Forum -
November 13, 2023
POSITION OF THE ANCHOR CHAIN
Hello,
I am the future owner of an Excess 11, a boat I’ve carefully studied. I’m intending to make a modification to the non-structural part through which the anchor chain passes.
In fact, I find the current system to be detrimental to getting the most out of the trampoline, which led me to the following thoughts:
- Do away with the GRP section over which the chain passes.
- Add a PVC protective section which will be padded with a curved shape and fixed to the trampoline
- When the boat is under way, the anchor chain will be entirely in the locker, and the anchor will be held in place with rope (thinking even further, we could cover this rope with a Velcro system, but anyway...)
- Add stainless steel protection on the chain lead next to the windlass and at the bow if necessary.
The advantages of this system are:
- Make the most of the trampoline (for children having fun jumping, or for relaxing on the trampoline in any direction without worrying about bumping into something)
- avoid the risk of bumping or hurting oneself
- improve the aesthetics of the boat, as the trampoline at the bow won’t be split in two
- avoid the noise made by the chain banging on the GRP in rough seas.
There is, of course, one drawback:
- an additional maneuver before anchoring would be to bring the chain back to the anchor and secure it with the shackle...
I’d be grateful if you could advise me if this can be done without damaging anything on the boat.
Thanks
3
comments
I know someone who has debated between a Nautitech open 40 and excess 11. Being both competitive price and both with a more performance oriented design, they are fairly comparible.
The nautitech has the anchor at the start of the trampoline rather than on the front crossbeam like on the excess does have somewhat advantages. The anchor being further aft means that when in worse off seas, the chain and anchor bounce is far reduced. This ultimately reduces stress on parts of the boat. It also reduces the weight at the bow of the nautitech allowing the boat to perform minutely better.
This could be applied to the excess in the future design however does come with its disadvantages aswell.
Alternatively, in terms of controversial design, what are thoughts on a heavily asymmetrical anchor and chain design e.g. In one of the hulls (when bridle ropes are attached then the chain would return to centre).
Avant toute chose je vous remercie de poser la question avant d’entreprendre toute modification. Votre proposition peut intéresser d’autres lecteurs du Lab et donne donc l’opportunité de partager l’info plus largement.
Malheureusement je vous invite fortement à ne pas faire la modification que vous envisagez, et ce pour deux raisons :
1 : En navigation
La tension de l’étai est reprise au milieu de la poutre avant transversale en alu.
Cette traction se traduit par 2 composantes :
- Une composante verticale, qui tire la poutre vers le haut, et qui est contrée par la martingale de la poutre
- Une composante horizontale, qui tire la poutre vers l’arrière, et qui est contrée par… notre fameux chemin de chaîne en composite
2 : Au mouillage :
La tension du mouillage, même si elle est généralement plus faible que celle de l’étai, est également reprise par la poutre transversale alu.
Là encore 2 composantes :
- Une verticale, vers le bas, contrée par la rigidité intrinsèque de la poutre et la tension de l’étai
- Une horizontale, vers l’arrière, contrée par la rigidité intrinsèque de la poutre et… le chemin de chaine en composite
En somme, cette pièce en polyester est bien structurelle, elle est régulièrement sollicitée en compression lors de l’usage du bateau.
La retirer vous ferait courir le risque, au mieux d’avoir un étai très mou, au pire de tordre ou casser la poutre aluminium puis de démâter…
Je ne peux donc que vous inviter à la conserver, et suggérer aux enfants de sauter chacun de son côté… ;-)
Merci encore pour cette question, que vous n’êtes probablement pas le seul à vous poser…
Cordialement,
Hervé Piveteau
--
Hello,
First of all, I’d like to thank you for asking the question before making any modifications. Your proposal may be of interest to other Lab readers and therefore gives the opportunity to share the information more widely.
Unfortunately, I strongly advise you not to make the modification you are considering, for two reasons:
1: When under sail
The forestay tension is taken up in the center of the aluminum transverse forward beam.
This tension has 2 components:
- A vertical component, which pulls the beam upwards, and which is countered by the martingale stay.
- A horizontal component, which pulls the beam aft, and is countered by... the famous composite chain lead.
2: At anchor:
Anchor chain tension, although generally lower than forestay tension, is also taken up by the aluminum crossbeam.
Again, 2 components:
- One vertical, downwards, countered by the beam’s intrinsic rigidity and the forestay tension.
- A horizontal one, aft, countered by the beam’s intrinsic rigidity and... the composite chain lead.
In short, this GRP part is indeed structural, and is regularly subjected to compression during use of the boat.
Removing it would run the risk, at best, of having a very slack forestay, at worst, of bending or breaking the aluminum beam and dismasting...
So I can only invite you to keep it, and suggest that the children carry on jumping on their own sides… ;-)
Thanks again for this question, which you’re probably not the only one asking...
Best regards,
Hervé Piveteau