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The Editorial Staff
Have I Seen My Cradle Lately?
By Jeff Strunka, Yard Manager, Crowley’s Yacht Yard, firstname.lastname@example.org
|Rusting cradle support|
For many boaters, the condition of their cradle is one of the last things on their minds. The fact is that most boats in the northern regions of our country will spend ½ of their lives sitting on these structures. When in the water, the boats are buoyed up by equal pressure on the entire hull. While in storage, a majority of the weight is placed on the keel and the remainder on the pads or bunks. In many cases, the main function of the uprights or bunks is to keep the boat upright. So, my boat is safe on its cradle … right?
When judging your cradle, the fact is that all cradles are not created equal. Inferior cradles lack proper support and may be make of improper materials. Let’s take a look at some factors that lead to a weak cradle.
Some of the characteristics of these cradles are;
1) Excessive flex from thin gauge steel
2) Point loading from narrow bunks
3) Non-adjustable pads
4) Not enough uprights for proper support
5) Inadquately protected metal (see photo 1)
Inferior cradles can be modified by fortifying the base, swapping fixed pads for adjustable pads and adding more uprights. It is all about properly supporting the boat. Once the base is bent or very rusted, this modification is not recommended.
|Cradle poppet pushing into a hull|
The largest danger to your boat caused by an inferior cradle is the uneven loading on the hull. When the boat is placed on an inferior cradle, there is a great amount of flex in the base which transfers the load up to the hull of the boat through the pads or bunks. If the pads or bunks are not adjustable, the amount of pressure on the hull is not easy to assess. This upward pressure will only become noticeable with a “punch-in” or depression in the hull of the boat (see photo 2, don't worry this boat is going to the junkyard). The only way to relieve this pressure is to place some shims under the keel when the boat is placed on the cradle. Over time, shims can compress and again transfer pressure upward. This can lead to cracks in the hull or tabbing inside of the boat. Some additional blocking can be added to help, but this is not the long-term solution.
So what do I need to look for when inspecting my cradle?
|Large boat on a 4 poppet cradle|
First, check for the amount of flex in the base; look at the points where the pads or bunks contact the hull and the check the condition of the welds or bolts are the first things to consider. If your pads or bunks are not adjustable, this may be more difficult. If you have screwpads, you should be able to turn is slightly to know if too much or little pressure is on the hull.
Next, look at the entire boat. Is there enough support (see photo 3)? A four pad cradle may work fine for smaller boats (under 28’), but a six or eight pad cradle offer more support. Another advantage to having additional supports is the ability to work under the pads by lowering one at a time per side to access the hull. In order for this to work there has to be enough adjustment in the supports as well (see photo 4).
|Poppets with little adjustment|
Some boats need more support forward due to having a “swept back” keel. There is a lot of pressure that is transferred forward that can cause a separation of the hull and keel at the front of the leading edge of the keel when the boat is placed on its cradle. By adding an angled V-screwpad or “kicker” to meet the leading edge of the keel, we can greatly reduce the pressure exerted on the front pads or bunk (see photo 5).
|Full keel forward support|
Some of the new hull designs have the keel positioned more forward on the hull. This requires that the boat be moved more forward on the cradle and add additional upright support aft. There is a simple way to determine if you may need additional support. Look at your boat and ask if the boat were set down on its keel, would it be balanced or would it fall forward or aft. If the answer is “it would fall forward or aft”, then you may consider adding a set of uprights forward or aft.
The last check is to notice how much movement there is on the boat when you are aboard. If the boat sways from side to side, additional supports are recommended.
Since sailboats have cradles that are easier to see, we did not include any pictures of powerboat cradles. However, do not let our omission lull you into a sense of security, power boat cradles certainly can have these same issues and require regular inspection.
It is best to check your cradle while the boat is on the cradle. Take a look at your cradle this spring when you are visiting your boat. If modifications are needed, we can note them and do the work once your boat has launched. Each boat has its own needs to achieve proper support. If you have any concerns about your cradle or have any further questions, you can contact me, Jeff Strunka, at email@example.com.
Thank you and think spring!