They are angled a small amount aft (ball leaned aft, bottom of rod forward), perhaps 10º or less. Makes sense with mast rake.
Yes, the entire idea behind the V-strap is to create an engineered truss, much stronger than a 4" beam could supply. The load still tries to bend the truss,(creating tension on the bottom of the tube & V-strap & compression on the beam top), but the strength now approaches that of using a beam with a diameter equal to the length of the DS rod. A 14" beam would achieve the required strength, but would be difficult to mate with the hulls, & probably weigh more than the truss.
The Mast ball serves as a means to connect the mast to the truss & transfer the vertical loads to the DS rod, & thereby to the truss.
The truss is strongest when the load is vertically through the DS rod, & weakens as the loads move away from vertical. The extreme would be a horizontal load,(mast falling), failure would occur at the load required to bend the DS, or tear the hull fittings/straps loose.
Edited by Edchris177 on Dec 01, 2014 - 03:29 PM.
I have not forgot about the dimensions you asked for but the boat is in the barn not here and I have to pick a day to go dig it out and get the measurements you wanted. Nice work so far. Richard.
RicardOben wrote: I have not forgot about the dimensions you asked for but the boat is in the barn not here and I have to pick a day to go dig it out and get the measurements you wanted. Nice work so far. Richard.
Hi Richard, no worries, and thanks for checking in. I won't make you go to the trouble anymore as I've blasted ahead and built the new beams and assembled the boat. Everything seems to be lining up so far.
I've been busy! I built my new beams, and assembled the hulls, along with finishing the trailer. No tramp installed yet, and need to overhaul the rudder assemblies. First test today putting the mast and sail up, checking the stays were the right length and all my calculations add up (they did!). Very exciting to see it come this far!
One concern - with the sail up I noticed the old adhesive outline of a removed sail marking that reads '18s' (as in 18 square). You may be able to just make it out in the photo, below the Nacra logo and the red 5.5 numbers. So my 5.5 uni, made up of 18sq hulls, with previously chopped down 18sq beams, may now also have an 18sq sail?! I guess I don't really care what we should be calling it, but I would like to know if it truly is an 18sq sail, and if so, how that might affect the boat on the water. Bigger sail area comes to mind, with added power, but not sure if this will change the handling adversely (besides the extra healing moment). The mast is 29'6" long (excluding casting) and the sail seems to fit it well. I know early 18sq had a boom, then they went to boomless. This sail almost looks like it was made for a boom. Perhaps the silver colored clew plate could have been added later?. Even hooking my mainsheet to the most inboard hole of the clew plate, sheet tension isn't pulling outboard enough, and the foot of the sail won't tension properly. On the most outboard hole it looks just ridiculous - the foot of the sail has a giant flapping belly in it. I know the rear beam/traveller is meant to angle slightly forward on boom less, and slightly aft on boom rigs, but I don't think that will matter the way things stand. Any thoughts appreciated. 5.5 uni boomless sail, or 18sq boom/boomless sail? Issues?
I really know nothing about boomless rig but the rear beam look too much forward if we compare it to the 5.5SL in the classified.
Maybe the angle of the shot make it look like that.
Well it is certainly not a 1990s style boomless 5.5 sail, those had a 'boomlet and a distinct triangle and flat part. From what I can see, it does appear to be an 18 sq sail that a hefty 'boomlet' plate has been attached to. The good news is that the sail does have a distinct downward triangle below the lowest batton, the same as the boomless sails. I think the 18 sq sails were made that way, or the previous owner (or even the factory) may have modified it for boomless. So the boomless rig should tension correctly. So that sail will likely work for the intended use as long as you hook the mainsheet up to the forward or middle holes only. If you get behind the main beam you definitely wont be able to tension it with the mainsheet properly.
The only thing that really worries me a bit is that there may not be enough room under the sail to get enough tension on the mainsheet. It doesn't look like there is a lot of room on the mainsheet to tension the sail. I'm not too worried about the tension in the foot, you can't really gauge it unless you are under load I'm more worried about running out of mainsheet to tension the whole rig. Is there any room at the top of the mast to raise the sail a few more inches? If so you should adjust your halyard so you are as close to the top of the mast as possible to buy you a few more inches. Also if you have any rake in the mast try and straighten it out. This will give you more room but could limit your adjustment ability to fix other performance issues.
I would try it out on the water before investing a lot of money or parts in it. Chances are with a few adjustments it will work fine. If you find it doesn't work well then you have a few options.
#1, rig a boom to it. Not as hard as you might think. You can get a swivel from another old Nacra then its just a piece of aluminum tube (2" dia by 1/8" wall will do) a couple of cleats pad eyes and some dyneema rope to make the connections and a workable outhaul. I can send you most of the parts (except the mast connection) for the shipping cost if you can wait til spring.
#2 buy a used sail. Maybe you can find a real 5.5 sail or you could even pick up the 5.0 sail pete has and that should work just fine (maybe a little underpowered) or even find a 5.7 sail.
#3, get the sail recut. Probably the trickiest option but if you find someone knows what they are doing it could be done.
#4, get a new sail designed. THat would likely be more money than its worth.
Google some Nacra 18 square pics, should answer boom questions. Looks like most of the boats used one,
bacho wrote: Google some Nacra 18 square pics, should answer boom questions. Looks like most of the boats used one,
Very early 18sq used a boom, and I believe later versions went boomless. It's difficult to figure things like this out when the Nacra models spanned many years, and were constantly evolving, especially since 18sq were a development class. I've looked at more 18sq photos on the internet than you can imagine - usually pictures of boats on the water from a distance and difficult to make out much detail, and most have a much more modern (square top) sail than what I have.
Anybody who has some good detail photos of boom setups on any Nacras, I'd love to see them. Like Wolfman says, I should probably sail it first as is before putting any money into further mods, but I can already tell the mainsheet angle and poor sail tension long the foot and elsewhere is going to bother me. I might go ahead and just make it a boom rig. The 20' stick of aluminum I bought for the beams (4" x 0.125) was only $100, so I'm guessing 6 or 8 ft of 2"x 1/8 or even 1/16th won't break the bank. Especially if kind folks have some fittings to send me! (thanks Wolfman).
Wolfman, great info as usual.
So the boomless rig should tension correctly. So that sail will likely work for the intended use as long as you hook the mainsheet up to the forward or middle holes only. If you get behind the main beam you definitely wont be able to tension it with the mainsheet properly.
On the most forward hole, as in the pic, the mainsheet is almost dead vertical, or perhaps just very slight rearward pull. It does weird things to the sail and doesn't look right at all. Obviously the boat will still sail, but I think it would drive me crazy.
The only thing that really worries me a bit is that there may not be enough room under the sail to get enough tension on the mainsheet.
s there any room at the top of the mast to raise the sail a few more inches?
I didn't pay a lot of attention to way up there unfortunately (the test rigging was fairly hurried, not only because it was 28 degrees out). I'm pretty sure though that the sail was raised to the max.
Also if you have any rake in the mast try and straighten it out.
We guessed the hole position on the 10 hole chainplates, pretty much the middle, and found the stays too loose and the mast too vertical. So we went lower in the side stays, but didn't mess around too much since there were other things to test out (I was just happy the stays seemed to belong with this rig and were close enough). We need more tension still I feel, and more aft rake, so next time I'll put the side stays on the bottom holes and the bridle connections on whichever holes needed to get it tight. When making my new v-strap and cutting the beams etc. I deliberately wanted the mast rod and ball to only protrude from the main beam the minimum distance needed for stepping and rotation clearance, plus a bit. I ended up with about one inch of exposed threaded rod between the top nut and the bottom of the nylon ball (about right according to my veteran nacra source). Anyway. I see rather a lot of pics of mast rods extending waaaaaaaay out of the beam - several inches of exposed rod - mostly because the replacement rods were made longer than the originals to cater for all models, bigger and smaller. Anyway, in hindsight my nice low profile mast ball may have put some extra slack in the stays with the decreased height. Hopefully I can still soak this up and get the right rake. If not…. damn.
I digress. In the first photo, where you don't see much clearance, the main sheet is cranked pretty tight. I was seeing what would happen with the foot tension, and also checking out the mast bend. I think I'll be ok with enough clearance, although you have me wondering if it'll be a squeeze to get under the sail when going about, especially with a boom!
As for your suggested options, # 2, 3 and 4 aren't an option financially. Besides not doing anything at all, I think making a boom would be the cheapest option, and not overly difficult. Especially if you send me some parts! (thanks! - lets talk more once I have a solid plan for this boom design).
#1, rig a boom to it. Not as hard as you might think. You can get a swivel from another old Nacra then its just a piece of aluminum tube (2" dia by 1/8" wall will do) a couple of cleats pad eyes and some dyneema rope to make the connections and a workable outhaul. I can send you most of the parts (except the mast connection) for the shipping cost if you can wait til spring.
Leaning toward this. Not concerned at all with the process of fabricating it, but more so finding the right parts and getting the dimensions and mechanics of it working correctly together. I realize its a pretty simple part once it's in use, but I like to do things right. I have seen google search images of various nacra gooseneck parts, but no detailed pics of them fitted to a boat, so I really can't visualize the attachment between boom and mast properly. I would prefer to go off the mast, not the main beam, since I'll sail with a partner most of the time, I want as much clearance from the tramp up front as possible.
Someone suggested a strop/loop of line *around* the boom and through an eye on the clew plate, directing the pull straight to the sail and not through the boom. This would allow for a lighter boom construction. I like it. But would I have just one loop, and pick one of the three holes to thread through, are have three loops (one through each hole) to maintain adjustability in the pull direction? I think I can almost answer my own question (one loop?) and that the outhaul will take the place of changing the sail shape (e.g. flattening it out) instead of changing the pull point or using a clew traveller (that's another thread 😎 )
And the mast rotation wishbone - currently mounted facing forward (boomless). Would I need to remove and face aft with a boom? I basing this question on stuff I've read here previously. e.g. "All boomless rigs you want to induce rotation, especially off the wind. On rigs with booms the rotation is induced due to compression from the mainsheet on the boom, so you want to limit rotation"
I hope my questions don't seem to daft. I'm rebuilding a boat I've never sailed, and my last significant cat experience was 15 years ago!
About as clear an image as I can find. This is a forum member's 5.2. Still can't quite make out the connection detail.
And the mast rotation wishbone - currently mounted facing forward (boomless). Would I need to remove and face aft with a boom?
Yes.
Will a 5.2 boom work for you?
The fitting that holds it to the mast is a fairly strong piece of kit, SS plate.
I have a spare boom & the fitting that joins it to the mast,(exactly the same as in the photo above) I can measure the boom for length, but the mast fitting is at one of my other houses...& I'm out of country til end of Jan.
The first factory 18 squares produced by Nacra were based on the 5.2 hulls but a later model used the hulls from the 5.5 .
I don't know if the 5.5 based Nacra 18 Square also used the same mast, if it did I would think the sail would extend further behind the rear beam the standard 5.5, but just guessing on that.
Factory Sails Sheet for the 5.5 based 18 Square.
DamonLinkous wrote: The first factory 18 squares produced by Nacra were based on the 5.2 hulls but a later model used the hulls from the 5.5 .
I don't know if the 5.5 based Nacra 18 Square also used the same mast, if it did I would think the sail would extend further behind the rear beam the standard 5.5, but just guessing on that.
Factory Sails Sheet for the 5.5 based 18 Square.
I'm aware the early 18sq used 5.2 meter hulls. Looking at the flyer, its clear that it used to be labeled as a Nacra 5.5, when that usually means something else now to most people (5.5 uni or SL) and we specifically refer to this guy as an 18sq. So the simple '5.5' decals on my hull and sail aren't entirely misleading. I just wish they'd added "CHOPPED DOWN" decals. Hey, that's a great name for my boat! haha!
Edited by sierracat on Dec 31, 2014 - 11:13 AM.
Try it before you go to a boom. Chances Are it's fine. Off not , between Chris and myself we can get you set up with a boom proper. But it sounds like it should work.
D.
Wolfman wrote: Try it before you go to a boom. Chances Are it's fine. Off not , between Chris and myself we can get you set up with a boom proper. But it sounds like it should work.
D.
I don't want to make more work for myself… but I'm sure it needs a boom! I wish I had taken clearer photos from different angles. The main is not pulled aft by the sheet angle, period. With a bigger sail than the boat is meant to have (+20sq ft I think) I think I'll really need to be able to flatten the sail properly to depower. I used to enjoy going out in a good blow, and that probably hasn't changed.
The other issue is: I'm about to install the tramp, and more importantly, about to rivet the padeyes along the rear beam for the tramp. The angle of my beams is not fixed yet. That's why I put the mast and sail up as a test, before the tramp was ready. I wanted to check the angle of the mast rod against the mast rake, to rotate the main beam and get them in line, and I wanted to check the angle of the traveller to the sail for proper pull, and rotate the rear beam so that my tramp padeyes will be in the correct place.
I'm going to go ahead and rotate the rear beam a little aft, anticipating the boom addition before summer, and install my pad eyes and get this damn tramp on.
Will a 5.2 boom work for you?
The fitting that holds it to the mast is a fairly strong piece of kit, SS plate.
I have a spare boom & the fitting that joins it to the mast,(exactly the same as in the photo above) I can measure the boom for length, but the mast fitting is at one of my other houses...& I'm out of country til end of Jan.
between Chris and myself we can get you set up with a boom proper
Chris/Dave, that would be great! I'll buy the tubing, but some fittings would be great to get hold of second hand - happy to pay and save a Murrays purchase.
Cheers guys.
I'll buy the tubing, but some fittings would be great to get hold of second hand
Why bother with buying tubing, then trying to cobble it together? I'll send you a 5.2 boom WITH all the fittings, mast attach/gooseneck, adjustable outhaul, cleats mounted etc.
I have 2 complete 5.2 booms assemblies.
Only problem, I'm in Hongkong as I type,(yeah it's 02:30am here) heading for Singapore in a few hours. Travelling through Cambodia & Vietnam for most of Jan, so I wouldn't be able to ship you any parts til then. I do have a bunch of photos on this computer, send me your email, (via PM, don't post it here) & I'll send you some, give you ideas if nothing else.
Edchris177 wrote:
I'll buy the tubing, but some fittings would be great to get hold of second hand
Why bother with buying tubing, then trying to cobble it together? I'll send you a 5.2 boom WITH all the fittings, mast attach/gooseneck, adjustable outhaul, cleats mounted etc.
I have 2 complete 5.2 booms assemblies.
Only problem, I'm in Hongkong as I type,(yeah it's 02:30am here) heading for Singapore in a few hours. Travelling through Cambodia & Vietnam for most of Jan, so I wouldn't be able to ship you any parts til then. I do have a bunch of photos on this computer, send me your email, (via PM, don't post it here) & I'll send you some, give you ideas if nothing else.
Hi Chris,
I was mainly thinking about the cost of postage. You are in Canada, correct? Also, I just assumed a 5.2 boom would be too short, given its a shorter boat with a smaller mainsail. But I have no way of confirming this. I'll try and unroll my sail and measure the foot, maybe that will give us a better idea. If we can figure all that out, then a whole boom would be awesome! Like I say, no sweat otherwise making my own if a small parcel of fittings can be sent economically. No hurry, I have all winter. I'll shoot you and email and we'll figure something out. Gotta run - three 1 year olds tugging at my leg! (how I ever managed to get this far on the boat I have no idea 😎
Edited by sierracat on Jan 02, 2015 - 12:52 PM.
Hiya all,
If you have been following this, then the latest is that the tramp has been restitched (fingers crossed) and installed on the boat. The trailer is finished, except for lights, and the front upright for the mast (the rear upright is finished, and pivots down for boat unloading). Still need to paint my welds. Also need to remove what's left of the ancient hiking straps and install new ones (line through eyelets, with pipe insulation foam wrapped around them). Also had the upholstery guy make a simple pocket on the front of the tramp (the white thing in the pic) with a velcro closure, for stashing the main halyard and the righting line.
I've committed to making this a boom rig (given the sail is an early 18sq and was made to have one) and because of the angle I chose for the rear beam/traveller, and the eyelet positions for the tramp lacing. No going back now. Boom is the last project on the list.
Working on the rudders right now. That's a whole other story. I'll start a new thread then post the link here.
Summer is coming!
Edited by sierracat on Feb 22, 2015 - 11:02 PM.
Finished! Maiden voyage last weekend was in very light winds, but enough to test everything out, and it went very well. Rigged quickly and without issue on the beach, and away we went. So happy to be done and looking forward to a great summer of sailing and exploring local lakes. Thanks everyone for you helpful input as I navigated this project.
Before: Dirty, damaged boat in pieces, as retrieved from a barn after sitting many years
Almost done, weather warming up. Stay hydrated with some good homebrew.
Maiden voyage, all that hard work about to pay off.
After:
nice work. can you post a pic of your finished rudder system : tiller arm to cross-bar joint?
Jim Casto
NACRA 5.5 uni
NACRA 5.7
Lake Travis Austin TX