Guest Post: A 21 foot Shanty Trawler – Inexpensive and Easy to Build

Most of my life I’ve been a sailboat guy and have owned several sailboats ranging in size from 21 to 25 feet. When the wind did not cooperate, I was always content to simply motor along at about 5 mph. It doesn’t take much power to move a sailboat hull through the water at that speed. I never used an outboard larger than 5 hp. Recently, I gave up sailing and switched to power. But I’m still perfectly content to move along at a slow, enjoyable speed.

The boat that I would really like to have would be an inexpensive, mini trawler, that would have a little cabin, look unique and could be powered by a small outboard. It was no surprise to my friends when I decided to design and build exactly what I wanted. What was a surprise, was that I would start with an old 21 foot sailboat and convert it into my new mini trawler! The sailboat I chose was an abandoned, 1973 MacGregor 21 footer, with a 400 lb swing keel. The fiberglass hull was solid but the deck of the boat had been damaged and repaired many times.

Why start with a sailboat?

1. In the first place, I’m no “boat builder”. The thought of designing and building a hull was way beyond my capability. So, I’m using the fiberglass sailboat hull as is, just going to give it a new paint job.

2. As I said before, sailboat hulls can be pushed along with very, very little power. So, the boat will be economical to operate, even if I take it on extended adventures. I intend to use my existing 6 hp, extra long shaft, 4 stroke outboard.

3. Sailboats of this size typically come with a small cabin, with molded in bunks for sleeping, plus room for some storage, cooking and a portapotti. My design uses the cabin as is. I plan to build a wooden “false” top over the existing cabin to give the boat an old fashion look. I want it to look like a boat from a hundred years ago.

4. The swing keel (400 lbs in this case) is designed to keep the boat upright even when strong winds are hitting the sails and trying their best to tip the boat over. This amount of ballast will keep my little trawler stable and up right even after my construction adds considerable weight above the waterline. Being a swing type keel, the boat draws less than 12 inches when the keel is in the up position.

5. Sailboats like the MacGregor 21 were very popular in the 1970’s and 1980’s. There were a zillion made and they were all trailerable and easy to launch. Most of them today have been sitting unused in someone’s back yard for many years and can be bought, trailer and all, for a few hundred dollars. I paid $500 for mine and figured most of that cost was for the trailer. So, a sailboat like this gives you an inexpensive way to start with a good hull, an enclosed cabin and a trailer.

6. The aft one third of these boats is always an open, self draining cockpit, with seats molded in along both sides. Over this area, I plan to build a canopy top with plenty of standup headroom. The forward 4 feet of this area will be partially enclosed with sides and a front panel with windows. The rest of it will be open. I plan to steer the boat with a tiller, while standing in the open area. If the weather is bad, I could move forward and steer where the side panels are, with the use of a tiller extension.

The false top and the canopy will all be constructed from exterior plywood, painted with top quality latex paint. The new deck will be covered with pressure treated boards, stained to the color I want. The windows will be plexiglass. The rudder will be removed and replaced with an outboard motor mount.

I’ve already stripped off all the un-needed sailboat stuff. I hope to sell the unused mast, boom, sails and rudder on CraigsList. I’ve patched holes in the deck so water can’t get in. I pressured washed the hull and plan to sand it lightly before painting it. If all goes well, I hope to have all the exterior completed in a couple of months. Then, I’ll turn my attention to the interior of the cabin.

If this boat turns out well, I might build a few more to sell. I would call the boats RetroCruisers and my business would be Xsail Boatworks. But for now, I’m finalizing design details and getting ready for construction .


Rod Edens



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Originally posted 2012-12-11 19:39:18.

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  1. I would very strongly advise to move the cabin forward over the center of the boat. I have built one and the sketch you drew is the same as the original that I started with. When in the water the boat will not track as it pivots on the stern. When it is in sailing mode the weight of the wind on the sail pushes the bow down and lifts the stern. I was advised to do what you have done against my better judgement with disastrous results. My boat can be seen on in the older posts. Cheerrs Iggle

  2. Iggles blog is fascinating – it looks, however, that the boats he’s referring to are much smaller and lighter.

  3. Interesting comments. I’m confident as I move forward. (By the way, I hope to post my second installment in a day or two – with pictures and a progress report.)

    I’ve motored along many times, many miles in a swing keel sailboat this size. I’ve owned four over the years and used them a lot. When motoring, the sails would be down of course. So, there was no force on the sails at all. The boats always moved along in a very level position. I never experienced any tracking trouble. None.

    The swing keel almost insures good tracking. In the case of the MacGregor 21, the swing keel is about 6 feet long, 12 inches wide and 4 inches thick. When motoring it is kept in the raised position. In the raised position, it is horizontal, but extends about 6 inches below the bottom of the hull. So it becomes 6 foot long, 6 inch deep keel running lengthwise under the center of the hull. That’s a lot of tracking keel! Much larger and more effective than any you would find on power boats.

    So, I’m optimistic and working away. Keep the comments coming.

    Rod Edens

    • Here is something else I meant to add to my last posting. I’ve estimated the net weight I’ll be adding to the boat at 300 pounds. That’s only the equivalent of a couple of people. And, the design will split this weight almost equally between the front half of the boat and the rear half. So, I’m not expecting the added weight to cause any bow or stern dipping.

      Rod Edens

      • It may be the type of hull I have used and it tracks worse with the keel down. The weight of the cabin is small about the weight of the sails and spars and rigging. I have to admit the sails are higher with a greater leverage and this is not the trouble. The concept is great with the low amount of money spent. I am in the process of changing the propeller as I was advised to use a power prop, I am now going for maximum pitch and diameter Iggle

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