DJE
Well-known member
Does it include any requirements for structural strength? Do you think that such requirements would be beneficial?
IMOCA 60 Design Rule
- Thread starter DJE
- Start date
dunedin
Well-known member
Well this year may prove to be a bad one for the Open 60s, partly as they have “pushed the envelope” hugely with the foilers and partly as Covid-19 meant that the boats had much less racing miles to test things out before the left.
But let’s not forget that the survival rate for the super light and super fast Open 60s in the last race was much better than for the slow / heavy / long keel boats in the Golden Globe Race, which had a huge attrition rate.
But let’s not forget that the survival rate for the super light and super fast Open 60s in the last race was much better than for the slow / heavy / long keel boats in the Golden Globe Race, which had a huge attrition rate.
flaming
Well-known member
FYI, the rate of retirement is currently exactly the same as 2016. 5 out on day 28. It is better than 2012, with no foilers, when 7 were out by this point, and 2008 when 6 were out by this point.
But as you can see it is well within the margin of error for the number of boats out by this point. And to be honest, other than PRB and Corum, it's pretty tough to point any fingers at the boats or the sailors when the reason for retiring is hitting an unseen something. Take out the UFOs and there would only have been 2 retirements to this point. Though admittedly PRB's was somewhat spectacular...
DJE
Well-known member
But there doesn't seem to be any damage to the one-design keels just the foils, rudders, and hull structures where there is weight-saving pressure on the designers.
Ingwe
Active member
I think the basic issue is that if you hit something at 20+knots something is going to break. I would actually expect them to have engineered the foils / rudders to break first in that type of collision as which would you rather a broken foil or a hole in your boat?
flaming
Well-known member
Well, kinda.
PRB seems to have been a rather spectacular structural failure. But it's worth remembering that the boat was exceptionally light when first built, and was retrofitted with foils. There's just no way that any structural rule that you could write now could catch this sort of situation in the future when the boat is taken way outside of its original design brief.
Leave the rudders for a moment, expecting a rudder to survive a strike at 20 knots is just not realistic. I suspect that future designs will look at easier replacing of damaged blades. Ironically given your OP, this probably means they need to be significantly lighter than they are now for a solo skipper to be able to change one in mid ocean.
And then the rule does have structural elements. For example after the well publicised snapping in half of Cheminees Poujoulat, alloy honeycomb has been banned as a core material.
cause of Stamms yacht disaster
But... Part of the point of the IMOCA class is to push the boundaries. Every 4 years we get excited about what the latest boats look like, whether they have significant performance advantages etc. IMOCA reacted in the past to reduce the negative press of a raft of dismastings with an OD mast. And the number of dismasting since is very low. Ditto keels falling off and the OD keel fin and mechanism. More broadly though it is a development class, and pushing the boundaries of the engineering is really the point. And not finishing due to the boat suffering structural damage is supposed to be enough penalty...
Really, would the race be anything like as interesting as an OD? We have the Figaro for that, and as great as it is, it's not the Vendee.
TLouth7
Active member
I would say that it is testament to the successful design of these boats that so many manage to get to safety under their own steam following damage. Additionally the small number of actual rapid sinkings (just PRB?) this century is a seriously impressive record.
It's hard to argue that the nature or scantlings of the designs are putting lives at risk.
It's hard to argue that the nature or scantlings of the designs are putting lives at risk.
dunedin
Well-known member
The damage due to hitting debris is certainly due in part due to the sheer speed of these boats, but also the width of the path that they carve through the sea - from windward part retracted foil, hull, rudders to leeward foil.
Many / most of us have sailed through patches of thick weed or debris - but on a conventional leadmine cruising yacht the bow pushes most down the sides, and as long as it doesn’t go under the bow, the keel and the rudder generally escape being caught as a result.
Very different if we had foils 4 metres or so to the side, and the bow (and often the majority of the hull) flying high above the water at 20 knots.
Even at 6-8 knots we twice broke the Watt&Sea generator off the stern in Saragossa weed, and it was just 50cm off the centreline on the stern. Eventually had to stow it and sail without.
And as for hitting a 50 metre section of wind farm debris which wrapped round the keel this summer, I was very glad it was flat calm and only doing 5 knots.
Many / most of us have sailed through patches of thick weed or debris - but on a conventional leadmine cruising yacht the bow pushes most down the sides, and as long as it doesn’t go under the bow, the keel and the rudder generally escape being caught as a result.
Very different if we had foils 4 metres or so to the side, and the bow (and often the majority of the hull) flying high above the water at 20 knots.
Even at 6-8 knots we twice broke the Watt&Sea generator off the stern in Saragossa weed, and it was just 50cm off the centreline on the stern. Eventually had to stow it and sail without.
And as for hitting a 50 metre section of wind farm debris which wrapped round the keel this summer, I was very glad it was flat calm and only doing 5 knots.
Buck Turgidson
Well-known member
Difficult to police "structural strength" without load testing to destruction as we do in aviation. That's expensive!
Daydream believer
Well-known member
I broke the oar off my Aeries in 2019 when it hit an underwater object whilst I was surfing a wave at 8kts. The bang frightened the life out of me & there was also some glancing damage to the rudder. If the oar had not sheared, then I would probably had some damage to the transom, because the rest of the Aeries( lift up pattern) is substantially built.
Now take that to am Imoca doing 20kts with a 4 m leverage & I would expect that the designers must allow for the foil to shear off.
I would expect the next step would be similar to rudders. ie find a way to replace a foil. Do Imoca foils retract, I assume they must?, So why not eject the broken section & somehow lower the replacement part in from a halyard off the mast. It would be fitted into a socket, The socket would be inboard with a shear point just outboard of the hull. The socket would have the adjustment mechanism so the foil could still be effective. How heavy would one be? Could deck slots be made so the spares sat on their sides on deck ready with minimal lugging around for the helmsman. Perhaps acting as spray boards whilst sitting on the deck to push water rushing down the deck over the side.
Now take that to am Imoca doing 20kts with a 4 m leverage & I would expect that the designers must allow for the foil to shear off.
I would expect the next step would be similar to rudders. ie find a way to replace a foil. Do Imoca foils retract, I assume they must?, So why not eject the broken section & somehow lower the replacement part in from a halyard off the mast. It would be fitted into a socket, The socket would be inboard with a shear point just outboard of the hull. The socket would have the adjustment mechanism so the foil could still be effective. How heavy would one be? Could deck slots be made so the spares sat on their sides on deck ready with minimal lugging around for the helmsman. Perhaps acting as spray boards whilst sitting on the deck to push water rushing down the deck over the side.
Laser310
Well-known member
a few of the 60's racing now have been listed for sale, some with foils - in case anyone is thinking of giving it a go next time...
Buck Turgidson
Well-known member
I've got my eye on BOSS
Daydream believer
Well-known member
Will not fit in my berth at Bradwell
Daydream believer
Well-known member
Yes but just think where it is now & how much Halcyon yachts would charge you to deliver it back to UK. Possibly a deal breaker?I've got my eye on BOSS
Bet they would stick a video of the delivery all over the place though- Not advertising, of course , only out of interest mind.
Buck Turgidson
Well-known member
Alex is doing it for free ;-)
Daydream believer
Well-known member
So I see. I understand he is coming straight back to UK. Surprised he did not drop in to the finish line for a bit of publicity though. That is what pays for the boat after all.
Buck Turgidson
Well-known member
Some kind of bug going around I'm told. Best to keep clear.
Daydream believer
Well-known member
Diesel bug?? dodgy stuff, needs to be treated ASAP Isolate it
Actually I see that France has today closed its boarders to all wanting to enter from outside the EU. Bit of a bummer having sailed round the world & half a mile from the finish being told "Sorry you cannot come any further". "Clear off back to where you came from"-- " But i came from !!!" " Oh sod it"
