By Story and photos by Paul Adams, EAA Chapter 675 President
In the title you may notice two things. First, the word “BIG,” and second, “Part 1.” Well, these two comments are related. This is the first of a three-part set of articles on the making of a propeller, a “BIG” propeller. The story starts with “I did it again.” The event I’m referring to was back about a year ago. We were at Oshkosh at the Weeks Hangar working on the Allison engine stand project. We were discussing the propeller need for the Allison, and I jokingly said, “I make propellers. I’ll make one for the Allison.” The key word was “jokingly.” Now fast forward to the end of the Allison project when we were discussing with the boss, John Hopkins [EAA’s aircraft maintenance manager], the need for another project, and John said there was work that needed to be done on the EAA Pheasant biplane.
The Pheasant was damaged in a windstorm during AirVenture 2022. We walked over to see what needed to be done, and there sat on a shelf among other bent or broken parts a propeller, a “BIG” propeller.
John, who must have a memory like a steel bear trap, said, “Paul, you make propellers, how about making one for the Pheasant.” I said, “Sure” without putting much thought into it, and now here we are writing about the project. The first thing that really brought this project into perspective was when I made a full-size cardboard pattern from the half of a propeller that we had brought home from Oshkosh which we planned to use as a pattern in Dave McCurry’s duplicator. It’s a “BIG” propeller.
The second thing that helped bring home the magnitude of the project was the scimitar shape of this “BIG CURVY” propeller. For example, it didn’t fit in Dave’s duplicator‼
We love a challenge, so after redefining the project, we got started. First was buying the wood. John wanted mahogany, so after an unsuccessful trip by me and Dave to Menards, I called Liberty Woods in Des Moines. After recovering from the shock of being quoted $1,400 for mahogany, I called Bruce Grumstrup. Oh, by the way, did I forget to mention I told boss John we could make the prop for a material cost of under $1,000? Props of this size purchased on the prop market range from $9,000 to $15,000. Bruce and I discussed wood alternatives, and he got a quote from Liberty for enough cherry, the same wood Dave uses and a wood that is good for props, for $471. So, off to Des Moines to bring home to Bruce’s shop the load of cherry wood.
Does that look like a lot of wood for a prop? It is‼ But it is a “BIG SCIMITAR” prop. We needed six planks, 18 1/2 inches wide and 103 inches long with a finished thickness of 11/16 inches since the hub area is 4 1/8 inches thick. Did I say “BIG” and SCIMITAR”! Now the glue. We bought a one-gallon kit of resorcinol epoxy from Aircraft Spruce. Ready to make what I refer to as the “BIG” cherry prop billet. We also tested the resorcinol since it was our first time using this epoxy extensively. Tough stuff! And it’s waterproof, which we found easy to use with water cleanup. Here is the result of our test. No glue line breakage, only wood! Ready to go.
Thank goodness for Bruce’s great workshop and lots of clamps. First, we glued boards together to obtain the 18 1/2-inch width. Some trimming and joiner work had to be done for a wood weight loss of 78 pounds, i.e. scrap! Then we had to plane each plank to the 11/16-inch thickness. Good news, Bruce knew someone who had a 22-inch-wide planer here in Marshalltown within a mile of his house. Thanks, Scott Bauder! Did I mention that this project was going to make a lot of chips! That is 36 pounds worth of compacted chips from planing, and that’s just the start of the chip making!
Each plank was cut to a rough shape. More weight loss. Down to a billet weight of 75 pounds out of the original 271 pounds of wood, more scrap.
Next was the bonding of the six roughed out planks with the resorcinol epoxy to make the billet. Ending weight of the billet was 75 pounds and even heavy to carry. Ready to carve. But no duplicator. The manufacture of a new duplicator is the subject of Part 2, coming next week.