Brodhead Pietenpol Association

Original Posted By: John Greenlee
Subject: Pietenpol-List: New guy with fir/spruce question.>Hi Folks,>>I'm new around here, so get ready for a lot of questions. First of all, abig>"two thumbs up" to Steve Eldredge and Richard DeCosta for maitaining and>archiving this list. Both look like tremendous, invaluable resources.>>Next, a quick background check: I bought the "Improved Air Camper" plansfrom>Orrin Hoopman and joined the BPA nearly a decade ago, shortly after meeting>Dick Alkire and Howard Henderson at an airshow in Dayton, OH. I wasfinishing>college and starting grad school at the time (i.e., quite poor) so the woodand>tools I purchased for this project were diverted to a less ambitous wooden>boat. 5 boats later, I have more resources to draw from, and I have>enthusiastically returned to this project. I've been researching for a few>months now, I've acquired a 110 hp Corvair motor, and I've ripped andplaned>cap strips. Building rib jig this weekend.>>OK, let's start with materials. I have located a local source ofbreathtaking>Douglas Fir T&G deck planking that was recovered, unused, from an old>shipyard. Some planks are quarter sawn with hardly a single graindeviation>over 14' of 3/4" x 4" wood, all for about a buck/lineal foot. I've donesome>stress tests which show that it is abot 20% stronger than Sitka Spruce fromthe>same source, but I'm concerned about the added weight. I spoke recentlywith>Howard Henderson who says that he used primarily fir throughout his ship>(spruce tail to maintain CG), but he reduced most cross-sectionaldimensions by>25%. Seems to have worked out quite nicely.>>Questions:>Are there others out there who have done this?>How has the W&B turned out?>What do you think about laminating spars from this material (since they'rea>bit less than 4" across)?>If you approve of laminated Fir spars, would you reduce thickness from the>standard 3/4" spruce spar? (5/8" sounds thin to me).>Any references to documents with extensive comparisons of these materialsin>airframes?>>Thanks, more to come...>>Peter Frantz>________________________________________________________________________________

Original Posted By: John Greenlee
Hi Folks,I'm new around here, so get ready for a lot of questions. First of all, a big"two thumbs up" to Steve Eldredge and Richard DeCosta for maitaining and archiving this list. Both look like tremendous, invaluable resources. Next, a quick background check: I bought the "Improved Air Camper" plans fromOrrin Hoopman and joined the BPA nearly a decade ago, shortly after meeting Dick Alkire and Howard Henderson at an airshow in Dayton, OH. I was finishingcollege and starting grad school at the time (i.e., quite poor) so the wood andtools I purchased for this project were diverted to a less ambitous wooden boat. 5 boats later, I have more resources to draw from, and I have enthusiastically returned to this project. I've been researching for a few months now, I've acquired a 110 hp Corvair motor, and I've ripped and planed cap strips. Building rib jig this weekend.OK, let's start with materials. I have located a local source of breathtakingDouglas Fir T&G deck planking that was recovered, unused, from an old shipyard. Some planks are quarter sawn with hardly a single grain deviation over 14' of 3/4" x 4" wood, all for about a buck/lineal foot. I've done some stress tests which show that it is abot 20% stronger than Sitka Spruce from thesame source, but I'm concerned about the added weight. I spoke recently with Howard Henderson who says that he used primarily fir throughout his ship (spruce tail to maintain CG), but he reduced most cross-sectional dimensions by25%. Seems to have worked out quite nicely.Questions:Are there others out there who have done this?How has the W&B turned out?What do you think about laminating spars from this material (since they're a bit less than 4" across)?If you approve of laminated Fir spars, would you reduce thickness from the standard 3/4" spruce spar? (5/8" sounds thin to me).Any references to documents with extensive comparisons of these materials in airframes?Thanks, more to come...Peter Frantz________________________________________________________________________________

Original Posted By: Peter P Frantz
Peter,Use the Fir and put the balance of your $$ in your pocket. Build carefully,add nothing not shown on the plans, and reduce dimensions thoughtfully.You'll not notice the weight. I know of one airplane built using 1 * 3/4"fir longerons. Should be roughly same strength and weight as Spruce. Inother words study reducing the amount of fir by about 20-25 percent.Get EAAs book on Wood. It has some good articles about fir vs. spruce.John-----Original Message-----

Original Posted By: Steve W
Peter Frantz asked:> I have located a local source of breathtaking > Douglas Fir T&G deck .... I've done some > stress tests which show that it is about 20%> stronger than Sitka Spruce from the aame source,> but I'm concerned about the added weight....> Are there others out there who have done this?> How has the W&B turned out?One builder here in southern New Hampshire usedfir from a local lumber yard, leaving the dimensionsas per plans. Don't recall how much heavier it cameout than a comparable plane. I think it was around25 pounds, but it could have been a bit more. He didhave to move the wing back three or four inches toimprove the balance and reported that it was still abit tail heavy. Nonetheless, it climbed better and flewfaster than other C-85 Piets he had encountered. Heattributed this to having slightly rounded the nose ofthe airfoil instead of using Bernie's exact plans. Thatand building a really straight airframe.Owen Davies________________________________________________________________________________