Ready for some serious carving? Here we go! For this prop I used a prop block which I laminated from dyed and undyed wood. This gives me a nice pattern, but also gives handy reference lines on the prop blades which can help in cutting a symmetrical prop. If you use a solid block for carving you can skip step 1 and 2, but for drilling the hole for the propshaft the use of a pillar drill is recommended.
Step 1: I cut 7 layers to make the prop block, marked the center and drilled a hole for the prop shaft. For drilling you can use a simple hand drill, a pillar drill is not needed. I dyed half of the parts to accentuate the layers. The dye does not penetrate the balsa, so all this will do is creating a dark line between the layers. To get a prop with alternating layers of dark and light wood you need to use dark and light wood.
Step 2: I glued the stack together. Not shown in the picture is the long pin I used to line up the holes. This pin also was used to check if the prop axle was perpendicular so the finished prop wouldn't wobble. For gluing I used water based glue which gives enough time to readjust the layers.
Step 3: I used a saw to shape the blank. Notice that the dye didn't penetrate very well.
Step 4: Using a knife I tapered the tips to the required thickness. To get the correct pitch distribution the block is thick and narrow near the hub and thin and wide near the tip. The shape of the block provides a guide to get this pitch distribution. Connect the opposing edges of the block by carving away on the bottom. Continue carving until there is a flat line between those edges.
Step 5: The back of the prop is carved. Your experience in carving and the sharpness of the tools determine how far you can go in carving. At a certain point it is better to continue with sandpaper to get a smooth shape.
Watch out for the grain direction while carving. The upper part of the prop must be carved from the hub towards the tip, the lower part must be carved the other way.
Step 6: The front is still left as it was. Here is a picture of the tip of the prop. Note that the back of the blade is slightly undercambered.
Step 7: Now the front of the blade is carved. First do the trailing edge of the blade and carve the rear part of the blade as thin as sensible.
Step 8: The front of the blade. The rear part of the profile is OK now, but now the front has to be carved to get the thickest part of the profile at 30% of the chord. It can be handy to draw a pencil line at the required place.
Step 9: The tip is rounded and the rear portion of the hub area is cut away.
Step 10: The front is smoothened to get a nice profile. The carving is finished. Time to sit back and admire the beautifull curves. Apply a few coats of dope to protect and strengthen the prop.
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