In Part 3 we set the rake and bend and tightened all the rigging up just firm, which is the core part of doing a good mast tune.
Now let's tidy up a few important details so we can get on with the sailing tune (Part 5).
The Offshore Voyaging Reference Site
In Part 3 we set the rake and bend and tightened all the rigging up just firm, which is the core part of doing a good mast tune.
Now let's tidy up a few important details so we can get on with the sailing tune (Part 5).
Previous: Rig Tuning, Part 3—6 Steps to a Great Tune
Great article and series. Question are you re-pouring the Spartite every time you step the mast? or are you using the Spartite blocking to help reset the mast in the correct location?
No, you can reuse the Spartite. In the last part I will cover a whole bunch of tips and hacks to make subsequent stepping very easy, including that.
And no, the whole point is that mast blocking changes nothing. The mast position is set before we block. Please see parts 2 and 3 for more on that. Particularly the theory in part 2. Also, in this chapter I write:
Continues to be an excellent series. Thanks.
There are two other reasons besides boat movement to consider when tightening the rigging screw and you find the tension on the shroud/stay is not increasing that have come to my attention over the years. A couple of times I know of the mast base being corroded to a thin section (hard to see from the outside) and the mast was literally being ground into the mast step with the compression tensioning of the rigging screw. The other time, the shroud had a wire or two broken at the entrance to the swage at the top of the mast and tightening the shroud just was unraveling the shroud from the swage.
Lots to watch out for.
My best, Dick Stevenson, s/v Alchemy
as clear as this sounds it leaves me clueless – so it should be prudent to get atop to check all wirings after finishing the tune? How are you handling this?
Thanks for pointing out the need to clarify. I was merely trying to say that I have bumped into other reasons for the lack of increase in wire tension when tightening the rigging screws. That said, it is always a good idea to eyeball all swages after the rig is tuned.
My best, Dick
A couple of very good points, thank you.
On the same subject, I was wandering around a boat yard looking for masts to photograph to clarify flat butt syndrome, and was distressed to find that the vast majority had no butt fitting at all. Meaning that the raw extrusion is being placed directly on the step, a recipe for corrosion over time, and very poor practice.
This is the problem that I have. There is a piece if 1/4″ aluminum plate in the bilge and the extrusion just sits on that. I think the plate is held down by a couple of machine screws. I have been trying to find a design for a butt fitting and an adjustable mast step. So far I have not found anything. So i have started to design my own. Any suggestions?
I’m pretty sure you can get both from Selden mast. Not sure if they will do a custom job for another mast manufacturer section, but that’s where I would start the search.
If not, a mast butt is simply machined from a solid block of aluminium to the OD and shape of the mast, with a insert part of say 1″ machined to ID of the section.
The bottom should have a slight arc as discussed in Part 1.
Then the two pieces are mated together with a heaping helping of TefGel and fastened with SS machine screws.
I will write more about this, and screw jacks, when I clarify “flat butt syndrome” and what to do about it.
By chance I had the mast out of the boat when your articles were first published, so it was very interesting and helpful thanks. I thought our production boat experience might be helpful for others as it also lead to some head scratching on my part as we have no butt fitting in our Z-Spar mast. The mast rather sits in a solid cast aluminium shoe that is bolted in place to a cross girder – and I gather this acts as a “female” plug and mast base in one. There is almost zero play once the mast is in its shoe and no way to adjust the mast base position when in there. The partners are formed by an opening in the deck above with a bolted on alloy mast collar, also with very little play around and no adjustment. With the mast in place, it is almost perfectly raked and centred with the stays slack (as in your instructions). I know that with moderate pre-bend settings we are so balanced (small to moderate amount of weather helm in most wind strengths) when sailing upwind or reaching she will usually sail herself with no autopilot – I guess one blessing of a well worked out production boat (Beneteau 473).
Anyway, following your article I questioned our rigger who was replacing the stainless rigging (after 15 years) and he said ours was the most common set-up and they seldom see boats here (production or otherwise) with a mast plug. Given we have little play fore and aft (nor seem to need it) and there was no visible wear or damage on the mast butt, there seemed little point fitting one. The rigger’s advice was to leave it as designed.
We did have corrosion in the aluminium mast shoe, but this was around the stainless tie rod that ties the mast collar to the shoe and prevents the deck from working from halyard loads.
So please excuse a different kind of “plug” – we decided to replace both the Z-Spar shoe and collar which arrived by courier with some other rigging mast parts in just 4 working days from the USA to NZ. It seems every single part for our 16 year old mast is available (almost entirely ex-stock) at a very reasonable price from their web-site: https://www.usspars.com/boat-information/?vendor=Beneteau&model=OC+473#section-display.
Our rigger was mightily impressed – great service US Spars!
Hi John and everyone,
I am sure I have seen mast butts, but I do not remember having done so in all the boatyards I have walked around, nor have I ever owned a boat where the bare mast extrusion did not sit directly on the step. And the same for all the friends I have helped with their work over the years. So, I am intrigued and wonder what the benefit/drawback would be of a retrofit. Mine is a quite dry boat, so I have little corrosion. I would also have to see whether the turnbuckles could tolerate whatever the length the mast butt would add to the overall mast height.
My best, Dick Stevenson, s/v Alchemy
Distressingly, you are right, a proper mast butt fitting is not common. That said, its still good practice, both for corrosion prevention and so that the bottom can have a slight arc to make tuning easier and more consistent. And yes, if we add an butt fitting, we need to trim the bottom of the mast the same amount. Often not a bad idea because of the very corrosion you mentioned in an earlier post.
I’ve seen them, but only in the context of some sort of depression in a deck-stepped “tiny tabernacle” where the mast butt, often a chamfered sort of rectangle, fits into a matching “female” spot on deck, after which a pin is put through a second extrusion.
We have a very large tabernacle (over a metre high) for our deck-stepped mast which allows the mast to pivot down for canal transits and related service or transport. But we do not have a fabricated mast butt; the mast sits on a rubber pad to keep it from metal on metal wear, but it wouldn’t be too hard to have one made and to remove whatever length of mast it augmented to leave the mast height at zero. Thanks again for getting me to consider something I had never really thought of!
It’s good to hear that the builder got this right and given that they did, it sounds like you are all good. I think what we can learn from this is that for a long production run boat like yours, with a builder who has deep experience, there is a good chance of getting things right without leaving any adjustment. However, with boats that have shorter runs, and are less “manufactured” I still feel happier if the builder has given us room to adjust.
Further, I suspect that the general move to deck stepped masts in the last few years is because builders no longer want to provide adjustment, or risk getting the partner to step relationship wrong.
Also good to hear about the great parts service.
Regarding Spartite I found a nice 3-part series on youtube showing how the Spartite tightening is done: https://www.youtube.com/watch?v=PTakwY3JcY8&start_radio=1&list=RDPTakwY3JcY8
Just hope you have thoughts to share on how to tune a solent rig. Can get the forestay to have no appreciable sag but not the solent stay. Also we have a removable inner stay for our storm jib. It’s only set up for passage. At present set it up to be tight and not deflect beyond 1/2” when pressed on at shoulder height but clueless as to whether this is good thinking. Doing so does seem to put a bit of pre bend in. Finally uncertain as to how to handle the hydraulic backstay when using the storm jib. Would seem more tension would give more sag. Have noticed with the solent you flatten things initially but then get nothing by going further.
Hum, I don’t think that the solent rig is at the core of your problem. Rather I think your basic tune is flawed, and that, in turn, is making everything else a problem.
So, I would recommend that you do a complete, from scratch, tune job, starting from chapter 1. The only variation I would add, would be to slack the fore stay completely and tune as if the solent stay was the only one forward.
Once you have rake and prebend all set, but before you tighten the backstay and solent stay to sailing tune (see above) tighten the forestay to just firm, but on no account tighter than the solent. Then proceed as above, but tightening all three (backstay, solent, forestay) together. As you do that, monitor the prebend with the reference line (part 3) and make sure you are not getting a hard spot in the curve near the top or changing the prebend much.
Your goal is to end up with an even curve and the solent just a bit tighter than the forestay since it is the solent that you will be using in heavier weather.
As to the storm jib stay, see Part 2 and Part 3 for how that should be set in relation to the running backstays. (If you don’t have runners opposing the storm jib stay, then they should be added.)
Another good post. A few thoughts in reaction to it:
I agree completely on Spartite. I have been that guy trying to put wedges back in. It is not that I think wedges don’t work, they just need to have a very low taper angle which also makes them quite long so that you can get a good fit which often interferes with stuff mounted on the mast above the partners. Spartite is also much quieter which is a big deal for me at least.
On how much tension to put in the backstay/forestay, I am not sure that all 40′ boats would do well to have a strong person really crank on a set of 12″ wrenches. On our boat with a 5/16″ backstay (often found on 40’ers) and corresponding 5/8″ thread size in the turnbuckle, I can get to 20% of wire breaking strength quite easily with a set of 8″ wrenches. I do a good job of cleaning and lubricating the threads and have a lot of experience dealing with highly torqued fasteners. If you assume a k factor of 0.2 (which is really like using loctite on clean threads, grease will be even lower) on a 5/16-18 thread, it only takes about 26 ft lbs to get to 2500 lbs of tension which is 20% of breaking strength. This would only be 26 lbs of force at the end of a 12″ wrench which is not a whole lot if you have good body position. I suspect that many people have poor threads and don’t lubricate appropriately which leads to very high k factor and resulting difficulty in getting to tension but if done right, it isn’t that hard. I suspect that part of the reason for the results you posted are also likely related to diameter, as diameter goes up, you need more torque for a certain tension and I would assume your backstay turbuckles are significantly larger diameter than what you would find on a 40’er.
We do use a tension gauge in 1 place which is to set forestay/backstay tension. Due to geometry, our forestay has slightly more stress so we put the gauge on it and adjust until it is at 20% of breaking. If we had hydraulics, we would just look at the gauge there but we do not. This results in more tension than ideal in lighter air but seems to be the best overall compromise.
One other silly thought is that I find it much easier to use the vice grip style crescent wrenches for tuning although I have never seen them in large sizes so it may not apply to boats over about 40′.
That’s great, thanks. I agonized about that tension part, more than any other, to the point that Phyllis and I tried it twice to see what we ended up with. That said, I think you are right that relative diameter between your turnbuckles and ours may be the variable. Anyway, really good to have your analysis on that. I will add a note to the chapter pointing at your comment and caution.
What do you think of my graphing idea to determine when a hull can take no more? I know that back in the day when I ocean raced we tended to pump up to truly frightening numbers when going to windward in big breeze, and typical only stopped when the gauge stopped going up. Of course, these were not our boats and a lot of this went on when the owner was off watch!
I noticed that in one place in my previous post I said a 5/16-18 thread where I meant a 5/8-18 thread. The numbers should otherwise be right. If the thread were 5/16, it would take about half the torque for the same load which would be very easy to get into trouble with.
I have not previously given much thought to your question about graphing load versus displacement on the backstay, thankfully I have always sailed sufficiently stiff boats to not run into that. I have no special knowledge in this area so my comments are only educated guesses. My initial reaction is that if you are only finding the stiffness of the hull, that is not a big deal as stiffness of a structure tends to be relatively constant across its stress range (this is why you see the Modulus of Elasticity) and relative deformation doesn’t tell you anything about stress, only absolute. However, if you truly get to a point where there is no backstay tension increase at all with displacement of the ram, then there is an issue as that would imply you have gotten into plastic deformation which is not reversible. Telling the difference between these can be tricky as the slope can be low but not zero and you can have no plastic deformation. One thing that would worry me is if I slowly needed additional piston displacement to get to the same loads over time. This wouldn’t be a valid measure on new rigging but once it has settled, you could measure piston extension and if you had less over time for the same pressure, that would worry me (I am assuming that creep of the fiberglass hull is small enough that it would not be an issue with this but I haven’t actually tried to check that). Of course, shock loading while sailing can get higher than the load that you set things at and if you were actually plastically deforming structure, you would expect to see some amount of slackening. Regardless, your suggestion to not keep cranking if the load isn’t increasing seems valid.
I suspect that the designers of lightly built racing boats have had to give this some thought so they probably know what it means much better.
Eric, we have 12 5/16″ stays and it takes some time to tweak them. I use either a long screwdriver (with a lanyard around my wrist!) or vise-grips of the pointy kind. I agree that if the threads aren’t galled, it is not hard to get them to the state where the deflection suggests they are in the desirable 20% zone. Still, as I used to use the simpler Loos Gauge for my old boat (1/4″ wire size), I feel I should invest in its bigger brother just to be sure I have even tension on opposing sides of the mast. I know to look for slack on the lee shrouds, but “slack” is a very imprecise term! I prefer foot-pounds or Newtons or whatever I can verify.
Ah the days of sticking a screwdriver through an open body turnbuckle. I found a crescent wrench with long jaws that I used to put across the turnbuckles. This spring when we got new rigigng, we went with the Stalock supajust ones which have a proper flat for a wrench.
I am someone who is a big believer in knowing exactly how to tighten or adjust every faster and/or adjustment. In my production designs, I specify how to tighten and what thread treatment on every single fastener or other adjustable feature, usually with some form of bolt torque although most designs have a few items that use a different method. Of course, torque is the poor man’s bolt tension. In this case, I am with John that measuring tension is not necessary to get what you want as you won’t know what tension to set to other than for the forestay/backstay. Regarding getting the two sides equal, I am pretty sure that the mast is effectively very flexible compared to the rigging so if you have the mast properly straight, tension is equal side to side. In the end, what we want is a mast that has the shape we want and rigging that doesn’t flop around when the wind gets up. Tension is certainly one way of looking at this but knowing what tension to set to is the trick, an engineer could calculate it but it would be extremely labor intensive and require very good correlation of the design drawings and the actual boat. Since we don’t have this, the first time tuning is done sailing and then there are easy ways to get back to that tune that are position based although tension would be an acceptable way of doing it. I suspect John’s next section will be covering exactly how to do this.
Like you, I’m a holly terror for setting things like torques right (we carry two torque wrenches) and there is nothing I would like more than if boat builders published appropriate tension settings for each rigging component based on full engineering analysis. But in the real world that’s not happening so I think we also have to guard against falsely thinking we are being “scientific” when in fact we are not.
For example, I always have a bit of a secret chuckle when I see sailors carefully checking the shrouds each side for equal tension and nodding sagely when they end up being the same, since, as you say, they always will be, or at least when measured by the inaccurate tension devices commonly available.
Bottom line, we need to recognize the limits of our understanding.
On that note, what do you think of the Selden mast stretch test for determining rig tension? It seems like a good idea to me. But on the other hand, I suspect we must also guard against not being really clear in our minds about the potential inaccuracies due, but not limited, to age of the wire and different wire manufactures. http://www.pbo.co.uk/gear/pbo-tested-4-rig-tension-gauges-45215
All that said, I can’t tell you how much I appreciate you keeping an “engineering watching brief” on my efforts, particularly around tuning, but also over the last few years as I have delved into other technical areas. So, as always, thank you.
I just looked at the “folded rule” method for the first time and in theory, it is perfectly valid. To carry a load, all structures must deflect. Another way of saying this is that stress is proportional to strain, the proportion being the modulus of elasticity. Stainless steel is one of the nice materials where this modulus is pretty constant over the stress range. All this goes to say that if you known the amount of deflection in a structure with known geometry, you also know the stress (actually, this is one of the best ways of measuring it). The numbers given by PBO are for 1X19 stainless wire but this method would work just fine for other constructions if you know what the correct displacement this corresponds to. I would think that 1X19 is consistent enough and there should be no other factors unless you have something like really severe corrosion.
The question that I have would be in how consistently it can be implemented. The deflections are quite low so you need to really have a stiff rule that is well attached to the shroud so that your setup is repeatable. Also, different people will start with different amounts of tension in the shrouds which will have some effect. In theory, you won’t end up putting exactly the same number of turns on each side but it will be pretty close and if you count, you could always even it out in the end. I believe that all of these effects will be pretty small but they will be there.
Overall, this seems like a reasonable method to me although I have never tried it.
Once again, thanks very much for your help. In light of our discussion, I’m thinking about a partial rewrite of the above to recommend either a gauge or the “folding rule” method for setting head stay/backstay tension. And further recommending that tension not exceed 25% of break load of the wire. That recommendation would also apply as the upper limit for those with adjustable back stays—conservative I think, particularly when measured against common practice on racing boats, but then we are cruising here, so no need to take silly risks.
I will leave in the stuff about being mindful about the limits of some hulls to take even that load.
Would you agree that was a good way to go?
I am happy to try to help, I enjoy reading and contributing to your site and also learn a lot from it.
What you are proposing seems reasonable to me. 25% of breaking is a reasonable number. As you say, someone like you who has a lot of experience can probably do it without a measurement tool but for less experienced, some way of measuring tension for the forestay/backstay seems like a good idea whether it be a hydraulic gauge, tension gauge or the folding rule method.
Great, I will get the rewrite done based on that. Thanks again for the help.
I appreciate your comments. I also agree that if you get the important parts of tuning and mast bend correct, you are most of the way to a proper tune that allows the sails to work effectively without stresses the rig unnecessarily. I will still probably get that larger Loos gauge as I had a considerable improvement in sailing characteristics when I used its little brother to tune up my previous boat’s rigging.
I don’t see any referens to the “folding rule” method as described in the Selden rigging brochure. It is a simple way of measuring the actuall tension in a wire by measuring its elongation.
No, simply because I have never used it. That said, it does sound like a good option for those that want to get really scientific about this. Also, you will note that I linked to an article that does explain the method.
Hi John, in the context of your hydraulic backstay adjuster notes, what formula are you using to convert from PSI to pounds tension? Are you basing the conversion on the cross-sectional area of the 1×19 wire? Working back from Harken/Navtec specs, I have 2.1 lbs. pull force = 1 psi, but I don’t know how they are calculating that.
To convert from PSI to tension on any hydraulic cylinder we just need to multiply the PSI by the pressure area of the cylinder, which is the area of the ram surface minus the area of the rod. Or to put it another way, the area that the hydraulic oil pushes on. So, for example, if you read 1000lb on the psi gauge and the pressure area is 2.1 the tension on the stay will be 2100 lbs.
Thanks John. Without detailed specs of the cylinder it’s difficult to know the piston (ram) diameter, so I’m just going to go with the manufacturer’s pull-force specification, which in the case of my Navtec adjuster (and repeating what has been said), is PSI * 2.1 = pounds pull-force.
That should work. That said, if you want to verify and dig into the Navtec site you will find detailed specs on each of the cylinders. I did this myself for the article, although I do remember that finding the information took a while.
Hi. I would like to ask about the use of the inner forestay (cutter-stay) and the runners, as I find it very confusing, and I really struggle to find information on how to use it. If anyone have any book or website, or knowledge to recommend/share on it, I would be very grateful!
My OVNI has a removable inner forestay. I can easily adjust it with a handle on deck. I also have fwd and aft lowers, and as you say, those are the ones to use to set the prebend (especially since my inner forestay is removable).
However, if I am to put any amount of tension on the inner forestay, it will immediately start bending the mast unless I have the runners tensioned. And to get a decent tension for the sail to be used in the stronger winds that I tend to use the staysail in, it will bend the mast a fair bit without the runners tensioned! I think I have realized that I’m mainly supposed to adjust the tension on the inner forestay with the runners (in the same way that you would adjust the “normal” forestay with the backstay).
I now want to go to windward, tacking, and that’s easy, because I can close haul with both runners tensioned. Bear off and I just slack/remove the leeward runner. Easy.
But now I want to do a gybe, and now I need to slack both runners to make room for the boom on the leeward side, AND the new leeward side after the gybe (or pull the mainsheet in quite a lot, which makes the boat feel very “skittish”).
Is it okay to not use any runners for a few minutes during a gybe, which will allow the mast to bend a fair bit?
And also, is it okay to tighten up the inner forestay to induce additional mast bend during sailing (with or without using the staysail or runners)? I do not have an adjustable backstay, so it won’t tighten the forestay, but as I see it, it will flatten the mainsail.
I feel like I am asking very basic questions here, but I have tried really hard to comprehend this. I’ve read all of the sail handling and tuning chapters many times over, and done countless hours of experimenting onboard, but I just struggle with this one. Sorry if I’m beating a dead horse here!
Kindly, Arne 🙂
I started to answer this, but it got way too long for a comment, so I will deal with it in a Q&A article.
May be a few weeks as I have a lot of other stuff on the go at the moment.
Hi, that is way better than I could have hoped for, and I’m happy to wait for it, well aware you got a lot on your plate with so many useful and big topics being tackled these days (and working on your own boat)! 🙂
Feel very free to edit my question for clarity and brevity.
Kindly, Arne 🙂
It’s a good question and exposes a gap in our Online book, so definitely need to fix that right. Thanks for your patience.
I’m working on tuning my mast after having it pulled and new rigging installed. I was doing pretty well until I saw this weird through-bolt setup in my box of parts and remembered that at the partners there was a 1/2″ SS threaded rod going through the mast with blocks on them. Essentially through bolted blocks. They’re messing with my tune, and it actually looks like I’d have to lift the mast ever so slightly to even get the rod through. It seems some of the weight of mast would then be sitting on the deck and not the keel. I don’t see anything like this on any mast I’ve looked at, and am considering leaving it out, hard spots, partially unloaded mast step, etc etc being my considerations. Has anyone seen this sort of thing before?
Wow, that’s a first for me too, and I’m at a loss to come up with any purpose for it.
That said, I did have one nasty thought: maybe the reason the bolt won’t go through is that the mast step has compressed down since the boat was built. Unfortunately mast step problems of this type are quite common on older boats.
And maybe someone in the past thought that adding this bolt would move some of the compression loads to the deck. Not a good idea in my view since there is no way I can see that the deck would be able to support much load in that direction.
The other option is that the deck has bowed up, which is quite common in the absence of tie bars, which again is quite common.
So if the boat does not have tie bars, this was probably someones idea to stop the deck bowing up under the inward loads from the chain plates…hum…more I think about it, the more I like this theory. Are there any tie bars present to hold the deck down? If not, you definitely don’t want to leave the bolt out.
I would also check around the step very carefully for any deformation. It might even be worth pulling the mast again to really check this area. Also check outside the boat around the keel in the way of the step for any signs of deformation.
What sort of boat is this?
Hi John, the boat is a Passport 40. It does have a tiebar and turnbuckle on the fwd face of the mast to keep the deck from rising up. This threaded rod appears to be original as the hole is very true and had the original paint on the edges, and the wedge bits are very nicely machined.
The mast step is an aluminum shoe on a mild steel plate, and it needs some love as the steel plate has exposed edges but I don’t think it’s compressed at all, both appear flat and they rest on a solid resin block atop the ballast plug.
For the moment I have it in with the original blocking because I have to get somewhere (breaking my own rules with a schedule!), but I’m going to pull it when I get where I’m going and then use spartite instead of these blocks and that rod. I had to “tune” to the existing wedges for now, but I think plumb and true situate the spar offcenter in the partner
This guide has been invaluable and I’ll have to say makes tuning a fairly easy task. I have a double spreader rig and the intermediates are continuous so that makes getting wows out even easier as all adjustments are on deck.
Hi John and Tim,
I too haven’t seen this but I think John is likely on the right track as to why it exists. On a keel stepped mast, the mast is pushing down on the mast step with a huge amount of load, something like 90%+ of all of the stay tensions added up before you put up any sails. Depending on how the base of the mast is setup, if there are halyards, reef lines, outhauls, etc that leave the mast, if the turning block is deck mounted, that turning block is pulling the deck up while the other end of that line is pulling the mast down. As John says, you tend to get mast step compression and deck lifting with the usual solution being a tie bar, rod, wire, etc.
From a design perspective, it would be very seductive to do what appears to be the case here as it will be lighter. Instead of having a mast section in lots of compression next to a tension member, you could just react some of the mast compression at deck level and have less compression in the mast below deck. I think where this gets tricky is the tolerances of it. Given general boatbuilding tolerances, I doubt you could have a standard dimension where the hole for this partners fitting goes as all your tolerances will add up to a significant portion of boats not having the load where it should be. It would probably be possible to have a procedure for drilling it as an assembly the first time it is put together. It would also be possible to have a shimming procedure although it seems like it would be quite likely these would be lost or messed up in the future. And then of course, you have the issues related to tuning as making 2 points rigid during tuning at the bottom of the mast really changes how you have to do your tuning procedure.
When you say you can’t get the bolt through, is there tension in the rig? It is quite possible that when you slack it off, it would assemble.
Seeing Tim’s latest comment, the Passport 40 is a Bob Perry boat and he used to do consulting for a reasonable fee. I would certainly hope he would have guidance on what to do with this if it is original. You could also see if there is an owner’s forum as that would also probably confirm if it was original or a later addition.
Thanks for the fill on that. All makes sense to me.
One other thought on getting the bolt through: could it be that Passport intended the tie bar at the front of the mast to be preloaded a bit, as well as the rig being slack, before the bolt goes through?
Anyway, I think asking Perry is the best bet. And, on balance, I would be nervous about leaving it out, even though installing it does complicate tuning.
I strongly suspect that this piece is at least intended to be installed with the rig slack so that it shares some load. Whether it already carries a preload or has a small gap that takes up as the rigging is tensioned would be a function of the design purpose and the stiffness of the hull, deck and mast section. It should be possible to figure out but the amount of calculations or testing is quite high and it would be better to hear what the original intent was.
It is also entirely possible this is a hair-brained idea that seemed good until you dive into the details, there are certainly tons of examples of those in products. One of the rules that I make my team live by even in early prototypes is before we add an adjustment, we need analysis to prove it is needed and if it is needed, we need to have a procedure for adjusting it before releasing the design. The reason for this rule is that I have seen so many issues from people who don’t follow it and I have been pulled into help fix these messes more than a few times.