Pietenpol-List: Building a Scimitar Prop
Posted: Wed Mar 07, 2007 10:19 pm
Original Posted By: "Douwe Blumberg"
Subject: Pietenpol-List: Building a Scimitar PropIn a message dated 3/7/2007 7:31:56 PM Central Standard Time, ggower_99(at)yahoo.com writes:Hello Chuck,I will love to learn carve a scimitar prop also, some day, I will appreciate any lead for info on carving one... Dificult to find this type of info...Please post as you learn... I carved almost all my props, only bought one for one ultralight years ago (IVO) not a great prop...SaludosGary Gower.Hey Gary,The very best information I have on the Scimitar Prop, is a few short paragraph's, and a few sketches, from the book by Eric Clutton, called 'PROPELLERMAKING for the AMATEUR'. I've got the clamps, and the wood for the jig required,and I'm looking around for prices of a stack of 24 birch planks, measuring 1/4" thick, 3 1/2" wide, quarter sawn, and 7 feet long. It's basically the method to get the extreme curves in the wood, to make the Scimitar. I'm thinking of steaming the 1/4" planks and pre-bending them, before gluing the stack together. Then place maybe five planks at a time in the jig, clamp it down with Resorcinol Glue, then clamping down the next seriesof planks with glue, and so on with each stack till it's about 6" across, which is the width of the hub of the prop. I think this stuff works better underclamping pressure. I use T88 exclusively, but I don't think it would work in this application, because you're not supposed to clamp it very tightly, but then if it had a layer of Scrim Cloth, it would maintain the bond line to at least .002". But then this bond line would probably be much more prevalent thanif it was Resorcinal Glue. After it's all glued up, I'll use the plan view of the prop that I have drawn on the top of the flat, straight, steel top table that I use to build props on. I make a templet for each 6" station of the blade of the prop. Planethe for and aft faces of the prop hub so they are parallel with each other, and use a carpenters square to check the plan form of the wood, against the sketch on the table. Then it's just a matter of whittling away everything thatdoesn't look like a Scimitar Propeller !! For the Continental A65, I'm going tostart out with a 74 X 44...maybe even 46 This is certainly a time consuming and learning process, so I'll have to see what works. I've already started a video of the beginnings of the planning process. In the correspondence I had with Eric, it wasn't in his book, but he mentioned it might be better to use a kind of face plate (about 1/4" thick) onthe forward and aft hub area of the prop, so the clamping pressure wouldn't be against the edges of the 1/4" planks. If it is successful, I'm going to build a Scimitar for the 150 hp Tailwind. Steve Wittman was obviously very much into the Scimitar design, as youcan see on the back wall of his hanger at Pioneer Field in Oshkosh.Chuck G.NX770CG************************************** AOL now offers free email to everyone. Find out more about what's free from AOL at http://www.aol.com.________________________________________________________________________________
Subject: Pietenpol-List: Building a Scimitar PropIn a message dated 3/7/2007 7:31:56 PM Central Standard Time, ggower_99(at)yahoo.com writes:Hello Chuck,I will love to learn carve a scimitar prop also, some day, I will appreciate any lead for info on carving one... Dificult to find this type of info...Please post as you learn... I carved almost all my props, only bought one for one ultralight years ago (IVO) not a great prop...SaludosGary Gower.Hey Gary,The very best information I have on the Scimitar Prop, is a few short paragraph's, and a few sketches, from the book by Eric Clutton, called 'PROPELLERMAKING for the AMATEUR'. I've got the clamps, and the wood for the jig required,and I'm looking around for prices of a stack of 24 birch planks, measuring 1/4" thick, 3 1/2" wide, quarter sawn, and 7 feet long. It's basically the method to get the extreme curves in the wood, to make the Scimitar. I'm thinking of steaming the 1/4" planks and pre-bending them, before gluing the stack together. Then place maybe five planks at a time in the jig, clamp it down with Resorcinol Glue, then clamping down the next seriesof planks with glue, and so on with each stack till it's about 6" across, which is the width of the hub of the prop. I think this stuff works better underclamping pressure. I use T88 exclusively, but I don't think it would work in this application, because you're not supposed to clamp it very tightly, but then if it had a layer of Scrim Cloth, it would maintain the bond line to at least .002". But then this bond line would probably be much more prevalent thanif it was Resorcinal Glue. After it's all glued up, I'll use the plan view of the prop that I have drawn on the top of the flat, straight, steel top table that I use to build props on. I make a templet for each 6" station of the blade of the prop. Planethe for and aft faces of the prop hub so they are parallel with each other, and use a carpenters square to check the plan form of the wood, against the sketch on the table. Then it's just a matter of whittling away everything thatdoesn't look like a Scimitar Propeller !! For the Continental A65, I'm going tostart out with a 74 X 44...maybe even 46 This is certainly a time consuming and learning process, so I'll have to see what works. I've already started a video of the beginnings of the planning process. In the correspondence I had with Eric, it wasn't in his book, but he mentioned it might be better to use a kind of face plate (about 1/4" thick) onthe forward and aft hub area of the prop, so the clamping pressure wouldn't be against the edges of the 1/4" planks. If it is successful, I'm going to build a Scimitar for the 150 hp Tailwind. Steve Wittman was obviously very much into the Scimitar design, as youcan see on the back wall of his hanger at Pioneer Field in Oshkosh.Chuck G.NX770CG************************************** AOL now offers free email to everyone. Find out more about what's free from AOL at http://www.aol.com.________________________________________________________________________________