Sailboat to Trawler Conversion

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Deep Sea

Member
Joined
Oct 2, 2021
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15
Thanks for the welcome.

I'm currently in the process of converting my small (21') sailboat into a trawler. I'm interested in knowing if anyone on this site has any knowledge of this conversion process. I'm trying to learn as much as I can for my conversion. I am a member of a few sailboat forums and some of those people are not to happy about my desecration of one of their own. I'm hoping that you will be a bit more understanding. :)
 
Welcome aboard. Are you trying to make the sailboat into a trawler or selling the sailboat and buying a trawler?
 
Deep Sea, Welcome.

What is it that you would like to accomplish with the “conversion”?

If a “trawler” is a seaworthy boat that travels efficiently at hull speed, you likely already have that with the addition of a stabilizing sail and some get-home back up.

Are you thinking about just keeping the hull and rebuilding cabin to create an indoor helm?
 
Hi. My plan is to strip the keel, mast, and most of the cabin and cockpit. Then lay a fixed keel, large cabin and short (covered) cockpit. Mount an engine and cruise.
Deep Sea
 
Deep Sea said:
Hi. My plan is to strip the keel, mast, and most of the cabin and cockpit. Then lay a fixed keel, large cabin and short (covered) cockpit. Mount an engine and cruise.
Deep Sea
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Got it. Sounds like an interesting project.

To be honest, unless doing the work is an end to itself, I’m not sure the finished project would be worth the effort. I would think finding an old powerboat that needs some love may be a more efficient project.

However, the journey is much of the fun so nothing wrong with that.
 
Conversion Hull

Here is a picture of a converted sailboat.
Notice the clever raised fwd deck.

The hardest part of doing a conversion it finding a sailboat w full ends. A sail boat has a low “PC” .. prismatic coefi-ficent. Like sharp and pointy bow. Most sailboats are diamond shaped as in pregnant amidships and skinny and pointed at both ends.
Trawlers are slab sided and full at both ends w a constant beam 70-80% of their length.
So that’s what you look for. There is an Albin (Swedish sailboat) 27’ long that may be a good conversion base. Full at both ends.

The next thing that needs converting is the nature of it’s rolling personality. Hard to do w/o the mast, ballast and other aspects of the sailboat hull shape. You may find most sailboats to be much too rolly most of the time. You might consider large bilge keels.
 

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Yeah a sailboat without a keel or sails will roll like crazy. There’s a reason sailboats look different than trawlers. I’m all for crazy diy projects but people have been building boats for thousands of years and it’s pretty well understood stuff - no reason to re-learn old lessons. I’d suggest putting the energy and time into restoring and improving a vessel that was designed for the allotted task.
 
socialrider,
I think it’s a worthy undertaking and not just a foolish notion. Sailboats have a degree of efficiency that trawler owners can only dream about. But a hacked up and seriously changed sailboat likely will loose much of what is good about sailboats unless one is lucky and somewhat skillful in the execution of the modifying process. Stability and righting moment abilities are probably the greatest challenge

But old sailboats are really cheap and the act of modifying one into a trawler would be a satisfying and fruitful endeavor. And then one would need at least a big dose of good old fashioned luck to pull it off successfully. The cat’s meoww would be a brother that was a NA. But how many of us have one of those in their pocket?

The OP certainly won’t get real help on this forum as most all would advise to get an actual trawler and leave the experimentation to those a bit addled in the head. I admit to being one of those persons as I was on the road to converting a sailboat myself .. but I found Willy my Willard and was relieved of the need. But I was also deprived of the challenging experience of succeeding at the mod game. I took a different route in the 70’s designing and building a boat .. not a trawler but an ultralight small cruiser. I thought it was a wonderful boat and even put up a picture of it on TF. No response at all. Avoided like the plague. There’s a mentality here that if it isn’t available on-line or in a store it has no value. A huge number of posts on TF are about “what is the best radar?” What is the best ______ you can buy? We Americans are the consumers of the world to the extent that It’s the only way people see that is viable to achieve their wants. And our wants are elephant like in size TBS. Just look at our trucks for the average guy.

So people that want to modify something to fill their wants are rare. And considered as mostly fools that need to be better consumers and avoid building and creating things that avoid the high price of manufactured, distributed and marketed goods to eager consumers skilled at making choices as they spend their money. Ahh .. the great Consumer Report.

So I support the OP but agree w most all that success is elusive at best. America was raised on creativity and individualism but those days are gone.
 
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dhays said:
Got it. Sounds like an interesting project.

To be honest, unless doing the work is an end to itself, I’m not sure the finished project would be worth the effort. I would think finding an old powerboat that needs some love may be a more efficient project.

However, the journey is much of the fun so nothing wrong with that.
Click to expand...

You are right. The work is a major part of my journey. I’m retired and enjoy building wooden boats as my hobby. I’ve had this old (broken) sailboat hull sitting around for several years and just recently learned about this conversion idea, which has been around for quite some time. Going to have fun with it but need design ideas and conversion problems identified. I’ve been informed about several issues from sailboat forums (side roll and stability) but want to learn as much as I can.
Deep Sea
 
So I assume the sailboat currently has a weighted center board. I can understand the desire to remove that to free up cabin space. I wonder though if it might be worth keeping that?

The swinging centerboard not only makes the boat easily trailerable, but would likely provide better stability, maneuverability, and efficiency than any keel you might build.

I grew up a sailor and only converted to power 5 years ago. I’ve had 21’ sailboats with a swing keel and they glide through the water with just a tiny bit of power. As was pointed out above, a sailboat hull is super efficient.
 
Nomad Willy said:
socialrider,
I think it’s a worthy undertaking and not just a foolish notion. Sailboats have a degree of efficiency that trawler owners can only dream about. But a hacked up and seriously changed sailboat likely will loose much of what is good about sailboats unless one is lucky and somewhat skillful in the execution of the modifying process. Stability and righting moment abilities are probably the greatest challenge

But old sailboats are really cheap and the act of modifying one into a trawler would be a satisfying and fruitful endeavor. And then one would need at least a big dose of good old fashioned luck to pull it off successfully. The cat’s meoww would be a brother that was a NA. But how many of us have one of those in their pocket?

The OP certainly won’t get real help on this forum as most all would advise to get an actual trawler and leave the experimentation to those a bit addled in the head. I admit to being one of those persons as I was on the road to converting a sailboat myself .. but I found Willy my Willard and was relieved of the need. But I was also deprived of the challenging experience of succeeding at the mod game. I took a different route in the 70’s designing and building a boat .. not a trawler but an ultralight small cruiser. I thought it was a wonderful boat and even put up a picture of it on TF. No response at all. Avoided like the plague. There’s a mentality here that if it isn’t available on-line or in a store it has no value. A huge number of posts on TF are about “what is the best radar?” What is the best ______ you can buy? We Americans are the consumers of the world to the extent that It’s the only way people see that is viable to achieve their wants. And our wants are elephant like in size TBS. Just look at our trucks for the average guy.

So people that want to modify something to fill their wants are rare. And considered as mostly fools that need to be better consumers and avoid building and creating things that avoid the high price of manufactured, distributed and marketed goods to eager consumers skilled at making choices as they spend their money. Ahh .. the great Consumer Report.

So I support the OP but agree w most all that success is elusive at best. America was raised on creativity and individualism but those days are gone.
Click to expand...

Thanks Willy,
Listening to you it sounds like it takes an old timer if you want to create any experimental mods. Those skills and that mentality is hard to find theses days. Good thing I’m an old timer. I may not have all the skills needed for this conversion but where I’m lacking in specific skills I make up for in crazy determination and stubbornness.
Deep Sea
 
dhays said:
So I assume the sailboat currently has a weighted center board. I can understand the desire to remove that to free up cabin space. I wonder though if it might be worth keeping that?

The swinging centerboard not only makes the boat easily trailerable, but would likely provide better stability, maneuverability, and efficiency than any keel you might build.

I grew up a sailor and only converted to power 5 years ago. I’ve had 21’ sailboats with a swing keel and they glide through the water with just a tiny bit of power. As was pointed out above, a sailboat hull is super efficient.
Click to expand...

Yes, my Cal 21 has a weighted swing keel. I sailed her for several years and had fun doing it. As I posted earlier the keel housing is damaged and leaks pretty bad which is why she’s been on the hard stand for several years.

My plan is to repurpose the keel and position it as ballast. Positioning will be important here. With this pre-positioned ballast, a deep keel, and a pair of decent bilge keels she should power along comfortably at trawler speeds.
Deep Sea
 
Don't do it.
Think about full sails up and no keel. Your plan to build a cabin adding weight to the top will likely end in an overturned boat. IMHO.

If your desire is to work with your hands to bring to life a project, there are many cheap to buy boats already designed to be trawlers that need TLC.
 
Deep Sea said:
Converting sailboat into a trawler. Should be fun.
Click to expand...

Ok, it sounds like you are determined to go down this route. If you do I would recommend getting a Naval Architect to look it over and make suggestions. You may otherwise end up with a severely compromised boat that might be dangerous. Good luck with it, but get some professional advice.
 
The Obvious Alternative

Deep Sea,
Could be about the same amount of work to build a trawler.

With the sailboat conversion all you're really interested in is the hull. So build your own. Give it a flat bottom w some rocker and the worst thing that can happen is some pounding. There are lots of great designs out there from J Atkin to Jeff Spria. Spira's designs are VERY easy to build w many people building. Atkin boats on the other hand are for folks w more skill but beautiful boats and very capable. And browsing plans is fun. I have many bookmarked. PM me.

But a curvy lined sailboat hull that would be a long drawn out project. I bought an old dory about 22-23' for like $50. in the 70's, cut off a bit of the stern, inserted a bigger transom and a 5-6hp OB and had a sizable boat. Had I continued on I could have had a slow cruiser (much like a trawler) ant a ridiculously low cost. The red and green boat we saw on the floats at Prince Rupert BC.

Re the ballast you may not need much or any w big enough bilge keels. And if/when you go aground you'll literally be siti'in pretty and likewise at anchor when the tide goes out.

And I can still say all the advice here looks good. It's useable depending on to what degree you take it.

social rider writes " I’d suggest putting the energy and time into restoring and improving a vessel that was designed for the allotted task.

I hope you don't go this route as trawlers are very much an extended, expensive and long drawn out project that will kill your enthusiasm. And to some degree be wary of FG boats a hidden rot, delimitation and other evils are likely.
 

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While I would still do a lot of planning and estimating, be careful of people warning about stability. Many here judge stability on pictures which is entirely comical in itself if you just know the basics to understand stability.

Its a pretty daring project on little sailboats as there is less boat for error, but more than a few have done it and been happy with the results.
Take it in stages with float testing in between and that may be all you need.

Even thought of doing it myself as the hull is a bunch of work and a used hull had way cheaper than the materials to build new...especially if you already own one that isn't likely to sell for much.

May want to visit some boatbuilding forums if you havent for leads on the good and bad of your idea.

Look up St Pierre Dory....looks like the picture above.
 
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Yes I agree the St Pierre Dory would be an excellent easy home build and I’d call a 27-30’ foot equipped as a trawler would be one in reality. A 5-8hp OB would drive her at 5-6 knots. Being FD no more power or speed should be expected.

I thought Spira offered Pierre Dory plans but I don’t see them.

Atkin boats, even simple designs, are known to not be simple enough for those W/O experience. But I don’t know to what degree. Spira plans are for the novice I’m sure.

My comments on some Spira boats I am recommending as possibles.
27’ Valdez, 24’ Key Largo .. my favorite that I’ve threatened to build, 13’ Juneau as a first build, 14’ Seneca, 17’ dory with OB well.


Atkin designs;
Little Effort — easy to build w the straight lines where they make the boat really easy to build. I suspect 5-15hp should drive her at appropriate speeds.
Marigold and Esther are great designs. Both w flare but only above the WL. These are serious boats.
27’ Marcia is my favorite. I really like this boat and would build her as an OB w 40 to 60hp.
Wader is a lot of boat re the build difficulty w the straight lines where the’re needed such as the topsides.

Geroge, Ration, and Punch round out my picks (off the cuff) for Atkin boats. But not to be discarded lightly as the Atkins (father and son) are a pair of the most well regarded NA’s ever.

I don’t offer this only for the OP Deep Sea. We have others that will be at least interested in browsing boat designs. I usta go to the library in Seattle (when I was about 11) and spend hours looking at boat books. Many of them had the Atkin name on or in them.
 
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Deep Sea said:
Converting sailboat into a trawler. Should be fun.
Click to expand...

1) It'll never be a trawler - the same as strapping an outboard onto a bathtub does not make it a trawler.
And
2) Have you ever been on a yacht that lost it's rig and motored in any sort conditions without?
It ain't a pleasant experience
 
I thought of this many many times, I have bought and sold a lot of boats over the years ,I will find a Boat that needs work keep it and use it for a while and move onto the next one , I run into great deals all of the time ,there is a 36 foot sailboat down at the port close to where I live , been sitting for at least five years a little rot in it here and there the interior is a little rough it’s has a like new inboard diesel engine in it that would be great, Everything you need inside birth head galley , everything including Some old electronics, I could buy this boat from the port or $50 but it Has to be moved , Shorten and modify the Keel , Strip the rigging , leaving a winch or two that might help you out down the road,Build a small pilot house , plywood and two by fours whatever ,clean up the fuel tank filters oil , head off to Alaska for a summer of your lifetime ,Total investment thousand bucks you could probably sell it for five when you’re done with it
 
A bit offensive re the bathtub Simi.

And if it has the essence of a trawler it is.
Heavy, non-planing, fair range … but it may not be a trawler w an OB. I say that and know that if one put an OB on a 25 Albin .. I think that’s a trawler but it’s lacking trawler essence on three counts.
1. Not heavy.
2. Lacks the trawler look.
3. Only moderate range.

There’s an iffy range of trawlerness. There’s a “Finn” boat on this forum that is deep into the iffy range .. but I’d but at least inclined to call it a trawler. Re the OB power I’d say hull bottom aft and speed range says much more about trawlerness than OB or not. But not many OB boats will have heavyness in their soec’s.

But here on the forum I can (or you can) talk about a specific boat repeatedly and use the word trawler. Few will call me out and many more will think badly about me and think of me as a horses ass.

But speed I think shoots more boats out of the trawler name that anything else IMO. If it planes it’s not a trawler IMO. But many will disagree … mostly those w boats that look like a trawler but know their not .. because they plane. And planing boats are not heavy.

Don’t misunderstand me. I’m not saying weight is a virtue by itself. Weight used wisely is great but just plain heavy is almost always sinful IMO. But in a lumpy sea weight does a lot for comfort. But I know of no boat where weight serves that purpose intentionally. That is just adding weight cuz less people complain.

What if I was to design and build a boat that tic’ed all the boxes of trawler but had a planing hull. I still wouldn’t call it a trawler.
 
Hey Scoby5959,
Great outlook for a young man but we’re mostly old here. Not complaining at all tho as I love to see things like this.

Where’s “Ocean Park”?
 
Scooby5959 said:
I thought of this many many times, I have bought and sold a lot of boats over the years ,I will find a Boat that needs work keep it and use it for a while and move onto the next one , I run into great deals all of the time ,there is a 36 foot sailboat down at the port close to where I live , been sitting for at least five years a little rot in it here and there the interior is a little rough it’s has a like new inboard diesel engine in it that would be great, Everything you need inside birth head galley , everything including Some old electronics, I could buy this boat from the port or $50 but it Has to be moved , Shorten and modify the Keel , Strip the rigging , leaving a winch or two that might help you out down the road,Build a small pilot house , plywood and two by fours whatever ,clean up the fuel tank filters oil , head off to Alaska for a summer of your lifetime ,Total investment thousand bucks you could probably sell it for five when you’re done with it
Click to expand...

I love these projects! Reminds me of high school kids working on cars in the backyard.. Not especially "mechanic approved" but just some creative peeps fixing up something and having a ball and learning a bunch of stuff like life skills in the process.
Just because its not ABYC or whatever approved doesn'tmean it can't be done and have some real fun with it..... I have "rat rodded" many boats in both my youth and adulthood that wouldn't be politically correct in front of the local yacht club crowd but had lots of fun...
 
No young but I wish I was

Nomad Willy said:
Hey Scoby5959,
Great outlook for a young man but we’re mostly old here. Not complaining at all tho as I love to see things like this.

Where’s “Ocean Park”?
Click to expand...

We’ve talked a couple of times or communicated ,I guess on craigslist when you had your Willard for sale ,I’m assuming you sold it ,always wanted a Willard but I decided to back off on your boat once I realized how attached You were too that boat I didn’t wanna beat you up trying to buy form you. Like I said always wanted a Willard but I haven’t found one I could steal yet ,I have a trailer I could’ve put it on but there are plenty other boats ,I hope you don’t miss it too much or you’ll be looking for another one,Ocean Park is part of the Long Beach Peninsula , southwest Washington coast close to Port of Ilwaco ,a rather significant Coast guard Station Cape disappointment etc.
 
Some on here have said you can call anything you want a trawler.

I'd think what's most important is what do you want to do with it when done. 21' is awfully small. Putter around sheltered water, 1 or 2 people. Head, galley, and sleeping area. I'm guessing outboard powered. Not much room for enclosed steering.

What will you end up with that you don't have or can't do now ?? Other than no sails I don't see any advantage. But still you can always do it for the doing of it...
 
Solly said:
Some on here have said you can call anything you want a trawler.

I'd think what's most important is what do you want to do with it when done. 21' is awfully small. Putter around sheltered water, 1 or 2 people. Head, galley, and sleeping area. I'm guessing outboard powered. Not much room for enclosed steering.

What will you end up with that you don't have or can't do now ?? Other than no sails I don't see any advantage. But still you can always do it for the doing of it...
Click to expand...

I think a lot of the attraction of these conversions is because you can get a hull and maybe an engine for free or close to it. I don't believe they are "Trawlers" but still folks have fun with them..
 
Deep Sea,
I've seen it done, was really impressed. Wish I had taken pics. It was a converted high performance daysailer, a mini sled. Cuddy cabin stock, big bimini built aft. 9.9 Johnson would push it faster than my boat. Shallow draft, could stick it in places my boat could never go.

Go for it. Keep it simple and light.
 
Nomad Willy said:
A bit offensive re the bathtub Simi.

.
Click to expand...

To who - the bathtub?
I was not referring to the op's vessel as a bathtub, I was referencing an actual bathtub ;)
I could have used a ski boat or an inflatable boat in the same analogy.
 
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