Carbon fibre gangway (passarella)

Hi, I would like to DIY a foam-cored carbon gangway. Nothing fancy, just a straight 210 × 40 cm panel, made by hand lamination and vacuum bagging.
Could you please advise how many layers of 200 g woven or UD carbon fibre I should use on a 2 cm foam core to achieve a minimum SWL of 150 kg?
Would a 2 cm core be stiff enough, or should I use a 4 cm core to avoid excessive bending under load?
Thanks Tamas

 

Hi Amadeus, are you sure that a minimum SWL of 150 kg is adequate? A well fed westerner carrying equipment on board over the gangway may exceed that weight, and if a failure or an accident occurred you may be sued. Allow for shock loads, eg. wake waves increasing stress, imbalance, and unforseen circumstances. Err on the side of caution for the sake of everyone, you included. Foam core may not be up to it.

 

Good point. what kind of simple, practically achievable structure and sizing would you recommend?

 

One of the NA's or engineers frequenting here would be a better source of technical load bearing info than me, but I would start with maybe 25mm -1 inch structural ply wood with several longitudinal runners of similar thickness underneath to stiffen it, and several layers of fibreglass, more on the bottom than top. 210 cm = longer than 2 metres, which could get quite bendy and bouncy in the middle. Maybe an aluminium build would be lighter and stronger, eg. one side of a tall aluminium ladder with 8 - 10mm plywood screwed to one side, becoming the top, and several runners underneath to limit the bending. Its just a guess, since i'm not qualified in engineering, only handymanology.

 

I built one out of a section of aluminum extension ladder. I glued and screwed 9mm ply to the top. Finished with non-skid. Its fairly light, very rigid and has held up well. Might be the easiest way. Be hard to get one stiff enough with thin foam without adding longitudinal members.

 

Last time I built one it is covered by Rules. Statutory or Solas. Can't remember, please check. Covers length, load, height of guide rails.

 

@Amadeus what type of boat will this gangway be used on?
If it is one of those very flashy and fancy fast day boats, then I can see why you would want to have a state of the art carbon gangway as it would compliment the boat well.
But if it is for your liveaboard yacht, and you are just looking for something practical and sturdy and relatively cheap, then something like what @BGW mentioned above is probably the easiest way to go.

 

Can you imagine flat foam with foam longitudal members with smooth transitions for easy laminating .
@ Amadeus here is thread "trimaran with tornado/nacra hulls " some glass scaffoldindg platforms are available .

 

On my previous boat I used a gangway made from an aluminium ladder. It worked, but it was not very nice looking. I could easily build a better-looking one from wood, but that would be heavy.

Now I have some carbon cloth and epoxy left over from another project, and that gave me the idea. I would especially like a design that could also work as a lee board.
It will be painted, nothing fancy, not a showcase piece.

But everything I have read so far suggests that it would need to be about 4 cm thick, which seems a bit too thick for that use. That is why I am asking for advice from the experts here.

Montero, Thanks for the trimaran thread. I will check

 

2 or 4 cm thick is only tip of iceberg ... lot of variables .

 

This business has a PDF covering their products for design ideas, you will have to come up with a laminate schedule yourself.
https://www.exitcarbon.com/manual/gangways_exit_en.pdf

 

Thank you, very useful reading.