Rudder lashing issues

[Thomas Nance]

Hi Wharramers

I have recently purchased a Simpson Woodwind 9.1 catamaran. The last owner/builder used a few Wharram ideas in the build. It has a tiki 30 rig, which is going very well, it also has lashed rudders. This weekend while sailing in some larger seas the rudders started moving from side to side. The lashings were creaking and the whole rudders were twisting. I have added a video of this happening on my page here. Can anyone help me? Are they too looses? Have they stretched?

I know a lot for people are switching from pintle style attachments to lashing, I don't want to go back the other way if I can get the lashings to work.

Any advice would be a big help.

Cheers

Thomas

[Robert Hughes]

Thomas - I'd think really carefully about the choices here.  Sailing to Tasmania with dodgy rudder fixings sounds like a very bad idea.  You might get away with that sort of weakness in rivers or sheltered water, but at sea it's asking for trouble.  Cats can put a big strain on their rudder fixings - I seem to recall James Wharram had trouble on his early Atlantic crossings.  In your situation I'd be calling the delivery skipper and saying a problem has been found and it might be necessary to re-plan.  I'd get his view on whether he'd be happy to do the trip with the lashings re-tightened, and let him have a look at them.  I couldn't send him off with a problem I knew about and he didn't.  Maybe when the lashings are tightened they'll be ok, but they need to be properly tried out before setting off on a serious trip.

[Galway Bay]

Thomas - I am happy to hear the boat has had a good survey. And that you are holding onto your sense of humour. This looks like it will be a very fine boat once this is sorted.

I cannot tell you what to do [ even if it might sound that way ! ] but some things I would be thinking.....

I would consider any more time spent on these lashings as wasted. You might get them good enough to set out on that delivery but possibly they will loosen again  half way through and the skipper will abort take his fee and leave the boat in a marina somewhere for you to start over. If he doesn't call for a tow altogether.

Likewise I would consider that the simple and obvious solution is to fit a set of strong rudder hangings to the rudder you have. If you do not know what to use get a local boatyard to do it. Or ask a local engineering firm to make up a set to suit. Best of all ask them both and go with whoever seems most competent. If you get on the phone now they might have a proposal for you for the weekend ?

Be honest with this skipper. He might advise you on a solution or at least steer you in the direction of someone competent. Again the sooner you do this the better.

Also any more changes will need a lot more thought than I am seeing here. This is a shallow draught cat - less than a deep "V". Centre boards and lifting rudders are appropriate to it. It probably only draws about 40 cm ? So if you fit skegs and fixed rudders they will be only 40 cm deep too? I would not be happy at sea with rudders this small. This is why the designer drew lifting rudders. Or more accurately drop rudders.

For what it is worth I would concentrate my efforts on getting what I have fixed once and for all, and not get bogged down in side shows and diversions.

I see study plans available on the net. You might get enough information there. But a competent yard or engineer should know anyway.

Concentrate on the positive. I am sure you will get great value from this boat once this one problem is solved.

[Thomas Nance]

Thanks everyone, I must admit my sense of humor is fast fading...time to get on the phone i think. Thanks

[Björn]

I would not worry about lashings which are proprtly done,they will typically stronger than the commercially availablr rudder fittings with often cheap stainless steel. Quite some time ago I had seen a Tiki crashing right into the rudder of another one and the rudder broke off just above the top lashings, this settled my initial doubts quickly.
However all tis is provided they are done properly and the rudder nd the stem post is enforced properly.

[boatsmith]

 We have built three Tiki 8ms and they all have had kick-up rudders. This does necessitate a shorter lashing span. With tillers set up for Akerman  effect the weight of the tillers and tiller bars will want to torque the tops of the rudders inboard and the bottoms out. We tighten up the rudder lashings as much as we can and then epoxy the lines into the holes. Two of these boats have seen continual daily service for the last three years and have provided excellent service. These rudder blades are balanced to reduce the rudder load as the aft cockpits required shorter tillers which provides less leverage. The lack of a skeg allows the boat to tack much easier. 

[Thomas Nance]

Hi Boatsmith

Thank you for that information. I must say that makes me feel better. I would imagine the length available to lash your rudders would be similar to mine, and that was an issue I was wondering about. Do you epoxy the line into the holes in both the rudder and stern post? I do like your solution to kick up rudders with still allowing balanced rudders. That may be a mod I make in the future as I think in an impact the vertically retracting rudders wont kick up as well as the rudders on the Tiki 8m. Thanks.

[Thomas Nance]

I have found this information from the Gleda project website, quoted from Beat of Aluna fame.

"So it is crucial that once they are in their definite place that you epoxy the hinge ropes into their holes, otherwise they will slide. Aluna still has one of her rudders off center, because she has not been out of the water since Hawaii, where I repaired one rudder with the epoxy treatment of the hinge ropes, but unfortunately not the other. As soon as we were underway again on some waves that rudder slid to the side and has been there ever since. Not that it affects its function much…"

This is exactly the problem I have had. I think epoxying in the lashing should fix the movement issue.

[Peter Brook]

I can understand the logic of epoxying the lashing to reduce movement of the lashing through the lashing holes.  However, will this lead to stress concentration in the lashing itself and cause a failure in that manner?  When lines are knotted for example, they lose a significant amount of their strength in the knotted area.  That said, the reduction in frictional wear and tear might more than compensate.  The real life experiences outlined above seem to indicate so, but I wonder if there have been any material studies of strength/fatigue with epoxy saturated lines?

[Galway Bay]

Good work Boatsmith. Once again we owe you one.

Looks like Thomas will be ready for his delivery which is great news.

[Thomas Nance]

Yes that could be something to think about. However modern lines are so strong I think a little loss of strength wouldn't be a problem. I think the wood in the rudders would break first before the line.

[Thomas Nance]

Thank you everyone for all your help.  Thank for Galway for your thoughts, I will have a good look over any mods to the boat with a critical eye. This weekend I will relash and will let you all know how it goes. Thanks again

[steve martland]

bass straight is not really a good place to be testing the viability of a rudder adaptation like that.. I would suggest for your delivery that you  use as little projected rudder area as possible to maintain steerage and lessen the  strain in the lashings.

if you have the rig balanced is doesn't take much rudder imput to maintain course .( on off the beach racing cats it is common practice to only have one rudder down to reduce drag upwind and downwind)

Just a thought.. leeward rudder I/2 down .. less  stress..