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Anybody got thoughts or theorys on lashing a tangaroa without the through bolts,just using rope?

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The bolts dont go through the bulkheads.

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In order to use lashings only without beam locating bolts, you would need to create locating blocks (Tiki 30 style) on the deck and beam, as well as lashing stops,  in order to keep the beam from shifting. This is how I will be doing it on my Narai build.

Thanks for the replys. Thats what i wanted to hear..I was wondering as to what added strength the bolts would give on the freak chance the ropes gave way,which i imagine would be practically impossible. Apart from the fact i dont fancy drilling into my brand new beams,the slots recommended on the plans seem a potentially difficult thing to line up perfectly. I have considered a central lacing over the beam between the two lashings as a extra measure. Also locating blocks on the top of the beam to hold the beam in place. But you think locating blocks in the beam trough also? This is on a Tang mk4.

The locating pin provides a pivot point for the hulls to "rock" back and forth on as well as an anti-slip device to keep the beam from sliding back and forth across the hulls. When you eliminate the pin, your beam connections will become closer to monocoque type connections. In order to prevent the slippage, you will want to create some type of locating block system inside the base of your beam troughs with a mate on the bottom of your beams to lock them in place.

Consider a "U" shape inside your beam troughs: Two "U's" on each end of the trough with the open ends of the "U's" facing each other.

Then put a "T" shape on the bottom of your beams: Two "T's" on each end of the beam, with the tops of the "T's" facing each other and installed so that the vertical of the "T" fits inside of the "U" and the horizontal of the "T" fits across the top of the opening of the "U."  This will prevent movement in all directions.



matt connolly said:

Thanks for the replys. Thats what i wanted to hear..I was wondering as to what added strength the bolts would give on the freak chance the ropes gave way,which i imagine would be practically impossible. Apart from the fact i dont fancy drilling into my brand new beams,the slots recommended on the plans seem a potentially difficult thing to line up perfectly. I have considered a central lacing over the beam between the two lashings as a extra measure. Also locating blocks on the top of the beam to hold the beam in place. But you think locating blocks in the beam trough also? This is on a Tang mk4.

Thanks Budget Boater,there's a photo of Don Brazier's narai Katipo with something like that except he's lashed his differently. Im wondering about the movement with this set up,i guess if the fit of the locating blocks isn't to tight there still could be some movement but not enough to allow beam sliding?



Budget Boater said:

The locating pin provides a pivot point for the hulls to "rock" back and forth on as well as an anti-slip device to keep the beam from sliding back and forth across the hulls. When you eliminate the pin, your beam connections will become closer to monocoque type connections. In order to prevent the slippage, you will want to create some type of locating block system inside the base of your beam troughs with a mate on the bottom of your beams to lock them in place.

Consider a "U" shape inside your beam troughs: Two "U's" on each end of the trough with the open ends of the "U's" facing each other.

Then put a "T" shape on the bottom of your beams: Two "T's" on each end of the beam, with the tops of the "T's" facing each other and installed so that the vertical of the "T" fits inside of the "U" and the horizontal of the "T" fits across the top of the opening of the "U."  This will prevent movement in all directions.



matt connolly said:

Thanks for the replys. Thats what i wanted to hear..I was wondering as to what added strength the bolts would give on the freak chance the ropes gave way,which i imagine would be practically impossible. Apart from the fact i dont fancy drilling into my brand new beams,the slots recommended on the plans seem a potentially difficult thing to line up perfectly. I have considered a central lacing over the beam between the two lashings as a extra measure. Also locating blocks on the top of the beam to hold the beam in place. But you think locating blocks in the beam trough also? This is on a Tang mk4.

I have Don's sketches, and he installed locating pins (unless he has recently changed it.)

If you install locating blocks, I would make sure they have a good fit with very little room to move in any direction. The blocks prevent side-to-side and back-and-forth movement, while the lashings prevent up and down movement as well as keep the hulls together.

matt connolly said:

Thanks Budget Boater,there's a photo of Don Brazier's narai Katipo with something like that except he's lashed his differently. Im wondering about the movement with this set up,i guess if the fit of the locating blocks isn't to tight there still could be some movement but not enough to allow beam sliding?



Budget Boater said:

The locating pin provides a pivot point for the hulls to "rock" back and forth on as well as an anti-slip device to keep the beam from sliding back and forth across the hulls. When you eliminate the pin, your beam connections will become closer to monocoque type connections. In order to prevent the slippage, you will want to create some type of locating block system inside the base of your beam troughs with a mate on the bottom of your beams to lock them in place.

Consider a "U" shape inside your beam troughs: Two "U's" on each end of the trough with the open ends of the "U's" facing each other.

Then put a "T" shape on the bottom of your beams: Two "T's" on each end of the beam, with the tops of the "T's" facing each other and installed so that the vertical of the "T" fits inside of the "U" and the horizontal of the "T" fits across the top of the opening of the "U."  This will prevent movement in all directions.



matt connolly said:

Thanks for the replys. Thats what i wanted to hear..I was wondering as to what added strength the bolts would give on the freak chance the ropes gave way,which i imagine would be practically impossible. Apart from the fact i dont fancy drilling into my brand new beams,the slots recommended on the plans seem a potentially difficult thing to line up perfectly. I have considered a central lacing over the beam between the two lashings as a extra measure. Also locating blocks on the top of the beam to hold the beam in place. But you think locating blocks in the beam trough also? This is on a Tang mk4.

I thought I might just add a little explanation to this thread. When I modified my Narai IV beams from the classic bolts and rubber blocks system to longer beams, lashed down, I used a centre bolt on beams two and three . These beams sit against thin hardwood pads on the bulkhead head side of the beam trough. There is a bolt sized hole in the beam horizontally through the beam but a hardwood reinforced slot in the bulkhead side of the beam trough with a large metal washer on the inside. Everything is well epoxied . There has been no water ingress into the inside of the hull along the bolts .
The beam lashings are like Tikis to wooden 'cleats' on hull sides and are tight. The beam sits flat in the beam trough on 12 mm thick conveyor belt rubber.
Beams one and four again sit flat on conveyor belt but have wooden guides glued to the beam trough base and a block on the beam between them either side to prevent slippage . The lashings go through eye bolts but standard lashing points on the hull sides might have been easier and cheaper.
I have just returned from a 3000 mile voyage from NZ to Tonga and Fiji and back and all is still well. In fact I have not had to tighten the lashings in the last 8000 miles.
It seems that there is a little leeway in how things can be organised, but if in doubt it is simpler to stay with James Wharram's design systems.
Don
Thanks Don, how necessary do you think the locator bolts are on 2&3? And do you think Australian iron bark would be too heavy for strakes?
It is hard to answer your question about the bolts . If you omitted them you may find out the answer when it was too late to do anything about it ! It is a belts and bracers system to some extent I suppose and it would also help with accuracy etc when assembling hulls and beams.
Having said that I know that Don Henderson omitted them on his Tehini which he has been sailing I the Pacific for years. He has the older brackets, rubbers and vertical bolts through the deck system.
Another boat similar in many respects to Wharram Designs which uses just the lashing system only is Hans Klaar's 70 foot Ontong Java .
The reason I drilled a round bolt hole in the beam with a small slot in the bulkhead was that it was easier to do and should there be and deterioration in the slot area, it might be easier to repair in the bulkhead. However in about 9000 miles so far since I made the change to lashed beams there has been no evidence of wear ( or rot ). The beams in general in fact seem to move only very marginally.
If you had some other system to prevent possible sideways movement of the beams, as has been discussed before ,then perhaps the bolts are not so necessary??????
As for Australian Iron bark , I am afraid it is a wood I am not familiar with. But one issue with some hardwoods you may have to consider is how well will it glue to the hull side.
Don

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