CRAFTSMAN S CORNER

Author's Note: I would like to thank Casimer Porowski, 725 Maple Ridge Rd., Milford, OH 45150 for his idea for a propeller carving jig and templates. Casimer has some members of EAA Chapter 174 (Cincinnati) who are interested in propeller making and he came up with a method that works well. It also takes the guesswork out of carving the blade section. The side view shows the templates that are used. The prop laminations are stacked on a metal beam that is used to ensure the templates are level and centered properly. Although the drawing shows a template only for the top side, it is possible also to prepare a similar template for the bottom and turn the propeller over for that. You can make a template by using the drawing of the section and pasting it on sheet metal, then cutting out the template. Locate the section template on the carving beam using one template section at a time. Start from the tip end and work to the hub. The prop blank is held on the base by the center bolt and tip centering base. The saw can be run by an air

motor or die grinder. After the cuts are made on both sides, the carving can begin. The carving can be done by a draw knife, finished with a draw blade and sanded to the bottom of the cut on the blade. The saw itself is held in place on the template by a groove made up of washers attached to the side of the saw arbor. The template is made of .032 to .060 sheet. Care should be taken to ensure that the centerline or "stacking points" of all sections is the same and that the centering post on the tip intersects the center of this "stacking point." It will be necessary to trim the rough wood so that the templates can fit in and excess material can also be removed from the laminations. After cutting the station, start carving at the heavy stations first. The principal of the saw cuts is that the distance from the guide on the saw to the propeller surface is the same as distance "A" shown on the template drawing. The designer can make as many templates and profiling cuts as is necessary. The designer used information from Aircraft Propeller Design by

Template Side View

3.00

Ben Owen

Fred Weick, who designed his propeller. EAA also has a manual titled "Propeller Making For The Amateur" by Eric Glutton (new, revised) for $7.00 plus $2.50 for mailing. The bottom template may not be totally necessary for simple flat bottom sections but for special airfoil sections it is recommended that the bottom templates also be used.

Propeller Bottom Surface Template Hub > Bor»

Washers Provide i Groove

Stacking Point of Sections

SPORT AVIATION 77