Warren's Build Log, CAN 573

[Warren Nethercote]

I have always had a bit of a leak in Blondie, probably around the keelbox, but it's buried under 'berth flats' and hard to access. One day .... Until then the underdeck volume tends to be a bit fetid, so this year I added a couple of cowl vents. The aft one was easy - I just bored a hole in an existing hatch to fit the ventilator opening. Forward I needed to run a tube from the foredeck to the cockpit sole to access the below-deck volume. A 100mm pipe would have been ideal, but this is inches country for building centre pipe.

I wrapped a cardboard mailing tube with bubble wrap to bring it up to diameter and laid up 2 layers of 6 oz cloth, a single layer of 14oz uni, and two more layers of 6 oz cloth, all glass. Cutting the glass tube to fit between the deckhead and the sole was fun and I can't vouch for the beauty of my filleting.

The cowls get replaced by blanking plates when we sail. Time will tell as to effectiveness.

[Tim Ford]

Interesting.

Folks may remember my mentioning I have the same issue. It's well ventilated but I'd still love to find the leak and fix it.

Any thoughts on where your water ingress may be located, Warren? Mine fills dedicated empty spots on both side of the keel box. Without tearing everything out, I'm at a loss as to how to address the issue....sheesh.

Luckily the boat is dry-sailed.

[Warren Nethercote]

Mine is more of a seep: a litre a day maybe and less as the leak path swells up. If you review my build log you will see that I prefabicated the keel box, including a 'pad' at its bottom to double the bottom thickness in way of the cut out. I think I didn't get enough thickened epoxy on that pad when I glued on the bottom planking. I need to cut a few more holes in the berth flats to access the edges of that pad. The forward end of it had clear voids. I also did my best to seal the edges of the keel cut-out in the bottom skin, but was my best good enough? And it might be somewhere else entirely, but I doubt it.

[Warren Nethercote]

Update on the cowl vents - they seem to be effective in holding the below-deck humidity down.

[rballentine]

Hi Warren
How well does your spinnaker launcher work? I am considering something similar. Any changes you would make if building it again?

Great photos and description of your build! Thank you!

Roy Ballentine

[Warren Nethercote]

Hi Roy,

Initially we struggled a bit with the launcher. It worked well with our 29M2 A3, but quite often choked on our 40M2 A2. The A2 generally went up well but often hung up coming down.

Two years ago I modified the deck opening by increasing the radii everywhere the chute 'rubs' and after that the A2 went up and down quite well.

But we also got a new, 33M2 A 1.5 that proved to be just like Goldilocks' porridge. Juuust right. It is a lighter cloth than the A2 as well as smaller, so goes up and down really well, and is effective across a broader windspeed range. Our crew weight is often under 450 lbs so the 40M2 A2 was often just too big for us in afternoon sea breeze conditions. I do wonder about the monster chutes that many people have, but then again, not everyone is blessed with reliable 10 to 12 kt sea breezes.

Our A3 sees little use after acquisition of the A1.5, since the A3 doesn't like to go very deep at all.

(Edit - here is a picture of the A1.5, from another computer)

Note of caution: since the halyard tail is the recovery line (like a 29er), rigging is picky and whatever spinnaker we rig is going to be what we use all day.

[Warren Nethercote]

Supplemental to the last: I neglected to mention two things. First is the importance of the recovery sock and specifically its size. I will add an edit with dimensions. It took three attempts to make one 'fat' enough so the sock could swallow the pig without choking. And if I were to build again I would use skiff sheeting for the main rather than a centre traveller because the traveller compromises sock length and placement.

Finally, recovery has to be fast - take up tension on the recovery line, blow the halyard cleat and pull like mad on the recovery line. If you go slow the chute gets in the water and you are toast.

[rballentine]

Hi Warren,
Thank you for your reply. If you can stand it, a few more questions. For context, I am likely to be sailing single-handed much of the time. My other rides include a Corsair 760 and an iFly-15 foiling catamaran, both of which I sail solo. The Corsair has a giant spinnaker, which I have arranged to fly solo.

1. What dimensions do you recommend for hole in the deck for the launcher? I am thinking about putting mine just behind frame 18. As you know, there is lots of room there.
2. Dimensions and other recommendations for the sock would be really helpful, please.
3. I am surprised by your comment about the sock interfering with the main traveler. The sock comes that far aft?

My hull is still completely open, so I can go any way I want with the above issues, but not for much longer....unless I delay construction during sailing season.

Thank you!

[Warren Nethercote]

I have owned three boats with spinnaker launch and recovery socks: a long, long time ago, an I14 in the pre-skiff days; after that a Goman 20 with a launching sock on deck (I launched through the pulpit), and now, my i550. I have sailed on Fireballs and Merlin Rockets with launchers, but those chutes are small enough to be irrelevant to the present issues.

I note that Melges 20s seem to be using launchers, based on some Ulmer videos, but their sock mouth is at the mast partners, so I suspect they may be constrained by some class rule or another. I do not know.

The length of the sock is driven by how you finish the spinnaker. With a single recovery patch, the patch is located equidistant from the head and the clews (or maybe the head is (say) 6 inches farther away). That distance (patch to head and clews) is the required length of the sock. The sock can be shorter, but the recovery patch will appear out of the tail of the sock and the first block in the recovery system has to be far enough aft so that you get the head and clews all the way into the sock. If the clews are left hanging out a wave can grab them and suck the chute into the water (don’t ask how I know). The recovery line runs OUTSIDE the spinnaker foot to the patch to help keep things out of the water on recovery. This assumes port-side launch and recovery with port-hand roundings.

My current chutes (like those on the 49er, which has a similar sized rig) have three recovery patches in line running up the chute. The distance from the head to the top patch, and the distances from the clews to the bottom patch are the same. The middle patch is halfway between the top and bottom patches. The recovery line runs outside the foot to the first patch, through the grommet in the first patch, then up and through the grommet on the second patch, and then dead ends at the top patch. My sock is about 61/2 ft long from the aft edge of the deck opening: my 29M2 A3 stays entirely within the sock but both the 33 M2 A1.5 and the 40 M2 A2 emerge from the tail of the sock and then get stuffed back in after recovery. The sock doesn't reach the traveller, but there needs to be room between the sock and the traveller for the crew to pull the recovery line.

A three-patch spinnaker goes into the sock with a big lump in the middle as the recovery line pulls the centre of the sail together to reduce the required sock length. If I used a single patch (which makes for an easier recovery), the sock would need to me MUCH longer, 10 ft perhaps, but need not be as large in diameter. It took us three attempts to make a sock ‘fat’ enough for our A2. North made the A2 in a heavier cloth than the A1.5 or A3 so it takes up a lot of volume in the sock. Flattened out, the half width of my sock is 27 inches (so the circumference is 54 inches).

The recovery line is usually the tail of the halyard but can be a separate line. A combined halyard/recovery line must NOT be too long, because then the bight of the recovery line can get into all sorts of nasty places (like under the forefoot or wrapped around the sprit – it is not fun). A short enough halyard/recovery line requires that a temporary tail be added to the halyard end during rigging as the halyard end will need to go into the air to get enough recovery line for rigging. A separate recovery line makes rigging MUCH easier but leads to more mess in the cockpit. I used a separate line on my Goman, quite successfully.

The size of the deck opening is arbitrary – it must be big enough, but beyond that, extra just lets in more water in a big seaway. On the forum there is a picture of an on-deck sock with a fiberglass bell-mouth that isn’t very big at all (Jon maybe?). But I don’t know how well that worked. My opening is 27 inches long on the centreline by 23 inches max width, but I have sketched the size of a circular opening that would probably work. It is what I would try if doing it again. Oh, if I were doing it again I would lower the cockpit sole a couple of inches because I don't need quarter berths, and I could use a bit more room when wiggling under the foredeck to rig the maze of lines that live there!

Shape of the mouth is arbitrary, although tight corners are taboo. E scows now use asymmetric chutes and launchers and I believe that circular openings are popular. The REO 7.7 sport boat (search UTube) has a circular or near-circular opening. The cross-sectional shape of the opening is MUCH more important than opening size. I first finished the opening with a half-inch round-over bit and the recovery patches would hang up on the edge, requiring someone to go on the foredeck to clear the hang-up. I then added a couple of layers of plywood to the top of the opening and reshaped things to a much bigger radius. We have not had a hang-up since. The photo indicates about 2 inches thick at the bearing surfaces with about a 1 inch radius. You can see a rope burn just above the scale – loads can get pretty high during a recovery. Incidentally, I run an external spinnaker halyard to minimize friction.

I originally set the boat up so that I did the launches and recoveries but my crew persuaded me to pass the job to them and steer better. To do so I relocated the spinnaker cleat forward in the cockpit instead of aft of the traveller.

A lot of the ideas I used rigging the spinnaker came from the Swift Solo website. Like the Swift Solo you might want to consider a self tacking jib … The Swift Solo rigging manual is available at

https://www.yumpu.com/en/document/read/ ... swift-solo

It is a bit of a irritating interface but the information is golden.