When I go to a yard and observe boats blocked up for bottom jobs etc. I wonder about the science of storing on the hard.
Getting ready to transport my boat for maintenance, I would like to hear from the experienced and perhaps about the science of securing a Commander 31 on the hard. Where do I place the stands? Where is there needed support of the keel? Directing the crane operator for lifting straps placement. These issues are probably second nature to some. I have already been the observer, but now I am getting ready to be in charge for the first time. Thanks, in advance to those who know and sharing their wisdom on the subject.
I know somewhere in the archives Dick Morland penned one of his novels on this subject. If you can’t find it the headlines we use in a yard is simple. For a 31 six stands and chain from one side to another on each set. 3 blocked areas equally separated . Roughly 1/3 of the weight on the keel be careful not to crush. And the rest evenly distributed on the stands. Stands should be close to the hard chine just under the outer edge for its strength. Further inward will not be as strong and push in. As for the lifting straps the rear strap should be just in front of the shafts entrance to the hull but as close to the shafts as you can get them without touching the shafts. Good luck and hope this helps you. When we haul out boats its all in the yards shoulders and we just advise where things are if they ask. It’s ultimately their liability.
Gotta love the Archives!!!! Dick had a 38 Sedan at the time.
#18018 From: "Jim Wick" <JimWick@...>
Date: Wed Jan 26, 2005 11:39 am
Subject: Re: [CCCC] Proper Blocking
From the factory, a cradle was made supporting the boat evenly from need the
keel to out to the chine. The first bunk stated 4'11 -1/2" inches from the
chine corner at the transom. The next bunk was 10' 1" from the aft bunk.
That should put it about on the forward engine room bulkhead. Length from
the aft bunk to the forward bunk was 19' 2". The overall length of the
cradle was 24'. Add 24 and 4' 11-1/2" and you can see that almost 9' of the
boat nose was hanging out.
With the bunk system, the weight was evenly distributed. With point
support, I think keeping all points as equal in load bearing would be best.
The chine is a strong area. The keel should not be pushed up if possible.
For what it's worth department....
#18025 From: Dick Morland <dick.morland@...>
Date: Wed Jan 26, 2005 4:51 pm
Subject: Proper Blocking
As usual, I have a couple
of opinions :-) I've been around boats for a long time and have had
cradles up to 3 years ago. Remember, the purpose of a cradle or
blocking system is to support the weight of the boat when out of the
water. Think for a moment how this weight is supported when the boat
is in the water--- The load is distributed evenly across the whole
bottom, an ideal situation. Think now how the load is supported when
on land and you quickly realize the support area is much less than
when in the water. For this reason, it behooves us to select the
support points carefully. As Jim Wick pointed out, the original CC
cradles were designed to support the boat under a structural bulkhead,
but no weight was supported by the keel with this system as there are
clearance cut outs for the keel on cradles. I was happy with cradles
for many years, even rebuilding a couple of them for previous boats.
When I got Patty Wagon, the heaviest boat we ever owned, I started
noticing some racking of the hull when on the cradle. My nephew &
myself used a heavy duty hydraulic jack to attempt to block the cradle
so all 3 bunkers were pressing equally against the hull, but at best
this is guess work. Most years the sliding glass doors of our sedan
would bind a little, indicating hull distress.
As my cradle approached the end of it's life, I began planning for
keel blocks & jack stands, the most popular system in the North. I
observed many blocked boats and was shocked by many that I observed,
noticing blocks that were obviously carrying unequal loads. This was
very obvious by some of the shimming wood really being crushed, while
other blocks under a given boat appeared to hardly being carrying any
load at all. Observing our yard blocking the keel, it quickly became
apparent that under the best scenario, 1/4" was about as close as they
were going to get, as this was the thinnest shim the yard has. If you
can't get a 1/4" shim in, they leave that block as is, while another
block would just barely take a shim, with no additional clearance
between keel & block stack. Sorry, 1/4" isn't close enough for Patty
Wagon (& me). About that time Todd mentioned on the list he equalizes
keel block pressure with the use of tapered shims that he can pound
laterally until tight against the keel. OK, cool idea, but PW
deserves something a little better :-) A few nights of engineering
thought process resulted in the design & construction of 7 adjustable
keel blocks, as shown in attachment "Keel Blocks 2". It's pretty
obvious how they work--- a 6" X 6" X 12" wood block cut on a shallow
angle to act as a shimming system with threaded rod & nuts to keep it
just where I adjust it to equalize keel load.
OK, Lee asked "How many blocks & stands do you need?" I don't know if
there is such a thing as too many, but a large yard in Michigan City
has a system that absolutely shocks me. Even for boats as large as 50'
Sea Rays they use two keel blocks total and two jack stands on each
side. I have heard that this is a Sea Ray approved system. Well Lee,
Patty wagon is currently sitting on 7 adjustable keel blocks, the
first being placed at the very stern, the next one just under the
straight section of keel, then equally spaced to the last portion of
straight keel just under the v-berth port lights. She also has 5 jack
stands under each side, with two being placed at the very stern, then
equally spaced along the hard chine to about the same spot as the
forward most keel block. Attachment "Winterizing 1" show this
placement. Now, how much pressure on the jack stands? This is
certainly personal preference. When our yard is blocking a customers
boat when the customer is present, they ask how the customer wants the
jack stands adjusted, loose or tight?
Obviously, my nephew & myself do all this work, as the yard just
brings PW over to her winter resting place and watch Doug & I do all
the work. They love it! The last thing we do is a final adjust on the
jack stands, and I take up pretty hard on them (with oiled threads). I
estimate each jack stand is carrying at least 500 # or a little more.
Anal? Perhaps, but when I walk away from PW in early October, the
sliding glass doors slide like they are on ball bearings, just as they
do in the spring when I next see her. I sleep well all winter, knowing
she is properly supported and the hull is not racking or in any
distress. Overkill ? Perhaps, but what is peace of mind worth?
Regards,
Dick Morland
dick.morland@...
On Thu, 27 Jan 2005 09:15:24 -0500, DBosak wrote:
> Great idea -- I'm going to do this for The Irish Lady for next season -
> Now -- The details:
>
> What is the "shallow angle" you used? 10°
> What size is the threaded rod? 5/16"
> What gauge is the steel rails? 3/16"
> Did you consider using slide plates made of low friction plastic similar to
those things used on woodworking tools? No, but it would work well.
> Also, are you suggesting that the weight of the boat be mostly carried by the
jack stands? I was always told that the weight of the boat should be carried by
the keel when on the hard.
--------------------------------------------------------------------------------\
------------
I'm going to send Dennis a print for the shims & a few more pictures
of the finished item. The above question, however, deserves an answer
to the whole group. As I mentioned in my dissertation, how much weight
is carried by the jack stands is purely a matter of personal
preference. As I mentioned, I think I have about 500# on each jack
stand, certainly not an inordinate amount when you consider that they
are directly under the chine of the boat, a very strong area. Fully
loaded, PW weighs well over 20,000#, and this is pretty much how we
store her, removing only electronics, food, and all liquid items. If
my 500# estimate is relatively correct, it means that the 10
jackstands are supporting 5,000# of the 20,000# plus total, or roughly
20 % - 25%, while the keel blocks carry by far the majority of the
weight. Again, just my personal preference in jack stand loading, and
where I place them.
--
Regards,
Dick Morland
dick.morland@...
Reply by Dick Morland on October 6, 2013 at 5:29pm
Interesting subject, and very subjective. As a very minimum, a local very large Sea Ray dealer uses 2 wooden keel blocks and two jack stands per side. I've seen 470 Sun Dancers blocked this way. Their yard is full of boats blocked this way, and over the years I'm assuming someone from the factory has seen this and approves. I think it's crazy. Our current 45,000 47 is currently sitting on 4 wooden keel blocks and 3 jack stands per side. See picture below for the way I used to block our previous 38 --- 6 adjustable keel blocks I designed & built, plus 4 jack stands per side. Yeah,I know, probably a case of overkill, but nobody has ever accused me of under engineering something :-) The jack stands (other than the 2 home brew ones at the stern) are Brownell, available directly from Brownell, or I believe West Marine also sells them.
God I miss his wisdom…. Glad for the Archives!! ❤️❤️
Obviously good advise here already. I would like to stress the part about overloading the keel at any given spot with excessive weight.
By far the hollow keels on our boats are the weakest place on their bottoms.
I've seen several commander hulls with severe stress fractures on their keels caused by bad blocking.
Here's some photos of some of the damage on the keel of mine
My 31' sat about 40 years balanced on two blocks of wood: one under the keel at the transom, and one a bit forward of mid-ship. The keel put some serious dents in those 4x4"s. The 31' Commander is light enough to do that, but I prefer three keel blocks, and four or six jack stands along the chines. I use thin plywood to pound and shim the keel blocks. Jack stands with oiled threads, and a long screwdriver or bar to turn the threads and tighten the pads under the chines. I do a lot of turning the jackstands, getting the waterline level and trying to even out the weight on each support.
My 31' Sports Cruiser has no structural bulkheads to carry significant weight. The engines, fuel tanks, and decks are mostly supported on the four stringers.