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"Mast slap"

Dferr

Member II
Does anyone know of a possible way to quiet down mast slap? I'm not sure what is cousing it, but it's going to drive me crazy! I really don't want to drop the mast just yet. Is it possible to remove the top cap with the mast up, look down inside and possible do something from that end? I have to go up and replace the windex indicator anyway.

Thanks,
Don
 

treilley

Sustaining Partner
If it is anything like mine('85 35-3) it is welded. I believe you should have the rig with internal halyards and the wiring conduit behind the sail track so you should not have any "slap". Of course, I have heard of people dropping wiring in a mast because they were too lazy or did not want to take the mast down to use the conduit.

I would try to pinpoint the source first. Is it wiring or an internal halyard? Maybe try and recreate the slap at anchor by rocking the boat and then grabbing the wiring and pulling taught.
 

Dferr

Member II
I've tried what you said. What ever is slaping, sounds very big! It doesn't take much movement to get it going, but when she gets going, you can actually feel it if you hold on to the mast. The halyards are tight, and I tried loosening them. The only thing I can think of, is the VHF cable. I tried pulling that tight also but no luck. I just wish there was someway to take a look in there.
 

Chris Miller

Sustaining Member
pole lift sheave

you might try removing the pole lift sheave (and run a messenger in there), the hole there should give you some insight... and a nice view of the deck:egrin:
 

e38 owner

Member III
Harbor Freight

I was just looking through the harbor freight catalog (this weeks ad)
They have a pipe inspection camera setup for 399. maybe you can find one to rent
 

Dferr

Member II
Pole lift sheave

Chris, I'm not sure what the pole lift sheave is. Could you explain please!

Thanks,
Don
 

treilley

Sustaining Partner
There is a sheave on the front of your mast between the top two spreaders that is for lifting the spinnaker pole. It is likely the biggest hole on your mast.
 

jkenan

Member III
Don-

Last year I took my mast down on my E-29 to address several issues. Among other issues, electrical needed to be replaced, and I wanted halyards run internally. Mast slap was a problem from loose internal electrical wire and also from external halyards, and I wanted an effective solution.

The electrical was pretty straightforward - 1.5" Conduit was riveted at 2' intervals all the way up mast (less a foot from the top and bottom), with an opening at spreader level and steaming light level for respective lights. There is technique to hold the conduit in place while it is being riveted I'd be happy to explain in more detail if you like.

The halyards were a bit more complex, and maybe someone will shoot holes in this strategy, but so far it worked well for me:
There are four sheaves at the top of my mast (two fore and two aft, with two sheaves in-line from a port/starboard perspective offering a fair lead fore–aft for two external halyards - Jib and Main). To internalize and effectively create management for four halyards, I drilled 5/8 holes in the masthead in-line with the inside of each sheave (holes had to drilled first through the masthead sheave cover, then through the plate underneath the sheaves welded to the top of mast column). Since my mast is 36', I thought there would be enough play in halyards even when pulled tight to generate a slap, so I rigged a harness at spreader level to restrict the oscillation of halyards as they vibrated (an 18' wavelength has less amplitude - ie. slap - than a 36' wavelength given the same energy). My harness was designed as this - I welded a plate (about 4"W x 3"H) to the bottom of the compression tube between the spreader tangs, and fastened to this plate (using #10's with hi-strength thread lock), four standard deck fairleads (two fore and two aft on the plate - directly opposite each other). Halyards ran from masthead sheaves thru holes drilled in plate atop mast column, thru this harness, and finally thru exit plates just below boom level. There are a few more details that are important to understand if you will undertake this project, but this is essentially it. I have no slap, nor any chaffing on the halyards. Only risk is the harness coming apart, but good welding and good threadlock should prevent this.

Let me know if you're interested in further explanation.

Best of luck.
 
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