Trimaran break-up, anyone know the design? Options

[MartinRF]

If I remember correctly, back a decade or so ago when I subscribed to Multihulls, a Dragonfly had a serious problem when a waterstay (or at least some stay on an ama, and not the mast) let go. I don't remember if there was a precipitating accident or collision. In the amateur after-action analysis, it was reported that the stay didn't have any safety factor designed in, i.e. was designed to 100% of max load. Of course, I can't vouch for that. I think it was a swinging-ama boat, and somewhere in the NW.

That boat fell into the hands of someone who put it back together, maybe even Kurt Hughes, but don't trust my memory. Whoever it was thought the boat was very squirrelly and gave her a new rudder.

The boat you are refering to is Magic Hempel, the original dragonfly 25. A nice write up is here:
http://smalltrimarans.com/blog/?p=254

I would say Magic Hemple was a one-off version of the Dragonfly 25 for the Round Britain and Ireland Race. Of all the Dragonflies I have sailed I like the original 25 best. It has dinghy-like qualities lost in later designs and it does not feel like three hulls in close company like the swing-wings do. But it has its weak points like the water stay attachments to the cross beams. They drilled a big hole where the maximum stress in the aluminum will be!

/Martin

[peejay]

But it has its weak points like the water stay attachments to the cross beams. They drilled a big hole where the maximum stress in the aluminum will be!

/Martin

Since you're obviously an expert failure mode analyst, who, without any doubt whatsoever, are able to determine the initial failure mode just from watching a picture of a Dragonfly lying on it's side, maybe you can share with an ignorant like me exactly how many Dragonfly 25's that have failed due to this "weak point"?

And don't include Magic Hempel. As the article says Magic Hempel was a racer with smaller-than-spec waterstays to save weight.

[THOR]

its all photoshopped
every DF "fold-up" is photoshopped

better pj ?





thor

[peejay]

its all photoshopped
every DF "fold-up" is photoshopped

better pj ?





thor

Not really.
I just happen to be looking for the truth, rather than heresay being presented as truth.

[MartinRF]

But it has its weak points like the water stay attachments to the cross beams. They drilled a big hole where the maximum stress in the aluminum will be!

/Martin

Since you're obviously an expert failure mode analyst, who, without any doubt whatsoever, are able to determine the initial failure mode just from watching a picture of a Dragonfly lying on it's side, maybe you can share with an ignorant like me exactly how many Dragonfly 25's that have failed due to this "weak point"?

And don't include Magic Hempel. As the article says Magic Hempel was a racer with smaller-than-spec waterstays to save weight.

In Eric Quornings own words as printed in our club rag in early 1986: "Om morgenen kl. 04.00 kunne jag se, at den agterste tvaerbjaelke var böjet ca 10 of flaekket på tvaers. Bruddet var sket hvor bjaelken möder pontonen og kun eb fjerdedel af aluminiumsröret var intakt."

In brief English translation: At four am I saw the rear beam was bent ten degrees. The crack was located where the beam meets the side hull and the crack covered (is that how you put it in English?) three quarters of beam section.

So, stress crack in beam, not broken waterstay.

The boat was brand new but they had pushed it very, very hard. Most DF25 owners will sail many happy seasons before this happens but it will happen.

I have studied the structural engineering of multihulls some since early in its history I had cross beam problems on my own boat. In 1989 I decided band-aiding the cross beams was not good enough and designed a complete new set of cross beams together with a friend starting from a clean sheet of paper. Much, much later I created this rant on cat cross beams:
http://hem.bredband.net/b262106/Boat/beams.html

/Martin

[Ben UK]

But it has its weak points like the water stay attachments to the cross beams. They drilled a big hole where the maximum stress in the aluminum will be!

/Martin

Since you're obviously an expert failure mode analyst, who, without any doubt whatsoever, are able to determine the initial failure mode just from watching a picture of a Dragonfly lying on it's side, maybe you can share with an ignorant like me exactly how many Dragonfly 25's that have failed due to this "weak point"?

And don't include Magic Hempel. As the article says Magic Hempel was a racer with smaller-than-spec waterstays to save weight.

In Eric Quornings own words as printed in our club rag in early 1986: "Om morgenen kl. 04.00 kunne jag se, at den agterste tvaerbjaelke var böjet ca 10 of flaekket på tvaers. Bruddet var sket hvor bjaelken möder pontonen og kun eb fjerdedel af aluminiumsröret var intakt."

In brief English translation: At four am I saw the rear beam was bent ten degrees. The crack was located where the beam meets the side hull and the crack covered (is that how you put it in English?) three quarters of beam section.

So, stress crack in beam, not broken waterstay.

The boat was brand new but they had pushed it very, very hard. Most DF25 owners will sail many happy seasons before this happens but it will happen.

I have studied the structural engineering of multihulls some since early in its history I had cross beam problems on my own boat. In 1989 I decided band-aiding the cross beams was not good enough and designed a complete new set of cross beams together with a friend starting from a clean sheet of paper. Much, much later I created this rant on cat cross beams:
http://hem.bredband.net/b262106/Boat/beams.html

/Martin

Hi Martin,

I think you have just pissed on Peejay's fireworks!

You are clearly a very knowledgeable chap, Ok if I pass a few beam design issues past you for a future project?

Ben UK

[peejay]

I think you have just pissed on Peejay's fireworks!

Not at all, I just kind of let it rest, until you reminded me of the fun I had, so here we go:

In brief English translation: At four am I saw the rear beam was bent ten degrees. The crack was located where the beam meets the side hull and the crack covered (is that how you put it in English?) three quarters of beam section.

So, stress crack in beam, not broken waterstay.

Two different incidents. The incident that was dicussed in the thread was a broken waterstay and happened several years after the incident you describe. And again: both incidents relates to the racing prototype.

Most DF25 owners will sail many happy seasons before this happens but it will happen.

This is like saying that most sailboat owners will sail many happy seasons, but eventually their mast will fall down (unless they maintain it). Technically it's true, but in reality it's a worthless generalizing statement.

[THOR]

back on track gentleman
we are not trying to muddle things up .....or are we ?
the 25 is/was a racing proto and broke some years ago.....
lets move on ...
the bigger one was operator error .... supposingly the safety pin wasnt inserted as the waterstay broke and it folded up.
lets move on




the current one is the third ..
the waterstay is/was in place when the aka broke. ..... interestingly enough there is talk about that aka have been repaired/replaced earlier in the year ...
Question is , if the aka has been repaired/replaced by Dragonfly themselves or was it a shotty repair job from somebody who had no business working on anything like that.
and the next question would be why had the aka been replaced to start out with ...


Thor

[Triplet]

back on track gentleman
we are not trying to muddle things up .....or are we ?
the 25 is/was a racing proto and broke some years ago.....
lets move on ...
the bigger one was operator error .... supposingly the safety pin wasnt inserted as the waterstay broke and it folded up.
lets move on




the current one is the third ..
the waterstay is/was in place when the aka broke. ..... interestingly enough there is talk about that aka have been repaired/replaced earlier in the year ...
Question is , if the aka has been repaired/replaced by Dragonfly themselves or was it a shotty repair job from somebody who had no business working on anything like that.
and the next question would be why had the aka been replaced to start out with ...


Thor

Small correction - the large one you mention as the second, a Dragonfly 35, was indeed an operator error, but having nothing to do with the waterstay: The operator forgot to attach the diagonal wires that prevent the 35 from folding in case the line to fold out the ama slips in the spinlock clutch under extreme conditions (strong wind and waves). This system is a bit different from the one used on the 920 (tube and safety pin). As an additional safety feature, there is now a large red LED by the instruments to warn you if you forgot to attach them after unfolding.

There is also a discussion on the Dragonfly forum (www.dragonfly-forums.org) with respect to the cause of this last incident, but the investigation is apparently not done yet, so for now we will just need to wait and twiddle our thumbs (IMG:style_emoticons/default/wink.gif)

[THOR]

back on track gentleman
we are not trying to muddle things up .....or are we ?
the 25 is/was a racing proto and broke some years ago.....
lets move on ...
the bigger one was operator error .... supposingly the safety pin wasnt inserted as the waterstay broke and it folded up.
lets move on




the current one is the third ..
the waterstay is/was in place when the aka broke. ..... interestingly enough there is talk about that aka have been repaired/replaced earlier in the year ...
Question is , if the aka has been repaired/replaced by Dragonfly themselves or was it a shotty repair job from somebody who had no business working on anything like that.
and the next question would be why had the aka been replaced to start out with ...


Thor

Small correction - the large one you mention as the second, a Dragonfly 35, was indeed an operator error, but having nothing to do with the waterstay: The operator forgot to attach the diagonal wires that prevent the 35 from folding in case the line to fold out the ama slips in the spinlock clutch under extreme conditions (strong wind and waves). This system is a bit different from the one used on the 920 (tube and safety pin). As an additional safety feature, there is now a large red LED by the instruments to warn you if you forgot to attach them after unfolding.

There is also a discussion on the Dragonfly forum (www.dragonfly-forums.org) with respect to the cause of this last incident, but the investigation is apparently not done yet, so for now we will just need to wait and twiddle our thumbs (IMG:style_emoticons/default/wink.gif)

somebody should know why and who fixed the akas before they broke .......


leds ?
you are kidding right ?
are they self powered, solar cell backup , kinda like the tackticks ?

thor

[MartinRF]

In brief English translation: At four am I saw the rear beam was bent ten degrees. The crack was located where the beam meets the side hull and the crack covered (is that how you put it in English?) three quarters of beam section.

So, stress crack in beam, not broken waterstay.

Two different incidents. The incident that was dicussed in the thread was a broken waterstay and happened several years after the incident you describe. And again: both incidents relates to the racing prototype.

What about re-reading my post, the one you get so worked up about? And read the stuff I quoted including the stuff you quoted.

Done that?
OK, do it again.

Most DF25 owners will sail many happy seasons before this happens but it will happen.

This is like saying that most sailboat owners will sail many happy seasons, but eventually their mast will fall down (unless they maintain it). Technically it's true, but in reality it's a worthless generalizing statement.

No, they have weakened the structure where they have the biggest stress. No amount of maintenance will prevent stress cracks from forming here.

Neglected maintenance will ruin even a good design.

/Martin

[THOR]

I understand the owner got blamed
( again ....like in all DF break ups )


supposingly he rigged the boat wrongly in the spring .... that must have broke the akas .....

yeah right
thor

[Triplet]

leds ?
you are kidding right ?
are they self powered, solar cell backup , kinda like the tackticks ?

I am not kidding about the LED - here is a picture of the instruments: The LED is to the right of the depth instrument, and though it looks small on the picture, it is quite bright and impossible to miss if you look at your instruments. It is powered by the boat's batteries, and connected to the switch and fuse for the instrumentation so you will always turn it on when going sailing.

 Safety_LED.jpg ( 117.08K ) Number of downloads: 19

I understand the owner got blamed
( again ....like in all DF break ups )


supposingly he rigged the boat wrongly in the spring .... that must have broke the akas .....

yeah right
thor

Again, we are talking about three different boats:

First was a racing prototype - we all know what that means (see DOGzilla today - 26'000 data points per second didn't prevent a dismasting today).

Second boat was a DF 35 - here is an image of the capsize, with the boat on its side (hidden behind a wave - it actually floated a lot higher than it seem in this picture). You can clearly see that on the intact side, there is no safety cable attached, so it was an operator error: The cable would run from the bow to the outer end of the beam: For a comparison, you can see the cable in the second picture on the lower right.

Not attaching the safety wires is in my opinion about the same as not securing your keel on a monohull after lowering a retractable keel and the consequences are much worse doing this on a monohull.

 15639_thumb_edit1223222373.jpg ( 75.83K ) Number of downloads: 37
 IMG_1958__Medium_.JPG ( 70.8K ) Number of downloads: 29


Third boat: My understanding is that the investigation is still underway, and after it is finished and has been cleared with the owner, we can expect a response, and not before. Anything else would be unprofessional (though apparently not as much fun to some (IMG:style_emoticons/default/rolleyes.gif) ).

[Brian Boserup]

leds ?
you are kidding right ?
are they self powered, solar cell backup , kinda like the tackticks ?

I am not kidding about the LED - here is a picture of the instruments: The LED is to the right of the depth instrument, and though it looks small on the picture, it is quite bright and impossible to miss if you look at your instruments. It is powered by the boat's batteries, and connected to the switch and fuse for the instrumentation so you will always turn it on when going sailing.

 Safety_LED.jpg ( 117.08K ) Number of downloads: 19

I understand the owner got blamed
( again ....like in all DF break ups )


supposingly he rigged the boat wrongly in the spring .... that must have broke the akas .....

yeah right
thor

Again, we are talking about three different boats:

First was a racing prototype - we all know what that means (see DOGzilla today - 26'000 data points per second didn't prevent a dismasting today).

Second boat was a DF 35 - here is an image of the capsize, with the boat on its side (hidden behind a wave - it actually floated a lot higher than it seem in this picture). You can clearly see that on the intact side, there is no safety cable attached, so it was an operator error: The cable would run from the bow to the outer end of the beam: For a comparison, you can see the cable in the second picture on the lower right.

Not attaching the safety wires is in my opinion about the same as not securing your keel on a monohull after lowering a retractable keel and the consequences are much worse doing this on a monohull.

 15639_thumb_edit1223222373.jpg ( 75.83K ) Number of downloads: 37
 IMG_1958__Medium_.JPG ( 70.8K ) Number of downloads: 29


Third boat: My understanding is that the investigation is still underway, and after it is finished and has been cleared with the owner, we can expect a response, and not before. Anything else would be unprofessional (though apparently not as much fun to some (IMG:style_emoticons/default/rolleyes.gif) ).

You seem to be the one knowing the most about DF’s. Why don’t you present yourselves?

[Triplet]

You seem to be the one knowing the most about DF’s. Why don’t you present yourselves?

I certainly don't know most about Dragonflys (and I am in no way commercially connected to them if that is what you think). But I do know the DF 35 a bit firsthand because I bought one (and enjoy sailing it very much), and I had a close look at the capsize and the safety record of it and of all the designs I was considering.

I don't like getting involved in discussions of which design is safer than another one etc., and I think these speculations are bad for the multihull community as a whole. But when there is something I can contribute where there is clear evidence such as in the DF 35 capsize (pics or it didnt' happen (IMG:style_emoticons/default/wink.gif) ), I am happy to post it.