Tom Thumb 24

1983
Designer
Grahame Shannon
Builders
?
Associations
?
# Built
?
Hull Type
Long Keel
Construction
Steel/ALU

Dimensions

Length Overall
23 9 / 7.3 m
Waterline Length
22 0 / 6.7 m
Beam
9 6 / 2.9 m
Draft
4 0 / 1.2 m
Displacement
7,900 lbs / 3,583 kg
Ballast
3,000 lbs / 1,360 kg

Rig and Sails

Type
Gaffhead Sloop
Reported Sail Area
350 ft2 / 32.5 m2
Total Sail Area
?
Mainsail
Sail Area
?
P
?
E
?
Mast Height
?
Foresail
Sail Area
?
I
?
J
?
Forestay Length
?

Auxilary Power

Make
?
Model
?
HP
?
Fuel Type
?
Fuel Capacity
?

Accomodations

Water Capacity
?
Holding Tank Capacity
?
Headroom
6 0 / 1.8 m

Calculations

Hull Speed
6.29 knots
Sail Area/Displacement
14.12
under powered
Ballast/Displacement
3.8
less stiff, less powerful
Displacement/Length
331.22
heavy
Comfort Ratio
26.81
coastal cruiser
Capsize Screening
1.91
better suited for ocean passages

Notes

From BlueWaterBoats.org:

The Tom Thumb 24, designed by Grahame Shannon sits at the extreme for steel boat designs. At 24 feet of length this little boat by conventional standards would be too heavy to work, but Shannon shed weight with clever use of steel as a skin over a frameless interior, stiffened by only interior furnishings much like the interior lining in modern fiberglass designs. And so the wee Tom Thumb 24 makes an appearance as the smallest of steel go anywhere cruisers.

She’s a sturdy little boat and capable at sea. In spite of her short hull, heavy displacement and wide beam, the Tom Thumb 24 has a reputation for surprising speed. She can easily surpass her theoretical maximum hull speed of 6.2 knots, can point reasonably well, and thanks to her weight her motion remains comfortable.

Interior space has been described as “roomy”, owners under 6 feet in height will have standing headroom.

Many have been built worldwide, quite economically, by amateur boatbuilders. As with the nature of home build projects you can expect interesting variations between boats. The design has enjoyed unexpected success and has inspired a range of siblings including the Tom Thumb 26, 28, 305 and 330. They can be built in multi-chine steel or aluminium. Plans and kits are available from Bruce Roberts Yacht Design.

Comments from the Designer

I designed the Tom Thumb 24 in about 1983 as a bit of a joke. I had designed other steel boats and used to get a lot of people asking “why are there no small steel boat plans?”. I used to give the standard answers (too heavy, can’t make the plating thin enough without distortion, etc.). Then I had the idea that if we designed her like a GRP boat with a monocoque hull, frameless, using interior plywood furniture as stiffening, that the weight would be within reason. After a few calculations, I saw that this would work.

I thought “Let’s give them what they want” and drew up a list of requirements, including full keel, bowsprit, standing headroom, and inboard diesel, with a “shippy” look.

I drew up the plans over about 8 weeks with assistance from John Woods, who also had worked for Bruce Roberts when I did. Then I placed an advert in Cruising World offering plans for $99 with a small line drawing. Response was amazing and within a year we had sold 300+ sets of plans. Then I sold the rights to Bruce Roberts, and he has sold many hundreds more, I don’t know how many exactly. He also designed the similar Tom Thumb 26 based on the 24.

I designed other frameless steel boats, notably the Amazon 29 and the Opal 28, neither of which came anywhere near the 24 in popularity. In fact until I designed the Walker Bay 8 dinghy, the Tom Thumb 24 outnumbered all of my other designs put together in terms of boats built.

Not only did the plans sell better than expected, the boats turned out well and we received many reports of her good sailing characteristics.”

» The Tom Thumb 24 on the official Bruce Roberts website
» Furled Sails audio webcast, an interview with designer Grahame Shannon [Tom Thumb mentioned 30:00-31:50mins].
» Rainbow Chaser, owner blog.

Credits

Thanks goes to Tony Fountain (co-writing and research), and also designer Grahame Shannon (designer comments used under permission). Additional owner feedback from Bruno Caroit. Use of line drawings kindly granted by Bruce Roberts.


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