Converting a Closed Transom to an Open Transom

[SV.Maverick]

Just add a nice swim platform, easy practical you can even buy folding hinges and fold it up against the transom when not in use.

[sailscubasurf]

I purchased a 1972 Santana 37 that originally had a closed transom. Rather than cutting into the transom, the previous owner added a sugar scoop, which also added a few feet of waterline.

This is one way you can get a swim platform without altering the structural integrity of the boat.

GG

[Scaramanga F25]

Please, do not assume that this boat is presently structurally sound.
I worked with the designer of that series...not his fault.

[GrahamHO]

Originally Posted by Leatherneck

First I would like to say hello to the forum, I am a recent member and have greatly enjoyed reading through the various postings. It seems that there is a bonanza of knowledge here and I am really glad to now be apart of the community. Now on the the post....

So I am thinking of buying an 1980 Irwin Citation 40 as a long term project boat. The boat seems to be in good structural shape but there is definite work to be done. I want to do all of the repairs myself. I enjoy getting my hands dirty and the only way to really learn something is to do it in my opinion. Most of the work that needs to be done is aesthetic but nothing too crazy. My idea however may indeed be crazy and that is why I come here seeking advice.

The boat has what i guess you would call a closed transom, what I want to do is to cut out a section and convert it to an open transom with built in steps leading down the the water. Below is an example of what I want the transom to end up resembling.

First, is it even possible? I have searched the forums and couldn't find anything about someone doing it before.

Second, if you have done this before what are the major things i need to be aware of as far as structure and bracing?

And before any of you start saying just go buy a boat with a transom the way you want it I have to say that I am getting this boat for an extremely ridiculously good deal

Yes I think that is a good thing to do. I know of yachts that have been modified that way. I also know of designs that have been changed to make that standard.
I don't know your particular boat and whether there are problems involved.
I contemplated modifying my own boat but rejected the idea as mine has a stern hung rudder. Then I considered twin rudders. Then I thought that was too much work with the boat out of commission. Instead I made a small boarding platform on either side of the rudder. You could if you wanted make an exterior boarding platform and a small entry through the transom. Sketch several ideas before you get out the jig saw. You can make full size cardboard cutouts to test ideas.

[Cheechako]

I see no problem with doing it. A lot of work for the gain and as mentioned you will need to reinforce the transom. How much depends on how you cut out; a minimal cutout with large radius rounded corners in the notch will be better than a deep cut with square corners etc. Bottom line is , over reinforce it. Not sure Irwin's are very strongly built in the first place.
A modified open stern pulpit and ladder to a swim step may more useful.

[Leatherneck]

Wow, Thanks to everyone for all of their input! I really didnt think I would get so many responses in such little time. After reading through all of the posts I have come to the conclusion that it is a fool hardy idea. From what it sounds like, the process of doing this is even more intense than I had originally thought. I know it was a little bit of a pie in the sky idea but I figured asking couldn't hurt.

@leftbrainstuff, I think i will take your advice and just tidy up the boat, maybe sail it for a season and sell it in hopes of buying something more attuned to what I am looking for.

If i do end up buying the boat I will let everyone know and perhaps start another thread to talk about my progress and the challenges I encounter with it.

Cheers!

[RaymondR]

There are a lot of reasons that people go into boating. Some folks like to sail, some just want to be on the water, some like building boats, some don't want to build entire boats but like mucking about doing small projects, some want another status symbol, there are even some perverted types who actually live for the maintenance. What you buy and what you do with it for your own enjoyment is yours to choose.

What you want to do is not pie in the sky, if you have the requisite skills and are motivated there is nothing to stop you doing what you want with the boat including changing the structure.

However there are a few things you should do if you wish to be a prudent boat owner. These include seeking appropriate advice regarding any changes you might want to make. Learning to swim before you jump into the deep end of the pool is generally considered prudent and from the tone of your second post you appear reasonably switched on and intend taking this course anyway.

If you buy the boat and sail it and find you like it you might contact the designer and see how they feel about your suggested modifications.

[chris95040]

Originally Posted by valhalla360

Cutting out the transom and bolting a door on in it's place will reduce the strength pretty much the same as just cutting out the transom.

Adding the door provides almost no structural value.

Otherwise, yes, I've seen similar designs and they do appear to be a nice option.

Cutting out the transom certainly would. Not sure why you'd do that. The one I saw, like i said, just had a facade over a complete transom. No structural impact.

Can't just "walk right down to it" without doing what you propose, i reckon.


-Chris

[japarker11]

Originally Posted by Leatherneck

Wow, Thanks to everyone for all of their input! I really didnt think I would get so many responses in such little time. After reading through all of the posts I have come to the conclusion that it is a fool hardy idea. From what it sounds like, the process of doing this is even more intense than I had originally thought. I know it was a little bit of a pie in the sky idea but I figured asking couldn't hurt.

@leftbrainstuff, I think i will take your advice and just tidy up the boat, maybe sail it for a season and sell it in hopes of buying something more attuned to what I am looking for.

If i do end up buying the boat I will let everyone know and perhaps start another thread to talk about my progress and the challenges I encounter with it.

Cheers!

LN,

We recently bought a +30 yo cruiser of a 1970's design with the reverse transom. Our intended usage is world cruising. As we are of the age where artificial body parts start showing up on the yearly to-do lists, we analyzed our exposure to injuries boarding a reverse transom boat at either the funky flip down ladder or at a side gate. We decided a shoulder rebuild was $30K and six months of rehab. A fiberglass modification in either a fold out step or sugar scoop would be $20k.

As our boat is currently available for production and the tooling is available, we opted for the fold out. We addressed the structural and rigging (split backstay) issues, hardware and gelcoat work came in at yard prices under the $20k.

So far, with 5000 nm and averaging three boardings a day, no injuries to report.

If you are young enough that the injury risks are negligible, spend your time and money elsewhere on a +30 yo boat.

We were the first retro conversion. Since, the builder has sold two or three more.

We all would do it again.


Good Luck with your project.

John

Sent from my LG-V410 using Cruisers Sailing Forum mobile app

[Scaramanga F25]

Best advice.

If you are to rebuild a cheap boat you are wasting your money.
It costs no more to re-build a Hinckley than an Irwin.

Because:

Engines cost the same, mast, sails, hardware, teak, fiberglass
paint varnish, hatches, ports..etc etc, for one or the other.

You will lose less on a prize boat, and will have pride of ownership.

[Cheechako]

Originally Posted by Scaramanga F25

Best advice.

If you are to rebuild a cheap boat you are wasting your money.
It costs no more to re-build a Hinckley than an Irwin.

Because:

Engines cost the same, mast, sails, hardware, teak, fiberglass
paint varnish, hatches, ports..etc etc, for one or the other.

You will lose less on a prize boat, and will have pride of ownership.

Yep, a lotta truth to that. Ditto for boats wearing out, rigging, sails, engines, electronics, pumps etc go bad as fast on an expensive boat as a cheap one... with just a few exceptions though...

[GrahamHO]

Originally Posted by Leatherneck

Wow, Thanks to everyone for all of their input! I really didnt think I would get so many responses in such little time. After reading through all of the posts I have come to the conclusion that it is a fool hardy idea. From what it sounds like, the process of doing this is even more intense than I had originally thought. I know it was a little bit of a pie in the sky idea but I figured asking couldn't hurt.

@leftbrainstuff, I think i will take your advice and just tidy up the boat, maybe sail it for a season and sell it in hopes of buying something more attuned to what I am looking for.

If i do end up buying the boat I will let everyone know and perhaps start another thread to talk about my progress and the challenges I encounter with it.

Cheers!

I don't think it is a foolhardy idea. I don't know that particular design though. A friend of mine is at present making a more radical alteration to his yacht. He has cut his entire cockpit out and grafted in a fibreglass cockpit with an open transom taken off the mould for another design. It looks good and I'm sure is structurally sound. If you did your modification you would be well advised to seek a professional opinion first. Also if your workmanship was poor you may not be able to resell.
However if it passes those tests there is no reason not to do it as long as you can commit the time.
The greatest stresses in a hull are between the keel and the chainplates. The least stress I think is in the transom area, depending on the rudder and back stay arrangement.
The way I would carry out the modification would (briefly) be to make full size cardboard plans of a structure to replace the existing transom. You can layup glass onto sheets of balsa or boatbuilding foam and treat it like plywood. Then construct the replacement transom away from the boat by cutting out filleting and bonding the already glassed panels together. Then install the replacement transom by glassing it in. That requires making jigs and patterns to make sure it all fits.
It would take me about 2 months of regular commitment to do that.
There is no end to the modifications that are possible. For example when the Americas Cup (monohull) racing trials were being held here in Auckland NZ at least one yacht had its entire bow section from somewhere in front of the mast replaced. They seemingly made the change almost overnight to a different shape.

I know of a 40' yacht that was being delivered by road. It had to go through a tunnel but wouldn't fit around a bend. The owner took out a chainsaw and cut the stern off and replaced it later. The sky is the limit as long as you have the time and skill.

I did read about a racing yacht where they cut into the bridge deck to install a compass. The bridge deck happened to be an important part of the structure and it cracked at the hole under the stress. Being able to get insurance is also important which is another good reason to seek professional advice.

However as I mentioned earlier I considered the same idea for my yacht and simply fitted a couple of boarding platforms either side of my stern hung rudder.
All I needed.

[Lepke]

I am a former shipwright and have done similar things in wood, steel and fiberglass, but only with a design by a competent authority. They all worked out well, properly done, and maintained strength the stern needs for safety in the ocean. Not easy for a beginner to do.
Use a good grade of epoxy and stay away from bargain resin and cloth. Especially polyester resin.

[Stu Jackson]

Originally Posted by Snowpetrel

An easier solution would be to add a folding swim step, or even a slightly extended stern with a small step in it, and a set of steps. Up and over into the cockpit.

This is a really good idea. In fact, it's actually what Catalina did during the production runs of the Catalina 34. Closed transom to sugar scoop to open.

You can see the pictures here:

Evolution of the Catalina 34 - c34.org

I agree about the structural issues - incredibly important.

Some of us actually find it easier to board amidships, less bouncing.

Good luck. And welcome, again.

[CarlF]

I think open transoms on cruising boats (not so much racers) is an unfortunate development as it usually means even fewer comfortable places to sit underway.

Too many boat designers today think that a 6" tall backrest or a foam sleeve around a 1" stainless tube is adequate for a long watch.

While the Irwin was never a top boat, they did a better than average job getting the seat back angles and ergonomics right in the cockpit.