Whipstaff steering

Mediaeval ships of any size were generally steered not by a wheel but by a whipstaff. This was a vertical lever, pivoted somewhere in the middle. The top came through the deck where the helmsman pulled and pushed it sideways. The other end had jaws grasping a conventional tiller. So the helmsman pushed his end of the whipstaff to port, and the bottom end moved to starboard, moving the tiller in the same direction.

This could have advantages in model yachts, particularly for those who do not want to buy very expensive transmitters able to ‘fake’ their inputs on the stick. How do we make a modern miniature whipstaff?

Suppose that we mount our servo with its shaft on the centreline at right-angles to the rudder stock (i.e. roughly horizontal, pointing aft).

On the top of the rudder stock we mount a tiller made out of a piece of brass rod, carbon rod or whatever. If the rudder stock is a piece of brass or steel rod, all we have to do is to bend it over at right-angles.

The whipstaff (i.e. the servo arm) is a similar piece of rod, which is vertical (as seen from ahead) with the servo in its central position and at right-angles to the shaft of the servo seen from the side (i.e. parallel to the rudder stock).

Both tiller and whipstaff a fitted with tubular sleeves (a good sliding fit) over them so that both sleeves can be extended to meet at a point. The two sleeves are then connected by a ball joint. If a ball joint is too complex, you can make do with a simple hole in one of the sleeves, but this must be elliptical to cope with the position when the helm is over and made quite accurately to avoid play.

Why is this a good thing? First, it is probably simpler and lighter than conventional yoke-bar steering. Second, it eliminates any possible inconvenience of a transom rudder under the Footy rule. Most important, it enables us to duplicate mechanically the ‘input faking’ features of very expensive transmitters.

With a yoke-bar, we get maximum angular deflection of the rudder per degree of servo movement in the straight ahead position. As the helm goes over further, the increase in rudder angle per degree of servo rotation gets less.

This is the exact opposite of what we want IMHO. With the boat well balanced and in the groove to windward, we want a relatively coarse input on the stick to have only a small affect on the rudder so that we do not start to zigzag all over the place. When life gets hard and we want a lot of rudder, we generally want it now and are slightly less fussy about how much we get. Coarser adjustment will do as a trade-off for speed.

A whipstaff does this, all by itself. If you want to get clever, go can do all sorts of marvellous things with the speed at which the helm goes over at different points in its travel by altering the angle of the whipstaff and the tiller relative to the rudder stock.

Any comments?



Sounds very promising, but the attachment of whipstaff (servo arm) to tiller needs a little clarification or maybe re-engineering.

If I understand your design correctly, the contact point of vertical to horizontal will be moving “out” relative to the servo shaft and to the rudder shaft as you go hard over, so a simple joint may not suffice for any non-sloppy control.

I could be (and usually am) wrong, though. :lol:


Exactly. If I have the kinematics right, this can be done either with a very precise eliptical hole in the other tube or by a ball joint between the two. Given the availability of model car parts, I suspect that the latter is easier - although finding a joint hat will operate through the right angles may be hard!


Having actually planned a whipstaff for my Graham McAllister Kittiwake trial horse, the geometry comes out as follows.

Tiller length (c/l or rudder stock to c/l of whipstaff) 42 mm. This is with a forward/raked transom with a vertical standoff on it). The length of the tiller allows a HS-55 servo to be butted up against the transom with the servo arm at the front.

Assume maximum helm angle 30 degrees. Assume total servo rotation (full starboard helm to full port helm) of 90 degrees.

This gives a throw of the tiller of 12.3 mm either side of the centre line. The increase in tiller length that the slide has to cope with is trivial - about 2 mm.

90 degree servo travel gives us a vertical height from vertical c/l of tiller to c/l of servo shaft of 12.3 mm (= tiller throw) and an elongation of the whipstaff of 3.7 mm. This should be accomodatable if the sliding joints are reasonably free of distortion. I am therefore using carbon tube/rod for all components. It’s initially expensive (about USD 16 for all the bits) but I now have a lifetime supply under the bench - and it shouldn’t corrode/seize.

Assembly will be with a rod tiller and tubular whipstaff. This means a) that the whipstaff is easy to attach to a butchered standard servo arm while leaving clerarance for the extension and b) that the whipstaff/tiller joint can be done as a simple pin joint with jaws at the end of the tiller sleeve. This joint must have clearance to operate through 30 degrees. In my earlier thoughts on ball joints, I had forgotten that the sleeves can not only slide but also rotate.

The whole system is incredibly neat and compact. Let’s see how it works.


At long last some pictures of an almost complete whiptaff gear. The actual construction is a bit brutal. Making a T and toggle joint in carbon tube and rod proved harder than I thought and the result is cobbled together out of wood and eoxide. The right answer is probably to use metal, at least for the joint. This said, it is actually a very simple joint with no free play (NB the pivot pin in the joint is the drill I broke making the hole!).

In the pictures the helm is hard over to starboard. The whiptaff guide tube on the servo arm has yet to be fitted: the whipstaff itself is just blu-tacked to the arm.

Hope this makes things a little clearer. I’ll try to post some sketches in the next day or so.


Very nice Angus, could be easily built out of brass or aluminium. Could be made to be very light and compact out of AL. I will draw one up in Solid Works.

I like this idea. I may use for my next rudder. I’m a little concerned about mounting the servo so low. Is it more exposed to water as Angus has it?

How about making both arms horizontal? This would allow the linkage to be moved fore/aft to set the maximum angle. The servo could be higher in the hull too. I’m worried about the sail sheets tangling in the tiller/whipstaff with my modification. Hmm, I have to try some things.

Bob, how much to have one made for a 3/32" rudder shaft?


Finally pictures Angus… :stuck_out_tongue:
Now I understand… now I like… now talk to me Bob.

There may be whipstaffs in my future…



As it happens, the height of the servo top bearing is almost exactly what it would be if it were fitted vertically in the standard servo tray of the Kiitiwake.

Both arms horizontal? Unless you’ve got your herad round something I haven’t the rudder stock (shaft in US) and whipstaff have to be roughly parallel. Of course you can change the ratio between servo movement and rudder movement at different parts of the swing by altering the angles of whipstaff and tiller.

OK, here are some preliminary drawings. This is based on using .25" square aluminium stock for the yoke and .1875" rod for the sleeve. A .125" rod will fit thru the sleeve and a .09375" rod will fit the back of the yoke. Angus, please correct me if I drew anything wrong!!!



That looks fine Bob. I’ll try to do a GA drawing just to check.


There’s a crude but (I hope) comprehensible GA drawing at


Bob. Before I glue the whole thinng together, you’ve got a second order if you want it. Just gimmee a price! Those drawings look beautiful.

After much faffing around on my part, we at last have some pics of Bob’s whipstaff gear. Much more elegant than my cobbled together junk, although the geometry is the same.

Note for Bob’s sake: these were rushed off as soon as the prototype worked: the job needs fettling to bring it up to Bob’s usual high standards.


Angus is going to force me into posting a more finished model! It’s a prototype:) . It actually works quite nicely, but I already have ideas on how to improve it

Reading with interest Bob and Angus on this topic tweaked my memory.Went to my parts bin where at a surplus store here in Toronto I picked up a few black nylon or plastic universals - total length 1.8cm, able to bend to 90degrees with a 3/16 in hole at the end of each,which is flat spotted–perfect for carbon fibre rod. The best part is they were $.50 each CDN. Just a thought–may work. Bill.

Very good Bob… moving the sliding portion onto the servo was a good idea to save the servo extension projecting above the coupling… more room down there.


That might be a bit on the large size. Altho a universal would work, this really not one. The yoke on the transom is 1/4" rod x 3/8" long. All the rods are 3/32" and the tubes they slide in are 1/8". Not much room in Footys:)
Graham, I do have a slot in the yoke piece too, just to keep it free moving

Got Bob’s prototype gear in the post. Looks beautiful. We’ve got to sort out how the rudder stock works - my lousy drawings and English/American faulure to communicate - but it really looks promising.

I was a bit servous about the slotting in the whipstaff tang, but on reflection I don’t think it causes any play in any meaningful direction.

Thanks Bob

Glad to hear that you recieved it and they didn’t confiscate as some sort of contraband:lol: Play with it and make the necessary revisions and we will get it built. I am not really sure the slot needs to even be in the tang. It is an ingenious little design and I think it does hold promise.

Happy New Year

Don’t flatter me too much: the original concept is mediaeval and the detail design is mostly rom a Danish sheet folder in a hospital laundry. A diverse career is a marvellous thing!