small daysailor - comments?

[dalan1]

I'd like to solicit the group here for opinions/comments on a 14' sloop, intended for glued ply lapstrake construction.

I'll build a 1/6 scale model first to prove out the lines.

So, whadya think?

http://www.dpulaski.net/dalan14/dp14pro1.jpg

http://www.dpulaski.net/dalan14/dp14sta1.jpg

[ishmael]

The rudder looks a little small, but I'm no expert.

[dalan1]

Ya think? Rudder area is 2 sq.ft., centerboard is 4 sq.ft. Those areas are pretty consistent with what I've seen in similar designs. The big radius at the lower leading edge corner prolly isn't a good idea, but I haven't worked out all the details of the appendages yet anyway.

[johnw]

One trouble with the verticle high-aspect rudder is you can't scull very well with it. Rake it aft a little and it will scull just fine.

[Todd Bradshaw]

I'd be tempted to lower the tail end of the boom down to level. In use, it will actually lift a bit and look more like what you have drawn. As it's shown, it will only look like that when sheeted in very tight and the rest of the time it will be even higher than shown.

Raising the aft end of the boom also creates a bit of a sail raising and lowering problem, especially when combined with the raked mast. When the tack angle (the angle between the luff edge and the foot) is less than 90 degrees, it means that the straight line distance between the clew corner and the back of the mast is less than the distance between the clew corner and the tack corner (the foot length). Unless you build the sail with slides or hoops and some sort of jack-line system which temporarily releases or loosens the bottom ones, the sail binds going up and down and may not even be able to be raised.

Confused yet? Years ago I was, until I built a similar sail and proved it to myself. It doesn't mean that you can't have the raked mast and the sub-90 tack angle, but you need to be aware of the problem and be prepared to use slugs or hoops and a jack-line to deal with it. The only way to deal with the problem if the sail uses a typical boltrope and mast-slot system is to raise the sail all the way up and then attach the boom, either to the sail or to the gooseneck if the boom is already attached to the sail. To lower the sail, you remove the boom or detach the boom at the gooseneck before easing the halyard to lower the sail itself. This is how sails have to be raised and lowered on most modern iceboats, which almost all have slotted masts and sub-90 tack angles.

[imported_Conrad]

What software are you using?

[dalan1]

JohnW: good thought about raking the rudder. I had a JY15 a few years ago - that boat had a plumb rudder and it didn't scull well at all. Come to think of it, I used to manually "rake" the rudder myself by taking up on the rudder's uphaul line a bit when it was time to skull. But if I forgot to lower it back to plumb once I was sailing, the rudder was way heavily loaded and the helm very twitchy. I think a high-aspect plumb rudder gives a nice, fairly light, responsive helm feel, and the uphaul gives you the rake to skull.

Todd: thanks! I hadn't considered the ramifications of a sub-90 degree tack angle. I intended all along to use an aluminum sailtrack screwed to the mast with slides on the luff, but I'll redraw the boom perpendicular (or at least dead horizontal) to the mast just the same. The mast rake is 6 degrees; with a level boom, do you think the resulting 84 degree tack angle would cause a problem if I used a sail track w/slides?

Conrad: I did the basic hull form with Nautilus ProBasic, then exported the stations, plan, and profile to DXF for use in QuickCAD, a generic 2D CAD program.

I used the CAD program for everything else - lining off the plank lands, designing the foils, the rig, figuring the CE of the sailplan and the underbody's CLR, etc.

[ 02-27-2003, 08:57 AM: Message edited by: dalan1 ]

[Todd Bradshaw]

A tack angle of eighty-six degrees should be better and may or may not need a jack-line. To find out what you're in for, line-up one end of a ruler at the clew corner and find the shortest distance between the clew and any part of the aft side of the mast. Draw a line from the clew to this point, which should be somewhere fairly low on the mast but slightly above the gooseneck. Any sail slides that normally sit below that point on the track (if there are any - both at full height and when reefed) are liable to bind when raising or lowering sail. There is a little bit of wiggle room, since we're dealing with cloth and rope, rather than a rigid structure which doesn't give at all, but rigging and using a jack line, if needed, is usually easier than trying to stretch things and wrestle the slides on and off of the track if they want to bind.

Notice that raising the tail end of the boom (as in the initial plan) would raise the point where the reference line would strike the mast. The higher the boom's tail, the more slides which may wind-up below the line and which need to be attached with a jack line. Once in a while, you see a sail with unusual angles which require that all the slugs or slides on the bottom half of the luff ride a jack line, instead of just being attached to the luff. The same situation happens on jibs with reef lines or clubs added where some of the lower hanks are on a jack line.

It would also be wise to mount the fitting on the boom where the sail's tack grommet will attach as close to the mast as possible. This limits the amount of "tack-setback" that you need to build into the sail (think of it as cutting the sail's corner off a bit to bring the corner-ring back to the boom fitting). This has to do with slide spacing.

There is no exact standard for slug and slide spacing. "Normal" is usually about 26", and is probably a throw-back to the early days of sailmaking and the widths that fabric was once manufactured in. Putting the slugs at panel-seam overlaps added another layer of fabric for more strength. These days, it's not as critical, yet the old spacing still hangs around and usually gives adequate support with minimal slug or slide-to-mast friction.

If the boom fitting is well aft of the mast, requiring a large tack-setback, it usually means that the first slide above the boom needs to be pretty low on the mast (positioned just above the point where the setback begins - maybe 12"-18" up the mast) to bring the sails luff up close to the mast and keep it there. On the other hand, if the boom fitting is close to the mast and the required setback is minimal, it may be possible to go up the full 26" before you have to place the first slide. If the clew-to-mast reference line for your sub 90 tack angle sail happens to strike the mast below a point 26" up from the boom, you're in good shape. There will be no binding slugs and no jack-line required unless you decide you want to add a reef line.

You also usually gain a few degrees of tack angle due to foot round, cut into the sail. Even though the mast to boom angle may only be 86 degrees, the actual angle of the finished sail's luff to foot intersection may be 90 degrees or greater. For an 86 degree tack angle, I'd probably make the sail without a jack-line, try it out and see if it needed one. If it does bind, the operation to add the jack-line is very simple.

Sorry this is so long and confusing, but certain aspects of sailmaking and design get pretty tedious yet still can have a profound effect on how well and how conveniently the thing works out on the water. Guess that's why they pay us the big bucks, huh?

[ 02-28-2003, 03:51 AM: Message edited by: Todd Bradshaw ]

[Tom Lathrop]

Todd's point is well made but all you need to do is leave the clew outhaul loose until the sail is up and then tighten it. Boats like the Lightning are set up with a lot of mast rake and handle it this way. On the other hand, what is the purpose of the large amount of mast rake?

[dalan1]

Thanks again for sharing your expertise, Todd! I was about to ask a question parallel to Tom's comment - on any small boat, I've always been in the habit of leaving the clew outhaul slack until the main was all the way up anyway. It just seems easier to properly set up the right amount of foot tension after the main is fully raised.

Any thoughts on a loose-footed main for this sort of rig?

As to the question, "why the make rake?" Well, I like the way it looks! smile.gif I've always liked the way a mast looks with a bit of rake. I've loved raked masts since the first time I saw "Pet", a smaller reproduction of Ticonderoga.

Unless someone can give me a technical, construction, or performance-oriented reason why not to do it, I'll stick with it for purely asthetic reasons. Todd's discussion was the closest thing to a technical discouragement I've heard so far, but I'd be interested to hear what he thinks about just leaving a loose-footed main's outhaul slack until the sail is up.

[Buddy Sharpton]

Just a thought, but this boat seems to have a noticeably high freeboard. Knowing it is 14 feet long, I'd say 4" or more than I would expect. As headroom in accommodations is not involved with this open boat, why are you adding this much extra windage. Given the likely height of the seats this gunnel could be something like 10" above them. What benefit are you trading off for here?

[dalan1]

Buddy: you're absolutely right, there is a lot of freeboard. I was wondering if anyone was ever going to say anything about the hull form (she's rather beamy, too - 6').

I know it will cost me something in terms of windage, but I did it intentionally because I wanted a boat that could be sat comfortably IN rather than ON.

Reasons? Three small kids to teach sailing - deeper hulls just feel more secure. The wife and I both have long legs, and boats with seats only 8" off the floorboards aren't comfortable at all. Locale also played a role in my decision: we sail in Long Island Sound, and I figure the extra freeboard might add a degree of dryness and security on what can frequently be a fairly nasty body of water. I like seats a good bit below the gun'l.

On the other hand, a downside of the high freeboard that I'm trying to evaluate is its impact of capsize recovery. This hull would ship a lot of water, and I'm unsure how hard it will be to re-right. Then again, the wide beam, fairly firm bilges, and high freeboard ought to mitigate the risk of capsize anyway.

Always compromises, eh?

The rig is pretty conservative for her size, and I plan on having the main made with a reef point.

I suspect that she might be able to get up on plane with a good breeze and two average-sized adults aboard. I've drawn the run with that in mind, but her main purpose is definitely not that of a racer. Am I being overly optimistic about planing potential?

To my eye anyway, the freeboard doesn't make her look too high-sided, and I think that visually the plank laps and the bow sprit distract from the freeboard and make the hull appear longer. Or maybe I just like the look of "tubby" little boats! :D

[Old Salt]

We build boats that meet our specific needs. Without knowing the design criteria its rather harsh to say the boat is "tubby or too beamy. There are lots of boat designs out there with less freeboard and beam of simular design. If all we are going to do is recreate an existing design, we are not being very creative. I like the design. Good job! Keep it going.

[Ian McColgin]

It almost looks like porportions that would be happier in the 8' range. From just the picture she's cute but everytime I think of her at 14' I really wonder.

Anyway, G'luck.

[Joe ( Cold Spring on Hudson )]

Yea she looks proportionally closer in length to my 9ft. Dhow . I agree without the freeboard, rudder and boom. She seem a bit bulky and stubby with small strait rudder. I think its a great idea to construct a model, you will see it all clearer in 3D. Great drawings though. How is the mast fixed?

[Venchka]

Why not just build Paul Gartside's "Skylark"? We know it works and looks stunning.

http://www.boat-links.com/DepoeBay/99/Gartside-1.jpg

http://www.boat-links.com/DepoeBay/99/Gartside-2.jpg

http://www.boat-links.com/DepoeBay/00/Skylark.jpg

http://www.boat-links.com/DepoeBay/00/Bonus/Skylark-2.jpg

[Venchka]

PS-

Alternate sloop rig shown on "SKYLARK" plans.

[Todd Bradshaw]

Going loose-footed may do the trick, although not always. Sometimes you have to slacken the outhaul and also unhook the tack from it's fitting to get things to work smoothly, which is a lot of trouble compared to just temporarily slacking the jack-line, doing your halyard task and snugging the jack-line back up.

For performance, a loose foot is fine - as long as you use it. All too often, people seem to set the outhaul at the beginning of the season and leave it that way for the duration. With a laced-on foot, sheeting in hard to go upwind bends the boom and flattens the lower part of the sail, which is good. On a loose footed set-up, sheeting in hard may do more to just bend the boom than affect the sailshape. The bending boom actually shortens the distance between the tack and clew with no connection to the sail between them to pull on the middle and may inadvertently add draft to the sail's bottom unless you also tighten the outhaul tension to make up the difference. It's not a huge deal and you won't lose most of your windward performance if you don't adjust things on various points of sail, but it's something to keep in mind if you're trying to get the most out of the system.

[dalan1]

Skylark surely is a pretty boat. Correct me if I'm wrong, but that's "traditional" lapstrake, isn't it? Nothing against it; I just want to do glued ply lapstrake. I like the rudder; I agree with the comments that the rudder as I drew it doesn't look right (ok, it sucks, I know).

Ultimately, I'm sure I'll go with a more rounded affair like Skylark's. I just did a quicky rough approximation of the rudder at this point so I could figure the hull's CLR so I could draw the rig.

Yeah, I guess her proportions are pretty much like big Dyer. That's what I was going for. ;)

Joe: The bow will be decked back to just past the mast - the mast goes through partners in the deck, with a step on the keel (actually, the step will be on the end of the inner stem). Nothing fancy. I didn't have all the layers turned on for that drawing - it gets to hard to read.

I'm getting the definite impression that folks think I'm nuts with these proportions (particularly the hull depth) - that's cool, that's why I came here asking about it. I have a thick skin; if you think it'll be butt-ugly, go ahead and say so! tongue.gif Maybe I'll think so too after I see a model of it in three dimensions (I'm gonna start the model this weekend).

Here's the particulars: at her 6" DWL, she has 22-3/4" of freeboard at the lowest point amidships, and the tip of the stem is 28" above DWL. Total maximum hull depth is 34".

[Carlsboats]

From your body plan, I see a fairly full bow.
I have a similar hull, an Alden X dinghy designed
in the 1930s. It's a great little boat, but be warned -- It is wet! In any kind of chop, that shape bow throws water all over the place. Also, it probably will not tow well. At sea, my X dinghy sheers left and right behind the mother ship, and will even run up alongside --then get yanked back in line so roughly that it may swamp. On one trip from RI to ME, we felt we were risking losing the dink altogether in a seaway, and thus "retired" the X to day sailing in fully protected harbors. For a tender, I built a Shellback. It tows and rows much better. Still have that X though. With all that varnished interior, lapstrake, oak ribs, etc., she is too pretty to ever let her go. Also, that shape bow is not terribly fast, but you probably don't care about that. I don't, anyway.

[dalan1]

:eek:

Wow. I'm glad we had this discussion about freeboard - last night after I went back to the CAD design and took the measurements for the overall hull depth, I realized that I wouldn't have been able to get the thing of my cellar! So I've now reduced her overall hull depth by four inches, sweetened the sheer a bit, and made a slightly finer entry.

Here's what she looks like now:

http://www.dpulaski.net/dalan14/plnpro.jpg

http://www.dpulaski.net/dalan14/stations.jpg

I didn't touch her 6' beam. Yeah, she's still pretty tubby, but again, that's what I'm going for. Now the only drag is, I have to line her off all over again! :mad:

I appreciate everyone's input tremendously!

[Hwyl]

Maybe your search for legroom stemmed from your JY15 experience. They are incredibly uncomfortable boats, but remember; they have that false/flotation bottom so your legs are not actually on the bottom of the boat.

On the design and it's use,; I am surprised that no one has talked about "lead" (difference between clr and c of e). My understanding is that if you are sailing a performance dinghy (and go to any effort to keep it flat) you don't need "lead" but if you intend to sail in a leisurely manner (with some heel) then you need "lead". John Teale says that "lead" should be 12% to 14% of waterline length for a centreboard boat.

[Buddy Sharpton]

1) Like the freeboard and bow much better.
2) Six feet is not too beamy on a modern daysailor.
3) I would reduce the beam toward the stern. You do not nedd to support a spinaker. As this stern heels it will float higher and depress your bow effecting steering. I would narrow it six to eight inches and ease up the run- but that won't aid planing. I wouldn't look for your rig to plane your hull in any wind you would take a wife and kids out into. Noit twice.
4) You are right to be concerned aboutthe possible volume of free water inside. You would/could/should incorporate foam flotation, bouyancy bags/ water tighter storage lockers to reduce the flooded volume. A little tricker on a lapstrake but doable. Under the seats and leaving a deep floor/ narrow floorboards would be the diraction I'd take. Usually something like this floats bow down, won't sink , but can't self recover. Flatation bags under the foredeck would be easy and necessary to me, even if you had "watertight doors" to close off the whole storage area.