Neeves
Well-known member
I would start by giving the decks a darned good clean before posting images
Why does the OP take his pictures at midnight? or is it normally this dark in the UK in winter
Jonathan
Stroppiness
- Thread starter zoidberg
- Start date
Why does the OP take his pictures at midnight? or is it normally this dark in the UK in winter
Jonathan
Neeves
Well-known member
Glue?, are you serious (or is the OP serious) - it must be very good glue.
Further thought, still using the amazing glue.
The 'flange' or plate to which the LFRs are to be glued. Drill a bigger hole, the size of my threaded LFR suggestion, make sure the hole/LFR is a tight fit (I'd thread it to match but don't see that being easy) and then glue each half of the threaded LFRs into the hole. The plate/LFR become one tight unit - the 'glue' does not need to be strong. You can then improve the angle through which the 'mazing' strop passes.
Jonathan
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Neeves
Well-known member
This is a link
Aluminium Threaded Through Deck Bush
I thought they also made them from stainless but did not see reference, but I lost motivation.
Their Tii fittings might also suit - same link.
Jonathan
noelex
Well-known member
Selden has a similar commercial aluminium bowsprit. You could replicate their fittings.
The end fitting utilized is similar to a spinnaker pole fitting. I suspect a standard spinnaker pole fitting could be adapted to function satisfactorily.
The end fitting utilized is similar to a spinnaker pole fitting. I suspect a standard spinnaker pole fitting could be adapted to function satisfactorily.
LittleSister
Well-known member
Wasn't it Ken Dodd that sang -
'Stroppiness, stroppiness, the greatest gift that I possess
I thank the Lord that I've been blessed
With more than my share of stroppiness'
- ?
'Stroppiness, stroppiness, the greatest gift that I possess
I thank the Lord that I've been blessed
With more than my share of stroppiness'
- ?
Neeves
Well-known member
Glue?, are you serious (or is the OP serious) - it must be very good glue.
Further thought, still on use of the amazing glue.
LFRs, or at least aluminium LFRs are anodised, often with pretty colours. Some anodising contains Teflon, or something similar (I'm not sure how this works as anodising is a chemical/electrical process). Coating devices that are being used for their slipperiness (hence calling them 'Low Friction rings'), adding a coating to make them even more slippery and then expecting the surface to accept 'glue' is a big ask (or bigger than I'd accept without testing the idea first). Anodising is an aluminium oxide hard layer (and aluminium oxide is very hard - even though its a thin layer - lasts a long time - so the whole idea of developing a chemical bond by the JB Weld of the flange and the LFRs looks questionable. Might be worth a trial before committing.
I don't know the thread characteristics of Allen Brothers 2 part threaded rings but maybe a plumbers thread cutter, die, might be a match - and then you could drill and thread the flange to accept the 'deck bushes/LFRs'
Jonathan
Further thought, still on use of the amazing glue.
LFRs, or at least aluminium LFRs are anodised, often with pretty colours. Some anodising contains Teflon, or something similar (I'm not sure how this works as anodising is a chemical/electrical process). Coating devices that are being used for their slipperiness (hence calling them 'Low Friction rings'), adding a coating to make them even more slippery and then expecting the surface to accept 'glue' is a big ask (or bigger than I'd accept without testing the idea first). Anodising is an aluminium oxide hard layer (and aluminium oxide is very hard - even though its a thin layer - lasts a long time - so the whole idea of developing a chemical bond by the JB Weld of the flange and the LFRs looks questionable. Might be worth a trial before committing.
I don't know the thread characteristics of Allen Brothers 2 part threaded rings but maybe a plumbers thread cutter, die, might be a match - and then you could drill and thread the flange to accept the 'deck bushes/LFRs'
Jonathan
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zoidberg
Well-known member
They do indeed.... I looked at their prices and harumphed 'How much!'
Rather than replicate their fittings ( although I considered that at length ), I did, however, use their 'bowring' which is visible in my pic and also here:
I determined the tube diameter and wall thickness of the unit they recommend for my weight/RM of boat, found an alloy tube supplier, and acquired a sufficient length ( in T6061 alloy ) in a larger diameter and beefier wall thickness. I've also kept the UnSupportedLength and DistanceBetweenSupports USL/DBS distances well within recommended.
The cost to me is under 1/5th of the retail package, which saves rather a lot of beer tokens.
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Dutch01527
Well-known member
I would have a local stainless fabricator knock up a simple fitting to bolt through deck on either side and bridge over the bowsprit. Would be pretty simple and stronger than the original. This is not an area to bodge up a makeshift solution. You could lose your rig and kill someone if the line was to chafe.
boomerangben
Well-known member
I am not familiar with the Evo Mx10 shackle, but looking at your drawing and a photo of the shackle, it looks like there will be a high stress point contact of the shackle vs top of alloy tube. Moreover, I don’t see how you will be able to get sufficient tension in the dynema line. From your drawing all the vertical load from the stay will be transferred to the low friction rings and thereby held by your JB glue. It just doesn’t look right to me
boomerangben
Well-known member
Just to add….
I don’t know which of the many JD Weld products you are planning to use, but the couple I looked at have a tensile strength of 4-5000 psi. 5000 psi is about 35N/mm^2. Good Structural steel (and I am aware that I am being very general here, the strength of steel varies a lot) is about 10 times that.
Daydream believer
Well-known member
I do not think that the JB Weld is meant to take a great deal of load. Just ensure that the rings stay in place. Comments about threading the rings are not very practical when one considers that the central piece is possibly only 5-6 mm thick/ Packing the rings with washers would cause side stresses that would weaken the fittings & cause upward bending.
Although the load on the dynema is quite high the compression load on the tube is not that high. What might happen is that when going to windward the dynema might want to rotate & pull the tube sideways placing strain on its mountings. But I cannot see the tube itself being crushed, To demonstrate this, get a loop of cord pull it from end to end & then see how easy it is to pull the 2 strands apart at mid length for a short distance ( replicating the tube). One can pull very hard on the ends but still easily part the strands a short distance
But going back to the OP's query- How many strands of dynema? I would try as many as possible. I would also suggest not one piece but 2 then if one chaffes the second would still be there & a close inspection could recover the situation before full failure occurs. The second loop would be very slightly looser than the first so that failure of the first is obvious
Although the load on the dynema is quite high the compression load on the tube is not that high. What might happen is that when going to windward the dynema might want to rotate & pull the tube sideways placing strain on its mountings. But I cannot see the tube itself being crushed, To demonstrate this, get a loop of cord pull it from end to end & then see how easy it is to pull the 2 strands apart at mid length for a short distance ( replicating the tube). One can pull very hard on the ends but still easily part the strands a short distance
But going back to the OP's query- How many strands of dynema? I would try as many as possible. I would also suggest not one piece but 2 then if one chaffes the second would still be there & a close inspection could recover the situation before full failure occurs. The second loop would be very slightly looser than the first so that failure of the first is obvious
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Neeves
Well-known member
And a good weld should be stronger than the steel, if there is to be a failure its the steel that fails - not the weld.
Jonathan
Trident
Well-known member
You have two issues with the dyneema - both should be ok with 3mm multi pass - the radius of bend will be well over 2D and the attachments are not so small that you lose too much with having dyneema on dyneema to get lots of loops through. Chafe is easily dealt with by a cover and regular checks.
However, the JB weld is the weak point - there are some very strong methylcrete adhesives that will bond steel or ally with the strength of an actual weld by JB Weld, unless they have changed the formulation is not it. Antal do some lovely and quite inexpensive padeyes for dyneema - even on sale at Force4 right now - these can bolt to the deck securely. Or go even simpler with a through deck fitting (even a nice cheap TruDesign through hull is fine) to guide the dyneema without chafe (they're nice and smooth on the inside) and the load is then below deck on a suitable backing plate with a dog bone or even just a big stop knot. The Forestays on some IMOCA 60 are done this way for the full forestay load and I've used the same method for backstays, LFR loops for the jib sheets (on a 50 foot cat so the loads are much bigger than your projections ) with no issues
However, the JB weld is the weak point - there are some very strong methylcrete adhesives that will bond steel or ally with the strength of an actual weld by JB Weld, unless they have changed the formulation is not it. Antal do some lovely and quite inexpensive padeyes for dyneema - even on sale at Force4 right now - these can bolt to the deck securely. Or go even simpler with a through deck fitting (even a nice cheap TruDesign through hull is fine) to guide the dyneema without chafe (they're nice and smooth on the inside) and the load is then below deck on a suitable backing plate with a dog bone or even just a big stop knot. The Forestays on some IMOCA 60 are done this way for the full forestay load and I've used the same method for backstays, LFR loops for the jib sheets (on a 50 foot cat so the loads are much bigger than your projections ) with no issues
thinwater
Well-known member
The main downside of a threaded low friction bushing is that the deck fitting would need to be built with a larger hole. Let's assume we've move past JB Weld. I'm pretty sure I've seen big boats with forestays lashed to a bushing like that.
The other obvious option is a fitting that amounts to a split forestay. More complicated to fabricate, but not bad.
The other obvious option is a fitting that amounts to a split forestay. More complicated to fabricate, but not bad.
zoidberg
Well-known member
I'm grateful to those who have sought to guide and contribute. It's difficult conveying all the relevant aspects and considerations, given one limited photograph and a ropey sketch. In particular, Daydream Believer, Neeves and Trident have made points I will seek to incorporate.
Here's a pic I took earlier... up a ladder, in the wind and rain of an approaching new storm.... showing the arrangement of deck fitting/LFRs/JBMetalWeld/Bowsprit tube.
It will be seen there are 4 holes, with two LFRs 'jbwelded' into place. The purpose of the LFRs is simply to provide a good 'D:d' bend ratio and a smooth non-chafe surface. It will be seen that there's capacity for TWO multipart strops ( as suggested in #31 ) which will also fit into the Wichard EVO shackle - and I intend to do that.
I should be able to fit 2 x 9 'bare' loops, capacity >2 x 14850kg.... or 2 x 7 'sheathed' loops, capacity >2 x 11550kg.
I should be able to inspect routinely for cracking of JBWeld bond and for chafe.
Should the JBWeld bond fail, among my options is A: removing the bowsprit tube and welding on a steel capping piece, and B: also securing LFRs with 'methylcrete'.
Further, I have fitted an inner stay, also in 7mm 1x19 s/s, which should retain the mast in place should the Wichard/Dyneema strops setup fail totally.
Here's a pic I took earlier... up a ladder, in the wind and rain of an approaching new storm.... showing the arrangement of deck fitting/LFRs/JBMetalWeld/Bowsprit tube.
It will be seen there are 4 holes, with two LFRs 'jbwelded' into place. The purpose of the LFRs is simply to provide a good 'D:d' bend ratio and a smooth non-chafe surface. It will be seen that there's capacity for TWO multipart strops ( as suggested in #31 ) which will also fit into the Wichard EVO shackle - and I intend to do that.
I should be able to fit 2 x 9 'bare' loops, capacity >2 x 14850kg.... or 2 x 7 'sheathed' loops, capacity >2 x 11550kg.
I should be able to inspect routinely for cracking of JBWeld bond and for chafe.
Should the JBWeld bond fail, among my options is A: removing the bowsprit tube and welding on a steel capping piece, and B: also securing LFRs with 'methylcrete'.
Further, I have fitted an inner stay, also in 7mm 1x19 s/s, which should retain the mast in place should the Wichard/Dyneema strops setup fail totally.
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Neeves
Well-known member
I'm grateful to those who have sought to guide and contribute. It's difficult conveying all the relevant aspects and considerations, given one limited photograph and a ropey sketch. In particular, Daydream Believer, Neeves and Trident have made points I will seek to incorporate.
Here's a pic I took earlier... up a ladder, in the wind and rain of an approaching new storm.... showing the arrangement of deck fitting/LFRs/JBMetalWeld/Bowsprit tube.
It will be seen there are 4 holes, with two LFRs 'jbwelded' into place. The purpose of the LFRs is simply to provide a good 'D:d' bend ratio and a smooth non-chafe surface. It will be seen that there's capacity for TWO multipart strops ( as suggested in #31 ) which will also fit into the Wichard EVO shackle - and I intend to do that.
I should be able to fit 2 x 9 'bare' loops, capacity >2 x 14850kg.... or 2 x 7 'sheathed' loops, capacity >2 x 11550kg.
I should be able to inspect routinely for cracking of JBWeld bond and for chafe.
Should the JBWeld bond fail, among my options is A: removing the bowsprit tube and welding on a steel capping piece, and B: also securing LFRs with 'methylcrete'.
Further, I have fitted an inner stay, also in 7mm 1x19 s/s, which should retain the mast in place should the Wichard/Dyneema strops setup fail totally.
The metal flange holding the 2 LFRs appears to be simply bolted through the deck. Why not remove it, make a new one with tubes in holes with an ID to take the Allen two part threaded deck bushes at their maximum length which will give you the best D:d ratio. Then you don't need to inspect the 'weld' nor worry about it. I do confess the deck bushes are not cheap.
Jonathan
zoidberg
Well-known member
The Allen deck bushes are excellent, and worth the money. I hesitate to remove the existing, original deck-mounted forestay flange for 'it ain't broke'....
It is, for me, extremely awkward attempting to gain access into that very tight underdeck space - I can get one arm and my head in 'partly'.... or two arms 'partly' but not my head. Keeping eyes-on while operating a tool in there has proved, for me, impossible. And the bruises hurt for days.
Fitting the Selden Bowring further forward with through-bolts, epoxy bog, spreader plate and lock nuts involved a considerable rigmarole and the help of a lithe and very slender slip of a girl - for I couldn't get to them. I don't want to go through that again.
It is, for me, extremely awkward attempting to gain access into that very tight underdeck space - I can get one arm and my head in 'partly'.... or two arms 'partly' but not my head. Keeping eyes-on while operating a tool in there has proved, for me, impossible. And the bruises hurt for days.
Fitting the Selden Bowring further forward with through-bolts, epoxy bog, spreader plate and lock nuts involved a considerable rigmarole and the help of a lithe and very slender slip of a girl - for I couldn't get to them. I don't want to go through that again.
Daydream believer
Well-known member
Hang on- 37 posts & you have only just told us about the lithe slender slip of a girl. That is not right. I think you had better come clean & give us the full QT on this project. We have been prattling on about JB Weld & you have been hiding slips of girls. What else have you not told us?
zoidberg
Well-known member
Oops!One of my more influential teachers was a Jesuit.
And one of my life's goals has long been to sail in my own boat, with an all-girl crew.....
