jfm
Well-known member
The SD vs planing hull debate is covered in other threads, so dont wish to repeat that. Gludy kindly sent me those pix of a Trader 575 and I've put them below, with some similar shots of Sq58 - same length, same hp, same weight if you carry same fuel /water. In this thread I'm asking the question: if you think a SD hull is more seaworthy than planing, then exactly what is it about the SD hull that makes it more seaworthy? Not picking any fight here, just curious.
FWIW my view is that there is virtually no difference in hulls or in seaworthiness (apart from the stabilisers). Look a the pix. Both have hard chines, deepish V at the bow, flatter aft, and a hard "chine" where the hull bottom meets the vertical transom. The 575 has a very flared bow and looks like it has more weight in the bow, which might make it lift less and crash through a head sea a bit more.
The 575 has a keel (looks like only one - not sure how you dry out. Legs?) and longer shafts and I suspect bigger rudders. And engines further forward. Plus stabilisers. So it has more nose weight and loads more appendage drag, which explains why the Sq58 does 33 kts compared with the Trader's 25kts, for the same bhp and same hull length and weight. So my theory is that there isn't much difference in seakeeping, and a SD is just a planing hull that's going a bit slower. Though the further forward engines might make a bit of difference. But in general, at 22 knots in each boat you are doing pretty much the same thing, whether that's planing or semiplaning.
I therefore think the thing that gives you the better ride in the 575 in bad weather is the stabilisers, not the so-called SD hull. That set up may well be worth having if your boating area demands it (as Gludy's does). But I think there is a big fuel cost to lugging all those appendages around, so with the same engines and the same passage times the Sq 58 is going to give better mpg over the whole season than the 575, isn't it? If not, why not?
FWIW my view is that there is virtually no difference in hulls or in seaworthiness (apart from the stabilisers). Look a the pix. Both have hard chines, deepish V at the bow, flatter aft, and a hard "chine" where the hull bottom meets the vertical transom. The 575 has a very flared bow and looks like it has more weight in the bow, which might make it lift less and crash through a head sea a bit more.
The 575 has a keel (looks like only one - not sure how you dry out. Legs?) and longer shafts and I suspect bigger rudders. And engines further forward. Plus stabilisers. So it has more nose weight and loads more appendage drag, which explains why the Sq58 does 33 kts compared with the Trader's 25kts, for the same bhp and same hull length and weight. So my theory is that there isn't much difference in seakeeping, and a SD is just a planing hull that's going a bit slower. Though the further forward engines might make a bit of difference. But in general, at 22 knots in each boat you are doing pretty much the same thing, whether that's planing or semiplaning.
I therefore think the thing that gives you the better ride in the 575 in bad weather is the stabilisers, not the so-called SD hull. That set up may well be worth having if your boating area demands it (as Gludy's does). But I think there is a big fuel cost to lugging all those appendages around, so with the same engines and the same passage times the Sq 58 is going to give better mpg over the whole season than the 575, isn't it? If not, why not?







