Water Sprite (oz15241)


Water Sprite (oz15241) by PMH Lewis 1938 - plan thumbnail

About this Plan

Water Sprite. Free flight seaplane model, for twin rubber power. Wingspan 50 in.

Note this is a low resolution plan, it has been enlarged up to full size 50 in wingspan from a very faint 10 x 6 reprint. This is all we have, at the moment. If anyone out there can send us in a clearer scan, that would be excellent.

Direct submission to Outerzone.

Quote: "Hi, The attached plan and pics are for the Water Sprite rubber powered flying boat. The green one [pic 003] is a 3/4 scale version which I built first. It flew quite well but suffered from motor bunching problems which led to it's demise. The cause of this was I think because the the rear of the nacelles were too narrow on the scaled down version also as you can see I used gizmo geezer props instead of handed ones.

The silver one [main pic] is fullsize, and flies well although unsurprisingly it does not have much of a glide.

The green biplane flying boat [pics 004-007] was built from the remains of 3/4 scale Watersprite and the wing and truncated (and duplicated) fuselage of a Veron Fledgling. I don't have a plan, but I think there's enough information to have a go at building one. It flies well under power but with the built in headwind glides like proverbial 'bag of spanners'. Have fun, Andy Snelson"

Update 9/5/2024: Added original article, thanks to Andy Snelson. This is an extract from the Book 'Models for Flying' see details below. Also alternate plan scan, still low res, now in greyscale.

Quote: "Hi Steve, With the help of two of my fellow SAM 35 members I have managed to get hold of a copy (attached) of a chapter from a book called "Models for Flying" by Rippon and Sparey. This chapter gives detailed building instructions for the Watersprite and is almost certainly where the plan I sent you came from. Incidentally I think this version of the plan is a bit clearer (what do you think). I have ordered a copy of the book and will keep you posted if there is any more relevant info.

THE obstacles that surround the successful design and operation of model flying boats are peculiar to this type of craft. These problems centre mainly around the take-off, as the drag of the water makes it difficult for sufficient speed to be attained to allow the model to rise into the air.

Large power and high initial thrust are the requirements, but the large amount necessary to propel the machine on the water may become a problem when the areoplane is actually in the air. The craft may be hopelessly over-powered when in free flight.

It seems that a high powered yet light machine is required a situation calling for considerable modification of the usual model aeroplane line-up. There is difficulty, also, in building a light aeroplane, when a large, floating hull, wing-floats, and high power are required.

The flying boat 'Water Sprite' built by Mr PMH Lewis, and holder of the British Rise-off-Water record, forms a good example of how these problems may be met. The control of power, when in flight, is achieved by an extensive use of downthrust - as much as 10° being used. Directional control is aided by the use of sidethrust as directional stability tends to be bad when such a machine is moving on the water. It seems that success may best be approached by a somewhat excessive use of all those 'safety devices' so common in the more usual types of model aircraft.

These general observations are well exemplified by the machine under consideration. It is of all-balsa construction, on orthodox and simple lines. The result, nevertheless, is a very graceful and efficient craft.

The intending constructor is advised to obtain a full-sized blueprint of the machine. The illustration in Fig.164 is a very small reproduction of the print available, and it will be noticed that all the instructions necessary for a successful job are given.

Hull: It is advisable to begin the construction of the hull, or fuselage, first, by building two flat and identical sides upon the drawing. It will be necessary to bend the longerons to shape, by soaking or steaming the in. square section balsa. The two similar longerons - one for each side - should be bent together, by binding the two lengths of balsa side-by-side, and bending in one operation. This will ensure uniformity. It will be seen that certain members of the fuselage call for hard balsa, while others are of soft balsa; and the specification should be adhered to, as there is a considerable difference in the weight of the two varieties.

When the two sides have been completed, they may be joined by the cross-members, the stringers added, and the celluloid cabin windows cemented in place. The small 18 swg wire wing-fixing hooks should not be overlooked.

To aid a speedy transit over the surface of the water, a step is formed in the bottom of the hull. This is done by means of a stringer, cemented over triangular, balsa formers; a system which is continued behind the step to the rear end of the hull. The sturdy, built-up nose should guard against damage from collision.

Wing: This is composed of two half wings joined by a centre section to make the wing one unit. This was considered a more suitable method than that of plugging two half wings into the fuselage, especially as the wing carries the nacelles containing the rubber motors and propellers. A plug-in system, strong enough for the purpose, might easily have added a considerable amount of weight.

Wing construction needs little description, as it follows general lines, but warren bracing for some distance between the main spars makes it somewhat sturdier than usual..."

Supplementary file notes

Alternate plan (greyscale).
Bitsa biplane notes.


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Water Sprite (oz15241) by PMH Lewis 1938 - model pic

  • (oz15241)
    Water Sprite
    by PMH Lewis
    50in span
    Rubber F/F Floatplane Multi
    clean :)
    formers unchecked
    got article :)
  • Submitted: 14/04/2024
    Filesize: 413KB
    Format: • PDFbitmap
    Credit*: AndySnelson
    Downloads: 207

Water Sprite (oz15241) by PMH Lewis 1938 - pic 003.jpg
Water Sprite (oz15241) by PMH Lewis 1938 - pic 004.jpg
Water Sprite (oz15241) by PMH Lewis 1938 - pic 005.jpg
Water Sprite (oz15241) by PMH Lewis 1938 - pic 006.jpg
Water Sprite (oz15241) by PMH Lewis 1938 - pic 007.jpg

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  • Plan File Filesize: 413KB Filename: Water_Sprite_oz15241.pdf
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  • Supplement Filesize: 1051KB Filename: Water_Sprite_oz15241_article.pdf
  • Supplement Filesize: 34KB Filename: Water_Sprite_oz15241_bitsa_biplane_notes.pdf
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* Credit field

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This model plan (like all plans on Outerzone) is supposedly scaled correctly and supposedly will print out nicely at the right size. But that doesn't always happen. If you are about to start building a model plane using this free plan, you are strongly advised to check the scaling very, very carefully before cutting any balsa wood.


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