skerry mast step

I have been through more than a hundred forum entries in the Skerry and I have not found a mishap like mine. My mast step assembly broke under an 11-12 kt side wind coming from port. The mast had its normal bent. I did not see the breaking process since I was focused on the sail and mast, purely enjoying the ride with my 15 years old son. My analysis is that under the lever effort, the side of the mast step box began gradually to pull the screws through the floor and tear the first layer of the oecume plywood upon which the box was firmly epoxy bonded see photos). Then the port side of the box broke in two pieces and the mast took a 45 degree angle. I quickly pulled the mast out to prevent complete break, pulled everything back in the boat and rowed two miles back to the shores of lake Saint-Louis near Montréal. Luckily, I had filed the underbody over the screw heads, so no water came in. But I was much surprised by that failure. Maybe I had sunk the screws a bit too much? I plan to build a different mast step using a 6”/6” solid piece of ¼ wood screwed and glued to the bottom, with an 1 inch high U-shaped piece of solid wood glued over it. Is there any reason why the normal mast step is 3 inches high?

http://i56.tinypic.com/1em4k1.jpg


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RE: skerry mast step

Karel,

Looking at your picture, the first thing that catches my eye is that the plywood has delaminated. The next is that both the plywood and solid wood have dark stains on them. Both are indications of water damage.

I agree with your analysis that the starboard side pulled loose first, forcing the port side to take the entire torsional stress of the mast. The solid wood failed along the grain and that was it.

The question is why. If the plywood on top of the step has been water damaged, the scenario is that the right side delaminates and can no longer transmit the stresses equally to both sides, the left side gets overstressed and fails. If that's the case, there's no need for you to replace it with an over-engineered step, just thoroughly waterproof it.

In fact, an over-engineered step can be dangerous. You want the step to fail before the hull, otherwise you may not be able to row back.

Finally, I'm puzzled by the plywood on the bottom of the step. Is that the bottom of the boat? Or is it a layer of glassed wood between the step and the bottom?

Anyway, the standard step has worked in thousands of boats (you yourself said that you couldn't find a failure like yours), so you should be able to replace the failed one with the original design.

Good luck,

Laszlo

 

 

RE: skerry mast step

Karel,

 A couple of obsevations. This is strictly from what I can see for the picture.

First, is that the screws would appear to be very deep and only clamping the top veneer and the glue layer beneath it. That alone is not enough to cause the failure.

The second observation is more what is missing from the picture, fillets. I can't see the other side, but there do not appear to be any fillets along the joints where it meets the floor or under the top of the mast step. The fillets would serve as extra support and spread the load over a larger area. If the step continually flexed, that could be the source of the water intrusion of the plywood and eventual failure.

 If it were my boat, I would replace the mast step with the original design, but add fillets where it meets the floor. I would also add a fillet where the step meets the bulkhead for addidional support. 

If you need parts to make the repair, send me an email and I'll see what i can do for you. 

 

RE: skerry mast step

Hi Karel!

Another Skerry in Montreal, eh? I thought I was the only one! They're awesome boats.

I second the suggestion for adding fillets. Once I developed a crack in mine in high winds. John Harris suggested I sand and fiberglass the top. Perhaps fiberglassing the sides would be beneficial also?

Personally, once the wind hits 20 km/h I start thinking about putting in a reef. That's just me though. I'm a wuss.

Ciao!

Jean.

RE: skerry mast step

Joey,

I just read this thread and my Skerry build didn't include fillets for the mast step to meet the floor.  I don't recall it being in the manual and we built ours in John Harris's class in Newport in 2008.  I do however like the idea of filleting the mast step at the floor and am wondering if the fillet can be applied over the varnished finish or do I need to sand completely through the varnish for a proper fillet joint?  Best, Bob

RE: skerry mast step

Joey,

I just read this thread and my Skerry build didn't include fillets for the mast step to meet the floor.  I don't recall it being in the manual and we built ours in John Harris's class in Newport in 2008.  I do however like the idea of filleting the mast step at the floor and am wondering if the fillet can be applied over the varnished finish or do I need to sand completely through the varnish for a proper fillet joint?  Best, Bob

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