When is heavy too heavy ? (Strange boat problems)

[Icarus]

Originally Posted by TiPegleg

Hey all, so I’ve been visiting boats with the intention to buy in the next few months. My focus has been French aluminum and steel center boarders and considering their rarity, I’ve been getting around! So here’s my issue:

I found a really great 42ft caroff/strong al built boat that’s amazingly built in galvanized steel. I did a survey, Everything looks great, very excited etc. but then the owner tells me the tonnage - 18t on a LOA 42ft and a LWL of ~36!

Now I’ve sailed some very heavy metal boats before, a 34t 52ft Bruce roberts in particular, so I know that weight isn’t everything. So I asked for the sail plan and that’s where I needed to ask the forum (first time posting!). The sail area (main+100% jib) = 635sqft... main and 130% genny = 930 sqft... this basically gives me a SA/D of ~10-14... pretty sure this is motor sailer territory, yeah?

Now keep in mind, the owner has the boat fully up to cruising trim, including 200gal of diesel and 100gal of water, 6 big ol AGMs, etc. The dink is in davits and the food stores are full. If I ignore the owner’s tonnage and go by the design spec, we’re talking about 14t, which changes the math considerably and put the whole thing more in line with a “heavy cruiser”. That said, I’d still expect a sail plan over 1000sqft for this boat.

Finally, one other oddity... this boat has a 110hp 6 cylinder diesel swinging a 23” prop on an oil sealed shaft... just absolutely massive...

If this boat was set up from the ground up as a motor sailer this is the first ever metal center boarder I’ve seen this way. The boat also has all the gear for a spinnaker and actually has a big asym... why would you spec a spinnaker for a motor sailer?? All of the winches on board are sized appropriately for a larger rig than the spec sheets and plans given to me by the owner show. Oh, and the mast- beefy doesn’t convey. Double spreaders, split back stay, double head stay, baby stays, and removable inner forestay... for 600-950sqft?? Very confusing.

So my question(s):
1) when using the usual calculators and metrics should I use 18t (cruising tonnage?) or 14t (design tonnage)?
2) how heavy is too heavy? I’m not looking for a motor sailer. Is this a motorsailer? Do motorsailers ever have spinnaker poles etc?
3) when using a SA/D calculator I always used 100% foretriangle + main but I read in Eric Spondberg’s excellent pdf about design ratios that you should use the “upwind area” in which case I’d be using the 130% genny area?

I’d really like to make an offer on this boat, but was stopped dead by all of this. I can’t do a motorsailer with my plans so if that’s what I’m dealing with... anyway, thanks for any help/opinions/advice!

If the design was for ALU and the boat was built in Steel it will be about 35% heavier, depending on the scantling dimensions.
Yes, it's a motor sailer.

[ewsponberg]

Originally Posted by Jim Cate

My apologies, Eric. I have a faulty memory at times, and screwed up royally this time.

Sorry...

Jim

Apology accepted, thank you.

Eric

[Shaneesprit]

You need to sail it first, and see how it is, and if your concerned then you probably already know the answer, your just looking for confirmation.
Don’t buy unless you have sailed it enough to know it’s the right boat for you,