PDA

View Full Version : Crossbeam breaking risk ?



catamangos
7th February 2010, 12:24 PM
Hello everybody ,

first , excuse my poor english : it was not so easy to learn english in french school !

Second , my question is : is there a risk to bend the crossbeam when using a powerfull sail (such as a laminate Code 0 , going upwind ) , because of too much pressure right in the middle of the beam ?

This concerns a Leopard 40' , wich doesn't have a lengthway piece of beam (such as the 43' ) : so that the bowsprit stress might cause a flexing, and why not bend or break the crossbeam ?

I use to sail with a gennaker , that doesn't give too much stress in the sheets down wind or no closer than 90° : no problem till now ; but now I just received a laminated Code O, terrific and very efficient sail ... you can sail close to the wind, boat speed increases more and more, apparent wind increases too, you get the sheets tightened , it's nice to feel the cat alive ... but I don't want to down the mast if breaking the crossbeam : should I reinforce the crossbeam by adjusting an aluminium tube between the crossbeam and the boat himself (near the anchor chain locker ) ?

What's your opinion ?

Can Peter or Gino Morelli give and advice ? Thank you so much , Eric .

catamangos
14th February 2010, 04:23 AM
Hello friends !

is there somebody who could give a (good advice) ? Thanks ! Eric .

Autodafe
14th February 2010, 06:25 AM
Hi Eric,

People may need a little more clarification on your question. Are you asking because your code 0 increases sail area above the design sail plan, or because you have noticed a large amount of beam deflection, or some other reason?

I'm no expert, but in general the cross beam should have been engineered by the designer to withstand any compression the mast can generate.
Most are designed based on the righting moment of the vessel, that is you will capsize before the beam is damaged, but I do not know if this is true for a leopard 40.

In some cases, particularly with larger cats there may be an upper limit on the sail area you should have up for a given wind speed.

I would recommend asking M&M design directly via email if they consider the sail appropriate.

catamangos
14th February 2010, 08:02 AM
Hi Autodafe ,

thanks for your reply , and your help in the way to write my question : yes, I'm asking because the code 0 increases sail area above the design sail plan . I didn't notice a large deflection on the cross beam yet , but I'd like to be sure not to take stupid risk ...

You're right when you say that "in general the cross beam should have been engineered by the designer to withstand any compression the mast can generate " : so I hope that the Code 0 won't be dangerous for the beam , knowing that when the Code 0 is up , the genoa is of course furled.

I sent my post to Mr Gino Morrelli , who kindly answered that he will reply after the A - Cup . I will tell you then : maybe it could be interesting for anybody who wishes to boost his cat with such terrific sail !

If anybody has experience of a cross beam deflection, I would be very interested by . Best regards , Eric .

Tabs
14th February 2010, 06:02 PM
I think that Eric might be referring to the forward beam, so the problem isn't compression loads from the mast, but from the bowsprit that he's setting the code 0 on. He talks about fitting a fore and aft beam back to the area of the chain locker, which sounds like a good idea to stop the beam flexing back towards the centre of the boat.

catamangos
15th February 2010, 03:41 AM
it's exactly that ! I'm talking about the aft beam (sorry for "cross beam" , might not be the right word) .

So , I would like to know wether it's useful to reinforce the aft beam , by fitting another beam "fore and aft" , in order to avoid a dangerous flexing when the Code 0 is up ? ... or is the aft beam itself strong enough ?

Thank you for advice ... and your replies help me to improve my english !

Regards , Eric .

Tabs
15th February 2010, 07:10 PM
Now you have me really confused, Eric! An aft beam would be one at the BACK of the boat, I think you mean the forward beam, the one the forestay is attached to, don't you?
If English isn't your first language, you are doing very well, the nautical terminology is an added complication!

catamangos
16th February 2010, 03:52 AM
I'm too stupid : of course I was talking about the forward beam, where the forestay is attached to . It's nice for me to write on this thread, I learn nautical terminology , that no English teacher in my small island (I'm living in Reunion Island , Indian Ocean, just between Madagascar and Mauritius) could ever teach me !

So according to you , what about this forward cross beam when a terrible Code 0 is up ?

Now that the A-Cup is done, (and well done !!) , the sorcerer Gino Morrelli must be back in his agency , and he said he would reply to my answer after the Cup ; of course I will let you know . I suppose that some of you would be interested by powering its cat with such new fore sail , mmm ? Just to forget the Diesel betweew 3 - 10 knots ...

Friendly , Eric

Tabs
16th February 2010, 07:30 PM
Not stupid at all - I'm really glad we are not writing in French!!
Putting an "aluminium tube between the crossbeam and the boat himself " gets my vote, Eric. I think such a beam is a good idea even without the code 0.
(Maybe even put two tubes and lay a rigid walkway between them, much easier to go forward on than a tramp!)

paulrack
17th February 2010, 10:05 AM
The catamaran I am buying has a double beam with a walkway down the centre of the trampoline. This makes for a very sturdy setup. It has a clever hatch that opens which makes it very easy to deploy/retrieve the anchor and attach the bridle. On the Leopard 46 I charter it was sometimes a bit of a squeeze to fit ones arm in to attach the bridle and turn the anchor around if it came up back to front. I have attached a picture.

catamangos
23rd February 2010, 05:47 AM
Good morning everybody ,

I think it could be interesting for anyone who wants to ehance his sail plan , so here's the reply from mister Morrelli about my fear of bending the fore beam when using a code 0 : even with a fore and aft reinforcement, I'm affraid that the mast may be suffering some day ... so I won't play the fool, and will "only" use the gennaker, that is a wonderful sail too!

Have nice sailing, and thank you again to Gino for his advice , Eric .


Eric:

Thanks for the email.

Yes it is probably a problem to add a Code 0 to this type of boat without a fore and aft compression tube. The loads of these sails is really high and can cause problems for the mast as well. I would not suggest using this type of sail.

The mast and beams were not designed for these loads and will probably break something even if used in only light upwind sailing.

If you have any other questions, please feel free to ask.

Sincerely,

Gino

Autodafe
23rd February 2010, 08:08 AM
Thanks for posting that reply Eric.

catamangos
23rd February 2010, 08:53 AM
And the ultimate advice from Gino Morrelli is the following , when I asked if the gennaker could be as dangerous as the Code 0 :


question :

Good morning Gino ,

thank you for your reply , and so quickly, it's nice of you .

So ok, I won't play the fool with this Code 0 (too bad , it's such a nice sail !!) ; but please tell me that the use of a gennaker is possible ! I suppose that the load on the beam is different , cause sailing from 80 to 140 ° gives less stress in the sheets ?

My gennaker is 95 mē , polyester 2.2 Oz "stormlite" : less dangerous than the Code 0, with his 47 mē laminate ?

Sorry to take your time with such basic questions ... but it's nice to get an advice you can trust in !

Sincerely , Eric .


Reply :

Yes, the gennaker you describe should be fine. The apparent wind angle range limited to 80 degrees is what keeps the loads down and the load vectors safe for the beam and mast hardware.

Best of luck.

Gino
Sent via BlackBerry from T-Mobile

03geek
15th April 2010, 05:23 PM
Good morning everybody ,

I think it could be interesting for anyone who wants to ehance his sail plan , so here's the reply from mister Morrelli about my fear of bending the fore beam when using a code 0 : even with a fore and aft reinforcement, I'm affraid that the mast may be suffering some day ... so I won't play the fool, and will "only" use the gennaker, that is a wonderful sail too!

Have nice sailing, and thank you again to Gino for his advice , Eric .


Eric:

Thanks for the email.

Yes it is probably a problem to add a Code 0 to this type of boat without a fore and aft compression tube. The loads of these sails is really high and can cause problems for the mast as well. I would not suggest using this type of sail.

The mast and beams were not designed for these loads and will probably break something even if used in only light upwind sailing.

If you have any other questions, please feel free to ask.

Sincerely,

Gino


In light of this, is the launch from Cape Town of a 38 with a "Bow Sprit and Code 0", an indication that something has changed with the mast, possibly to also support the "flat-top main"?
http://www.facebook.com/LeopardCatamarans

catamangos
17th April 2010, 12:31 PM
In light of this, is the launch from Cape Town of a 38 with a "Bow Sprit and Code 0", an indication that something has changed with the mast, possibly to also support the "flat-top main"?
http://www.facebook.com/LeopardCatamarans


Hello friends ,

That 's interesting ; but I'm not sure that something changed with the mast . Could it be possible to see more details about what they call " Code 0 " ?
Some people call Code 0 when it's a "classic" gennaker .

Consider the sheets : the way they follow is important ; if the sheets go the same way than the spinnaker's sheets , the sail will rather work as a spi, so won't be too dangerous for the beam (not so much pressure) ; but you won't go very close to the wind.

If the sheets are basicly the same than the genoa , you can get them tightened going upwind, you can use this sail to go really upwind : it's terrific , it's the ideal way to use a Code 0 ... but can give so much pressure on the fore beam that it can bend ! That's why Gino Morrelli advised me not to use a Code 0 , unless maybe a "fore and aft beam " is installed ...

Now I've tried half way : I do sail with my laminate 47mē Code 0 , cause it's so nice to shut the engines as soon as 4 kn wind !
Of course I've installed a "fore and aft" carbone tube to reinforce the fore beam , and the sheets go the same way than the gennaker : external from the boat . So it's impossible to go upwind less than 60 ° (true wind) , then I think there's no risq to bend the beam .
And more , I only use the Code 0 when the wind is less than 10-12 kn (true, which gives easily 16 kn apparent , cause boat speed increases nicely) ; if more than 12 kn, genoa is fine ; and when going downwind, the big 95 mē gennaker is powerfull !

Have fun ! Eric .