PDA

View Full Version : Can't see through dinghy sail



Jeff Kelety
08-11-2001, 11:31 PM
Hi all - Been having fun with the kids and sailing the Bolger Cartopper. But here's a thing. It was rigged to spec with a sprit sail, but no window was cut in as per plans. That means we simply can't see where we're going without lifting up the foot of the sail. Rather then messing with the sail itself, I am considering installing a foot longer mast. It would go from 9'6" to 10'6". Is this technically or morally unseemly? The builder used Bolger's alternative suggestion of PVC pipe for the mast. So it ain't no big deal to cut another one. Could even line it with the next size down for a bit less bend. Any thoughts about just uping the height of the sail config like this?

Thanks,
Jeff

Mike Field
08-12-2001, 01:09 AM
I don't have drawings of the Cartopper, Jeff, but if it's as small as it sounds I think I might be a bit concerned about raising the centre of effort a whole foot.

I suppose you could sail everywhere with one reef in, though.....

Jeff Kelety
08-12-2001, 02:25 AM
11 1/2', 61 sq ft of sail area Mike.

jgk

Mike Field
08-12-2001, 04:47 AM
Hhmmm. The trouble is, the higher the sail, the greater the capsizing moment. Is there a way you could rig a higher mast just temporarily, for a dry run, to try it out? Or could you sail her from sitting on the bottom-boards instead of a thwart, if you had to? But I rather suspect the right answer might to put that transparent panel in after all. (Or you could sail with a permanent bow lookout to tell you, "Left hand down a bit.")

Charlie J
08-12-2001, 09:48 AM
on our Dolphin srs, we commonly raise the sail a foot for daysailing and lower it for racing. Doesn't seem to make a bunch of difference except in much stronger winds. Ya just lean out a bit more with the sail up.

TomRobb
08-12-2001, 09:59 AM
Sew in a nice big window. It won't help all that much but you'll feel better.
Better yet have someone keep watch or if solo, regularly duck your head under the foot for a peek at what's out there.
Every one who sails has the same problem.
I'd vote NO on the higher mast thing. (the previously mentioned righting moment problem)
Plastic pipe? Yuck. Cartopper is one of Bolger's nicer looking boats. Why not make a nice wooden bird's-mouth spar? Think how proud you'll feel http://media5.hypernet.com/~dick/ubb/biggrin.gif

[This message has been edited by TomRobb (edited 08-12-2001).]

[This message has been edited by TomRobb (edited 08-12-2001).]

Jeff Kelety
08-12-2001, 11:49 AM
<Why not make a nice wooden bird's-mouth spar? Think how proud you'll feel >

Tom, you don't have three kids under 10 do ya? With all the other boating priorities, by the time I made a lovely wooden spar, the kids would be too old to sail the boat <g>!

<Or could you sail her from sitting on the bottom-boards instead of a thwart>

Mike, we couldn't be any lower. Our bottoms are on the bottom.

I think I'll try raising it a bit, like CS, and just see what happens. I could also cut a foot of sail, but more work.

Thanks all.
jgk

TomRobb
08-12-2001, 12:58 PM
Jeff, with three kids under ten you NEED to lock the shop door and build that spar. Your sanity is at stake. Everyone who's made them seems to say they're not that difficult or time consuming.

[This message has been edited by TomRobb (edited 08-12-2001).]

Mike Field
08-12-2001, 08:24 PM
I have to agree with Tom, Jeff -- make a nice job of it.

Or, here's a possible alternative. If you're already sitting on the bottom, what about cutting a couple of holes in it and dangling your legs through for a ballast keel?

Jeff Kelety
08-13-2001, 01:54 AM
<If you're already sitting on the bottom, what about cutting a couple of holes in it and dangling your legs through for a ballast keel?>

Now, why oh why didn't I think of this Mike <g>?

But I do agree, with my lovely new fir floor boards, I need an equally lovely wooden mast. But honestly, it takes all I can manage to get a bit of varnish on the Nais before show time in September. So I'll probably experiment in PVC this season, then if the dinghy doesn't blow over completely, I promise I'll make a bird's mouth spar in the winter. Of course I have yet to replace my sculling oar I lost in a sporty 30 knot race last year (not well lashed to the deck) and finish the trim on the new hatch and hang a cleat on the mast for the new spinnaker halyard and crawl up and put back the new and improved mast tang that blew out on the first outing with said, new spinnaker and...well you get the idea.

jgk

[This message has been edited by Jeff Kelety (edited 08-13-2001).]

TomRobb
08-13-2001, 08:40 AM
Well Jeff, at least you're too busy to be out in the streets looking for trouble http://media5.hypernet.com/~dick/ubb/biggrin.gif

Keith Wilson
08-13-2001, 10:45 AM
Yeah, that spritsail is very low; I can see why it's a problem. One point about raising the sail - the alternate rig is considerably taller, so the boat will almost certainly tolerate a somewhat higher sail. Sheeting positions are critical with a loose-footed sail, however, and you may not be able to get it to set properly if you raise it much.

Another alternative, when you get around to making a new mast, would be to switch to the other rig with the sprit boom. See:
http://www.instantboats.com/images/cartopperprofb.gif
Advantages of the other rig:
- You can see where you're going
- Better performance all around, especially downwind
- Much lighter sheet forces
- No need to switch sheeting positions, so you can use blocks and a camcleat
- More docile and forgiving sail
The obvious disadvantage is the longer 16' mast. Bolger himself says that the only advantage of the sprit rig is the shorter spars.

I just set up the mast and sail for my lapstrake cartopper-under-construction, and the whole sprit boom rig is now spread out on the living room floor. The birdsmouth mast was not hard, and I can lift it easily with one hand. I'll probably launch later this week if it doesn't get too hot to work again.

Jeff Kelety
08-14-2001, 02:33 AM
<Another alternative, when you get around to making a new mast, would be to switch to the other rig with the sprit boom. >

Yup, Keith. Gave this some consideration as I have all the drawings. But then I have to make a new mast AND a new sail. More work. So you're saying if the clew is raised up a foot or so, it may not "set properly". What's that mean?

jgk

Todd Bradshaw
08-14-2001, 03:37 AM
The relationship between the sail and the proper angle of the sheet is a function of the sailshape and design for sails that have no boom (spritsails, jibs, etc.) There is a fairly limited "sweet spot" where the sheet's angle provides proper tension on both the leech and foot at the same time, making the whole sail work for you.

This ideal sheeting angle does not change when the sail is set either above or below it's original location. This means that raising the sail an extra foot will shift the ideal position of the lead on deck (or gunwale, horse, bridle, traveller - what ever the sheet leads to) aft of it's original location. Setting the sail lower than the designed altitude would shift the ideal sheet lead position forward.

On a dinghy, if you raise the sail, you might run the risk of the ideal position winding-up being aft of the transom - which is a difficult place to put a block or even hand-hold the mainsheet.

In that case, the best option would probably be to rig another snotter and add a simple sprit-boom, giving you a sprit-boomed-spritsail. The clew would then be supported by the boom, rather than just by the sheeting angle. They are fairly uncommon, but most of the people with sprit-boomed-spritsails like them. It might be a workable alternative to ditching the spritsail and building a regular sprit-boom sail and rig.

Keith Wilson
08-14-2001, 09:56 AM
Right - exactly what Todd said. Sheeting angle won't change, but it looks like the sheeting point will be aft of the transom. The idea of adding a sprit boom to the loose-footed sail is a very good one, IMHO. I don't like boomless spritsails at all, having had several bad experiences with rythmic rollng downwind.

Jeff Kelety
08-14-2001, 12:02 PM
Hmmmm. Interesting. Well more stuff to chew on. Maybe Mr. Bolger had the simplest idea - just put a window in the sail.

Thanks,
jgk

[This message has been edited by Jeff Kelety (edited 08-14-2001).]