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 Post subject: transform an AC to be lighter....
PostPosted: Mon Jul 03, 2017 2:38 pm 
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Joined: Mon Dec 28, 2015 6:58 pm
Posts: 36
HI all

Next winter i'd like to transform top banana to be lighter.

Hull without fittings is 65 KGS
Carriage is 9 kgs
plank is 10 kgs
complete boat is about 95 kgs

What are your advices?

- Change the inside structure with foam and carbon?
- Change the ply deck for a foam/carbon one?
- Change the carriage or/and plank?
- change the uppers with dynéma?

What do you think i should do in first, second .....

thanks for your help.

Gilles

AC GBR261/FRA27 Top Banana


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 Post subject: Re: transform an AC to be lighter....
PostPosted: Wed Jul 05, 2017 7:41 am 
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Joined: Fri Jul 18, 2003 8:13 am
Posts: 49
Location: United Kingdom
Gilles

Replacing seat and carriage could give you a significant saving. Our current moulded seats are working out around 7kg finished with the carriage approx 3.5 kg (and design can be adapted to nethercott).

To reduce structural weight of the hull suggest that you would need to look at redesign/optimisation to achieve significant savings. The cumulative weight of "glue" etc is significant and makes it difficult to achieve theoretical savings. If you do go down this route start at the front, canoes like light front ends - dare I suggest you try sailing her without the spinaker gear one day!

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Rob Bell
IC GBR 327 Wild Venture


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 Post subject: Re: transform an AC to be lighter....
PostPosted: Wed Jul 05, 2017 8:28 am 
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Joined: Mon Dec 28, 2015 6:58 pm
Posts: 36
Thanks for your answer.

So i could save 10 kgs with a new carriage and plank, that's great! will do !!!!

But where can i find plans to make them ? or juste use the olds as moulds?

Olso, I think that the ply of the deck is a little damp after 22 years. That's why i thought replace it . Does a foam and carbon one will make a significant saving compare to a new ply deck ?

Sorry for my poor english......

gilles
Top banana


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 Post subject: Re: transform an AC to be lighter....
PostPosted: Thu Jul 06, 2017 12:51 pm 
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Joined: Mon Sep 12, 2005 7:45 pm
Posts: 742
Location: United Kingdom
You may find these pages interesting reading:-

http://www.devboats.co.uk/sailing/257rebuild/

Don't underestimate the amount of work to reduce a boat to a bare shell and start again, its really little different to building a complete new boat. When I did 257 the class was in the early stages of considering the new rule, and there was really little idea what a new boat would look like, or even what the rule would be, my preferred shell builder was booked up solid for months ahead and my boat was unsailable as it was. I think if any of those had not been the case - especially the last one - I wouldn't have gone ahead with the radical rebuild.

When I did the sums for mine I didn't think the cost/weight/effort benefit really justified a foam sandwich deck, and I went for 3mm ply foredeck and 4mm ply plus layer of kevlar dancing floor. The main weight savings were in internal structure, which on that boat was way over the top - what might have been appropriate for a lightly built wood boat, not the phenomenally rigid carbon/foam razorback shell of that era. I doubt it would be worth replacing your wood deck without also redoing all the internal framing, and if I were in your position I wouldn't consider that, I would build a new boat.

So, for whatever my opinion is worth:
- New carriage and plank - certainly worth considering. Not a bad thing to have a spare anyway. Clarke and son have been doing a lot of work in making lightweight homebuilt planks more accessible, or you could cross Mr Bell's palm with silver.
- Replace interior structure and decks - not worth the effort, build a new boat instead.


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 Post subject: Re: transform an AC to be lighter....
PostPosted: Sat Jul 08, 2017 4:43 pm 
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Joined: Mon Dec 28, 2015 6:58 pm
Posts: 36
thanks for your advices.

I have seen the PDF mesurements of the 2008 worlds where the AC's seems to be 89.5 kgs without the plank. Am i right ?

Top Banana without sails and foils is 95 kgs so its seems to be very good. Maybe the ply isn't wet.

I think i'll began to make a lighter carriage (foam and carbon) and i'll do a plank for light winds (and as spare.)


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 Post subject: Re: transform an AC to be lighter....
PostPosted: Sun Jul 09, 2017 9:42 am 
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Joined: Tue Nov 20, 2007 5:43 pm
Posts: 40
Hi Giles,

It's great to see activity of this type in France and also the work you have done to bring your boat up to spec again. It certainly looks great in the photographs and a real credit to you.

Since the weight reduction of 5Kg came in to force a few of us have thought about where the weight can be saved particularly as the Nethercott is essentially a boat for life as it is built so well. In AC form I believe it's the most challenging incarnation of the class and it's important that we all work together to maintain the numbers we have racing and bring more back on to the water.

The answers to weight saving have already been covered in the carriage and seat areas though when I refurbed my seat last winter it was pleasing to note the weight being still sub 10 kilos though I took all the old paint off which makes a difference. The issue you may have with the deck I think is worth looking at as it's possible that weight could be taken on particularly as you have ply decks on your boat. I'm no expert in the field of carbon fibre, there are others in the class who are and I am sure they could help with advice on upgrading. The AC's built by John Ellis were latterly all carbon so it can and has been done. It's also important to make sure that the kite system is rationalised and tuned as over the years I have seen sailors add or adapt it adding weight but not really adding any value. I would also check the diameter and weight of the pole. By the way removing the system altogether as has been suggested whilst hilarious is not an option!!!!

I am over in France several times a year visiting the Northern Loire, happy to catch up with you sometime for a grand cafe au lait!

Bon chances,

Martyn

AC302. Red a head.


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 Post subject: Re: transform an AC to be lighter....
PostPosted: Sun Jul 09, 2017 10:14 am 
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Joined: Mon Sep 12, 2005 7:45 pm
Posts: 742
Location: United Kingdom
On decks and weight saving, its worth noting that a sheet of 4mm plywood weighs less - if the lightest varieties a lot less - than 10kg. The amount of water a piece of ply can take up, even if sodden, which decks won't be, is strictly limited. Getting up to 50% moisture would be a fair bit, and one might guess that would be 50% more weight at tops. So the amount of weight in the decks themselves is very strictly limited and so is the potential for weight saving. Supporting structure is another matter of course, and I'm confident that internal framing is where I saved all the weight in mine -both in losing unnecessary structure and in using a relatively strong styrofoam grade for both the required buoyancy and supporting beams. But as already stated, in the light of experience I would advise against such a radical rebuild unless there was no choice.


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 Post subject: Re: transform an AC to be lighter....
PostPosted: Sun Jul 09, 2017 11:35 am 
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Joined: Mon Dec 28, 2015 6:58 pm
Posts: 36
@ martyn

Yes, my kite system has been rationalised. I was a RS700 and a MPS sailor......so the pump is fired ! just one cleat and two pulleys(less weight, less rubbing ) and it works very well : 5 seconds to put the kite off and 7 seconds for the oist. I have olso make a longer helm to be able to control the boat with my left leg during the oist, the halyard is 4mm dynema braid.

No problem even in waves and 18/20 knots.

I'd like to know if the weights on the PDF were without the planks or not. And what are the actual standart of AC weight ?

@jimc

I think your are wright, I will change the internal structure when i will have no choice....


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 Post subject: Re: transform an AC to be lighter....
PostPosted: Sun Jul 09, 2017 11:55 am 
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Joined: Mon Dec 28, 2015 6:58 pm
Posts: 36
Martyn O wrote:

I am over in France several times a year visiting the Northern Loire, happy to catch up with you sometime for a grand cafe au lait!


with pleasure, I am near Nantes at "Saint gilles croix de vie" on the west coast just as the south of the loire mouth.

Will you come with your boat ?


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 Post subject: Re: transform an AC to be lighter....
PostPosted: Sun Jul 09, 2017 11:59 am 
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Joined: Mon Dec 28, 2015 6:58 pm
Posts: 36
Martyn O wrote:
By the way removing the system altogether as has been suggested whilst hilarious is not an option!!!!
.


I also have an IC. (GBR 226) ...so don't worry !


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 Post subject: Re: transform an AC to be lighter....
PostPosted: Sun Jul 09, 2017 12:09 pm 
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Joined: Tue Nov 20, 2007 5:43 pm
Posts: 40
Giles,

My email address is Dewy67@aol.com, probably best to exchange details between us than clog up the Canoe site with how many sugars I have in my cafe au lait!

Cheers

Martyn


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