Thursday, October 24, 2013

PDQ 32/34 tacks through less than 90 degrees--Or Sheeting Angles Part II

Rev. 11-16-2013

Ever since I stretch the hulls from 32' to 34' I guess I've been on a performance quest. I'm not a racer but I do like sailing efficiently and I like doing it by proper tuning, not hurling money at the problem. No Kevlar sails, tapered sheets or high-tech halyards.

In Sheeting Angles and Keels I proposed that by moving the genoa track inboard to a better sheeting angle I could get the boat to tack through about 92 degrees over ground vs 120-128 degrees with outboard leads   and see a 21% improvement in VMG. Great expectations. And that is exactly how it turned out.

Tacks through 85-90 degrees full-and-by.
VMG up 20-25%

Yup, I gave up a little boat speed, but now she points the right way and is much easier to steer to windward, not so twitchy on the edge of shaking sails and irons. With the inside lead position there is a MUCH wider bucket of acceptable VMG, from 45AW to 55AW; even 60AW is a little faster with the new lead position, since it is full sail instead of near luffing. I'm sure there are many times when higher pointing will mean fewer or no tacks, and that increases the gain further. It is helpful that the PDQ 32 actually has slightly greater draft and keel area to sail ratio than the PDQ 36. It is also similar to the sheeting on the Stiletto27 and 30, also beach cat rigged boats. Anyway, it works and this should have been the factory layout with a few tweaks. Much faster and better balanced than the self tacking jib.

Note that the outside sheet is still attached but slack; I will be putting a soft shackle on this to make it removable. I like the low-profile Garhauer snatch blocks; a great value and a lot of strength in a small package. I switched to low lead cars later; snatch blocks are too high and cause winch overrides.

A bunch of notes for those who might want to try this. First, the basics:

Do other things to make the boat fast. Anything that makes the boat move better will reduce leeway by increasing flow over the foils. 
  • Clean bottom
  • Watch the weight
  • Watch the windage
 Outhaul. Many cruisers set-and -forget, but this is wrong. A full main gives more power reaching, but a flat lower main is mandatory for pointing high. With a full lower main...
  • The jib will back wind the main and the slot is closed.
  • The mainsail leach will hook to windward (slow) when the boom is properly located near amidships (the traveler will be about 6-12" above the center line when beating, depending on the wind).
The outhaul is typically adjusted with the winch on the mast. If you have a main with an attached main (factory) you REALLY have to crank up the tension to get it flat; you're stretching cloth. With a loose foot it is easier, but the result is the same. IF you are going to set-and-forget, leave it flat. With the reefing points, make certain the foot is pulled flat with each reef; there is no good reason for a full reefed sail; you are trying to de-power and reduce drag. There is a too-small cleat on the boom for the outhaul and it is tricky (lead the line under the cleat) to cleat the line without loosing tension; I may add a jammer to the boom; I'll see how the new sail fits in a month.

Lead location. The fore-aft location is critical. There must be some provision for twist; the upper genoa leach must be able to open. If the existing location is proper, the new location will be a few inches aft. I used a 2-foot track, but in retrospect I should have used a longer track in case I get a new genoa with a different geometry. Monohulls will often use an extreme forward position reaching to limit twist when the sheet is eased, but this is seldom done on multihulls; if you take the trouble to adjust for reaching on a multihull you use your beam and move the sheeting point forward AND to the rail, nearer the midships cleat for the PDQ 32. Monohulls don't have the beam to do this, unless they use a wisker pole, which will probably drag in the water and break if reaching in  breeze.

Sheeting. There are several option with an inside tack and I have played with them all. The best choice depends on what sort of sailing you are doing.
  • Use a 15-foot utility line as the inside sheet. Grind the sheet in with the outer sheet, hook on the utility line, release the outside sheet and grind the inside sheet. In fact, the 15-foot line can be left attached and allowed to flop through the tack; it's too small to matter. This is what you see in the picture above.
  • Use a spinnaker sheet. Again, it is used as a utility sheet, released for tacking. Or the outside sheet can be removed and the spinnakar sheet becomes the working sheet and tacking becomes normal. I'm going to try this, attaching the outside sheets with Amsteel soft shackles. One down side is the sheets are one size too small for this duty and there is one more turning block.
  • Dedicated inside sheet. At first I thought that would be too much mess, but today I tried a removable inside sheet (attached with strope) that was rigged continuous, like a beach cat; this shortens the line and makes for quicker tacking. Definitely a good plan for a boat that does not have a spinnaker; there is no need to install the outside track, particularly if a 120% genoa is selected.
  • Note that on starboard tack the mainsheet must be on the forward winch and that grinding is hindered; you cannot turn the handle more than 120 degrees. However, if the main is already mostly in, a rocking motion works fine for trimming. If your genoa sheets more forward the track will be further forward and the problem goes away. 
Update: I've gone to using a complete separate set of sheets, detaching the set I'm not using. This is much handier when beating to windward, which is practical with the new found pointing ability. I have also chosen to rig them as continuous, as seen on beach cats. This combination seems practical for single handing in breezy fall conditions, though it does seem to leave more rope in the cockpit. While there is more of it, however, it is easier to manage since it doesn't tangle (no ends to make knots) and can be reached from one spot for either coiling or tacking.

Furling. While it is possible to sheet a 150% genoa inside the shrouds, it is really simpler with a 120% genoa (one that ends at the shrouds). Sheets hang-up less too. Alternatively, you can do as I did during this test and furl the 150% genoa slightly. To save trial and error, it is a handy practice to mark the furling line with a thread whipping at 40%, 80%, and 120% (different colors or different number of stripes).

Tighter sheeting angles. The sheeting angle is now ~ 16 degrees vs. the 10-12 degrees found on some monohulls. While tighter angle swill work on a boat wit low windage and a deep keel, that would be a mistake on a cat with high windage, shallow keels, and better footing speed potential. Even my Stiletto with a deep board would often go up wind better (rough conditions) when I hauled the lead out to about 16 degrees. The inside positions were only for smooth water.

This has been greatest performance enhancement for the dollar I have found for the PDQ. If you have a genoa, this is a no-brainer. With Gauhauer parts it was ~ $280.


(although this is not the gear I used, it is what I should have used and what I ended up with.)
  • Garhauer 1 1/4-inch track, 2 feet long.
  • Garhauer low lead block LLC-2. (I started with Garhauer 30 SN snatch blocks on cars and got horrendous over rides.)
  • Backing plate (under the ceiling; I threaded 1" x 1/4" aluminum strip I had, but other things will work.)
This is a Garhauer LLC-3 on 1 1/4" track, but the LLC-2 would be better.

And don't forget to drill/remove core/epoxy/re-drill/butyl the track mounting holes.


I need to build a new speed polar. I'm working on it.

1 comment:

  1. How about if I buy you a plane ticket to Chicago and you can do the same on Phenix?!? haha

    Seriously, really great work you did here. I really should do this.