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-   -   Jury Rig Catamaran Propulsion (http://www.cruisersforum.com/forums/f48/jury-rig-catamaran-propulsion-106127.html)

MVLillyBelle 21-06-2013 19:56

Jury Rig Catamaran Propulsion
 
My son has recently acquired a 12-meter cruising cat in Norfolk, VA which he needs to move to the Vero Beach, FL area in the next month or so. She currently has two inoperative diesel saildrives (27hp Yanmars, I believe) which he would prefer to deal with after he gets to FL. Our plan is to lash an 11' RIB with a 20hp 4-stroke to the bases of the davits on the aft bridgedeck, triangulated with lines from the RIB's transom to the cat's transoms for lateral rigidity while still allowing some vertical flex to keep the outboard in the water in waves. This is intended to be used primarily for maneuvering out of the marina and negotiating bridges, etc. We hope to be able to sail most of the way in open water. Questions: (1) Does anyone here have any experience with such a rig? (2) Does anyone have a better suggestion? (other than the obvious "repair/replace the saildrives") (3) Given the vagaries of weather and the fact that it is hurricane season, should we go outside in hopes of getting favorable winds for sailing, with it's incumbent dangers, or should we take the longer and probably slower inside route with its potential bridge delays, etc. and very limited sailing opportunities? The mast is 55' (cutter-rigged) and the draft is 4'. All opinions are appreciated.

muskoka 21-06-2013 20:28

Re: jury rig catamaran propulsion
 
I presume you'll sail most of the way and only use the RIB to get into harbour? Anyway, with a 20hp RIB you can tow it in to harbour if there's no wind. If there's too much wind, drop anchor and wait till it abates.

Trying to lash it to the davits etc seems overly complicated. Just tow it.

FLLCatsailor 21-06-2013 20:49

Why not just get the engines fixed up north? How are you going to charge the batteries to power your steaming lights, GPS, etc etc...

ElGatoGordo 21-06-2013 20:49

Re: jury rig catamaran propulsion
 
Sounds viable to me. I'm sure the power is adequate, the use of it on a RIB may be a bit of a challenge. Can you control it from the cat, or are you planning to keep a rider in the RIB? I wouldn't do it if someone had to stay in the RIB except in an emergency. It wouldn't be fun at all. Which negated towing.

I'd be interested to know if there is any way you could rig a rigid mount at or near the center of the cat's aft beam, that's where I'd be looking. Too long of a trip IMO to be towing/pushing.

As to sailing outside...weather and your experience are the real limits...plus you're fighting the stream!

nimblemotors 21-06-2013 21:30

Re: jury rig catamaran propulsion
 
I towed my cat with my 18ft ski boat, and with any significant chop/waves the little boat was hopeless, even dangerous, the next attempt I installed an outboard.
I'd suggest you try to find a way to install an outboard for the trip.
Are you sure the sails/rigging/rudders are up for the trip by sail?
That is a pretty long way for an untested boat.
With the outboard you could keep it inland and just make it a slow trip.

ocean_groover 22-06-2013 06:35

Re: jury rig catamaran propulsion
 
Install a temporary outboards bracket on the cat for the 20hp, hang the dinghy from the davits.

valhalla360 22-06-2013 06:52

Re: jury rig catamaran propulsion
 
Far too long a trip for such a silly setup. Towing with a dingy is an emergency backup not a plan for long trip.

My first suggestion would be just to fix the engines before the trip.

If you are dead set on going, get one of the spring loaded motor mounts and mount it on one of the transoms. We keep the 5hp dingy motor on on mostly as a storage location but it will push the boat at 3-4kts. Being offset doesn't impact steering much as you are moving forward.

Boatguy30 22-06-2013 07:18

Re: jury rig catamaran propulsion
 
Seems like a bad time of year for such an affair. Better to fix the engines during hurricane season and head S in the fall with everyone else. Would be interested to see some pics of the boat.

MVLillyBelle 22-06-2013 07:36

Re: jury rig catamaran propulsion
 
First, thanks for the constructive criticism.... exactly what I am seeking, please keep it coming. This is a low-budget operation (as are most of our undertakings), but it is not our first rodeo (though it is our first venture into this particular arena). Between us, our saltwater experience is limited to beach cats and monohulls, both power and sail, up to 30' (I brought a 104' sternwheel towboat from Dubuque, IA to Mobile, AL a few years back, but that doesn't really count).

We plan on troubleshooting the diesels, but don't expect to find any quick fixes. My son has access to a shop and less expensive berthing in FL, where he is relocating.

The logic behind rigging up the RIB towboat-style is so that no one has to ride the RIB for extended periods. The outboard is remote controlled and the shift/throttle cables are long enough to reach up to the back of the cat's bridgedeck. The plan is to con from the RIB for close maneuvering, then lock the motor straight ahead and steer with the cat's rudders in open water.

We will evaluate the sail/rigging before committing to a course (inside/outside). Our thought was that the boat's relatively shallow draft (4'), would allow us to hug the Outer Banks fairly closely, thereby avoiding the worst of the Gulf Stream and hopefully taking advantage of morning and evening sea and land breezes. Bearing in mind the time of the year and vagaries of the weather, are we kidding ourselves with this option?

The boat already has a decent-sized PV panel and wind generator, condition to be determined. I have some more PV I can contribute to the cause, as a well as a Honda 2kw inverter/generator for backup.

What else?

MVLillyBelle 22-06-2013 07:46

Re: jury rig catamaran propulsion
 
Our first thought was to mount outboard(s) directly to the cat. My son has procured two spring-assisted outboard brackets for this option, but we are time-constrained for the design/fabrication of appropriate mounts for the mounts. The boat is early 90's vintage and has semi-sugar scoop transoms with small built-in steps. My son was thinking about hanging them off the bridgedeck, inside the hulls, but I am afraid they will not be low enough to stay deep enough in any kind of wave action. We will make this call when we get there. Anybody know any good(reasonable) marine fabricators in the Norfolk area?

DotDun 23-06-2013 06:15

Re: jury rig catamaran propulsion
 
My vision of your proposal may be wrong, but a problem I see is the seaway you could/will experience with a dinghy half tucked under the bridge deck. Any seaway will vary the bridgedeck clearance enough to sink the dinghy. You don't want to let the dinghy get caught with it's nose under the bridge deck.

Sand crab 23-06-2013 06:28

Re: jury rig catamaran propulsion
 
The outer banks are really windy and it blows mostly from the south. I'm talking sandblasting your skin type wind. This is not a place you want to be even with a 20 HP motor attached to the cat. You might not be able to make headway.
PS Really, really, really windy.

mark_morwood 23-06-2013 12:02

Re: jury rig catamaran propulsion
 
I can't imagine sailing offshore with a dinghy in the water lashed to the boat. It would be OK while motoring in flat water and to get in and out of harbor, but I think your setup would end up with real problems in any sort of seaway. I think you'll want to get the dinghy up in the davits or on deck once you leave the marina/anchorage.

Obviously the decision to go offshore at that time of year with no real ability to motor out of the way of an approaching hurricane depends on your sailing skill, experience and appetite for risk. (As an aside I have twice raced a Hobie 33 monohull single-handed from Newport to Bermuda with a 10hp outboard as my engine, so I am very familiar with the limitations of an outboard offshore).

You might try motoring the intra coastal waterway with that setup as long as you were very careful to make sure the dinghy never got anywhere under the bridge deck, because even a big wake will briefly reduce the clearance to zero under the bridge deck on any standard catamaran of that size. See all the threads here on pounding/slap for more info. It will however be a long trip, but I think that is always the case when taking a sailboat up or down the intracoastal.

Mark.

MVLillyBelle 23-06-2013 17:07

Re: jury rig catamaran propulsion
 
Very good points, all.....looks like the ditch is probably the way to go.

OK, next question is Dismal Swamp or Currituck Sound? Is there enough maneuvering room to do any sailing in the sound, or is the wind still generally too unfavorable there as well?

Thanks so much again for taking the time to share your observations and experience, guys.

Intentional Drifter 23-06-2013 18:15

Re: jury rig catamaran propulsion
 
Having done the E Coast a couple of times between those two points, both outside and on the ditch, I can't recommend the ICW with such limited maneuverability. You will be needing to either tie up at a marina or anchor every night, both of which will require better maneuverability than you will have. When backing down on an anchor, you want to be able to apply a generous amount of reverse to make sure you're stuck and I'm not at all sure that a 20hp outboard jury rigged will be able to do it. (The ICW has tidal effects in many areas, as well as some quite strong river currents.)

The ICW also can require you to keep station while waiting for bridges and traffic and that will be a challenge with such an arrangement. There are many jerks on the ditch who drive go-fast boats and seem to get an ego boost from making everyone else bounce around in their wakes. There are a fair number of shallow spots, too, where you want good maneuvering. (If you decide to do the ICW anyway, you will have an easier time doing Currituck than Dismal Swamp.)

From the perspective of "getting there", you would have a far easier and quicker time going outside -- assuming you have the navigation and sailing skills to simply depart Norfolk and make your next stop Vero Beach. Trying to go in and out many of the inlets in between will be quite challenging, and the sport fishing boats will show you no mercy.

Frankly, I recommend that you do the needed repairs in Norfolk. There's plenty of marine facilities and knowledge in the area, should you need them and they certainly won't be any more expensive than FL. That way, regardless of inside vs outside, or a combination of the two, you can then do the trip -- enjoyably and safely!

Whether it's a day sail, a weekender, or a long cruise, there's really no substitute for getting everything shipshape before you go. That's just good seamanship.

Dr. Murphy is lurking, everywhere, and when he takes over he is rarely satisfied with only one thing going wrong; hence, cascading failure effect. I'm concerned that what you are proposing, regardless of route, is a wide-open invitation to Dr. Murphy.

That's what I recommend.

Having said all that, if you decide to go, anyway, and you have the skills, then go outside. People have been sailing that route for centuries without auxiliary power and you can, too. You'll likely make many long tacks, but you might get lucky, too, and have a beam reach the whole way. (It's happened, or at least, I've heard of it happening!) That keeps your need for the jury rig down to two, and that minimizes the exposure time for things going wrong with it. (Obviously, make sure that all of your other equipment is functional and in good shape.)

ID

P.S. Sand Crab is on the money about the Outer Banks -- always, always give them plenty of room! Many of those who don't end up as shipwreck icons on the charts.


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