to say " I can imagine various Davits making it into the parts sheet"

acelanceloet thanks very much for that illustration- it does clarrify the situation greatly and is very helpful.

[Thiel]

As the above posts prove, it is doable, but it depends on a couple of things.
1. How is the boat stowed? Landing craft are usually flat bottomed and their cradles consists of little more than wood or rubber blocks and a couple of tie-down points in the deck. These are all easily removed once the boat is clear, leaves ample space for the troops to embark.
2. Operational tempo. WWII era assault ships usually carried landing craft on their decks as well as in davits. The second deck allows you to muster troops for more boats than you have davits which was important at the time. Today this capability is either abandoned in favour of a slower operating tempo or taken over by a dock.

At least that's how I understand it.