Thread: Is that a 12' GIS I see hull down on your horizon

It will be very interesting to get weights and bends as per the WIKI! Using a 10kg bucket of water. As the yard is not round to get a side bend figure would be nice too.

(oops ... I am tired and didn't read your info carefully enough) Possible to have a max measurement for the cross section fore and aft and sideways?

Great to have another approach.

With the glued track I would probably suggest putting in some very small self tapping screws at either end of the track just to prevent a tear starting. We used to use about 4 or 6 gauge with a countersunk head to keep the track clear for the bolt rope.

Very important to use a correctly sized pilot hole and to drop some epoxy in the hole and dip the thread of the screw too. One about 15mm from end of track, one about 40mm away from the first.

Maybe overkill ... if four tiny screws can be overkill.

Best wishes
Michael

Good idea Mik, you never know when the track might begin to pull off. I can put the screws through the flange outside the slot, which provides a large gluing surface. I got the idea of this track from the NZ Cherub site which you or someone mentioned.

Here are the dimensions and deflections of the mast and yard:
Mast. 4.5M long, 22.4 cm circumference, approx. 70mm diam. (slightly oval), tapering only above the halyard attachment. Weight 9.0 Kg bare. 3 layers of heavy carbon sleeves over the hollow wood core like the yard + 2 more near the mast partners, + one layer of glass. No bending so probably overbuilt. When I sit on it, it bends maybe 20mm.
Yard. 3.42M long, weight 3.5 Kg. max dimensions 70x50mm approx., teardrop shaped. Circum. 19 cm max, 16.5 cm at throat, 15 cm at head. Deflection with 10 Kg weight at halyard attachment: 13mm; with 20Kg, 20mm. I'm sure I put on much more load than that with a lot of tension in the 6:1 downhaul as the boom bends more, and the bend matches the sail cut nicely. I adjust tension along the yard (easy with slugs in tracks) as described by others here, specially Brian Pearson, independently of and much less tight than luff tension. In this photo it is a bit tight for the very light wind we are experiencing for the moment, but right for a moderate wind. That's why the sail has a temporary crease near the yard. It disappears with a bit of wind.

The downhaul attaches to the front of the boom and is countered by a vang, so I can move the boom forward and back with total control. Useful when running as more sail can be forward of the mast. The downhaul is double-ended and each end goes back along the gunwale to a clam cleat on each inwale a bit forward of the middle thwart. I can easily adjust it while sailing. After raising the sail I set the downhaul to a slight tension so that the luff is about parallel to the mast and then set the vang (6:1), which is attached to the base of the mast. Then I set the final downhaul tension which is adjusted according to the wind, as is the outhaul. The outhaul goes from the end of the boom, forward though a block shackled to the clew, back around a sheave at the end of the boom and forward inside the boom and out about 60 cm behind the mast, through a block attached to the boom, down to the base of the mast through a block, and then back to the middle thwart so I can adjust that while sailing too. The sail is loose footed.

The boom is a vertical rounded hollow rectangle of two 8mm pine planks separated by thin strips of the same creating a cavity in which the outhaul runs. It tapers both forward and back from where it lies against the mast. It is covered with a layer of heavy carbon and light glass. It bends a little bit both down and in in a breeze. I''ll measure it later as it is now wrapped up with the sail. I don't hold it to the mast by a line, as it moves out from it only a few cm when the boom is on the lee side. If I were to make another one, it would be wider and a bit deeper at the back. Reefing is standard slab or jiffy reefing using the same lines for both reefs. I release the downhaul and outhaul, drop the sail entirely and insert hooks into the luff and leech eyelets and pull the lines tight and cleat them with clamcleats on the top of the boom. I tie the reef points loosely around the sail to hold the folds. After raising the sail I then tighten the downhaul and outhaul again. A lot of spaghetti as a friend says, but I like to adjust things as I sail along.

Many of the details of spars and sail adjustments I have learned from this great group. Thanks to all contributors.

Peter

I like Peter's solution, but these spars, save for the timber parts, are not easy in construction and will cost a fair bit when adding carbon and such.

So, being the devil's advocate here...

The hull has an air of (sophisticated) simplicity and perhaps the rig should match that (both from a building perspective and intended use perspective). In other words: is the rig not straying too far from the concept (at least for the basic option)?

Mulling this over:
- stays make the rig more cumbersome
- freestanding stick would be simplest and cheapest
- simplest rig option would, I think, be a luff pocket sail idea combined with either a birdsmouth mast, a complete aluminium pole or a combination of an aluminium bottom mast and a wooden topmast (either solid or birdsmouth). This latter option is very usual for, for example, the B&B boats. This would give the builder quite a few options depending on available resources and building skills.
- the sail now sports quite an extreme squarehead top. What if this would be slackened a bit (less tension on the top batten and the mast making it easier for this batten to flip to the other side. So keep the sporting looks but make it a bit easier on the mast.

Just a few thoughts.

Joost

Actually, I'm getting more and more excited about the strip plank method as you could very simply achieve a very robust, sexy wing mast that will be very light as well, much lighter than an aluminium section. It would be quite easy for anyone to build using a timber mold every 50cm or so to keep the shape consistent. The molds can be very simply made from a template drawing included in the plans and can even be utilised as spacers afterwards, like we do for the box masts.

Another advantage is that you don't need to buy very long pieces of timber to make it, as these can be easily spliced in as you go (and held with a panel pin) so you can use very cheap knotty timber. You would simply discard any knotted bits after you've ripped your planks up into thin strips. For the track, I can see a cheap aluminium tube glued to the back edge and split to take the sail.

In the absence of a very long flat bench to build it on, most people would be able to find a piece of floor space long enough, and a cheap pair of knee pads!

https://www.woodworkforums.com/attach...g_1938-640.jpg

I like the strip plank method, but am not sure whether this would fit the basic simple option, that may be required to make the boat a success.

Both the strip plank method mast and the ceiling molds/carbon way would make fine masts but require more work to make them, more difficult and expensive materials, more tools and/or a perfectly set up building frame, and create more hassle to rig the boat. That is what I think, not ever having made such masts.

I believe that the hull will lend itself perfectly to people trying out all kinds or rigging ideas. And the people interested in such ideas will do fine anyway as they will generally have a good understanding of these more complex rigs, know what will work to create such rigs and have generally more experience to think through any technical challenges that may come up.

The first time builder (and/or inexperienced sailor!!!, let us not forget that perspective) however would look for something perhaps a bit easier, from a building perspective, rigging perspective and sailing perspective. I believe that such easier basic rig option should be the starting point for the boat.

It may be good to have two standard rig options: one for fun easy sailing and one more aimed at maximum performance. My earlier post had specifically the first option in mind.

Of course this is only an opinion and I could completely be in the wrong!

Joost

My method could be simpler. Using the 4 mouldings you could omit the carbon and make the mast a bit bigger diameter. The track can be glued onto the back, or use a sleeve. Seems a lot simpler than stripping a mast. Strip planking is the slowest method of building a kayak. Is the sail intended to be reefed, or is this to be a simple racing dinghy? If the latter, perhaps some defining rules need to be made before Duck Flat starts cutting kits. If the only limitation is the hull shape and sail area, anyone can make their own rig out of whatever they like. If there are to be restrictions such as only wooden or aluminium masts, sail construction only polytarp or dacron etc. they ought to be defined. I guess that is what this discussion is about.

The idea of a simple unstayed mast and rig has been an aim of mine in an attempt to design a 3.4 sq M rig for a sailing canoe. I wanted to avoid the weight of a yard so decided against a lug rig. I decided to try to use the principles of the Byte CII dinghy for sail control: without stays, bendy top mast, but sail draft and twist controlled by downhaul and snotter rather than sheet, outhaul and vang. Without the high tech sail material and mast. So I drew a flat top sprit boom sail with 3 battens. I carefully measured the bend of the mast under tension to make a graph of the deflection to give the sailmaker. The battens are of cheap rectangular plastic electrical conduit 12x7mm. The bottom half of the mast is an aluminium tube reinforced with a 12mm aluminum tube sail track at the back and a strip of small moulding planed to a round shape at the front. It doesn't bend. The top half is a tapering piece of pine stiffened by a 12mm aluminium tube at the front which takes the halyard. The top half weighs 1.0 Kg. It bends. The bottom half weighs 2.0 Kg, too much but it is low down. It has a tube sail track made of plastic electrical conduit. Track is necessary because I use a spritboom and the sail has two reefs. The snotter attachment to the mast gets in the way of rings or hoops or sleeve as the sail comes down when reefing. If using a regular boom or no reefs, you could use plastic rings cut from a pipe or cable ties or string to hold the sail to the mast, or a sleeve. The top mast ends at its bottom end as a moulded glass and kevlar sleeve which fits over the top of the bottom mast so it take apart for easy carrying. Lawn sailing shows that the rig works as I had hoped. Downhaul tension flattens the top half of the sail and releases the leech, and snotter tension flattens the bottom half of the sail. The battens are under tension but do flip over OK. The photos show the sail with a lot of snotter and downhaul tension. The snotter will be attached higher up the mast. The angle of the snotter with the mast could be used to adjust leech tension if you want to use two snotter lines, one to control height and one with blocks and tackle to control tension.

I have helped a friend rig his B&B Bay River Skiff and agree that this is a great simple rig, as MIK has done it for the OZ racer.

Howdy Peter,

One thing I did find regarding leach tension and sprit or wishbone booms - there is the theory that you can use the height of the front end of the sprit to control leach tension.

However it doesn't work that way- at least for more bendy masts.

With the first sails of the Oz PDRacer - later to be OzRacers - I was concerned that the foot was becoming a big bag in gusts and initially thought it was the polytarp stretching badly.

But actually it was the mast bending. If the snotter end of the sprit or wishbone is up high then when the mast bends the back end of the boom moves down as well as in. Shortening the distance between the clew and tack and turning the bottom of the sail into a bag.

Since I worked that out I have tended to carry the sprit booms much closer to perpendicular to the mast and only move up or down quite small amounts.

Putting one and one together ... you remember the world sailing speed record boat Crossbow II?

I remember that they had problems with the trim .. the sail would power up and a hull would start to fly and then they would lose power suddenly. Then the power would increase again. With very little sail trim change. They thought it was sail stretch. I wonder at the high front end of the wishbones.

Hi Bruce.

Any news on the rotating mast info - either way?

MIK

Geometry! Thanks for the tip. I'll find the best place on the mast for the snotter tackle by having a line holding it at a certain height and adjusting the tension separately and test different heights. At least to start with.
peter

But actually it was the mast bending. If the snotter end of the sprit or wishbone is up high then when the mast bends the back end of the boom moves down as well as in. Shortening the distance between the clew and tack and turning the bottom of the sail into a bag.

Since I worked that out I have tended to carry the sprit booms much closer to perpendicular to the mast and only move up or down quite small amounts.

Putting one and one together ... you remember the world sailing speed record boat Crossbow II?

I remember that they had problems with the trim .. the sail would power up and a hull would start to fly and then they would lose power suddenly. Then the power would increase again. With very little sail trim change. They thought it was sail stretch. I wonder at the high front end of the wishbones.

Originally Posted by Boatmik

Hi Bruce.

Any news on the rotating mast info - either way?

MIK

Hi MIK
Spoke to Darryl E yesterday and mast bend info is not available. However, we did discuss the spanner which limits the mast rotation. The spanner was separate to the vang fitting (on PTs it is often combined) and was bolted to the base of the mast. A line from the end of the spanner went to a block or eye on the boom and then to a cleat. By loosening the spanner line, the mast could rotate more than the boom angle.

This is how some PTs control mast rotation and vang using the same spanner fitting.

The rope and double cleat controls the amount of rotation independent of the vang tension. If the rope is tightened completely, the vang spanner operates as per the old-style vang spanners, where vang tension determines the amount of rotation. However, the rope can be eased out to allow the vang spanner to rotate further (providing more mast rotation) while still having the desired amount of vang tension.

Attachment 221019

However, this method would work just as well on the MS12 and is nice and simple.

Attachment 221020

Thank the Egginses for me! Really appreciate it! And thanks Bruce! I'll go ahead with the Bethwaite Cherub mast data that was archived on the UK Cherub website.

Rotation spanners, The second one was the one I was going for!

You found my photo from the Maritime Museum in Darling Harbour!





It was a bit of a nostalgic photo. The sail was the same sailmaker as mine and the mast was the same as the one I bought later. It is a bit of a mystery actually ... the rig is circa 1978 to 82, but the hull is a Javelin Mk2 (I think) which is from very early in the NS14s development - it is the original hull design before a series of dramatic shape refinements.

The NS14 rule is very open. 14ft long, 6ft wide, 140lbs, bow height has a minimum, bottom width has a couple of points above the keel line in the mddle aft to make sure the bottom cant be crazy narrow or too rounded. Sail area is 100sq ft (9.3m - I know that in metric!) with the whole sail area measured, the mast has to fit through a 4" diameter ring (so a rotating one can't have excessive area) and sail cannot be more than 18ft above the deck.

You can see the sail area is quite small for a two adult boat - 20% more than a laser. Two people for a much higher sailing weight and over a foot more beam. So the emphasis has been maximising sail power and minimising hull drag. The boats are really quiet to sail - no splashing sounds or bubbling sounds from the hull. At least until the waves get big. My favourite point of sail was always light wind running. The boat just rockets along for the low windspeed with no sounds and almost no wake

Back to rotation spanners. You can see the first photo used a classy fitting that costs maybe 120 bucks. But the lower one uses a simple jammer that costs less than 10.

We just tied a knot in it at the max rotation point for downwind.

It doesn't really get used that often. You have an angle for upwind and an angle for reaching with attached (wind) flow. Then in line with the boom for stalled sail downwind.

Upwind there might be slight variations for strong wind or choppy water - not more than a 20mm adjustment from the standard positions.

MIK

Hello,

Could the idea behind and working of the mast rotation system be explained in more detail for someone like me who has never worked with such system?

Do I understand correctly, the mast being the starting point of the airflow, that you want the mast to rotate in such way to match the camber in the sail (i.e. less rotation when sailing upwind, a bit more rotation when sailing on a beam reach when the outhaul is slacked and no rotation when sailing down wind)?

How does the rotation spanner slide over the bottom side of the boom and can you easily get the clamcleat(s) or camcleat(s) for the control line(s) for this system to the middle of the boat, or preferably the sides of the boat for easy adjustment (rather than the front of the boom)?

The bottom of the mast uses a rotation plate I guess. A swiveling stainless steel trolley wheel - less the wheel of course - may perhaps provide a cheap reliable solution?

Is my assumption correct that the stays attachment point in the mast uses one single attachment point in front of the mast to allow easly swivelling?

Joost

P.S. Do not be fooled by my previous posts that I, for myself, would not be in favour of a rotating mast system. I was just thinking out loud for people having less building/sailing experience or looking for more simplicity.

Yes, the simpler the better. I think the PTs have the extra complication because they can't easily get to the boom to make adjustments. Still, it's quite clever thinking and the fittings all seem to be home made and there are a number of variations of that theme, some even made from carbon fibre. From memory, the one in the pic was from Ian Markovitch's boat, but I can't be absolutely sure. Compared to most boats, Ian's was an essay in simple design that works. Hardly anything was off the shelf. A neat and unique idea he had was his mainsheet cleats attached to the stays. But I digress.

The NS14 rigs are incredibly powerful for their size and the hulls are so well developed. I think I would have loved that class if I'd lived here at that time. If not the NS14, then I think I would have had a Moth as I was way too light for a Finn and also the OK Dinghy.

I must get down to the Maritime Museum in Darling Harbour again some time. It's been years since I was there last.