[Rhodes22-list] Reply to Jay about Chain plates

[Gregg J. MacMillan]

At 9:27 PM -0600 12/2/05, Todd Zumach wrote:

>How do you inspect and replace the chain plates?

Todd--

The following is from Stan's site:

http://www.rhodes22.com/contruction_detail.html

I think the answer you're looking for is in the second to the last paragraph.

--Gregg

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THE CHAIN PLATES AND STAYS

Chain Plates And Stays - 9" That is the marquee for our current 
attraction.  Not many plunk down their coins for this feature.  It is 
a sleeper.  But its sequel, and the next coming attraction, is a 
block buster, not to be missed.  However we are getting ahead of what 
is now playing. 
Many lookers are concerned about the little stainless steel holder 
the mast sits in.  It couldn't possibly be sufficient to secure that 
big mast in any kind of blow.  They are right.  They would be even 
more disturbed if they knew that that little mast step was held to 
the deck by only three little screws !  ??

First let's look at the nine chain plates.  It is at these points 
that the real load of the mast is transferred to the boat.  If winds 
cause the mast to heel, the boat must follow, or the mast falls.  The 
more areas on the hull this load can be spread over, the less the 
strain on the boat and the safer you will be. 

Most 22s have six stays; and even less chain plates, because they 
send two or more stays to a single plate.  The Rhodes is the only 22 
we know of that sports nine stays, each going to its own chain plate. 
9 Chain Plates.  There is good support for our madness:

First is the better load distribution we mentioned.  Second, masts 
tend to pump, that is flex fore and aft in the mid section, if they 
are not supported here.  Having one pair of lower shrouds (stays on 
port and starboard below the spreaders) only dampens this pumping 
action in one direction.  There must be fore and aft lower shrouds to 
handle this properly.  Most 22s only have aft lowers.  Third, this 
big, flexible stick wants to be standing on your deck tall and 
straight.  The more stays, the easier it is to tune the mast and keep 
it tuned.  Fourth, you can lose an awful lot of Rhodes stays and that 
mast will not come down.  On most 22s, losing just the jib stay will 
bring down the mast, and on top of the cockpit at that.  And finally, 
for practical comfort:  The Rhodes' upper shrouds go vertically from 
the gunnel to the large spreaders.  The double lower shrouds go from 
the cabin top, diagonally to just below the spreaders.  This leaves a 
clear walkway to the bow deck.  More than that, since there are nine 
stays and since each stay goes to its own chain plate and since the 
chain plates are spread out, the shrouds become vertical life lines, 
grabbable at any height.  (As compared to regular life lines, that 
are at an awkward height to hold, and at a good height to crease you 
at the back of the knees for flipping over backwards.) One point for 
trailering boat people:  double lowers allow you the option of 
raising the mast from fore or aft. 

Our mast step worrier still isn't satisfied, particularly since he 
now knows the step is just held down by those three little screws. 
Because of the way masts are supported by stays, most of the force at 
the bottom of the mast is downward.  The very small horizontal thrust 
at the bottom of the mast is easily handled by fasteners in shear. 
On the other hand, if the stays supporting the mast are disconnected, 
there is no way that this huge lever called a mast, would not pry up 
its mast step, no matter how many bolts it had.  We once witnessed a 
22, whose builder had innocently bolted on his mast step, lose the 
cabin top when the mast came down.  Although Rhodes' owners are 
smart, we know of some absent minded professor types who drove off 
with their masts up.  It was amazing how little damage was done when 
the first bridge or cable they met took down their masts.  Their 
savior was those three little screws that make for a clean break away 
of the mast step from the deck.  I have replaced such break away mast 
steps by just driving three epoxy coated pieces of wood into the 3 
holes and re-screwing the mast step back in place.  We trust you will 
never have to take advantage of this wonderful construction detail. 
But even if a jealous neighbor pulls the pins from all your stays, 
the joke will be on him. 

Our worrier is grudgingly convinced, but now he has found something 
else.  Those chain plates will never hang in there with just those 
two little screws he spotted next to each shroud chain plate. 

The real fasteners for the shroud chain plates are not visible on the 
Rhodes, from the inside or the outside.  Those two little screws 
merely hold down the chain plate covers, making them easily removed 
for re-caulking chain plate slots after chain plates re-seat from 
sailing forces. 
Having read this far undoubtedly means you are a detail nut.  So let 
us tell you how the nine chain plates are really fastened.  The bow 
chain plate is through-bolted to the deck and hull (also helping to 
keep these two elements together in a key place).  The four lower 
shroud chain plates are glassed into the 1" cabin top you saw 
displayed at the boat show.  The lower shrouds, collectively are very 
important, but individually carry the least part of the mast load. 
The upper shroud is the real work horse.  Its chain plate goes down 
the deck to the deck/ hull seam, where it forms a "T" that is triple 
bolted through both the deck and the hull.  You do not see it because 
it is behind the rub rail on the outside and behind the seam strip on 
the inside.  (Yet, like so much of the hardware connections on the 
Rhodes and unlike some hardware on other designs, is accessible if 
ever necessary.) The back stays chain plates are bolted through the 
corners of the transom.  Corners are the strongest part of any layup.

Stay Summary:  The Rhodes has 9 stays, each going to its own chain 
plate for extraordinary mast load distribution, all placed to make it 
easier to walk the decks between them, culminating in the best mast 
support and shape integrity possible plus allowing mast raising from 
fore or aft.  All equalling the highest safety factor of any 
trailerable or any boat with a single handed hinged mast system.

-- 
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M a c M i l l a n  G r a p h i c s
1 . 8 0 0 . 7 7 1 . 3 1 7 1
2002 Ford Circle, Milford, OH  45150
mailto:gjm at macgra.com
http://www.macgra.com
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