DRAGONFLY Trimarans User Forum

Another DF 28 capsize ?
Surfing on the web ,this afternoon…..
"Silverruddet regatta" in Denmark ?
Only 30 knds wind (organisator Yacht Club infos )
Are our nice DF boats becoming too "ultimate" for us, ordinary sailors ?
Be carefull
J.Lo

jean louis wrote:Another DF 28 capsize ?
Surfing on the web ,this afternoon…..
"Silverruddet regatta" in Denmark ?
Only 30 knds wind (organisator Yacht Club infos )
Are our nice DF boats becoming too "ultimate" for us, ordinary sailors ?
Be carefull
J.Lo

30K and full sail is just pilot error.

Can you drive a Ferrari around a 90-degree bend at 100kph in rain?

Indeed, must have been a strong wind, locked sheets and wrong turn (upwind) to flip it without gennaker. And don't mention the resque completely destroying the boat!

Do anyone know the statistic of capsized dragonflys.

As I remember it is something like:
- 7 or 8 DF 800
- 3 DF 28
- perhaps 1 DF 920 but I am not sure

A couple of boats has capsized because of back swinging wings due to structural defects or forgotten safety lines but these are not included in above

If you look at the video of the recovery of the skipper on You Tube , the weather conditions don't appear so bad.
J.Louis

Virtual copy/paste of my table from another DF 28 capsize thread... the last line shows the "righting moment index": 28S is two times less stable compared to 35T....

the 28 was built to get under 10 meters when folded to get away with registration and tax in some Euro countries.

Here is my back of the envelope stability calculation. Sail force is linearly proportional to sail area, so at any given wind speed there is linear righting moment dependency on mast height, sail area, beam, and weight. 28 sport is clearly pushing the envelope compared to 920 and 35:

_________28t___28s__920t__920x__35t___35x
Beam m__6.5___6.5__6.8____7.8___8.2___8.2
Main sq m_35___42___37____44____54____65
Mast m__13.7__15.2__13.1__14.6___16____17.5
Displ, t___1.9___1.9___1.9___1.9___3.9____3.9
(Main X mast)/(displ X beam):
_________39___52____38____43___27____36

And sail force is a function of apparent wind speed squared, so at 30kt there is 4x as much capsize moment as at 15kt.

@jacob madsen: every capsize should be counted.

Operator error; design failure; material failure - it doesn't matter. The only thing that matters is that there is a catastrophic event. Compare these stats to any other boat, multi or mono, and you will see a pattern. Trimarans and catamarans have a higher proportion of of these events. That's why my insurance is at least double of what it would cost to insure a similarly priced mono.

28 is an undersized overcanvassed boat as EarthBM pointed out. And that is before accounting for wave action which is not even considered in standard loads and stability calculations.

I actually maintain a much more precise table of stability loads for my boat that accounts for reefing and true weight loads (not published displacement numbers that have nothing to do with reality). On my 920 (cruising) I do not want to be out sailing in anything much above 25 kn unless there is no other choice.

I was caught in a storm in a water spout - a tornado on water - during a race in a relatively safe Long Island Sound a few years ago on a friend's 40 foot mono. It was the scariest experience in my life. I ran all calculations for my boat and discussed this with a number of experienced mono and multi sailors. My feeling is that this type of event may result in a loss of life on a DF920. There are quite a few design characteristics that make 28 a far more dangerous boat, e.g. lack of traveller.

IMHO, 800, 28 and 920 are for protected waters. 35 and 1200 are blue water. 1000 is probably an overbuilt safe sturdy ocean boat (despite TC's desire to lighten up).

gminkovsky wrote:snip
IMHO, 800, 28 and 920 are for protected waters. 35 and 1200 are blue water. 1000 is probably an overbuilt safe sturdy ocean boat (despite TC's desire to lighten up).

The 1000 folding mechanism is not as strong as the 35 or 1200. The later designs are more rigid.

Its sad but it happens. What is important is to always inspect the reason why the given ship went down. Same as a plane crash. It can be only a fault of the inexperienced crew or there can be some severe design flaw.

Bad things can happen with any boat. That said experience with multihulls points to a common trend, push a multi too far and it may push back. The same rule holds for monohulls but at a higher level of forgiveness. I think of the times I pushed my multi into the high teens as being similar to ridding my motorcycle at high speed on a wet road. Serious racing in windy conditions usually precludes the wisdom of caution, so some boats may capsize.