Capsize test

[Designer]

I have been wanting to do this test in the water to confirm or deny the theoretetical calculations. The idea is to prevent the boat from going over so far that it becomes difficult to right without outside assistance. Any one who has much catamaran experience knows that you have to get to the daggerboards quickly or the boat will turtle. The same is true with monohulls also but the narrower beam of the CS's gives you a little more time.

First I duct taped the cockpit hatch to try and seal it and put a crab pot float on the top of each mast. Normal stuff like anchor and rode, pfd's and lines etc. was left onboard. When we pulled the boat over in 3' of water the masthead settled at about 2' under water and after a while it sank to the bottom, which I suspect was caused by the mast filling up with water. I added 2 more floats to the forward mast as the boat floated slightly bow-down. She then floated with the masthead about 15" below the water. I added a 8# hammer to the tip of the centerboard to simulate a weighted board, but it did not make much difference.

With 165# sitting on the centerboard she very slowly pulled the sails up through the water and then quickly righted.

My masts are heavier than drawn. The lower section is .125" wall instead of .083" and the top sections are wood 2 1/8" dia. at the bottom tapering to 1 3/4" at the top and appear to be solid.

Before venturing far out alone it is a good idea to go through a capsizing drill so that you can see what goes on with your boat, because even though it is rare, it can happen.

Before venturing out you should have the mast properly sealed, the hatches as waterproof as possible and dogged down. I am going to attempt to lighten my mast tops and experiment with foam in my luff sleeve.

If the worst happens, make sure that your centerboard is down and the sheets are free and then get around to the centerboard as quickly as you can to prevent the boat from turtleing. Do not worry about the boat's angle to the wind, just get your weight on the board and the boat will weathercock as the boat is being righted. Some people may not be strong enough to climb up on the board from the water so they should have a line coming over the gunwale that has a large diameter for grip and maybe some knots for enhanced grip.

After the boat was righted she had about 2"-3" of water in the bottom.

First picture shows how she floated with all of the floats attached.

Second shows her starting to lift the masts out of the water.

Third shows the floats.

Fourth shows how much water came in the boat from the capsize.

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[Designer]

Yes Ray the water is brown unfortunately. It is caused by tanic acid from the marshes. When it rains the water filters through the marsh and goes into the river looking like tea. There is very little tide in our area so it takes a long time to get flushed out to sea.

Floating higher does put more download at the masthead but the small amount of water onboard is a worthwhile tradeoff.

[Garry]

Thanks Graham. Very interesting experiment. This shows how important it is to have hatches that seal to maintain flotation. A hatch that simply keeps rain out will quickly fill and change the dynamics. If the boat is half sunk, sitting on the centerboard will do little good.

Prime conditions for a capsize, of course, are a windy day with a good size chop running. This presents several problems that add to the difficulty when righting the boat. If the masts are pointing dead downwind, the wind on the bottom of the hull can push the sails making them drive under and turtle the boat. And if the water is not deep enough, the mast can get stuck in the bottom (don't ask how I know this).

It might be worth considering having a flotation ball at the masthead particularly for windy days. Another idea might be to have a light halyard with a flotation device (inflated fenders?) that can be hoisted to the masthead after the capsize to prevent the masthead from sinking or possibly even to bring it back up.

The hull will usually weathercock downwind leaving the sails pointing upwind. As you sit on the centerboard trying to lift them out of the water, waves continually spilling onto the sails can push them back down thus preventing the boat from righting. I have had to swim up to the mast and physically pull the sail down to allow the boat to right. A line that is cleated off can be used to pull on the top gunwhale of the boat while standing on the centerboard to increase your righting moment.

It is very important to make sure the sheets are free and loose so that the wind doesn't blow the boat over again after its righted. Once the sails break the surface, the wind will get under them and quickly right the boat - so be ready to scramble into the cockpit and over to the windward side. Be careful of the flailing boom!!!

I had lots of experience with capsizes years ago with my Sidewinder 15. I loved to sail solo with a good breeze blowing. I learned to recognize the point when there was no way to prevent the capsize. I could release the sheets and scramble over the gunwhale onto the centerboard as she rolled. Then scramble back into the cockpit as she righted getting only my feet wet - IF I was lucky!

[Richard Whitney CS#70]

Thanks Graham

Good to see what it looks like in practice. I use to practice wet entries in my kayak - should probably try the same thing with the CS 17.

[JeffM]

Foam in the luff sleeve is an interesting idea. But, assuming it's evenly distributed, wouldn't it give too little torque to be useful?

[Designer]

Ray,

Filling in below the coaming would make the boat float a bit higher on it's side which would be a negative and it would move the heeled center of bouyancy a bit toward the masthead which would be a slight positive and would bring in a little less water into the boat while righting. Over all I think the pros and cons would be a wash.

Jeff,

I have to test it first. The foam might not have enough volume by itself but might have to be suplemented by a small masthead float. I always thought that those huge masthead floats that some catamarans had a few years ago looked hideous.

[Roger Peterson]

Graham,

Would filling the upper part of the alloy mast (built to plans) with 2 part expanding foam add enough floatation to keep the mast from sinking? Would that add to much weight up high? Also, How would you suggest keeping the mast sections from pulling apart if the boat does "turtle"

Roger

[Designer]

Filling the mast with foam will only help if the joins are not properly caulked. Mine are not caulked at the moment because I have not yet decided whether to leave the rig as it is or add a sail track and jiffy reefing, which is my preference. I had about a pint of water in each mast when I pulled them apart.

Free blown foam only weighs about 2# per cubic foot which would not add a lot of weight to the masts. My top sections appears to be solid wood, I might cut them down the middle and hollow them out and glue them back together.

[Tim]

On the positive side I had a chance to solo the CS 17 under some moderately windy conditions this past weekend and I was very delighted by the lack of heavy heel required to maintain speed. I was worried that I would have to sit on the rail all the time but I stayed seated, was happy with the speed, and based on this I really don't plan to improve the coaming like others have done to accommodate rail sitting. I should note that I left the mizzen on shore and sailed with the main only in the center position.

On the negative side - I don't think my seat hatches will hold water long if knocked down. I only have hook and loop holding them down. I probably need a gasket and latch that I can tighten down. I couldn't find a good latch that would not be a calf scrapper. Might be easier to just use duct tape. Would it be better to have the hatches on the the vertical part of the seat? - harder to get things but out of the water completely in a knock down.

I

[Joe Nelson CS#35]

Tim,

Try using shock cord under tension hooked to the underside of the hatch. If you install an eye strap to the underside of the hatch and a hook on the shock cord...attach the other end anywere you can get downward tnesion...you can lift the hatch and unhook the cord to fully open the hatch. Then no exterior latching hardware is necessary.

[Richard Whitney CS#70]

Joe

Thanks for that tip. I was about to fit latch hardware but will give your idea a go - less clutter

[Rob Blackburn]

If you did turn turtle the other thing to do is let the masts fall out. They are then tied on with the sheets and would still hang around. This would allow you to get the boat up, undo the sails, roll them up and bail the boat with a large Master and Commander style mess tied to the side.

You would then take a deep breath and plan your next move or open the spirit locker for a fortifying serve of rum.

I tie mine down to the deck with a 10mm shock cord with an adjustable sail tie on it to tension it up tight. I have put a piccie of the ones here. Not too clear but you get the picture.

This gives you a quick and easy safety mechanism ie quickly tie them down if you are going out in deep water but otherwise I don't bother as the thing is very stable particularly with a big load on board. Also you don't have to drill a hole at the masts most stressed point and it allows you to quickly reef by rolling up the sail on the mast.

Rob

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