|
|
Rudder
Jul 12, 2016 6:40:30 GMT
Post by Peter Jenssen on Jul 12, 2016 6:40:30 GMT
Hej Fred,
(+any other who might know the answers)
I am currently carving my rudder and have a couple of questions:
- For the iron pintle brackets and, -How thick are they? How deep are they sunk into their cutouts into the rudder? Looks to me like the cutouts are tapered? (deeper sunk in the fore end)
- Has the knowledge on the pintle/gudgeon location changed recently? The two upper ones do not seem to agree between the 1980s museum plan (my rudder cut) and the plan in Vasa I. (which incidentally, I just realised, is about 1/75 scale :-D)
- For the rope that holds the rudder (in case of accidental unshipping I guess, -or is it emergency steering?), -does it only go through one of the holes on the rudder and if so, which one?
thanks,
Peter
|
|
|
|
Rudder
Aug 9, 2016 13:05:14 GMT
Post by fredhocker on Aug 9, 2016 13:05:14 GMT
Hi Peter,
1. The surviving original pintle is 12 mm thick at the after end, thickening to 17 mm near the forward end. The pintles are more deeply inlet into the rudder near the leading edge, but lie on the surface at the after end. The inlet starts about 40% of the length from the pin, and is up to 10 mm deep.
2. I had not noticed the difference in pintle/gudgeon location! Well spotted, although the difference has more to do with the incorrect drawing of the sculptural ornament, I think. The plan in Vasa I (nominally at 1/75, although may be affected by paper shrinkage/swelling) is the more correct version in terms of pintle placement. There are still some small errors, but nothing significant enough to be seen at scale.
3. The preventer rope or ropes did not survive, so we do not know how many there were or how they were rigged, so your reconstruction is as valid as mine! I have looked for wear marks, but there are none apparent that would help.
Fred
|
|
|
|
Rudder
Aug 10, 2016 3:05:03 GMT
Post by Peter Jenssen on Aug 10, 2016 3:05:03 GMT
Hi Fred,
Thank you very much for your time with my question!
1. Thanks, according to my 1:75 calculation that makes the iron portrude 0.16mm aft and 0.9mm towards the forward end, 0.22mm thick iron to solder the pin to.
2. Thanks, Vasa I plan is great!
3. I think I'll rig her with one rope through each hole in the rudder then. With both gun ports open that would make her look like she's smiling! :-)
Drawback with investigating such a new ship I suppose. No wear to speak of..
Would you know if the preventer rope would typically be allowed to run free through the holes, or knotted in place?
I would suppose running free makes them useless as emergency steering?
I was reading
Nicolaes Witsen and Shipbuilding in the Dutch Golden Age
By A. J. Hoving, Diederick Wildeman - pg 159
As usual, more information raises more questions(:-))
"Against the lifting of the rudder, bars are hammered through the rudder irons; for which end a preventer rope also goes through the rudder."
I don't quite understand where these bars would go, or if they would be visible on a model. Was this done on the Vasa?
An interesting point that seems to pertain to the step cut in the rudder (as well as the protrusion of the three lower planking strakes on the keel):
"A groove, made in the bottom of the rudder, in the middle of the ship or keel, is thought to benefit the course of the ship, and to steady the rudder itself."
So, possibly, the cut step in the rudder may not be in order to streamline it with the sternpost, but rather the whole construction has it's own purpose?
It is also mentioned that the hole where the tiller enters the ship should be covered with sailcloth. Is this true for the Vasa too?
Thanks,
Peter
|
|
|
|
Post by fredhocker on Aug 15, 2016 6:48:32 GMT
Hi Peter,
Good questions!
We do not have any direct evidence for the lead or attachment of the preventer ropes, although I can imagine they were led in through the catholes in the transom. I think the traditional solution was to fix them at the rudder. In practice, they would be nearly useless for steering, due to the geometry (the holes are too close to the axis of rotation to offer enough lever arm) and, as Witsen and others indicate, they are primarily to prevent loss if the rudder comes unshipped. Not sure about the bars through the rudder irons he mentions, we do not have anything like that.
Interesting thought about the three lower strakes and the step in the rudder. I never thought about that as an explanation, but it could have some effect in smoothing or directing water flow over the lower, wider part of the rudder. Will have to ask a hydrodynamicist friend about it. I tend to lean towards the three lower strakes being thicker in order to strengthen the keel-sternpost join, but the step in the rudder surface has no structural function and appears to be only there to continue the contour of the bottom, so it has a hydrodynamic purpose.
I have not been able to find any obvious evidence of a canvas boot or cover in the tiller port, but the area is very difficult to examine. I will give it a good going over the next time I can get access to the top of the transom.
Fred
|
|
|
|
Rudder
Aug 16, 2016 6:25:37 GMT
Post by Peter Jenssen on Aug 16, 2016 6:25:37 GMT
Hi Fred, Thanks for the answers. Yes I can see how the leverage would be miniscule for turning the rudder. Especially compared to that of the tiller. I'll lead the ropes through the catholes with enough slack (plus some) to allow the rudder to move freely then. I'm having trouble finding models that actually include them. (Plenty images for later ships that use chains though) If the iron bars mentioned are not the solution, is there then nothing locking the pintles? The preventer does not really prevent the rudder from being unshipped. It just catches it afterwards. Like something simple like this would do: 3.bp.blogspot.com/-w6WxjU1O9Kg/T8__EwaryhI/AAAAAAAAAuo/F6hNhf28P6I/s1600/rudder+stop+close+up.jpgI may just be seeing things, but there seem to be some kind of notch in the stern post between the top two gudgeons?  Cheers, Peter |
|
|
|
Rudder
Aug 16, 2016 6:52:33 GMT
Post by fredhocker on Aug 16, 2016 6:52:33 GMT
Hi Peter,
That notch is a chip out of the upper end of the sternpost. The height of the sternpost is extended by about 60 cm by a separate head piece scarfed onto the main piece, and one corner of the scarf is chipped.
As for pintle stops or locks, only the lowermost original pintle and gudgeon survive, the others are all reconstructions based on nail holes and the inlets in the timber. The lower pintle and gudgeon appear to be complete. As you note, the preventer does not prevent the rudder from being unshipped, it only stops it from floating away.
Regarding the amount of slack to leave in the preventers, the maximum swing of the rudder is 22 degrees to either side, limited by the swing of the tiller inboard.
Fred
|
|
|
|
Rudder
Aug 16, 2016 6:58:41 GMT
Post by Peter Jenssen on Aug 16, 2016 6:58:41 GMT
I also found an alternative run of the preventer rope in this very forum (Discussion STAM's model) warshipvasa.freeforums.net/attachment/download/199About half a century after Vasa, probably though... (Also, the rudder here has a grove in it that is not necessitated by the planking run of the hull!) Surprisingly complicated topic, rudders... :-) Cheers! Peter |
|
|
|
Rudder
Aug 16, 2016 7:00:57 GMT
Post by Peter Jenssen on Aug 16, 2016 7:00:57 GMT
Thanks Fred,
Nothing for the modeler to be concerned with in terms of locking the rudder in place then.
Many thanks,
Peter
|
|
|
|
Rudder
Aug 17, 2016 8:07:48 GMT
Post by fredhocker on Aug 17, 2016 8:07:48 GMT
Hi Peter,
There is room to run the preventer ropes through the tiller port on Vasa as well, just as on the STAM model. This makes the ropes even less useful as an emergency steering system. There is no obvious place to attach the preventers on the inside, or at least I have not found it yet!
Fred
|
|
|
|
Rudder
Nov 22, 2021 9:53:13 GMT
via mobile
Post by Peter Jenssen on Nov 22, 2021 9:53:13 GMT
Hi Fred,
Not sure if you're still checking in here.
How have you been?
Picked up the model again, found the rudder with half rigged preventer ropes through.. :-)
I found an old discussion with Lars Bruzelius where he gave the limiting factor for rudder movement as the size of the mouth of the mascaron sculpture through which the whipstaff passes. This would supposedly give maximum rudder of 7 degrees. Could this be correct?
Cheers,
Peter
(PS Vasa II? ;-D )
|
|
