Lifting a catamaran from under the bridgedeck

[SMH976]

We are looking to haul out in Greece at the end of the year and we have had a quote from a yard that would use a tractor/trailer rig to lift our Prout 46 catamaran from under the bridge deck with no support under the skeg keels. I understand some catamaran companies (Lagoon) use this method without issue but I would welcome any advice about the strength of the under bridge deck for this lifting method. Prouts are very strong boats but I have some concerns that lifting the boat without supporting the hulls might risk damage.

[StuM]

That's very common.

Here's my FP and a Prout 45 both on lifts.

[ggray]

I prefer our cat being supported under the bridgedeck. AFAIK, all cats built in Capetown (probably rest of SAfrica too) are transported to the launch on a trailer that way.

Just try to block it close to the hulls.

[catsketcher]

If your cat can't handle being supported under the bridgedeck then you would not want to be offshore on it - it is less than one design load condition - where one hull is "tied" to a wharf and the tide goes out. This is called the cantilever design load.

The only things to check are that the trolley rails run fore and aft and that the bulkhead areas bear on these rails. On some cats the bridgedeck is curved. On mine there is a motor nacelle and 200mm deep and 600mm wide recesses on each side of the bridgedeck. A careful boatyard will check your cat, work out where the bulkheads are and ensure that your cat is well supported at the bulkheads. If the bridgedeck is flat this is easy, otherwise you might want to check the boatyard and how they do it.

One of the pictures above is at The Boatworks in Qld Australia. Those guys are super professional and packed my cat very carefully at the bulkheads. As the bridgedeck stringers on my cat are 60x60 Douglas Fir we ended up packing onto these. You may not be able to do this on some cats. Many Schionnings (these often have curved bridgedecks) have half PVC stringers so you can't use these to sit the boat upon.

You can be like a nervous dad at a delivery - it is your baby. Until you know the yard is good, check and double check. Make sure they know where your bulkheads are and don't let them pull you out till you are happy. There are too many stories of cats slipping off slipways, being jacked off trolleys and falling and the hull being put between bulkheads on a slipway, well I have heard of the first two ( The last one happened to me).

Do a sketch of the boat and show it to the yard manager. Ask how they will lift your boat on their equipment. Be proactive rather than ready to yell if things go wrong.

cheers

Phil

[StuM]

Originally Posted by catsketcher

One of the pictures above is at The Boatworks in Qld Australia.

Actually, they're both at The Boat Works. The "Gold Coast Marine Centre" sign behind the Prout 45 is what it was called before they changed the name to The Boat Works.

[thinwater]

PDQ recommends blocking their boats under the bridge deck, no problem. I've done this while working on the keels. Just make sure they are on the right spots.

[torrmundi]

I have personally seen a 62ft catamaran with a 1ft x 2ft hole punched in the underbridge by one the trailer lift bunkers. This was near Annapolis, MD. When I asked what happened, the worker repairing the hole claimed "the hydraulics slipped" whatever that means. I suspect that the boat shifted on the trailer, but that's only my guess. The fiberglass at that point was only 3/8" thick, chopped strands. It was not a cored hull at that point. So check with your hull's designer or builder before placing the lift bunkers and be damn sure the boat won't slip on the trailer.

[Chotu]

All you have to do is make sure they catch it at the main structural beams. Those are the bulkheads that go all the way across the boat from port to starboard. One is located all the way aft. The other is located typically underneath the mast. Those hold the whole boat together and will easily hold it from below.

[yeloya]

We have been doing this for more than 30 years. If it's done properly it's much better than lifting with traveller lift. Every cats underbridge is different and we use special wood supports designed specifically for each of them. The boat is coming in sitting on them, carefully tighteen to avoid the slip on the slip way. Using hydraullic arms seems to me more tricky but there are also many yards that are using them. If the yard you are talking to has done it several times and have an experience, there shouldn't be an issue.

Cheers

Yeloya