Westsail Owners Alliance - Thread: "Position Of Mast On Raised Step W32"
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Thread: "Position Of Mast On Raised Step W32"

12,268 posts on 2,444 threads   •   From Mar 07, 2004 - Jan 08, 2012

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Position Of Mast On Raised Step W32


Gary and Charlotte Burton

Since I'm about to mount my tabernacle for the first time I thought it would be interesting to find out where others have theirs. Our boat is 119 (first mould) never rigged.

Anybody with an older w32 care to say where their mast base is on the raised step? Is there a correlation between this and weather helm?

Thanks for any input.


Dave Kall
(Member)

To make sure the stays are correct you need to have the mast base centered on the upper shrouds so the mast is pulled in column. If you move the base then I would contact a Navel Architect to make sure you don't need to move the chain plates and if so how much. Personally I doubt the base moved a couple of inches for or aft will effect helm as much as changing any rake will.

Fair Winds


Gary and Charlotte Burton

Dave - I have noticed that the upper shrouds (middle chainplate) on one of the boats I have looked does not line up with the spreaders and top of the mast. This particular boat has been everywhere and had no problems....probably because the rig is overbuilt.
Probably not the ideal situation but then when the mast is re-raked you are effectivly doing the same thing.


Dave Kall
(Member)

The chainplates need to line up w/ the base of the mast, as the shroud rises to the top of the mast the pull is in the column of the mast. The lowers adjust for any camber you want but I can't imagine taking the 43' stick and pulling it out of alignment may be a good thing. Don't look at where the spreaders are; look at where the base is, in relation to the chain plates.


Gary and Charlotte Burton

I wonder if anyone knows for sure if changing the mast step position will alter the handling of the boat. Your comment about the cap shroud chainplate lining up with the base of the mast makes sense.


Ralph and Sandra Weiland

When you move the mast position along the boat, you move the center of lateral force of the sails along the boat. When you change the lie of the boat in the water, whether through heel or fore-aft balance, you change the center of lateral resistance of the hull to the force of the sails. So the answer theoretically is, yes you do, because unless these two force centers are completely coincident longitudinally, you will have either weather or lee helm. Now, in a practical sense, does 2" make a detectable difference? Probably not because I'm sure you can get that much difference with only modest heel, for example. The important issue is to eliminate any net fore-aft force from the shrouds (lowers must be balanced, uppers must be correctly aligned with mast in same plane as upper shrouds) because if you don't, you will have a cambered mast. Camber will increase with wind speed and sail area carried because higher wind and sail area increase the tension in the weather shrouds, and put increased bending moment on the mast. As long as you have zero camber, if you find the mast 2" aft or forward causes helm, you can always correct it by adjusting rake, so it's neither the end of the world nor a fatal error. The degree of helm is always changing anyway.


Norm Rhines

Gary & Chrlotte:

One point of ref.

location of tarbenacial Base plate is 8.75" back from the top front of the rasied section and the back side is 12" forward from the back of the raised section. w32 Hull #564 (late 1975 west coast boat)

I have two additional points for you
1.) The original compression post in the cabin was a bit to small for the loads (= if you can spread the load of the post across the whole of the beam) Wood is much stronger in compression orientented on the end grain but not as strong when the grain runs perpendicular to the load.

2.) If you follow Buds recomendation on the deck beam under the mast you will thank yourself later.

In my case there are also through bolts showing on the deck and they do line up with the pin in the mast and almost with the stays +/- 1".

Info from W32 #564

Hope this helps.

Norm

p.s. note: On the westsail yahoo group site there is, my rig tension data but no one else has added to it. Wish we could have more group input. but you are welcome to check it out.


Ralph and Sandra Weiland

Norm: We're re-standing the mast this week (Hull 610) and will be tuning the rig. I joined the Yahoo group a few weeks ago but have never been able to find your rig tension table. What's the URL?

Thanks,

Ralph


Gary and Charlotte Burton

Norm - did you position the tabernacle there? All the boats I've looked at have the base right in the middle of the raised step


Norm Rhines

Ralph:

The rig tension thing is in the
Datbase on the left menu then just Rig Tension W32.

Gary:
The mast was in place before I purchased the boat, it was a kit boat. ( I think it was placed so it was centered over the bulkhead) and without regard to the built up section.

As far as the rig (I had weather helm inspite of the mast postion) fixed with the removal of 20" of boom and a 14'-0" foot on the main.

Hope this helps.


Gary and Charlotte Burton

Very interesting Norm. Thank you


Gary and Charlotte Burton

Do the capshroud chainplates line up with the base of the mast Norm? Athwartship that is..


Norm Rhines

Yes for the most part the bolts are 1/2" forward of the bulkhead (= Chainplate was a pain to replace as the nuts were up aginst the bulkhead)
and yes they line up with the mast pin +/-

Norm


Ralph and Sandra Weiland

Just measured tabernacle position and alignment relative to chainplates. On Hull 610 (factory) the distance from the lip of the "platform" to the front edge of the tabernacle is 9-1/4 inches and the corresponding rear measurement is 8-3/4 inches. The tabernacle is not dead center on the platform, but its pin lines up perfectly with the upper chainplate.


Gary and Charlotte Burton

Thanks for that Ralph. Mine is going to end up slightly aft of center like yours when I line up the tabernacle pin with the upper shroud chainplates. Do you have any weather helm issues?


Ralph and Sandra Weiland

Still in the process of stepping the mast and re-rigging so cannot give a personall yes/no. But previous owner says there were none. If I find too much one way or the other, I'll just adjust the mast rake a bit.

Ralph


Tom Crank

First some background. My boat was circumnavigated by her prior owner but was on the hard when I bought her and has spent the past 5 years behind my house. I'm getting close but am probably a year away from completion. I removed the tabernacle base 2 years ago and rebuilt the raised base. Tonight I was beginning to install the new chain plates and things just weren't adding up. It appears to me that the previous location of the chainplates was too far aft. The old mounting holes for the tabernacle base are not visible from above but transferring measurments from below would seem to indicate that the mast was not previously aligned with the center chain plates. If I align the holes for the center chainplate with the pin on the tabernacle base the aft edge of the base is aproximately 7" from the aft edge of the raised mast base. This puts the center of the mast 4 1/2" forward of the main bulkhead.

I am not real excited about the idea of filling 24 3/8" holes in a boat that's already been painted. I also don't want the upper shrounds to not be in column with the mast. Nor do I want the mast to not be properly supported by the compression post and bulkhead.

What are you thoughts?


Jeff Matthiae

Tom, Bud,

I understand what you mean about not wanting to move the chainplates after painting. I just finished repainting the hull after glassing in all of those holes.

I have hull #431, a July '75 kit boat from the East Coast(?). In addition to the construction manuals it came with a few other Westsail blueprints. One of them is titled Critical Dimension. Amongst other things it shows the location of the mast step and chainplates. The drawing is dated 2-11-75 by A.P. Lynd. Can't quite make out the Rev.

The end of hull (bow) to mast center line is shown as 12' 8-3/4". Underneath it someone wrote in 13'0" which explains why may mast was to far back on the compression post.

It looks like the mast centerline lines up with the front edge of the main bulkhead.

A cutaway view shows the center of ALL of the chainplates 1/2" pin hole to be 3" above the top of the bulwark without the caprail installed. Easy for me as I have not yet installed the forward section of the new caprail. You may need to adjust for the thickness of caprail. They also show using a block of wood with a 1/2" bolt to get all of the chainplates at the same height.

Dimensions are shown for the center of the chainplate pin holes from the mast centerline. Also shown is the angle of the chainplate down from the top of the bulwark to the forward edge of the chainplate. They are as follows:
Upper: 1" forward, 95 deg.
Aft Lower: 14" aft, 97 deg.
Forward Lower: 21" forward, 93 deg.

I plan to put some painters tape on the back of the chainplates to protect the new paint if they rotate a little and step the new mast with just the top bolt in each chainplate. Once I'm in my slip and have the mast lightly "tuned" I'll drill the remaining holes (one chainplate at a time), remove the tape and install the chainplate. This is basically how Bud describes installing the split backstay chainplates. I think that for this drilling the top hole first instead of a middle one will make it easier to keep the pin location correct in relation to the mast centerline.

I'm a few weeks away from locating the chainplates. Need to build in the new compression post (stainless pipe replacing the wood post), finish the bottom and reseal the rudder (not happy with the dryout, I'll post about that and get Norm his dimensions next week or so). I had been planning to contact Bud and the mast builder to get their thoughts on the chainplate locations...so Bud do you know of any changes made to the dimensions over the years?

Good luck,
Jeff


Bud Taplin
(Member)

Tom, My drawings show the centerline of the bolts on the center chainplate to be 2" aft of the main bulkhead. The mast is 25'- 2" fron the bow of the hull, and it should be centered on the bulkhead. Considering that the mast is raked aft slightly, that would put the top of the upper shrouds in line with the center chainplates, assuming about a 2" rake at the top of the mast.

Since your boat went out as a kit, the builder may have installed the main bulkhead in a different location than the normal position.

If you do not want to change the location of the chainplate holes in the hull, then spot the center of the mast 2" forward of the center line of the holes. Check this location against the 25'-2" dimension noted above. You may need to add some to the existing mast post to have the post bear on the centerline of the mast.


Tom Crank

Thanks Bud. I also emailed the original owner and he indicated that the position was never a problem. Could you confirm the 25'-2" dimension seems a bit far to me.


Bud Taplin
(Member)

Tom, My apologies about the distance back from the bow. I was reading the wrong scale on my ruler. The 12'- 8-3/4" dimension is the correct one. The 2" dimension is correct though.


Gary and Charlotte Burton

Tom - also check to make sure that the spreader tips are in fact in the middle of the mast.


Gary and Charlotte Burton

Fore and aft that is...


Tom Crank

Thanks for all the help. I installed the stbd chainplates yesterday and hope to get to the port ones tonight. I used the original mounting holes. I won't be mounting the mast base for a bit. Still need to refinish the mast and paint the new base.

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