Transom - Open or Closed

[Nasher]

As some may have seen from my other posts we're at the stage of buying a Catamaran style SIB so we can go exploring places our RIB can't reach.

Plus I really miss the fun a small tiller steered boat can be, and our plans for a Motorhome in the very near future include a SIB.

My dilemma at the moment is the transom.

We've only ever had smaller boats with solid transoms and proper high rounded Bows. The last was our Bombard Aerotech 380.
This time I want to go down the catamaran route, Takacat style, and really like the idea of a wet boat with the minimal tube motor mount in place of a solid transom.

Obviously I realise it will be a very wet boat, but our Bombard used to fill up anyway climbing in and out of it, beaching it, etc.

I'd be really interested to hear anyone's experience of an open transom, the Pros and Cons they experienced, and did it become too much of a pain.

I did spend some time sailing an open transom Dingy, I can't remember the brand, but the open transom was a godsend as we spent so much time capsizing it we didn't have to bail it out each time, and we were wet anyway.

[User name]

With a smaller outboard I think I'd be happy enough, but I would be a bit hesitant to mount something particularly heavy on there, given that it's mounted with so much less surface area to distribute the load across the tubes.

I watch a guy on youtube that reviewed one and he loves it, though he's living in a really warm climate so getting a bit wet isn't so much of a big deal.

Another thing that would put me off a catamaran style SIB, at least on smaller ones is that you're loosing a chamber, so in the event of a serious leak out on the water, you may have much more difficulty getting back to shore.

On the plus side, repairs to an open transom are a lot easier, it'll be lighter and easier to fold too.

I like the idea of having one for convenience, but I think it would have to be as a smaller, second boat for the times when I'm not in the mood for the hassle of prepping the other boat.

[Old seahorse]

Hi Nasher. I’ve ownwed a Takacat Lx300 for 3 years. It is more suited to day trips, travellingFairly light, or at least with any vulnerable stuff in dry bags. Having said that, I’ve only got truly wet once, and that was 3 up, launching into waves off the beach.
When it did happen the water ran straight out through the open transom. In reasonable conditions, I’m not sure it is any wetter than a closed bow. The max h.p engine for that model is 10hp, but I run happily on a 6hp, at 15 knots, about 12 knots two up.
They are very stable, and you can stand up in them( I don’t tend to that much, but I have balance issues). I can walk onto the open bow to get in, as long as the boat is secure ( beach or slipway).
So far , I’ve had no issues with the open tube transom. The bars are actually secured over a large surface area to the tubes, fore and aft. It s a bit odd at first, but you get used to it. You can easily make( or now buy) a ply panel to reduce the open area in the transom. I made one , but haven’t used it. They are easy to row, and track well under power. They ar easier to swim from, and get back into, in the water, pulling yourself into the open bow. Ventilation/ cavitation can be a frustration from new, due to volume of air running under the boat floor. I resolved mine with a permatrim.
It is easy to pack, due to not having a fixed transom. ( but takes a bit longer to assemble/ pack away because of this procedure). The transom board is two piece boated together. It’s a bit of a faff initially( I prefer the Boatworld model transom fitting trialled by Chipko, and now owned by Easedale novice.)
Takacat make a range of sizes, smaller and larger, with tube and closed transoms, and with a ( small) enclosed bow tube. They don’t have bench seats, but come with an inflatable seat. I tend to sit on the tube.
Tuekit and Boatworld make similar cats each seem to have their own features.
Like all boats, it’s not the perfect boat, and doesn’t meet everyone’s needs, but it suits my needs pretty well.

[Old seahorse]

If it’s relevant to your needs, the air floor on the larger Takacats can be used as a S.U.P

[Old seahorse]

[chipko]

Didn’t notice this and half answered this in the current Kolibri Cats thread.

Kolibri Cats
https://www.rib.net/forum/f50/kolibri-cats-89851-post868040.html

We currently run an Elling tunnel hull sib that has a solid transom, put about 40 hours water time on the open transom Boatworld Katsport 330 we recently tested, and helmed a couple of 340 and 380 Takacats in the past.

Must admit really like the sporty look of the Takacat open transom. Sheds water instantly, no worries of soggy ply and makes the dismantled folded boat more compact. Despite popular belief water does not flood in as the stern wave catches up when stopping.

Downsides would be concerns long term of the tube fixing pockets and only limited to using the OEM transom wheels which are good but on the small side and have heard some welding failures to brackets after a few years.

As open bow cats have to be considered wet boats and rapid water drainage a must for safety, then difficult to fault the open transom solution in this respect. In practice we’ve found very little water actually comes over the bow in general use except when launching in surf or playing around punching through large surf at speed. In reality not dissimilar to any closed bow sib.

I’ve no real issues with solid transom cats either if honest. In fact if I was going big bucks on a Kiwi cat then it would be the 4m TrueKit…aluminium solid transom with a cool permanent rapid drain grill system. No problem either with say the traditional plywood transom on the Kolibri’s as I’d just fit a couple of large dia. transom drains to supplement the woefully inadequate standard bilge drains. A couple of these 42mm jobbies from Ribstore would be more than adequate:
https://www.ribstore.co.uk/products/...nsom-drain-kit
Already fitted a couple of similar smaller diameter drains on our Elling. Open drains on cats, even low on the transom, are well above the waterline and have found not even flooded by the stern wave when coming off the plane.

Also keen to try the Kolibri SeaCat and not phased by the closed transom as easily modified to rapid drain.

Still think the stainless steel open transoms look way cool though. [emoji3]