martin 'hoff

Carbon Kevlar prepreg trampoline?

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Just spotted a carbon-kevlar prepreg trampoline on a fancy new A-Cat here in Miami. Looks great. 

Does anyone know more about this? Google doesn't have any hits. On one hand, I am generally curious about it. On the other, I've been having some trampoline issues on my cat, and I'd be open to retrofitting something like this if it's practical...

 

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Pretty much standard equipment for a 2017/2018 A-class with a decksweeper main.  Saw several classic decksweeper conversions last weekend at the Nood’s.

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Stop by during Miami Race week and you can get some info on retrofitting a platform from soft tramp to carbon/Kevlar deck.

 

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Oh my aching knees! Still,it is the latest and the coolest. Go fast, look cool and take Advil.

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19 minutes ago, lamorak said:

Pretty much standard equipment for a 2017/2018 A-class with a decksweeper main.  Saw several classic decksweeper conversions last weekend at the Nood’s.

Carbon /kevlar tramps are only standard equipment on one make of A, namely DNA, while the other, Exploder, that built 9 out of the top 10 at the last worlds, has it as an option that has not proven to be that popular with their top sailors. The 4 new boats that arrived in Australia before Christmas didn't have those tramps. I asked why and there were a number of reasons. Although it might be developed in the future, you cannot go for under deck traveller and sheeting with the "solid" glued on tramp because it currently relies on 4 sides being glued to be strong enough. It is said to be far less comfortable than a standard tramp and it allows for far less flexibility on how the boat is fitted out. Stevie Brewin and his training team seem to be trying new control layouts regularly to improve the boat and a solid sealed tramp means that is next to impossible. There is little to no aerodynamic benefit compared with a  well made double side tramp being used at the moment while you lose the aero advantage of getting the traveller and mainsheet under the deck plus only a slight weight saving.

I am sure given time that somebody will develop the ability to do a cut out in a solid tramp so you can put the traveller and mainsheet underneath, but you still have the issue of not being able to play with the layout very easily.

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+ A Class Sailor. Add to those limitations long term durability. The carbon/kevlar tramps that have been used for 2 years don't look all that great to me, and a bonded tramp is more difficult to replace.

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No one will disagree with the lack of flexibility.  We will see how the new ones wear here.  So far, so good.

We have quite a few new boats with composite tramps but we also have people retrofitting them here.  Bruce Mahoney would be good to talk to about this.  He has installed them on several Nikitas and other classic boats.  They look sharp and are much tighter than a cloth tramp.  

 

 

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Are these tramps shipping with clear coat from the factory? If not, 2 seasons of sailing and there will be UV degradation of the resin and possibly the fibers. Kevlar is not great in this regard, and all the tramps I've seen have some kevlar in them for impact resistance. The concept of a forward solid tramp and aft soft tramp makes some sense to me if its the end plate effect that is of the most concern.

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It looks cool.  But, my 10 year old mesh trampoline (AClass) is still going strong.  When I replace, it will be mesh again with an added layer underneath to seal the DS mainsail.

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11 hours ago, macca said:

its not kevlar, they are made with dyneema.

 

 

The ones on the DNA perhaps. Their are custom builds here in the U.S that use the readily available 5.7 oz carbon/kevlar blended fabrics.

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8 hours ago, samc99us said:

The ones on the DNA perhaps. Their are custom builds here in the U.S that use the readily available 5.7 oz carbon/kevlar blended fabrics.

That would be a short sighted decision OMHO

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10 hours ago, Bob Curry said:

It looks cool.  But, my 10 year old mesh trampoline (AClass) is still going strong.  When I replace, it will be mesh again with an added layer underneath to seal the DS mainsail.

The underneath layer of the double skin tramp isn’t to seal the DS. It’s to provide streamlining of the boat through the air and water. The top skin provides the seal for the air flow at the bottom of the sail. Research by ETNZ has also shown that most of the turbulence occurs 20cm either side of the sail on the deck. So I have doubts that a full width sealed tramp is necessary. Maybe a 50cm strip of Dacron sewn to the mesh tramp will do the job. I’m also not convinced the underskin is necessary. The second and third places in the last Worlds on foilers had no underskin and one of the top ten has just gone back to a single skin tramp and is still recording 26.7 knots best speed on the latest classic boat. I find the sealed tramps a PITA. The nonstretch fabric has to be tightened all the time and the tape sealing the edges top and bottom needs replacing regularly especially after towing on the highway. Not being able to easily get to all the controls underneath is also problematic. 

We ordered the four AD3 Classics here with solid tramps. Time ran out to get that done in the factory and they came with Dacron double skin tramps from Bryt Sails which are similar to the Brewin tramps. The solid tramps have a few problems as mentioned by ACS and all four of us are changing straight away to simple mesh tramps with a strip of Dacron to seal the DS. 

BTW the new AD3 Classics with DS are FAST. 

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3 hours ago, WetnWild said:

Research by ETNZ has also shown that most of the turbulence occurs 20cm either side of the sail on the deck. So I have doubts that a full width sealed tramp is necessary. Maybe a 50cm strip of Dacron sewn to the mesh tramp will do the job.

I agree you probably only need a strip down the middle, bit I am not sure that is wide enough. You need to allow for off wind with rotation off. I suspect you need a strip closer to 75cm wide.

3 hours ago, WetnWild said:

I find the sealed tramps a PITA. The nonstretch fabric has to be tightened all the time and the tape sealing the edges top and bottom needs replacing regularly especially after towing on the highway. Not being able to easily get to all the controls underneath is also problematic. 

While I have tape sealing the bottom edge of my tramp, I don't have any on top, except at the very front. The new tramps from Stevie don't need any tape on either the top or bottom with the edges sealing through their design. All he has is the lacing for the rear edge which takes a short time to untie and retie if needed.

I am not sure why your tramp needs to be tightened all the time. I cannot remember the last time I needed to do mine. Do you have a single piece of rope down each side or individual ties on each button? Individual ties seem to be the answer with the rope going round 3 times. It's more of a pain if you need to remove the tramp completely or when fitting a new one, but it is worth it.

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8 hours ago, A Class Sailor said:

I agree you probably only need a strip down the middle, bit I am not sure that is wide enough. You need to allow for off wind with rotation off. I suspect you need a strip closer to 75cm wide.

While I have tape sealing the bottom edge of my tramp, I don't have any on top, except at the very front. The new tramps from Stevie don't need any tape on either the top or bottom with the edges sealing through their design. All he has is the lacing for the rear edge which takes a short time to untie and retie if needed.

I am not sure why your tramp needs to be tightened all the time. I cannot remember the last time I needed to do mine. Do you have a single piece of rope down each side or individual ties on each button? Individual ties seem to be the answer with the rope going round 3 times. It's more of a pain if you need to remove the tramp completely or when fitting a new one, but it is worth it.

Yes I think you’re right about the width. I did a good measure up this afternoon to take account of travelling out as far as I normally would. 75cm is about right to seal to get 20cm either side of the sail at all times. So it looks like we don’t need full width of the tramp sealed and certainly not the side overlapping the ties to the gunwhale. That will certainly simplify things. 

As mentioned above I’m also not convinced we need the underskin. People are going fast without it as seen in the last Worlds. Do you know of any research on the drag in the 20 to 30 knot range that would support their use? I suspect the advantage might be at much higher speeds. Most of us hanging out the side of these things aren’t very streamlined and probably create way more drag than what is under the tramp!!!!

 

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I think the picture on sealed tramps and double skinned tramps is blurred by the big differences in sailing ability, even among the top 10 or 20 boats. Did Stevie won races at the worlds by 6-800 metres because of his tramp? Some of the people without the underskins were people who had trained at the venue non stop and were simply better than others.

There was some CFD analysis done a couple of years ago that looked at tramps and some of the issues and on a purely technical basis, there are big gains in total platform drag reduction from having no gap at the sides of the tramp and having the under skin. I seem to remember the biggest gain was from sealing the sides.

I personally think that there are a number of reasons for using the underskin. Besides the potential for it being more aerodynamic, the skin also holds all the systems in under the boat. If a system goes slack, such as when you drop the mainsheet, nothing falls down. 

I won't be losing my double skin tramp any time soon.

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3 hours ago, A Class Sailor said:

I think the picture on sealed tramps and double skinned tramps is blurred by the big differences in sailing ability, even among the top 10 or 20 boats. Did Stevie won races at the worlds by 6-800 metres because of his tramp? Some of the people without the underskins were people who had trained at the venue non stop and were simply better than others.

There was some CFD analysis done a couple of years ago that looked at tramps and some of the issues and on a purely technical basis, there are big gains in total platform drag reduction from having no gap at the sides of the tramp and having the under skin. I seem to remember the biggest gain was from sealing the sides.

I personally think that there are a number of reasons for using the underskin. Besides the potential for it being more aerodynamic, the skin also holds all the systems in under the boat. If a system goes slack, such as when you drop the mainsheet, nothing falls down. 

I won't be losing my double skin tramp any time soon.

Yes of course sailing ability counts and we all have our anecdotal examples to support one theory or the other. A good example was the race you would be familiar with at last Nats. One sailor lapped most of the fleet not because of gear but using sailing smarts and best using the gear. I’m after some more pure evidence to consider. I just think we may have overcomplicated what was once a very simple boat and I’m trying to test each component and decide on it’s value to me. 

Got a link to those tests you mentioned?

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4 minutes ago, WetnWild said:

Got a link to those tests you mentioned?

Sorry, I haven't got a link. I honestly cannot remember where it came from. There are 2 places that spring to mind.

1. Dario posted something that he got from Martin Fischer, or

2. DNA posted it when they released the F1

What i do remember was the turbulence at the deck to tramp gap being far more than I would have expected, because I never expected there to be such a pressure difference between the gap between the hulls and the air over the deck/tramp.

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Thanks ACS I’ll try and find them. You doing either of the upcoming States?

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I will be at the Vics, but sorry, Qld is a bit far for me. I haven't got your stamina for long distances, even for prawns and coronas!

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What about open net tramps. Use them already for years; can take rolling waves up front.

See my cat :

20652782918_61114045db_c.jpg

 

See in the vid how the water comes constantly through the tramp instead of bumping to it.:

 

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northsea junkie,

   We are talking about sealed tramps for decksweepers on boats that generally don't sail in heavy sea state.

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Thanks Sam for your explanation, but what is a decksweeper???????

I must say that I'm not sufficient into A-cats to know this idea. Hence my post. 

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Okay, I just found out what a decksweeper is and the intention to minimize the turbulence at the bottom of the main.

Here's an alternative idea for that: 

11926512096_0a9bac9199_c.jpg

So use NO TRAMP at all.

Like in the picture of my very old Spanish Patin A Vega and extend the sailbottom for the turbulence downwards till between the hulls. And make a small tramp at the rear beam side for going from one hull to the other.

I made also such a small tramp on the pictured cat  (which you just can't see on the photo). But that little tramp was only for making jybing possible (this cat has no rudders!!)

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Ha, yes, excuse for the naked people on the photo. It was the only photo with my cat on the beach. Which was in Soutern France in a naturist compound.

Overdressed? you might say that, but I'm sailing outside on the mediterian sea with a cold offshore mountainwind. 

It was Always fun how people reacted overthere when I was making preparations for a tour.

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On 3/14/2018 at 1:30 PM, northsea junkie said:

What about open net tramps. Use them already for years; can take rolling waves up front.

See in the vid how the water comes constantly through the tramp instead of bumping to it.:

 

Hi, I also use nets but they are polyester. What are your made of, Dyneema? Do you buy it in Europe?

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3 hours ago, martin.langhoff said:

@lamorak @WetnWild -- I am mulling a tramp like this for an 18ft foiling cat. It's not an a-cat obviously.

Are there details anywhere to DIY? Does anyone build these in custom sizes?

Mahoney Projects builds custom carbon/kevlar tramps in the U.S. PM me for contact details.

 

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