If he is lifting with a single crane (such as a truck crane, public pier, or yacht club single point crane) then a square spreader set is necessary for slings. For a single crane and two lifting points, especially as long as the boat, the crane may require a spreader bar, because of the geometry of the angle of the cables from the stern and bow lifting points. With a spreader bar, the lift is directly straight up from the lifting point, to the bar, then from the balance point up to the block on the crane. If you have 10 feet of cable, it may exceed the vertical lift capacity of the crane, to clear the trailer etc; plus the loads are compressive on the hull both fore and aft, as well as athwartships in the bow. If he is using two cranes, as often used in seawalls in canals in Florida, then a spreader bar keeps the slings from compressing the hull (and cracking it) If you use two lifting points, with a single crane (as I have with dinghies or Boston Whalers, then you need a spreader bar to balance the boat and attatch the cables from the stern and bow lifting points.
If you assume that he has the canal side type of set of crane davits, not a lift. I have both at my house--and use the two crane lifts for a small boat. f In that case, I have a bridle aft, and a single point foreward. The crane davits are equally apart as the length of the boat, and each lifts up straight. Thus no spreader bar is necessary.
I believe that it would be possiable to take a single lifting eye on the foreward deck of the R 21 and attatch it at the lowest point to a plate glassed into the anchor locker/bottom of the hull, near the bow eye, where it is re-enforced. Boris picked up his expanded C dory by the bow eye--but the boat was light. If I was going to pickup the boat by the bow eye, I would certainlly want to re-enforce it--or have assurance that it was strong enough to allow direct lift dead lift weight. When you put two lines around the bow, into the eye, there are several problems--one is the mechanics of putting it thru the eye, unless you leave it there alll of the time. the second is not only gel coat scratching, but also compression load inward on the hull. The boat might take it--or it might not? That is why so many of the classic launches had the bow lifting eye on the top of the foredeck--it was also a cleat--it had threaded rod, and went right down to the keel and stem junction.
The stern eyes, if high enough and re-enforced may well be OK with out a spreader bar. Often there are the external eyes for towing and internal eyes for lifting. What is the objection to a short (equal to the beam where the boat is lifted) spreader bar? I carried a 14 foot spreader bar on my larger boat to launch the shoreboat--it was never a problem. Your bow spreader bar would be only a couple of feet long and would negate any compression on the hull structure at the bow.
Large yachts pick up much larger shore boats than the R 21 on a regular basis. They utalize proper lifting eyes. Even the RIB's come with these eyes.
I have an 18 foot Center console, which wet weight is 2600 lbs-very close to the R 21. I would not consider using Amsteel cable thru my bow eye around the deck and to a lifting point to hoist this boat out of the water--there would be too much compression on the bow railings/glass structure, even though this is the light end of the boat. Most yacht clubs would not allow you to use this type of set up either. If you had a lifting ring, yes. Our yacht club requires a spreader bar (running fore and aft) for the type of lift you are considering.
The factory will be more than happy to answer your questions-Andrew Custis
Customer Service Manager is your man to contact.
andrewcustis@rangertugs.com 253-839-5213
Let us know what you find and decide to do. Interesting problem.
