Jackstand Placement

[Ryland3210]

A winterizing publication recommends three jackstands on each side boats exceeding 26 feet. Mine is 28.5 and weighs 7300 pounds. The marina place two wooden blocks under each side of the boat. They are right at the aft end of the hull and at the out edge of the transom.

The two jackstands are at the locations where the lifting is indicated, also at the outer edge of the hull.

This seems like enormous pressure points are being created, especially at the transom. The marina also leaves outdrives in the full up trailer position, which I have been told can lead to premature failure of the bellows. The publication recommends lowering the out drive onto a block to help support the weight.

Should I worry?

 

[smokeonthewater]

outdrives should be down but NOT supporting weight... boat should be supported center (keel) plus both sides at the transom and center plus both sides forward for 6 total points...

 

[tpenfield]

Are there blocks supporting the keel in at least two places? Much of the weight should be resting on the keel. The boat stands at the chines are more for stability than support, they may only support a fraction of the overall weight.

Sounds like you might want to have a chat with the marina folks.

 

[H20Rat]

The marina also leaves outdrives in the full up trailer position, which I have been told can lead to premature failure of the bellows. The publication recommends lowering the out drive onto a block to help support the weight.

Seems like a win-win for the marina! One less step to do during layup, and you keep the service shop busy by replacing bellows far more often than would otherwise be needed.

 

[alldodge]

They want to do it as cheap for them as possible. They don't want to have to get back in the boat to raise the drives in the spring. Hey its not their boat, and having to replace parts sooner is another win. if they get away with it

 

[shrew]

All of the weight is on the keel. The blocks (Dunnage) should be stacked and placed where the keel and transom intersect, then about 2/3 forward from transom another set of blocks stacked. The forward stack should be aligned with an internal bulkhead.

the stands don't hold any weight. they only keep the boat from tipping over. Think about taking a long heavy object, then standing it on its end. There will be very little force required to keep the object balanced and standing. I remove 1 jack stand at a time to paint the hull every spring. No big deal.

Number of jacks and blocks is also a product of weight and height, not just length. I've commonly seen 2 sets of blocks and 4 jack stands on express cruisers up to 32-34 feet. However, a very heavy 34 ft aft cabin would probably go 3 sets of blocks and 6 jack stands.

I have a 28 ft express around 8,500lbs. I've used 2sets of blocks and 4 jack stands for many years with no problems.

Drive should be DOWN. If you're worried, remove it a take it home with you.

 

[JoLin]

All of the weight is on the keel. The blocks (Dunnage) should be stacked and placed where the keel and transom intersect, then about 2/3 forward from transom another set of blocks stacked. The forward stack should be aligned with an internal bulkhead.

This. My transporter uses cement blocks and wood to block the boat, but that's the principle. The weight rests on 2 keel supports placed as Shrew noted. The outer supports are there just to stabilize the boat.

My .02

 

[Ryland3210]

Thanks, guys. You have confirmed my instincts, with some very useful detail.
I did speak to the marina. They used the "we have always done it this way" argument, which I never find persuasive. They did agree to put another block under the keel. I plan on making two sets of jackstands. I'll leave the 4X4 posts they put in on either side to make them feel good. Taking another look at the two blocks at the rear transom corners, the shape of the hull is such that the wood supports are only contacting an area about 1/2" wide by 3 inches long. The contact pressure must be enormous. I estimate about 2200 psi. I wonder what damage that might do.

Once they shim the second block in under the keel, I am tempted to put my floor jack over there under the keel to take the pressure off those point contacts and put it on the new block. Am I on the right track?

 

[smokeonthewater]

If you modify what they did and something happens you will be responsible for your own damages and any damages to any other boat it falls into...

You are paying them... Instruct them on what you want done with your boat or have them launch it and find a new marina...
Just my $.02

 

[alldodge]

Thanks, guys. You have confirmed my instincts, with some very useful detail.
I did speak to the marina. They used the "we have always done it this way" argument, which I never find persuasive. They did agree to put another block under the keel. I plan on making two sets of jackstands. I'll leave the 4X4 posts they put in on either side to make them feel good. Taking another look at the two blocks at the rear transom corners, the shape of the hull is such that the wood supports are only contacting an area about 1/2" wide by 3 inches long. The contact pressure must be enormous. I estimate about 2200 psi. I wonder what damage that might do.

Once they shim the second block in under the keel, I am tempted to put my floor jack over there under the keel to take the pressure off those point contacts and put it on the new block. Am I on the right track?

Your between a rock and a hard spot. As a non-attorney, doing something now and if there is a problem they could say it's your fault, if you don't do anything they could say it was caused by what you wanted them to do now.

If something actually does happen (crack) you probably won't notice it, water will start leaking in and will take maybe years to show up. If you do notice a crack and if you can prove it was caused by them, you probably won't receive any restitution. Just takes to much time, expert witness and attorney fees. The way it sit's currently nothing may happen, they are correct folks do it this way all the time not knowing, or in most cases not caring

As I see it you have two choices, leave it as-is until next season and get someone else next season or hire someone else to do it right. That said, doing it right now, may now change the outcome for next season

 

[Ryland3210]

It's a shame how much fear of litigation in the U.S. affects our thinking. My priority is to protect my boat, although the damage may already have been done to the two point contacts.

I noticed that boats in the section of the yard I was placed in have been done the same way, whereas boats in the section nearest the marina office have been done with two or three blocks under the keel and four jackstands. It appears that better care is taken on some boats than others. I will talk to them again and request that my boat be provided the better method. They seem to be flexible on this. One way or the other, I am not confident in their motives.

Every other marina I visited in the area uses multiple blocks under the keel and at least four jackstands.

One detail, I would like to understand: My single I/O 5.7 liter is mounted on two stringes. There is nothing in the center under the engine that looks like a keel. Is the intersection of the transom and center (keel) still the correct place for the second block?

 

[tpenfield]

your boat should be supported something like this . . .



blocks under the keel in a couple of places and then the boat stands on the outside, at the chines. This is my 33 foot boat . . . 10K lbs.

Got any pictures to post of how your marina is doing it?

 

[smokeonthewater]

The keel support it mostly the transom... It extends acros the center..

Then the forward blocks should be under a bulkhead if possible but even if not, the keel is still very strong and centered between the stringers...
Your boat is built the same as every other power boat out there, including my 30' twin engine wellcraft that is currently in my back yard on 4 stands and wood cribbing under the keel at the transom and forward near where the keel begins to curve up.

This IS how it's done... Don't over think it, just have it fixed.

 

[Ryland3210]

Thanks. I bought four jackstands and installed another set of blocks (cribbing) under the keel where the sling goes. The marina's blocks under the transom corners were too low to get the keel block under the transom. I did manage to jack the boat up with two jackstands alongside the sling location, but not high enough to get the new block under the transom, as the boat began to shift because of the 4X4 posts alongside the front. These had no stability to speak of.

Ultimately the boat is supported by four jackstands and two keel blocks. I left the marina's posts and transom corner blocks in place, but very little load is not on them. The majority of the load is on the keel blocks, with most of the rest on the four jackstands. Belts and suspenders.

Thanks for all the goo advice. I now have a thorough understanding of how all this should be. Next year, I'll be supplying the jackstands and ask how the marina plans to set up the boat before I let them store it.

Over the winter, I may fabricate a couple of steel vee blocks with rubber cushions to custom fit the keel. Yes, I know I am being a bit obsessive about this, but I just don't like point contact anywhere on the hull.

I'll send pix when I get back home. I think they will be interesting to the readers.

 

[smokeonthewater]

Skip the steel blocks...

Much more risk of damage by applying pressure at the top of the V if the boat is not EXACTLY level...

Blocks under the keel are THE correct solution....

You COULD add more blocks but be very cautious as to have the weight evenly spread in them...

Example:

With 2 blocks, the boat automatically levels on them but with 3 blocks, if the center is low, it does nothing it if it is high it takes all of the weight off of one or both of the others...

You can crank up your stands a bit more to support a bit more weight but in the end, don't over think this... If he hull is not deformed as it sits you are fine...

 

[alldodge]

Just brought my new trailer home and while out it got me thinking about trailer manufactures, I know there are many other opinions here but you can take or leave.

There are several boat trailer manufactures which use only two bunks (exp load master in FL and Mayco). These type of trailers use only two bunks turned on it's edge (about 3 inch wide). So the boat while sitting on the trailer has two bunks on the side and one spot on the keel forward. Actually Hydrohoist boat lifts do the same thing.

Boat haulers want to come in, pick the boat up, move and set it down as fast as possible. While sitting a boat only on it's keel and balanced on it's side may be the best (don't know) but appears the industry has been hauling and storing has been going on for a very long time.

Will agree, the real heavy and large boats (thinking 40 foot and larger) may need more keel support. Not many large go fast boats use anymore then the two length supports

 

[tpenfield]

I'll also add the comment that although only 2 support points along the keel of a boat are generally used throughout the recreational boating industry, the size of those 2 support points is what would be & should be bigger for larger boats. If the contact point is too small of an area for a large boat, you could have the the support actually 'punch through' the hull.

So for a small runabout, maybe a 6x6 piece of lumber at the contact points along the keel would suffice, but for a large boat you would be doubling or tripling up in the lumber at the contact point to get something in the 12-18" range for support .

 

[Ryland3210]

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Here are before (Marina), and after (my "emergency") remedy. I managed to pickup used jackstands and installed them same day.

 

[Ryland3210]

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This is the original Marina "blocking". The one in the previous message shows the point contact of the transom by the Marina. Same on the starboard side, with no block under the keel in the aft area. I jacked the boat up enough with the jack stands to remove the 4X4's under the transom, placed a block under the keel in the area of the sling, and lowered the boat onto it. I put 2 X 4's where the 4 X 4's had been but very little of the weight is on them. Most of the weight is on the two keel blocks, with the Jackstands providing stabilization. The two Marina posts and transom 2 X 4's were left in just in case the Marina personnel got "worried". So it is belts and suspenders, but the Marina "blocking" is just along for the ride, except for the keel block they installed under the forward berth.

 

[Ryland3210]

It was a bit of a struggle to get the 2X4 between the 12X12 block under the keel aft sling position, but without that, the load would not have been spread more than a few inches. Since I have time on my hands and engineering degrees, I may design something over the winter to go on top of the cribbing or 12 X !2 that will automatically spread the load along the length of the metal Vee I spoke about earlier. I also would line that with a rubber cushion of the appropriate durometer to spread it sideways. The idea is make it simple and fast for the marina, while being as kind as practical to the boat.