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Once more, we would like your input so that, together, we can conceive an aspect of catamarans that is as practical as it is aesthetically pleasing, the result of numerous compromises: the aft transoms.

In the design of a catamaran, every centimeter counts, every shape, every component has an impact on the performance, the comfort, and the safety.  It is in this spirit that today we explore the topic of aft transoms of Excess catamarans, which are among their more distinctive elements.  Our objective is to initiate a discussion within the community of sailing enthusiasts to see what ideas might emerge and which creative solutions might be envisioned.

Why are our aft transoms short?

Short aft transoms on Excess catamarans are not the product of chance. They were carefully designed to optimize multiple aspects of our catamarans.

On our Excess 11 and Excess 14, a crucial decision was taken: to move the mast forward of the coachroof. This decision stems from multiple considerations, notably structural advantages, weight reduction, living space in the saloon, and improved performance, due to an increased sail area.  Following this evolution, our product managers found themselves faced with a dilemma:  to fix the aft transoms and shorten the nacelle, and thus the layout, or to move the mast further to conserve a spacious nacelle and long transoms, but in compromising our ratio of 1.5 for the nacelle/hull length overall (article on the boat’s performance by Bruno).  Contrary to the option of moving the mast forward or reducing the length of the nacelle, we chose to place the mast in the optimal location, by moving the nacelle aft, without reducing it, to improve the entire cruising experience.  This evolution then led to shorter transoms, a deliberate choice to optimize the handling, aesthetic design, and accessibility of the catamaran, all while maintaining a long nacelle moved aft.

If you have ever had the chance to sail aboard an Excess, you have probably noticed the short distance between the helm and the water’s surface.  This configuration simplifies handling by offering the helmsman a clear view over the boat’s stern, while also facilitating access on board.  Vincent, with Excess Delivery Services, demonstrates docking maneuvers for us in the Excess tutorial, with an ideal flow of movement via these aft transoms.

However, could they be extended?

Although short aft transoms present numerous advantages, it is a legitimate question to ask if they could be extended to meet other needs, notably space, water access while at anchor, or access to the tender.

At Excess, we have identified multiple systems to extend these transoms:

Make longer hulls:  A simple option would consist of increasing the hull length.  That would enable us to have more spacious transoms, but it would also increase the overall size of the boat, which would in turn lead to a cascade of additional costs and constraints for the user.  In fact, that would mean a larger boat with an artificial forward placement of the mast!  


Transom extensions in fiberglass:  fiberglass transom extensions, like those used on the Excess 11 and 12, could be considered.  They offer an economical solution for elongating the deck without affecting the architecture of the hulls, but they could affect the boat’s aesthetic design.

spaces below or alongside the transoms, to store marine equipment or even docking systems for the tender (inflatable swim platform).


Any suggestions from the Lab Community?  Pencils ready!


Call for Ideas from the Express Community

We invite you to share your ideas, your experiences, and your reflections on this subject.  How would you envision the extension of the aft transoms, and are you a fan of this idea?  Do you have other solutions for making the aft transoms more welcoming, more practical, and more ergonomic without compromising the benefits of a long nacelle?

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March 17, 2024
I wonder if it's possible to incorporate into an existing Excess 11 design a pair folding transoms with built in integrated folding seats. It's a bit hard to explain so I made a quick 3D sketch of what I'm thinking. I wish I could attach photos here but since that's not possible you can check out the screenshots here: https://photos.app.goo.gl/LndaDBncBA5npNk47

The transoms would have 3 modes as shown in the pictures:
1. Driving the boat from a standing position (transom raised with seat raised)
2. Driving the boat from a sitting position (transom raised with seat lowered)
3. Moored position (transom lowered)
February 10, 2024
I like the current length on the 11. However as with all things they could evolve into something even better. Some form of discrete protection on the after end to prevent the chips in the gel coat that the dinghy sometimes causes would be helpful. We have rigged a small loop of rope from the helm seat which can be grabbed when boarding the dinghy - it makes the process safer. Maybe a small s/s grab rail could be added on the future.
February 5, 2024
I think some other points to consider especially in being in the UK, is that often berthing fees run in bounds of sub 12 metre ~ 40ft and 12-15 metre and 15+ metre. By extending the aft transoms as seen on other catamarans such like lagoons/fountaine pajot, the small gain of easier access and swim access is less so important. What excess have done with shorter transoms is brilliant as it provides greater (more used) spaces however notibly after sailing the 11 in less than champagne sailing conditions (the Solent on an average October day) I can’t help but feel somewhat exposed especially when considering watches/ fine tuning whilst on passage. A transom as seen on the HH44 would be an option to consider however as stated by HH , the drop transoms are heavy and have to have a special system to lift it up and down. I may be wrong but I am not sure how to access the boat from the water (safety feature if overboard or you go for a dive off at anchor) it would be great to see this as maybe an alternative option to extending the aft transoms on future designs as they are less intrusive to design /aesthetics. I would also like to consider the side opening to the transom as a more accessible way onto the boat when docked alongside, this at helm height would be a great feature to see so that when you are docked to a pontoon (as happens a lot in the uk) you can access the boat still easily even if you opted for the drop down platforms.
Overall however, I think it’s great to see shorter transoms and more useful uses of the overall length as we all know boats and especially berthing are expensive to run!!!
November 30, 2023
I think "Enjoy Catamaran" makes some good points and yes, the transoms on the Lagoon 51 look great and are very functional for divers like myself :)
Enjoy catamaran
November 30, 2023
Hello Felix, merci beaucoup de cet article et des explications très précises sur la forme choisie des jupes qui sont finalement techniquement (position reculée de la nacelle…) et économiquement cohérentes (construire un cata plus « volumineux, plus long » c’est plus de matière, plus de contraintes donc plus cher). Néanmoins je rejoins 2 de mes copains sur le fait que les marinas nous facturent non sur la longueur de flottaison mais sur les dimensions hors-tout … du coup grâce, ou à cause, des bossoirs nous pourrions avoir des plateformes plus grandes. Sous forme d’extension horizontale et pas en volume bien sûr pour respecter les points cités plus haut. Pourquoi ? Parce que nous sommes plongeurs et bénéficier de plus de surface là où nous posons nos blocs équipés avec leur stab est gage de confort et de sécurité pour les charger dans le dinghy, idem pour décharger les courses lorsque il y a du clapot, pour mettre à l’eau une planche de wing équipé de son foil… Et pour ce qui nous concerne personnellement, il se trouve que sur notre poste au port, nous avons pile au milieu et au bord du quai la borne eau/électricité. Alors avoir des plateformes courtes va rendre plus difficile la récupération des amarres restées à poste et des pendilles. Pour ce qui est de ma proposition: reprendre le même système (en option par exemple) que les plateformes du lagoon 51 (mises à l’échelle bien sûr). Une belle pièce, fonctionnelle, robuste (en infusion ?), qui se poserait et se fixerait sur les plateformes moulées d’origine (collée, boulonnée mais restant démontable pour revenir le cas échéant en configuration d’origine). Avantages: le dessin (à adapter en proportion) existe déjà, ça ajoute la surface nécessaire, c’est relativement léger et ça ne modifie par la longueur à la flottaison et n’impacte pas la position de la nacelle, et ça permet de décaler un peu l’échelle de bain, et ça facilite les amarrages ainsi que les embarquements/débarquements que ce soit en longside ou cul à quai. Merci
Andreas Log Hofstad
November 30, 2023
Excess 11 #98

We find the short transoms really ggod looking. I would have liked something to hold on to when going on/off the boat. second thing I would have changed is the swim lather which is centered, it should have been moved as far towards the center of the boat as possible, its kind of in the way going on/off


November 26, 2023
If you decide to go with hull extensions it would be nice to offer a kit to enable a retrofit as well.
However if you feel that the hull extension is not feasible another option could be a solution like on the HH44. The transoms are extended by an element that's folding up or down. In the down position it extends the transom, in the up position it serves as additional protection / enclosure of the aft helm station.
So it would add value in both positions.
November 25, 2023
Hi Excess Lab,
on my 14#23 I am very happy with the transom as it is. It's easy to get ashore and access to the dingy is also ok if an extra line is available. Much more important to me would be a secure way of holding on to the railing when the cover is pulled over the helmseats.
It would also be great to have a solution for securing the helmseats, protected by a cover, in heavy seas. They move up and down a lot. We pull the cover over them to protect the helmseats from salt in bad weather.
Keep up the good work.
Rainer, SY Geronimo
November 25, 2023
I think Gio makes a good point, that's also what I was thinking. The relation between total length (including davits) and waterline length is a bit off. You pay for total length at the marina (15.5 m) but under sail get the performance of the waterline length (13.5m). However, as Gio pointed out, I also understand your reasoning behind this design decision. I think there's really no easy answer to this one. If it is possible from an naval architecture's point of view I'd offer transom extensions (= longer hull). Also from a purely aesthetic point of view I think extending the transoms further aft on the 14 would also look better.
Felix W.
November 25, 2023
1 answer
Please fix the link to article on the boat’s performance by Bruno). Error 404 does not work. Thank you.
Claire - The Excess Team
Claire - The Excess Team
November 27, 2023
Hello Felix, The video link works on our side. Could you please try with another browser? Thank you !
November 24, 2023
Et pourquoi pas des extensions gonflables, détachables et rangeables ?
November 24, 2023
Hi there,
The plus side of a wider transom is a comfortable space for my guests to put on flippers, snorkels etc before swimming and not to have to do this one person in sequence. Indeed a couple can be sat on the transom with feet in the water supervising children swimming.
It is also useful to inflate foiling wings or kites off a wider transom.
That said I wouldn’t want to add drag to the cat’s configuration or move the mast much further forwards than the 11.
Could I suggest a compromise where the transom is wider above the wetted surface then transitions to optimal below the water line?
Similar to how you grow cabin volume above the water line.
November 22, 2023
Hi, it is an interesting topic and to be honest one that I am struggling with for the final purchase decision. Not so much for the practicality by itself but for the overall concept. I understand the message above and the reasons for your design, with the final result in providing more space. On the other hand, when you see the 14 in its real overall length, including the davits and the bowsprit, you realize how the boat, while remains a 14m in terms of wetted area, is actually much longer from the administrative and marinas expenses point of view. Now, you can argue that you get a bigger boat for the price but I struggle on that as well since you end with more volume but still a 14m boat hulls.