A Photo & Discussion Forum for Wharram Design Enthusiasts
The Tiki rudders are supposed to be hinged with 4 millimeter polyester string. Have you been able to tie the string in the figure-of-eight fashion so tight, that the rudders do not move up and down. If not, how big up-and-down -movement is permissible? I think that it is unavoidable, that the rudder touches the stern post right in the center line of the stern post, chafing the paint. I guess the stretch of the string will not be an issue, since the string is glued to each hole both in the rudder and the stern post, but the question is: how to get it tight enough before applying the epoxy.
I had difficulties with the tiki 30 rudder. I think by its weight it should have a guide pin under the rudder attached to the skeg, as in tiki 38. But minor Wharrams should not have this problem. Alas, my cables are not glued. I change each year.
we wrap the hinge line around an axe handle for leverage on each turn. Once e have a turn tight we drive a wooden wedge into the hole to hold the tension while we rig the next turn. once all turns are in we glue the rope to the holes in the rudder and the sternpost with super glue. We do not reuse rudder lashing lines as extra length is needed to install and we drill out the line to unglue it.
We insert 7 mm dia aluminium tubes in the lashing holes in the rudders and sternposts. First you drill the holes large enough to accept the tubes , coat the inside of the holes with epoxy and when dried fix the tubes in place with sikaflex or similar . Purpose of this is that one can easily remove and replace the rudder when desired ,for example to repair damage . We use 6mm lashing rope . There is a little bit of up & down movement but we have never found that to be a problem . If it does worry you then Boat smiths' lashing method will work well.
Siam Sailing, Phuket
I fitted my rudders exactly as stated in the plans, except for using dyneema.
My plans show a clearance gap between the rudder stock and the sternpost, are they still like this?
Clearly, if you maintain this clearance, then no matter how tight you tension the lashings, there is going to be slack when the clearance packers are removed after the lashings are complete. But, if you don't have clearance, how can the rudders freely move without friction?
I am at a loss as to why no one seems to have addressed this obvious potential problem in these plain terms.
I tightened my lashings using an Estwing claw hammer pivoting/levering over a purpose-made rubber pad, with the dyneema cord wound around the hide handle of the hammer. I wouldn't use an axe, they are for chopping. A hammer head/shaft is an ideal lever.
So - in spite of the tightest possible tension on the lashings, wedged and clamped each time, there is at least 6mm vertical sag on the rudders against the stempost giving a potential cause of rubbing and ingress later of water into the rudder and /or stempost. Fortunately I allowed for this sag in offsetting the epoxied drillings for the cord. However, potentially the rudder can rub against the stempost; flotation of the rudder is ?/weight of tillers and tiller bar. Less I think.
Once again: I have lost time working out a simple retro solution to this problem, which I may comment on later - if it works.
Rebuilding a year or two after launch is not in my scenario, building takes too long. Wharrams need to address this, there are too many areas of design like this. I take plans literally and follow them to the letter, unless actual proved experience shows them to be wrong.
I would use conventional fittings in a rerun. Much, much. faster to fit and no sagging.
There is the thickness of the lashing rope between the rudder and the sternpost.They do not rub against each other. If your lashings are tight they will not sag appreciably, they will not clank, they won't break unexpectedly. They are also cool. I have not found an ax handle useful for chopping. Hammers are for beating. My ax handle is almost three times the length of my Eastwing and provides more leverage. Also it is very difficult to get enough tension on the lshings if dyneema is used. It would be extremely difficult to get enough tension on the dyneema to have it end up tight when tied off. With Stay Set double braid it will stretch about 1.7% at 200 lbs of tension. This allows one to tension it up and the stretch will absorb some of the slip from knotting it off.
I have the Tiki 31 plans in front of me. They show a clearance gap of approximately 20% of the thickness of the 4mm cord between the sternpost and the rudder stock. The sketch shows that the cord crossovers are embodied in the cutouts/recesses made in the stern and stem post.
I agree it is harder to get tightness with dyneema. I wedged each bored- out epoxy-filled hole with a wooden peg and also used small speed clamps where possible. I used a very long length of the cord each time so I could easily maintain pressure at the end. My dyneema was partially (staggering, like when underpinning a wall) glued (then completely) before all restraints were removed in order to maintain tightness, it is not knotted off for the reason you mention. If it relies on the knot, the glue is not working, although I have whipped in a stopper just for peace of mind.
Regarding achieving tightness with levers etc. When you say you use an axe handle, it's not clear to me how you employ it, or on first reading that there is no head on it. A claw hammer with a standard claw head is one of the best and easiest to use levers available to anyone, you just need a pad to protect the substrate from it. An Estwing has an integrated head and a hide handle which I find good for wrapping around as there's a bit of grip/give in it.
I checked my rudders yesterday: there is 6mm up and down movement as stated.
Marking-out, over-boring accurately, maintaining dryness in these borings while working outside, filling with epoxy, reboring accurately(not at all easy in this case as the overbore is not that much bigger than the rebore, unless you cut out the whole section and laminate in an epoxied plate), sanding off and repainting the cord hinge areas, lashing/gluing, then protecting the epoxy from UV...what a ball-ache.
As you fail to address my points as directly as I have made them, to be clear, are you saying that
1) 6mm rise/fall is unimportant
2) you lash the rudders tight against the stempost
3) there is/isn't clearance between the rudder/sternpost
4) there will normally/won't normally be contact between the leading edge of the rudder and the edge of the sternpost
5) there is/isn't rubbing in service between these two elements
and then wear and water penetration.