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Old 06-10-2015, 19:01   #1
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Converting a Closed Transom to an Open Transom

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
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Old 06-10-2015, 19:07   #2
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Re: Converting a Closed Transom to an Open Transom

Welcome to CF

If this is a project boat...I see no reason to not add this to your list if it is important to you
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Old 06-10-2015, 20:19   #3
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Re: Converting a Closed Transom to an Open Transom

Leatherneck,

I am not a naval architect. Where potential problems might come from is that your boat was designed to use the present structure of the stern to strengthen and stiffen it. So your issue would be how to provide the structural strength it needs, and at the same time, the stern features you desire. Consult a naval architect or a shipwright. They will be able to tell you if it is a good or bad idea, and if, good, how to go about it, for a fee, of course. Or find a sweetheart deal on a different boat that has the stern configuration you want.

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Old 06-10-2015, 20:26   #4
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Re: Converting a Closed Transom to an Open Transom

Quote:
Originally Posted by Leatherneck View Post
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
Your proposed modification will significantly alter the stiffness and structural integrity of hull and deck.

You'll need to add structure to regain lost stiffness in a way that minimises stress concentrations. Not easy to respond in a few paragraphs.

Perhaps sell on the boat after you tidy it up. Then you can buy what you want. That work alone will keep you busy enough.

Do you want to work on your boat or sail it?

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Old 06-10-2015, 22:05   #5
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Re: Converting a Closed Transom to an Open Transom

Possible yes. Anything is possible.


Practical not sure but probably not. The rig puts a lot of strain on the back of the boat and you will be drastically reducing that strength. Also what else is in that space you would be eliminating? You will have to find space for it.


Don't do all the calculations right and you could have a rig failure followed by a sinking.
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Old 06-10-2015, 22:17   #6
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Re: Converting a Closed Transom to an Open Transom

Doable yes, that is if you have a lot of DIY mentality. That boat has quite narrow transom typical of that era so not much room anything else but the the steps down. Add a bulkhead where the steps starts. And consider how the backstay needs to be arranged..

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Old 06-10-2015, 22:47   #7
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Re: Converting a Closed Transom to an Open Transom

I saw a boat once with what looked like a traditional transom plus a "facade" the same dimensions of the transom hung on a hinge. Folded up, looks like a normal transom. Folded down, now theres a bit of a swim platform hanging off the back. Looked pretty cool. Seems like a good way to retrofit that kinda thing without screwing up too much structure.
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Old 06-10-2015, 23:15   #8
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Re: Converting a Closed Transom to an Open Transom

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I saw a boat once with what looked like a traditional transom plus a "facade" the same dimensions of the transom hung on a hinge. Folded up, looks like a normal transom. Folded down, now theres a bit of a swim platform hanging off the back. Looked pretty cool. Seems like a good way to retrofit that kinda thing without screwing up too much structure.
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.
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Old 07-10-2015, 00:35   #9
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Re: Converting a Closed Transom to an Open Transom

To add some numbers (reality) to the above (good) advice. Assuming that you can find a reputable (competent) Naval Architect (NA) to do the design work & engineering behind such a conversion, it's likely that it'll run you $10K - $15K. And that's just for the design work, lists of materials, detailed instructions, etc.

On top of that amount, by the time you're done buying the materials, plus all of the consumables & such to do such a conversion, you're probably looking at the same amount again.
Keeping in mind that this is assuming that you do all of the work yourself, or 95%+ of it.

Then there's the new LPU paint job for the boat. As you'll want her to look pretty after all of that work. So, again, about the same amount as either of the above 2 other operations. Assuming that you hire it out to a pro. If not, then you might, sneak in at $5k +/- for such.

So, call it $30k+ (probably more) to add a feature which wont really work with the boat's design to begin with.
I say that as said design has a transom which is, by design, raised significantly out of the water at it's lowest point. By at least a foot (or more).

One cannot arbitrarily lower such features, as the whole ass half of the boat has it's lines designed to converge there in a particular fashion, in the shape which she currently has, & at that height. Such that the water flow is setup to follow those lines, in order to leave the boat's aft end in a relatively smooth fashion.

Thus, unless you want to redesign, & rebuild the aft third to half of the vessel, it's not going to work, from a hydrodynamic (fluid flow) standpoint. Let alone the giant alterations that opening up a transom usually does to a design/vessel, structurally... unless the designer had ideas & intentions for such when he originally designed her.

As an example, read about how much work went into the design, & rebuilding of the bow on a Freedom yacht (below). When the owner decided that he wanted more bouyancy up forward.
And to fully get the amount of work, time, & $ which went into it, look up (online) & or purchase the referenced issue of Professional Boatbuilder magazine. It'll give you a more complete picture of what mod's like that entail.
Also, there are some other great articles on Eric Sponberg's website.
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Old 07-10-2015, 02:29   #10
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Re: Converting a Closed Transom to an Open Transom

It is a big project for sure, but opening up the transom has become a pretty common modification of late. Typically it also involves a complete redesign of the cockpit mold as well. Redesigning the layout not just the open transom is often the goal.

An example of a well done conversion. Olson 30 Open stern mod.... - Sailing Anarchy - Sailing Anarchy Forums
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Old 07-10-2015, 04:45   #11
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Re: Converting a Closed Transom to an Open Transom

Greetings and welcome aboard the CF, Leatherneck.
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Old 07-10-2015, 05:19   #12
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Re: Converting a Closed Transom to an Open Transom

Those citation 40's look lovely, it would be a shame to change that nice stern, but I guess it could be done if you really needed to.

My brother opened out the transom of his wooden 32 footer. And a good mate has just done the same thing on his 37 foot steel boat. Both jobs worked out well, but the steel boat was being rebuilt in a shed, and the wooden boat had a simple wide transom. Yours will be much harder to blend in, being a moderately high narrow stern on a fibreglass boat.

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.

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Old 07-10-2015, 05:52   #13
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Re: Converting a Closed Transom to an Open Transom

It can be done, but keep in mind that a vertical transom makes installing dinghy davits and dinghy launching very easy. A folding swim platform under dingy davits on a vertical transom can give you the best of both worlds, and a lot more easily installed than reconstructing the stern into a sugar scoop.
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Old 07-10-2015, 06:07   #14
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Re: Converting a Closed Transom to an Open Transom

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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
And so now you are going to spend an "extremely ridiculous" amount of time and money to make your boat something it was never designed to be. And in the process, of course, completely destroy its resale value. That way, when you finally decide that it isn't working and you want to get rid of it so that you can just buy a boat that was designed with an open transom in the first place, you will have to practically (and perhaps actually) give this boat away.

No offense, but we see postings like this here a lot. "I want to buy a boat that is not what I really want, and then find a way to turn it into what I really wanted in the first place." This is almost always a very bad idea. I can almost guarantee you that you would be time and money ahead to just buy a boat that was designed with an open transom.

But not just time and money. You'll also get a better boat in the bargain. Mainly because (unless you spend a REALLY "extremely ridiculous" amount of time and money to do this right) it is going to end up half-assed, and ruin the structural integrity of this boat. And then it really will be worth nothing more than scrap.

But, you're going to do what you're going to do. Good luck to you.
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Old 07-10-2015, 06:16   #15
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Re: Converting a Closed Transom to an Open Transom

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And so now you are going to spend an "extremely ridiculous" amount of time and money to make your boat something it was never designed to be. And in the process, of course, completely destroy its resale value. That way, when you finally decide that it isn't working and you want to get rid of it so that you can just buy a boat that was designed with an open transom in the first place, you will have to practically (and perhaps actually) give this boat away.

No offense, but we see postings like this here a lot. "I want to buy a boat that is not what I really want, and then find a way to turn it into what I really wanted in the first place." This is almost always a very bad idea. I can almost guarantee you that you would be time and money ahead to just buy a boat that was designed with an open transom.

But not just time and money. You'll also get a better boat in the bargain. Mainly because (unless you spend a REALLY "extremely ridiculous" amount of time and money to do this right) it is going to end up half-assed, and ruin the structural integrity of this boat. And then it really will be worth nothing more than scrap.

But, you're going to do what you're going to do. Good luck to you.
I missed that line when I first read the original post.

These types of projects only make sense if you simply like to have projects to work on (and there is nothing wrong with that).

Its a fools errand to think it's a money saving option because of the purchase price. If you do an even halfway decent job, it will end up costing more than just buying the boat you want in the first place.
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