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As many of you know we have expanded the UL2 product line to include hoists up to 30,000 lbs capacity. These new UL2 hoists take the place of the old style “Big L” and “Mega L” lifts which used fiberglass style tanks. From time to time you will hear us refer to these lifts as ULE. The “E” simply means we “Expanded” the UL2 series to include capacities greater than the typical 4400, 6600 and 8800.
As every installer knows, correctly positioning the boat on the hoist is a critical step which will ensure longevity of the product. This positioning of the boat is simply a balancing strategy that places the boat’s center of gravity (CG) directly over the tank’s center of buoyancy (CB). In a perfect setup, with the CG placed directly over the CB, there will be minimal forces transferred to the dock. However, if the boat is not properly centered above the tanks, you will have an unbalanced system which will constantly be transferring forces to the dock (via torsion bars and arms) as the hoist uses the dock to try and keep the boat sitting level. This scenario will most likely result in unnecessary repair to both the hoist and the dock. (see picture #1)
With our 4400, 6600 and 8800 style of UL2, there are no provisions in the tanks for adjusting their positions. This is because the CG positions of boats in this capacity range do not vary much. However, when looking at boats that are 10,000 lbs and above, the CG positions can vary by several feet depending on the length and engine options. Since the transom should always be positioned at the end of the hull pads, the tanks must be adjusted fore or aft to line up with the boat’s CG (see picture #2).
As mentioned earlier, the more the boat weighs, the more important it is to properly position the tanks. A rule of thumb which seems to work in MOST cases is to measure the beam (width) of the boat. Now apply that same measurement from the back of the pad forward. This should be your approximate CG location of the boat. Now position the CB of the tanks directly under that. Now you may be asking “how do I know where my tank CB is”? For a two-tank lift, it is half of the distance of the tank. For three and four tank lifts, it gets a little more complicated. The formula looks like this: [(CB1*DISPL1) + (CB2*DISPL2) + (CB3*DISPL3) + (CB4*DISPL4)]/DISPLtot.
Since most people don’t enjoy math, there’s an easier way to find the answer while building the hoist. Since the CB of a single tank is always half of the length of the tank, you can apply that knowledge to work for multiple tanks. For example, take the total length of tanks (in feet) and divide it by two. This will tell you how many combined feet of tank will be on each side of the CB. The example below will walk you through the tank positioning procedure.
EXAMPLE: A customer has a 38’ Fountain Express Cruiser. Looking up the weight, we determine that it will require an 18,000 UL2. The boat’s beam measures 10’-6” or 126”. Immediately we can see that the CG will be located approximately 126” from the end of the hull pad. We also know that an 18,000 UL2 has three tanks which add up to a combined length of 76 feet (28’+28’+20’). This tells us that we will need 38 combined feet of tank in front of the boat’s CG and 38 combined feet of tank behind the boat’s CG. Laying out this scenario may take a few minutes of sketching on a notepad but will look something like this. Here I used 15’ for the outside tanks and 8’ for the inside tank (15’+15’+8’) to achieve the required 38’ of combined tank in front of the CG of the boat. As a check, you can also add up the length of tanks behind the CG. In this layout it will be 13’+13’+12’ = 38. (see picture #3)
In most cases, this should get you very close to a well balanced setup. After lifting the boat once, you should be able to look at the tanks and tell if they are level front-to-back. If not, you can reposition the boat fore or aft three to four inches to balance it out. Now install the guide ropes to ensure the customer locates the boat consistently and it will work perfect every time.
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