Bestevaer 49ST

[redsky49]

Originally Posted by Dockhead

Indeed. I had my grubby hands on that rudder shaft a couple of days ago, and it is an absolutely gorgeous piece of machined billet. Work of art. I absolutely love the way they machined the sides off it to make it fit inside the airfoil.


I was surprised at how small it was, however. Maybe full spades are so effective that more area is not needed? It is about 1/4 of the area of the rudder on my boat, although the displacement is similar. Also, the shaft is offset really far so that very little of the rudder area is ahead of the shaft axis, so there will be very little servo effect. What is the idea behind that? Wouldn't make any difference to the hydrodynamics I guess.

Also, the shaft is offset really far so that very little of the rudder area is ahead of the shaft axis, so there will be very little servo effect. What is the idea behind that? Wouldn't make any difference to the hydrodynamics I guess.

It appears to be appropriate for what would be considered a semi-balanced rudder. Were a greater portion of the rudder extended forward of the post, while you might achieve a sort of power steering, you are reducing the hydrodynamic qualities of the rudder. Same as oversteering or oversheeting.

What surprised me was that I had surmised the post as 130mm in stainless, as SWLass had said they oversized the rudder post. Why not 160mm if in aluminum? I am sure that the numbers have been run though and all is correct. Need something in the pic to give perspective.

Isn't it fun to be sidewalk supervisors for someone else's boat?

It is a massive hunk of machined metal.

[Seaworthy Lass]

Originally Posted by Dockhead

Indeed. I had my grubby hands on that rudder shaft a couple of days ago, and it is an absolutely gorgeous piece of machined billet. Work of art. I absolutely love the way they machined the sides off it to make it fit inside the airfoil.


I was surprised at how small it was, however. Maybe full spades are so effective that more area is not needed? It is about 1/4 of the area of the rudder on my boat, although the displacement is similar. Also, the shaft is offset really far so that very little of the rudder area is ahead of the shaft axis, so there will be very little servo effect. What is the idea behind that? Wouldn't make any difference to the hydrodynamics I guess.

Just doing a little reading. From what I can find, a high aspect "balanced" rudder has from 15-17% of the blade area forward.

I will do some measurements from the cutting files and check what ours is.

SWL

[Dockhead]

Originally Posted by Seaworthy Lass

Just doing a little reading. From what I can find, a high aspect "balanced" rudder has from 15-17% of the blade area forward.

I will do some measurements from the cutting files and check what ours is.

SWL

Ah, so little? I'm just not so familiar with spade rudders. I suppose my rudder (semi-balanced partial skeg rudder) has about that much ahead of the shaft, but because of the partial skeg, it looks different.

Yours is not a "high aspect" rudder, by the way -- it's quite moderate. And I think that's just right -- moderate aspect airfoils will be more resistant to stalling, and the construction will be stronger. You can afford a bit of extra drag for those qualities, I think.

But why is it so small? It's even smaller than the rudder on my previous boat, a 37' Pearson. Maybe it's for drying out? Most of these have lifting keels I believe.

By the way, here is your rudder, with my hand in the photo for scale

[Seaworthy Lass]

Originally Posted by Dockhead

Ah, so little? I'm just not so familiar with spade rudders. I suppose my rudder (semi-balanced partial skeg rudder) has about that much ahead of the shaft, but because of the partial skeg, it looks different.

Yours is not a "high aspect" rudder, by the way -- it's quite moderate. And I think that's just right -- moderate aspect airfoils will be more resistant to stalling, and the construction will be stronger. You can afford a bit of extra drag for those qualities, I think.

It took a while to do it accurately, as the shape is complicated. I get 15.1%, which seems about right.
Ours is the 26th Bestevaer and they have made a couple of Bestevaer 49STs before ours, so hopefully the proportions are correct. I guess we will find out when she is launched .

Originally Posted by Dockhead

But why is it so small? It's even smaller than the rudder on my previous boat, a 37' Pearson. Maybe it's for drying out? Most of these have lifting keels I believe.

Size wise, I am not sure. It does not look small compared to our current rudder proportion and the boat size is similar. I doubt drying has been taken into account, performance is a high priority with these boats.

They have done a few Bestevaers with lifting keels (eg the new Pure), but not many. Dijkstra's original design was fixed.

SWL

[Seaworthy Lass]

Originally Posted by Dockhead

Most of these have lifting keels I believe.

The number with lifting keels is higher than I thought (most I've seen have been fixed). I have just checked KM's website and 11 of the 26 are lifting on Bestevaers.

[Dockhead]

Originally Posted by redsky49

[I] . . . Were a greater portion of the rudder extended forward of the post, while you might achieve a sort of power steering, you are reducing the hydrodynamic qualities of the rudder. Same as oversteering or oversheeting..

No, no -- the water flow doesn't know and doesn't care where the rudder shaft is. Hydrodynamics are determined by the shape of the rudder itself.

"Balanced" rudders are all about the "power steering" effect. This is important and reduces the loads (maybe several times over) on the autopilot, not to mention the helmsman.

[Seaworthy Lass]

The first of the 3D interior images have been sent.

I am in my element here . I love playing with design and before this project commenced, I have never had CAD drawings to work with. I am like a kid with a new toy , although still in my infancy using the program without any instructions.

For those of you who have never worked with CAD, ever single layer can be peeled back from any side. The image can be rotated 360°, giving a 3D view of each space from any angle. The construction is broken down to every last tiny bit of material used. Items can be selected and moved around and rotated.

It must make construction hugely easier for KM, but also means they can have some confidence that the owner is not later going to pipe up with the dreaded words "I didn't know it would be like that and it's not how I want it". It must be bad enough having clients change their mind mid stream, without the added headache of disappointing someone due to misinterpretation.

The interior was basically fully drawn up in our plans, so for us this stage is more about polishing the details. I still have the rough pencil sketch of the interior layout that Eeuwe (the owner of KM) drew in about 10 seconds when we met for the first time just over two years ago and explained what we wanted. I smile looking at it, as it is virtually unchanged.

SWL

[JPA Cate]

You're reaping the rewards of careful planning. Good on ya!

Ann

[Oldmate]

First time poster, but wanted to say what an awesome boat!! No. 1 on my list of dream boats now. Thanks for bringing us along for the journey. Keen to see the "pure" photos you mentioned when you have suitable internet please!

[GordMay]

Greetings and welcome aboard the CF, Oldmate.

[Oldmate]

Thanks GordMay, long time reader, but really enjoying this thread for the constructive discussion.

[weavis]

TO keep grounded and not let the euphoria of this interesting build cloud our perceptive processes, just remember it only has one hull..

There I said it.

[weavis]

CAn you post any of the CAD pics SeaWorthy?

[Oldmate]

It's a good suggestion Weavis, but I think a second hull is about as likely as a generator. [emoji1]

[Seaworthy Lass]

Originally Posted by Oldmate

It's a good suggestion Weavis, but I think a second hull is about as likely as a generator. [emoji1]

Spot on!
I burst out laughing reading your comment. You have obviously read the whole thread.

Glad this thread has elicited a post from you. Welcome to CF as a posting member .

SWL