Scotty_Tradewind
Well-Known Member
Do the LM30's with a bilge keel roll a bit, say compared to a folk boat?
darn it.... couldn't correct typo in heading!!!!
darn it.... couldn't correct typo in heading!!!!
Lm 30 with bige keels - do they roll a bit?
- Thread starter Scotty_Tradewind
- Start date
Searush
Well-Known Member
That's 2 VERY different boats to compare, I'll be surprised if many people have recent experience of those two.
FWIW, a bilge keeler should not roll more than a deep keel, in fact it ought to be stiffer, especially if the keels are slightly splayed, as the righting moment will rise more quickly as the upper keel will be horizontal & applying maximum righting moment quicker than a fin keel will. But it must depend on the position, size of keel & type of ballast & concentration of ballast at the ends of the keels, etc etc.
I wouldn't worry about an LM30 rolling unless under engine only & with a beam sea. They have an excellent reputation as sea boats.
FWIW, a bilge keeler should not roll more than a deep keel, in fact it ought to be stiffer, especially if the keels are slightly splayed, as the righting moment will rise more quickly as the upper keel will be horizontal & applying maximum righting moment quicker than a fin keel will. But it must depend on the position, size of keel & type of ballast & concentration of ballast at the ends of the keels, etc etc.
I wouldn't worry about an LM30 rolling unless under engine only & with a beam sea. They have an excellent reputation as sea boats.
Scotty_Tradewind
Well-Known Member
thanks searush
my friends have a beautifully restored/rebuilt folkboat and like me their age has demanded more comfort and so they have bought an LM30. They have put the 'formula' into several boats specifications and wanted a wheelhouse and a tiller and a 'creek crawler' so it seems on paper to fit the bill for most requirements, including seakeeping and average speed.
I've been pulling their leg that they may roll all the way to France in future but at least they'll be cozy in the wheelhouse if conditions become inclement.
Just hoped there may be some forumites who have experienced an LM30 and poss' a long keeler too.
my friends have a beautifully restored/rebuilt folkboat and like me their age has demanded more comfort and so they have bought an LM30. They have put the 'formula' into several boats specifications and wanted a wheelhouse and a tiller and a 'creek crawler' so it seems on paper to fit the bill for most requirements, including seakeeping and average speed.
I've been pulling their leg that they may roll all the way to France in future but at least they'll be cozy in the wheelhouse if conditions become inclement.
Just hoped there may be some forumites who have experienced an LM30 and poss' a long keeler too.
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Spuddy
Well-Known Member
I came across a German couple in Norderney who had a LM30. I'd assumed motorsailor like the smaller model but this one sailed well. They'd cruised a lot: 3 times round assorted bits of British Isles, Norway, Lofoten islands; both were now in their 70s so not so far afield now. Seemed like an excellent choice of boat for decent sailing in changeable weather conditions. Dunno about the rolling altho my folkboat derivative rolls downwind.
grumpy_o_g
Well-Known Member
Actionoptics of this forum has one http://www.ybw.com/forums/showthread.php?t=246129. May be worth a PM?
Bajansailor
Well-Known Member
Our Challenger 35 (long keeler) rolls happily at anchor with just the slightest bit of wave provocation (perhaps because of a wineglass midship section), but not a lot when sailing downwind if she is really stomping along.
I would think that an LM 30 should roll less at anchor - many moons ago we had a Maurice Griffiths long keeler with bilge plates, and she was much more resistant to rolling.
Good background info re LM 30s here - http://www.yachtsnet.co.uk/archives/lm30/lm30.htm
I would think that an LM 30 should roll less at anchor - many moons ago we had a Maurice Griffiths long keeler with bilge plates, and she was much more resistant to rolling.
Good background info re LM 30s here - http://www.yachtsnet.co.uk/archives/lm30/lm30.htm
sighmoon
Well-Known Member
Only if the lower keel falls off, otherwise the CoG is between the keels, about where it would be on a fin keel of equivalent depth.
Scotty_Tradewind
Well-Known Member
actionoptics
Well-Known Member
LM 30 - a stable platform.
I've owned an LM 30 with bilge keels for 5 years. Been all the way from the Solent to the Isles of Scilly (and back with a force 8 chasing us until it caught us just as we rounded Ballard Down and sheltered in Studland.) over to France, Channel Islands and Brittany twice and round the corner through the Chanel de Four and the Raz de Sein to the Isles de Glenan so I think I have experienced a lot of weather one way or another. She has looked after us perfectly. We sailed round into the Bay of Biscay with a Victoria 30 and I can truthfully say that under way we were no more rolly than the fin keel Victoria and in the anchorages we felt more stable but we do have a wider beam. At no time have we felt that we were rolling uncomfortably, even the Ise of Scilly with the Atlantic rollers always present. A quartering following sea takes some concentration but as long as we kept the boat under the mast, she was OK.
We sailed across Lyme Bay with the auto pilot on but after at least 20 miles, realised that I had not engaged the pilot to the wheel so she had been sailing herself in a straight line for about 4 hours. It was a nice steady wind and quite smooth sea but still impressed us.
So, no she does not roll and is also quite stiff although of course sails best upright.
I've owned an LM 30 with bilge keels for 5 years. Been all the way from the Solent to the Isles of Scilly (and back with a force 8 chasing us until it caught us just as we rounded Ballard Down and sheltered in Studland.) over to France, Channel Islands and Brittany twice and round the corner through the Chanel de Four and the Raz de Sein to the Isles de Glenan so I think I have experienced a lot of weather one way or another. She has looked after us perfectly. We sailed round into the Bay of Biscay with a Victoria 30 and I can truthfully say that under way we were no more rolly than the fin keel Victoria and in the anchorages we felt more stable but we do have a wider beam. At no time have we felt that we were rolling uncomfortably, even the Ise of Scilly with the Atlantic rollers always present. A quartering following sea takes some concentration but as long as we kept the boat under the mast, she was OK.
We sailed across Lyme Bay with the auto pilot on but after at least 20 miles, realised that I had not engaged the pilot to the wheel so she had been sailing herself in a straight line for about 4 hours. It was a nice steady wind and quite smooth sea but still impressed us.
So, no she does not roll and is also quite stiff although of course sails best upright.
doug748
Well-Known Member
Yes, I remember reading a piece by Griffiths in YM and he was most insistent that his type were the best thing for comfortable downwind sailing - multihulls apart.
Moss
New Member
Re: LM 30 - a stable platform.
This is excellent feedback for someone, even years later, researching with a view to purchase. ActionOptics you are a true help. Thankyou.
Moss
This is excellent feedback for someone, even years later, researching with a view to purchase. ActionOptics you are a true help. Thankyou.
Moss
AngusMcDoon
Well-Known Member
Ignore the post by Searush, it's engineering nonsense. He's long gone anyway.
TSB240
Well-Known Member
I tend to agree with your technical critique but Santa is still around. I saw Sea Flush dried out at Abermenai recently and Steve still posts stuff on FB.
oldmanofthehills
Well-Known Member
Mataji
Well-Known Member
..and what do boy racers know about LMs?
oldmanofthehills
Well-Known Member
With exactly the same ballast ratio a deep keel and or fin might roll less as the restorative dynamic torque and the static torque might be greater as further from the C.O.G. Which is perhaps why the Scanyacht 290 based upon the LM30 went for a deeper keel. Having just bought a long keel LM27 I can already feel she rolls differently but I'm fine with that as the long keel will make her more stable course-wise.
LittleSister
Well-Known Member
The Scanyacht 290 was a UK built version of the LM27, not the LM30. They were available with a slightly deeper and heavier long keel than the LM27 as an option (along with a few other options). Link to more info: http://lmowners.proboards.com/thread/264/scanyacht-drawings-info-comparison-lm27
Scanyacht, previously the UK importer of LMs, bought the moulds and rights to the LM27 when LM ceased its production, LM having moved on to the later series LMs, the LM26, LM28, LM30 & LM32. Those later models refined the basic LM concept in more yacht (rather than fishing boat) shaped hulls, with saildrives and fin or (fewer) bilge keels, rather than the conventional drives and long keels of the LM24 and LM27.
LM (originally a furniture manufacturer) gave up boatbuilding (late 1980s?) and used their high quality GRP skills to become the world's biggest manufacturer of wind turbine blades.
oldmanofthehills
Well-Known Member
Youre quite correct the Scanyacht 290 is based on the LM27 - my finger trouble, but I didnt realise the LM30 was so different underwater as they are virtually identical above. However the point I was making is that different keel depths will affect roll both due to ballast moment and hydrodynamic resistance.
My Westerly Pentland has a 44% ballast as against the 37% on our LM27 and the Navigator immediately noticed a slightly different motion just by stepping aboard when purchasing. The LM30 has similar at 38% so on that basis might roll more than say the Pentland. The knockdown recovery angle on the LMs is quoted as 180 degrees against the Pentland which is listed somewhere hopefully as about 200 - though I hope never to test it on either of our craft. All are heavily ballasted sea boats.
grumpy_o_g
Well-Known Member
An important point to consider is that resistance to roll isn't necessarily a good characteristic. One of the key characteristics is actually the polar moment of inertia - all the weight in the middle will produce a snappy roll whilst weight at the ends of the moment arms (Mast, keel) will produce a much slower but probably more pronounced roll. A very stiff boat with a high aspect ratio deep keel may have an uncomfortably short and sharp feel to her movement, especially if her spars and rigging are high tech low weight composites. Obviously the shape of the hull plays a big part too. Keel area is also an important characteristic for slowing down roll as this simply dampens the movement.
Bilge keel versus fin keel is often irrelevant in a particular as there's probably other differences - maybe a shorter rig, maybe greater ballast on the bilge keels. And a bilge keel on an RM 1350 is very different to a bilge keel on a Maurice Griffith design. I think the LM 30 is pretty identical apart from the keels though. There's a reasonable draft on the bilge keels and the fin keel is fairly low aspect so I wouldn't expect a huge difference - in fact the bilge keel may well feel more comfortable.
Bilge keel versus fin keel is often irrelevant in a particular as there's probably other differences - maybe a shorter rig, maybe greater ballast on the bilge keels. And a bilge keel on an RM 1350 is very different to a bilge keel on a Maurice Griffith design. I think the LM 30 is pretty identical apart from the keels though. There's a reasonable draft on the bilge keels and the fin keel is fairly low aspect so I wouldn't expect a huge difference - in fact the bilge keel may well feel more comfortable.
DownWest
Well-Known Member
^^^^ G_o_g. A very extreme example was Hammond Innes motoring his new steel yacht from Holland to England, before it was rigged. He said the lack of inertia made the motion extremely short and unconfortable.
