Re: Singlehanding Pearson 35 Centerboard
I am a little pressed for time this morning, but it sounds like some good things were done to make the boat a better single-hander, but things like the conversion to a cutter rig and shortening the boom may actually be heading the wrong direction. Here is the mid-length version (if not exactly short). (I can give you the longer more detailed version if we happen to meet at one of the CHESSS Challenges. Also I don't know how familiar you are with terminology so I will define terms in parenthesis at times to make sure you, I and anyone reading thus understand the terms the same way. I apologize in advance if this is unnecessary.)
When you talk about a boat that is a good platform for single-handing there are a variety of aspects that are important. From my perspective, if there was single way to describe the collection of attributes that make a good platform for short handed sailing, it is a boat that is easily adaptable to changing conditions and which sail well across a broad range of windspeeds, points of sail, and sea states with a minimum of number of sail changes and reefs and which can change tacks easily. (This last is not as important for a long range cruiser than it is for a coastal cruiser.)
This general 'mission statement' can be broken into a number of components as follows:
Easily Driven Hull form: The P-39 actually has a pretty easily driven hull form. Its comparatively cylindrical cross sections mean a minimum of wetted surface for its displacement. It also has comparatively straight 'buttock lines' (This refers to the shape of vertical cuts made through the hull parallel to the centerline of the boat. Hull form drawings show 'waterlines' which are horizontal cuts, Sections, which are vertical cuts made through the hull perpendicular to the centerline.) This helps at the light air of the wind range. But the P-39 has a large displacement relative to its water line length which means that it will quickly and disproportionately build drag as the wind speeds increase. That early increase in drag with wind speed increases means that the P-39 will need to be able to carry more sail area than a boat will less drag in this same wind speed, but to do that the boat needs a lot of stability.
In order to stand up to a large enough sail area to sail well across a broad range of wind speeds, points of sail, and sea states, the boat needs to have a lot of stability across a range of heel angles. This is one of the main shortcomings of the P-39. The rounded sections, and narrow hull form, combined with the height at which its ballast is carried due to the comparatively shallow draft of the keel means that these boats do not have much stability relative to their drag. More than anything else it is the P-39's lack of stability relative to its drag that makes this a tough platform for a single-hander. On the other hand, by using the centerboard to balance the rig, this is somewhat mitigated by the fact that these boats will tolerate higher heel angles than a lot of designs which have greater stability relative to their drag.
Here is where it gets tough. In order to have decent performance in lighter conditions a boat needs to have an actual SA/D (sail area to displacement ratio) somewhere in the SA/D in the mid-20's range or more. The SA/D that I am referring to here is different than the accepted way of measuring SA/D. Normally SA/D is measured and published with the full mainsail and the 100% Foretriangle. The P-39 like most masthead rigged boats of that era has an SA/D around 16.35. (Yours with the shortened mainsail has something less than that). In order to achieve adequate sail area for light to moderate winds, these boats were designed to be sasiled with very large overlapping genoas. In the case of the P-39, the published sail plan shows a 170% genoa. But as the overlap of the sail increases the efficiency drops considerably. But there are also some other major downsides to large overlap headsails in that they are much harder to trim, stretch more and so need frequent adjustment, are harder to tack, and do not adapt well to changing conditions.
So, while it may seem counter-intuitive, because of the disadvantages of of having large overlap genoas, an ideal single-hander actually should have a standing sailplan (main and 100% foretriangle) somewhere in the low 20's. Of course, that is a lot of sail area. In order to effectively use that much sail area, the boat requires a lot of stability and requires a sail plan that can be easily and quickly be depowered (depowered=reducing heel force relative to the required drive force. I am not using that term to mean reefing or furling since furling a jib actually powers up the sail -i.e. makes it rounder).
But even if the SA/D of the standing sail plan of the P-39 could be increased to a number closer to 20-or more, the boat lacks the stability to stand up that much sail in a building breeze and the P-39 rig configuration makes it harder depower.
Wind range and Ease of Depowering and tacking:
It is the rig configuration that is one of the most critical elements of the P-39 that makes it a less than ideal platform for a single-hander. When we talk about depowering a sailplan, it is all about controlling the draft (depth of the camber), twist, and angle of attack to minimize heeling and leeway.
There are a lot of components to this but the quickest way to depower the whole sail plan is to be able to induce mast bend (flattening the mainsail and twisting off its upper leech) and tensioning the headstay, (flattening the jib and twisting off its upper leech). That can be coupled with dropping the traveler and tensioning the mainsheet (the combination reducing twist at the same time that the angle of attack is diminished). That works well in quickly adapting to a gust and for short increases in wind speed. But when coupled with increased halyard, mainsheet, vang, and outhaul tensions, this can greatly extend the upper wind range of the boat (especially when used on a boat with lots of stability).
To discuss your specific P-39, (set up as a cutter with minimally overlapping headsails), as configured the lower end of the wind range is greatly diminished. Cutters do not do well at the lighter end of the wind range. While the staysail adds luff length and sail area, it diminishes the efficiency of the headsail (I am using that to refer to the sail on the headstay which is your forward most jib) by congesting the slot and reducing air flow, which is very critical deterent in lighter winds.
To perform across a wider wind range the headsail needs to be properly shaped a little fuller for the upper end of light air to the lower end of moderate air, but it also needs to be flatter for heavier winds. That change in fullness can be obtained by tensioning the forestay to flatten the sail or allowing the headstay to sag a little adding sail cloth to the leading edge if the sail.
But it is still a very difficult battle to control draft. And this is where your options become limited. In order for that to work, the sail cloth needs to be light enough to allow the sail to hold a proper flying shape in light air while being low enough stretch to remain flat in heavy air. This is especially critical on a boat with a sail plan like the P-39 where the jib is the primary source of drive and so needs the proper shape. In your case this is made more critical by the fact that your jib is only 95% and your mainsail foot has been shortened, meaning two very high aspect ratio sails, and high aspect ratio sails, while theoretically more efficient, are also wildly less forgiving, i.e. requiring more attention to trim and course. The high leech loads on high aspect ratio sails mean that there is more stretch which can cause a hook and that can add to heeling.
Ease of tacking and sail trim:
Lastly, one of the shortcomings of a cutter rig is the need to drag the headsail over the forestay. This makes tacking more difficult since you need to wait for the sail to blow through, or drag it through and that usually means a lot more grinding (even on a small sail). But the cockpit layout on the P-39 makes it harder to sail as well. With the wheel as far forward as it is in the cockpit and the traveler on the cabintop, making quick and precise traveler adjustments are not easy. With the high aspect ratio jib, frequent sheet adjustments are very beneficial, but with the winch behind the wheel it means having to step away from the wheel to make adjustments or face aft. Anything that makes adjustments harder makes sailing shorthanded harder so in that regard, the deck layout of the P-39 also makes it less than ideal.
Lastly, I don't know whether you use spinnakers, but with only a 95% jib, some kind of downwind sail would greatly extend the sailing ability of the boat off the wind. The sheer size of a masthead chute will make it much harder to handle and there is less of lee of the mainsail to help drop a chute. An assym that large is harder to fly short-handed and the forestay makes jibing a pole harder. The smaller mainsail also hurts a lot downwind and reaching.
Anyway that is the mid-length version. I need to get back to work.....
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Curmudgeon at Large- and rhinestone in the rough, sailing my Farr 11.6 on the Chesapeake Bay
Last edited by Jeff_H; 06-16-2017 at 06:34 PM.
Reason: clarity, syntax and bad typing.