Cross trimaran

I am looking at a Cross 38. The current owner has stated the minikeel is not foil shaped and could use a tab on the bottom of it. Has anyone done this? What about daggerboards in the amas? He claims 8 to 10 degrees better point on the wind.
He also has a set of plans for a rotating rig designed by Morrelli.Has anyone got a Cross swith a rotating rig? How do you like it?
redhorse

 

I removed a keel from a Cross 46 a couple years ago. I went with moderate size daggerboards in the amas instead of one board in the main hull. One daggerboard in the main hull would have been a lot easier on the structure of the boat... but in our case... we were doing crewed charters... it would have taken away too much interior living space. The difference in the boat's performance was stagering. The old keel (1 1/2 feet deep by 24 feet long) was really useless as a foil... good as a grounding skid... but no mater what shape this long keel could have been, its just not going to perform well. We use to "tack" through 110 degrees in 8 knots of wind. The boat was very unforgiving, in that if you pointed just a few extra degrees into the wind, the foil would "break lose" and you would lose half your speed (and start to have a lot more leeway). The boat also took forever to get up to speed after a tack or if you pinched too high. Once we added daggerboards the boat was a whole different experience. We could tack through 95 degrees in 8 knots wind and maintain our speed on tacks. The boat carved turns instead of doing a hockey stop and then taking 5 minutes to get speed back. The boat was also very forgiving to sail after this... sailed more like a finned monohull. Another benefit was turning radius in a marina. With daggerboards we could make 180 degree turns inside the bulkhead of our local marina... before we needed to do the back and fill... back and fill... about 5 applications of reverse to make this turn.

The next year we replaced the rig and went from a conservative 720 sq ft (for the 70's) ketch rig, to 1200 sq. ft sloop rig. Our performance once again made a significant jump. We were then able to do wind speed in 8 knots of wind on a close reach and tack through 90 degrees with decent speed ( but the boat was happier sailing through 95 degrees). We kept the original main mast step, added a large boom (24 feet) and large rouch mainsail. We also went to a strong 105 % working jib to bring the center of effort of the sail plan to where we wanted it. For light air, off the wind, we built in a bowsprit to take a "screacher" / "code 0" sail. The downside was that the boat needed to be reefed a lot earlier and the larger mainsail was more difficult to handle for a crew of two... but we thought it was worth it for our boat.

One thing to look into is the added stresses you are going to be putting on the boat and especially the beams. These kind of changes can't be taken lightly... do your homework. If done right this can really modernize your boat... but if done improperly, you can have a dog on your hands... or worse break your boat's beams.

I hope this helps... I could go on and on about modifying my Cross... let me know if you want more details.

 

Cross 38

I have a multitude of questions. Who did the design work for your daggerboards? Are they canted? What are the trunks and boards made of? How much clearancebtween the boards and trunk? What foil did you use? How did you reinforce your beams? Did you use carbon? What about rotating the amas outboard ten degrees.
I have access to carbon and foam, and am thinking of building composite flush deck hatches in all locations where there are penetrations. Replacing all flooring with composites.
Down the road replacing all standing rigging with synthetic.
What I am looking for is performance close to my CC35. Of course I realize this is a cruising boat, but performance is always good.

 

daggerboards

I was comfortable doing the design work for the modifications myself... but I design and build foils profesionally. The foils were NACA 0012 sections. The areas of the daggerboards were conservative to minimize loading of the beams. The trunks were tied into bulkheads and reinforced sections of the hull. The daggerboards, even when fully deployed, extended slightly above deck level. The trunks were very robust, while the daggerboards were designed to break if critically loaded. One did after we sold the boat to the new owner. They were surfing down waves at 18-20 knots off the coast of Oregon- 40+ knots of wind and 25 foot seas. The daggerboard was fully down (it really should have been pulled 50% of the way to allow the boat to slide a bit if overloaded). The board broke at the hull... trunk and hull where fine... to me this was a success... the boards did exactly what they were designed to do.

We did not reinforce the beams ourselves... the beams were reinforced by the previous owner who sailed the boat 50,000 open ocean miles. He reinforced the main beam by sistering CVG fir along the deck and bridgdeck areas of the main beam creating more of an I-beam shape in these areas. I never had a chance to ask him about this, so I do not know what the reasoning was for this, if it helped, or if this was just to ease his mind offshore. Also, if you look at a cross section of the Cross 46 you will see the cabin top (not main saloon) extends across the amas making a very strong effective beam structure in itself. This makes it very difficult to engineer the loads on the beams themselves. We did enough math and measurements to make us comfortable with our decision to put the daggerboards in. Afterward there was no perceptable change in stiffness to the boat. The boat has since sailed to New Zealand back on a new set of daggerboards.
I hope this helps

 

more details

I realized I didn't answer a couple of your questions.
The daggerboards were made of plywood forms, foam, cedar in high compresion areas, a lot of uni-glass and some biaxial. All epoxy, with epoxy and graphite powder as final surface layer. I would build them differently today... now that I have a CNC... but they performed well on a limited budget.

The daggerboards were canted slightly, but only so they did not block the companionway stairs that led into the amas... oh, that reminds me... I rebuilt the stairs as a structural base to reinforce the daggerboard trunks. The trunks were plywood, with a lot of heavy biaxial e-glass.

Canting the ama... this would be hard to do on a Cross in that you would have to dissassemble a large portion of the boat in order to rebuild it with canted amas. I don't think it would have helped our boat... especially how we sailed her... we sailed her pretty flat and reefed early... we had paying customers onboard when we sailed and thus had to keep them happy. But I also don't think it makes sense for most Cross designs. They were designed as offshore cruisers and safety at sea was one of the largest design considerations. The amas are rounded terminating in a sharp V on their bottom. For a comfortable offshore cruiser, I would not want the leeward ama to dig in in extreme conditions...like surfing on a broad reach... or laying a hull in a storm. I would rather design it so it allows the boat to slide a sideways when you need it too (and when the daggerboards are retracted). Canting it would encourage it to "dig" when heeled... might be great for an offshore racer... but for an offshore cruiser I would rather have it start to slide in these conditions. That gets back to the daggerboards... one reason we chose to convert the boat was for just this reason... in rough conditions you can raise the boards and allow the boat to give in a seaway.... and comfortably lay ahull... which is a storm tactic in these boats.

I noticed you are in Hawaii.? The Cross 46 (now 50 feet) is being sold now in Hawaiiby the people who bought her from us and sailed her to New Zealand and back... her new name is Moxie... when we had her her name was Pelican.

But with all that said... I really appreciate and respect Cross designed trimarans... the interior layouts, construction, structural strength, and overall asthetics where way ahead of their time. It is also a testiment to their designer that our Cross (built in 1976), has at least 70,000 miles under its keel, and is still sailing strong. Just wish he designed them all with sloop rigs and daggerboards.

 

I just purchased a 1981 South Bay Multihulls, Inc., built trimaran, built in San Diego, CA. I have been unable to find out much information about the boat, or even who designed it. I would love to know that information. Also, it has a keel drawing 4 feet, and a through-hull rudder, which probably draws 4 feet, according to the former owner. The boat is 36 feet long, and just over 21 feet wide. It is a cruising boat, although it does appear that the designer tried to keep the above water profile reasonably low. I bought the boat in Houston, and could not find a boat yard wide enough to haul it out to see the bottom (yes I bought it cheap enough, hopefully, to take that chance)

Two years ago, on this thread, "Otter 33" made some comments regarding removing the keel and adding daggerboards, which he had done on his Cross 46. I am most interested in shoal draft, and want to explore the idea of daggerboards in both Amas and a transom hung rudder that would kick up, or be perhaps like a daggerboard and lift straight up in a case.

If anyone knows any history of this boat design, designor or builder, and/or has any knowledge of seaworthiness, sailing characteristics, etc., I would be grateful for the imput , in addition to the daggerboard/rudder issues.

Thank you.
Jim