Dead Confederates, A Civil War Era Blog

Blanket Boats

Posted in Uncategorized by Andy Hall on August 26, 2010

Bloggers sometimes follow a meandering, free-association path in their posting — I do, anyway. Case in point: Craig Swain of To the Sound of the Guns blog commented on this post of mine, which led me to read this post on his blog, which in turn led me to poke around the Library of Congress image holdings related to Civil War artillery, which in turn led me to this image (above), captioned as “raft of blanket boats ferrying field artillery and soldiers across the Potomac River.” The term “blanket boat” was new to me so that, in turn, led to further digging.

None other than Herman Haupt (via Google Books) does the knowledge:

In connection with the subject of boats and bridges, it is proper to describe a very simple, practical, and highly useful plan, for crossing streams by means of boats, constructed of a single rubber blanket, capable of carrying a soldier, knapsack, arms, and accoutrements, with only 4 inches of displacement. The size of some of the ordinary blankets is 6 feet long, and 4 feet 9 inches wide, but 7 feet by 5 feet would be preferable. If the height of the boat be made 1 foot, the length will be 4 feet, and the width 2 feet 9 inches, so as to be completely covered by the blanket. The frame may be made of round sticks, 1 inch and 1½ inch in diameter, in the following manner. . . .

One of these boats having a horizontal area of 11 square feet, would require 687 pounds to sink it 1 foot, and the average weight of a man would displace less than 4 inches.

In using these boats, it will be convenient to lash several together, side by side, upon which soldiers can be transported; the float can be paddled, or a rope may be stretched across, supported by floats, and the men can pull themselves across.

If used for cavalry, some of the men can hold the bridles of the horses, while the others can pull, paddle, or pole across the stream, the saddles being placed in the boats.

The frames are abandoned, or used for fuel, when the army has crossed over.

Several of these boats lashed together, and covered with poles, would form a raft, on which wagons could be carried over; but for artillery, rafts of wagon-bodies, or something possessing greater powers of flotation, should be employed.

Where the timber is of large size, and round sticks for making the boat-frames cannot be procured, the material may be obtained by splitting large straight-grained timber; and it is even preferable to the round sticks. . . .

Ferry of Blanket Boats. —  A ferry may be made of blanket boats in the following manner:

Rafts are formed by lashing together a number of boats, and covering them with boards, or poles, if boards cannot be procured. Twenty-five boats would make a raft 14 feet wide and 20 feet long, with power of flotation at 6 inches immersion of over 8,000 lbs; fifty men could easily be carried in one of these rafts, with guns and knapsacks.

Two ropes are stretched across the river, and the men on the rafts pull themselves over rapidly, hand over hand, one rope being used for the loaded rafts, and the other to return the empty ones.

The rafts can follow each other in rapid succession, leaving intervals not exceeding the length of a raft.

The whole number of rafts should be three times as many as would make a train reaching entirely across the stream, with the proper intervals. This will allow a reserve sufficient to insure a constant stream going and returning.

If the stream should be 600 feet wide, the number of rafts would be forty-five; the number crossing at one time loaded would be fifteen. At a rate of movement of 2 miles per hour, the time required to cross would be about 4 minutes; and the number of men thrown across in one hour, would be about 10,000. The forty-five rafts would require 1,125 boats which could be made by a single regiment of instructed engineer troops in an hour, if materials had been previously prepared.

One of these blanket boats would weigh less than fifty pounds; a man could carry one for a distance of several miles without inconvenience; and with the help of 1,000 feet of rope, a corps of ten thousand men could approach a stream at a point where the enemy did not anticipate any attempt at crossing, and, in two hours, could be landed on the opposite side, ready for an advance, leaving a body of engineer troops to prepare for the possible contingency of a retreat, by constructing pontoon or trestle bridges, if necessary. Even in retreat, the rafts would afford great facilities for crossing, if covered by good batteries on the shore; but without bridges, it would be difficult to save the artillery.

Where surprises are to be attempted, such facilities for crossing large streams, without designating the point by previous preparations, would prove invaluable.

They might prove very useful in cavalry expeditions, to operate against the communications of an enemy.

If the material for the frames of the blanket boats should be transported in wagons, they would, in that case, be prepared in advance, of dry lumber, and the materials for one frame would weigh but fifteen pounds. An ordinary wagon would carry material enough for two hundred boats.

Haupt’s description strikes me as hopelessly optimistic as to how quickly and easily these DIY boats could be assembled and deployed by an army in the field, but the principle is sound enough. The raft shown above employs 30 boats which, if they match Haupt’s standard measurements, would have a lifting capacity of 10,305 lbs. at six inches’ immersion.

So — how often were blanket boats used in actual operations? Did they ever develop much beyond the testing phase, as seems to be the case in the photo?