Narai With Modern Lug (Junk) Rig

[Budget Boater]

A list of the rigs I have owned:

• Sloop

• Ketch

• Cutter

• Hasler-McLeod Lug (junk) schooner

• Tiki wing sail sloop

Without hesitation, the junk rig was easily my favorite with the ketch rig coming in a very, very distant second. Now I know Wharram's philosophy on the Junk rig and catamarans, and if we were talking about high speed cats, I would certainly agree. However, on a 7 knot cruising catamaran such concerns will not be an issue (and with a family of 6 and all of their crap, I would be overjoyed to make 7 knots.) I normally drove my previous H-M lug rig to over 8 knots on my Colvin Gazelle, and if it can push that big steel 24,000lb hunk at those speeds, it can do similarly with Narai.

I could extoll the virtues of the H-M lug for many pages, but that would get boring. So instead let me highlight the pros and cons:

PROS

• Extremely inexpensive to build and maintain (1/5 of a Tiki Wing Sail rig)

• Simple to home build the entire rig and sails

• No standing rigging

• 30-seconds to put in or shake out any number of reefs

• Small children can operate

• Painless tacks (and accidental jibes) - just push the helm over and the rig does the rest.

• Any sail tears will not extend beyond a single panel and you can still sail with a full tear.

• Wing and Wong (wing) downwind sailing.

CONS

• None (well actually it is a low aspect sail, but so is the Tiki wingsail schooner rig)

This is not going to be a bi-plane rig (with masts in the hulls), but will have masts mounted on deck in tabernacles. This will allow the mast to be easily lowered to the deck for canal and intracoastal waterway work, or for moored hurricane preparation.

Personally, I cannot find what is not to love, especially since this rig will save me lots of time and money.

[Budget Boater]

With a tapered mast, there is no "upper mast support area," or at least there was not any on my Gazelle. There is only one mount at the base. Part of the conical design of a tapered mast imparts forces down the entire length of the spar to the base in an ever decreasing manner as the load experiences little resistance near the top, with an ever increasing resistance as the load moves down the spar. This was described to me by one of the aluminum light pole engineers. In effect, the flexing action of the top of the tapered spar acts as a stress bleeding mechanism to remove strain from the base. When coupled with the H-M junk's twist away bleeding action of the sail's design, one gets fairly limited high stress imparted at the base (other than the extra motion of a boat moving through the ocean.)

The tabernacle design I have in mind is not true in the full sense of the word. It would take far to many words to describe, and no pictures are available. Even if the mast case tabernacle is heavy, it is of little consequence when looked at as a percentage of the total loaded boat weight. So if I have 400lbs in mast supports, that is but 3% of the total loaded weight - quite negligible in the whole scheme of things.

As for the "tall forward raking mast in the bows" comment, I am not sure where this comes from. The rig is low aspect, like the Tiki Wingsail rig. Based on the initial estimate, the masts will be no taller than 35', and if forward rake is used, it will be less than 5˚ and probably closer to 2˚ (the rig will be most similar to the second photo above.) And if so rigged (as previously stated), the running backstays would limit forward and lateral whip in heavy seas. I do not intend to mount the masts in the hulls, but in custom built triangular/pyramid shaped mast case tabernacles on the central deck, (unless something along the way convinces me otherwise.)

Jeremy Walker said:

A sharpie or most any other monohull will heel easily enough to reduce sideways loads at the upper mast support area, Pitching will not load up the mast partners as much and because the forces are in a forwards direction the multipart sheeting system acts to lend support from behind.

In contrast a V hull sectioned catamaran has a very quick motion (compared to a monohull) and is going to load up the mast tabernacles a bit more than was the case with the sharpie. Structure to cope with this loading is going to cost a lot or weigh a lot more than rigging. Then again it all depends on where the craft sails and what stresses are imposed on the mast, so pottering between leeward Islands in fine weather is never going to be a problem.......if that amounts to full usage of the craft.

When the craft has to cope with violent pitching moment where it is brought to a full stop on meeting steep seas head on, then a tall forward raking mast in the bows is a liability hardly worth the risk. Whereas a mast with aft rake and back staying will carry much of the loading axially, rather than bending like a whip.

[Jeremy Walker]

The 'upper mast support area' is what has traditionally been called the mast partners. So there is a keel step at the bottom and then the 'upper support area' which is usually at deck level, bearing the load of a mast acting as a lever.

OK, you need to do away with this 'traditional' system and support the mast stepped within a very short socket, inside a squat pyramid structure, built onto or being part of the connecting beam structure.........that much I do understand.

What immediately comes to mind is the density of material needed to create this very shallow socket.

Off the top of my head I would say that mild steel has the required density/hardness at low budget cost, (along with a weight penalty) or else a carbon composite structure at lower weight. Both of these materials will introduce a galvanic corrosion problem when using an aluminium alloy mast............Immediately my thinking reverts to the 'traditional' set-up with wooden wedges holding the mast at the partners, and this automatically calls for keel stepping 

[Budget Boater]

I am familiar with the traditional version of the unstayed mast. But as I have said previously, my Gazelle was not built that way and worked perfectly fine with no mast partners. This worked because of the tapered mast, whereby no mast partners were required or desired.

Plywood composite box construction has the required strength - it is the principle upon which the Wharram is already built and derives it strength. When properly built any forces imparted by the mast upon the mast case "socket" will be against at least six pieces of endgrain ply - three pulling and three pushing.

In the end, the success of a deck mounted Hasler-McLeod Junk rig on a Wharram resides in the use of tapered aluminum masts.

Jeremy Walker said:

The 'upper mast support area' is what has traditionally been called the mast partners. So there is a keel step at the bottom and then the 'upper support area' which is usually at deck level, bearing the load of a mast acting as a lever.

OK, you need to do away with this 'traditional' system and support the mast stepped within a very short socket, inside a squat pyramid structure, built onto or being part of the connecting beam structure.........that much I do understand.

What immediately comes to mind is the density of material needed to create this very shallow socket.

Off the top of my head I would say that mild steel has the required density/hardness at low budget cost, (along with a weight penalty) or else a carbon composite structure at lower weight. Both of these materials will introduce a galvanic corrosion problem when using an aluminium alloy mast............Immediately my thinking reverts to the 'traditional' set-up with wooden wedges holding the mast at the partners, and this automatically calls for keel stepping 

[Marty Peters]

Interesting discussion.....
There was one of the boats that budget boater posted ( the second junk schooner with blue hull) anchored near me last week. The owner stated that it sailed really well and is very easy to reef on any point of sail. I asked specifically if the masts bend and he said no as they are solid wood, however he said the boat healed easily to spill the excess power.

I also met apatiki a month ago and he said his junk biplane rig had considerable bend but his masts are keel stepped.

Unstayed masts are fascinating as they don't seem to need much to hold them up. I guess the most famous common Unstayed mast must be the laser. It only has around 30 cm of the mast in a socket and it stays up, ok it's a mono but evenso, it Kinda defies what is possible as upon appearance you'd think the lever arm would be huge......

Cheers

Marty

[Jeremy Walker]

Budget B:       What I would do 'IF' ever I was to go this route..............is continue the pyramid structure below the beams as well, by having inverted pyramids below; This way you can increase the mast bury as well as lower the cg a bit.

Next, I would bend thick ally bar into  2 rings, with the top one bigger than the bottom one and weld them to the ends of a conical shape fabricated from alloy plate. THis conical shape plate will have scallops cut out of the top edge so that when welded to the top ring there will be eyes created for lashings.

Now, instead of somehow immovably fixing the tapered mast between many plywood webs in a pyramid structure, this conical case can be epoxy bonded into a double pyramid structure ( pyramids with their bases joined over the beams) relying on fewer webs.

Into this conical mast receiving case the mast can be held with 6 or more long, thick aluminium wedges, which will increase the effective bury of the mast. These wedges can be kept in place by lines pulling down on a ring at the top, all lashed down to the eyes in the conical aluminium mast case ..........easily  maintained tension will ensure that there is never any play in the mast support.

Maybe such a structure will prove sufficient, and I would at least contemplate it's use for the mainmast, but personal experience leads me away from a H/M junk schooner configuration

[Budget Boater]

For reference, we used schedule 40 3/4" aluminum pipe for the battens and each was inserted into its own separate sailcloth sleeve, then laced to the sail. We never experienced any chafing problems. The sailcloth simply slid over the painted aluminum masts with ease. Though I didn't own it long enough, I estimated that I would need to make new sleeves for the battens every 10 years.

Since we lived aboard full time, we never had a need to remove the sails from the masts. We simply dropped them to the deck with the sail covers intact, then lashed the whole bundle down to chocks on the deck.

Jean-Paul said:

Budget boater wrote on March 25, 2014 at 7:33am

"CONS

• None (well actually it is a low aspect sail, but so is the Tiki wingsail schooner rig)"

We discovered two cons :

• long process to install and de-install the sails at the beginning and at the end of the sailing season. On APATIKI we need one full day with two persons to install one sail.
• you have to take care of potential issues due to chafe (battens against mast). We experimented different methods and we will keep you posted after our next ocean crossing.

We fully agree on all the positive points explained in the PROS.

Cynthia and Jean-Paul

[Budget Boater]

We used 1.5mm Kevlar line (wrapped 8-12 times) spaced every few feet. The lashings never came in contact with the mast, and they were never touched in all of our years of cruising.

Jean-Paul said:

We still have to find a solution for the lashing itself as it doesn't resists days of chafe against the mast.  We are going to test 4 mm Dyneesta ropes on some sections.

Budget Boater said:

For reference, we used schedule 40 3/4" aluminum pipe for the battens and each was inserted into its own separate sailcloth sleeve, then laced to the sail. We never experienced any chafing problems. The sailcloth simply slid over the painted aluminum masts with ease. Though I didn't own it long enough, I estimated that I would need to make new sleeves for the battens every 10 years.

[Galway Bay]

The Narai is probably Wharram's all-time classic. When regular sailors describe a boat as a Wharram Cat this is what they probably have in mind.

I have been following this discussion and one thing I have not seen mentioned is the beam that will carry this tabernacle. At present the max. down thrust on the mast with shrouds is a ballpark figure of 2 ton. A  tabernacle with a base approx. 4ft each side will have a ballpark value of 8 ton down force at the leeward edge of the casing at the same conditions.

I am sure it can be done and possibly even has been done. I would be interested in your comments on the beam.

[Budget Boater]

This was addressed in the last paragraph of the last post I made on page one.

Galway Bay said:

The Narai is probably Wharram's all-time classic. When regular sailors describe a boat as a Wharram Cat this is what they probably have in mind.

I have been following this discussion and one thing I have not seen mentioned is the beam that will carry this tabernacle. At present the max. down thrust on the mast with shrouds is a ballpark figure of 2 ton. A  tabernacle with a base approx. 4ft each side will have a ballpark value of 8 ton down force at the leeward edge of the casing at the same conditions.

I am sure it can be done and possibly even has been done. I would be interested in your comments on the beam.