A Photo & Discussion Forum for Wharram Design Enthusiasts
After a summer of sea trials and preparations, we (my wife Kathleen and I) left Hornby Island BC on Sept.14 bound for San Diego using the offshore route. If only we had left a week earlier while the weather systems were more or less normal, we could have avoided all the unseasonally heavy weather that caused us to go inshore and seek shelter when needed in whatever port was nearest. The weather has been dreadful; 4 days of storm force winds and 7 at gale force. Even when winds were forecast at N. 5-15 we found ourselves in a whole gale (maybe more, we don't have wind instruments) rounding Cape Blanco at night and doing 8-9 knots under bare poles. Right now we are in Humboldt Bay, California, waiting for a weather window for rounding Cape Mendocino. Kattu has performed well under heavy going but for one unsettling issue...the movement and thumping noise of the rear beam. I have 8 turns of lashing on the insides instead of the six called for in the plans, as I had read of this problem in one of the older forums. All of the lashings have been re-tightened twice now, and there still is some movement. Off Cape Blanco I could have stuck a finger between the beam and it's rubber pad at times. I would sure like to hear from others with offshore experience whether this is just a normal situation for a Tiki 38 or do I need to add even more turns of lashing.
Well done guys, you have been thru some rough stuff,it will not always be thus.As for the rear beam issue, of tiki 38's I have no experience but would it not help if you tightened all the lashings of the other beams too? This may help, I am not sure.
With the aft beam movement we even had the problem that the bars that lock the beams were wearing all the Delrin gaskets and damaged the wood like an inch of the aft side hole.
In our case we have 6 turns lashings tensioned using the mizzen sheet blocks and a small rope which helps a lot to keep the main lashing in place to work out the knots very tight. This cannot be re tighten in open ocean conditions even if its calm , so we saw the rear beam moving and making noises with panic at first and with resignation later. the result of 2000 NM offshore passage was that we need to redo the entire bolt holes. I suspect that the ropes are not good enough for the work and they stretch some way. The lashings that are placed between the hulls seems to work much harder than those on the outside.
the other nasty problem we had is the water inlet that we had in all holes where the bolts are placed, and i don't see any decent solution for that other than take the bolts out and substitute them with another solution. But I didn't think about that yet.
fair winds in your trip..
The aft beam lashing on a T38 takes huge loads. I think this is from the twist induced on the rear part of the hull by a quartering sea on a big rudder and skeg and this twisting load is applied to the lashings. I did not have the problem when going up wind, but it developed in a seaway down wind.
I have tried to eliminate this...without success! But I was able to reduce the movement to about a millimeter by adding an extra turns as you did and using a line that had a limited amount of stretch in it. The line could then stretch and recover. A non stretch line does not recover, so I have found out.
Another answer is to add another lashing line over the existing lashing, say with 4 turns and the frapping turns. The initial lashing will get the beam down good and tight and the second lashing imposes a very positive loading which should prevent movement.
What I found when the lashing was this tight was the first time it moved the noise was horrendous. A screech which when it first occurred, scared the c**p out of me, especially as I was mid ocean. In the end I got used to the noise and took the view that while it was noisy the lashings were good and if it was quiet... there was a problem!
Good luck and good sailing. The T38 is a terrific boat.
Dave, that's interesting what you say about adding more lashings over the existing ones; did you actually try that or was that hypothetical? It seems like all the inside lashings might be better off reinforced this way. I also found, like you did, that the movement was worse going downwind, especially in confused cross seas. Your idea about the large rudder and skeg causing a twisting force is interesting....and I remember you once suggested that the downward force on the aft mast beam, all on the insides of the hulls, was at least part of the problem. I think now there might be something to this. Last time I re-tightened the inside aft beam lashings, I took them off completely (one at a time) and was surprised to see a space under the beam, with the boat at rest in calm water. This was not there when the boat was first assembled; all the beams rested perfectly flat on all their pads so it's not a built-in alignment error. Something is causing the hull to rack slightly, and the downward force on that short mast beam would explain that. During initial assembly, the masts were not up yet so no compression forces from the rigging on to the mast beam. Add to that the sideways forces on the rudders/skegs as you say, and we have a powerful force vector in addition to the loads normal to the other beams. If that aft mast beam continued through the cabin so it was structural, I'm sure this problem would not exist. But that would ruin the interior. So now what....a return to metal brackets?!!!
Anyway, thanks Dave, Alex, and Paul for your replies. Now...where is Jacques? Having pushed "Pilgrim" as hard as he did, I wonder how his aft beam fared.
Tomorrow we round Cape Mendocino, weather looks promising for dealing with this "Cape Horn of the North"
Ahoy Capn Alf,
I've just replaced beams #1 and #4 on a larger classic with the bolt and bracket beam attachments. #4 was the first one replaced and I could not eliminate the gap beneath the inboard brackets. I was afraid the remaining old beams had taken a set. This is a cutter rig with the mast stepped on the short amidships beam and also supported by beams #2 and #3. When #1 was replaced a few weeks later, I slacked the rig, letting out the shrouds very loose, and only using the running backstays to keep the mast up, but with little tension. The new beams were then able to be totally tightened, eliminating the gaps, then the rig was retightened.
Those funny looking free standing junk rigs now make a lot more sense to me, no mast compression on the crossbeams!
Thanks Jacques, I will learn to live with that movement then, and replace the lashings before they are one year old! A failure there would be pretty bad mid-ocean.
Andy, I have been fantasizing about free standing masts also....
We were getting noise from the rear beam on our Tiki 30 when it just had the straps. We added pads to the inboard gunnels and then lashings, tightened them up as much as we could and added frappings and the noise went away until the lashings worked a bit loose.
The noise was generally from a quartering sea so I reckon it is when there is maximum twist on the hulls.
We have also added a light netting beam on the stern and I was wondering if that might help - no means of assessing this without taking it off which I am not about to do!
I had a problem with lashings loosening off when sailing when I had the mast on a short beam as designed on a P 31. The mast step is typically under down pressure = approx. 25% - 50% of boat weight on a one mast rig. But this is only half the story. If the shrouds are on the outer hull sides then they pull up with an equal and opposite force. The total "couple" is massive - these forces [weights] added then multiplied by the distance between them ie. one hull width. Even for my P 31 this comes to anywhere up to 1,500 kg/m in normal use and 3,000 at max design load ! Frankly I consider these half beams to be poor engineering. Since I got rid of mine I have not had to adjust my lashings for two years. See also 3 x crossbeam Pahi 31 discussion.
For the ones who mention that a lose -not hard tied- rear beam is OK, I want to share another observation:
while we were offshore the aft beam got lose, probably because i tied it bad , or the rope was not in good condition, the bolt was carving a bigger hole, (with the result of water inlet and damage all what got wet).
added to some other problems we had, we started a routine to stop the boat each day at early afternoon (to have enough daylight hours to fix any possible problem) to make a general checkout of the important parts. We discovered that the rear tube was taking part of the stress that should be taken by the aft wooden beam. The wooden block that is used to leash the tube to the boat showed cracks on its base, it was a big concern for us, I was fearing that the aft tube collapsed, fortunately nothing happened but its a good example that when a part of the equipment is not doing its work, another part of the boat will take its place, probably triggering a chain breaks.. now after that experience I pay more attention to preventive maintenance.
When you get to San Diego, I would be happy to pick you up with my truck for a shopping trip. If you would like a hot shower when you get in, you are welcome to come over to my house. Would love a tour of your beautiful Tiki.
I've done that outside route down the coast from Cape Flattery to San Francisco on my Bristol Channel Cutter. Out of all the miles I've sailed those were the scariest conditions I've ever experienced. Of course after Point Conception, you'll be in the "swimming pool" of Southern Ca. and you'll be able to relax.
Alf, like Andy said, in order to tighten the beam lashings of a boat in the water, you need to take all tension out of the shrouds. Use the halyards led to a suitable support to support the mast. Bon voyage!
The double lashing came up when I was discussing this very problem with Adrian of Two Ticks (T38). They had just done a similar trip to us, Cape Town to NZ. He had the same aft beam inner lashing issues. He solved it by adding the additional lashing.
The other comments regarding slacking the aft main mast shrouds are correct. It does make it easier to get the lashings tight.
I replaced all my lashings before we did our trip. Dragon was 4 or 5 years old then. None of the old lashings showed any wear at all. The current lashings after the trip are still in good condition and havent been replaced. Next year Dragon will be 10, she'll get a re-paint but the lashings will probably stay!