# Recent content by Pete Plumb

1. ### Is there a way to calculate the lift curve slope vs aspect ratio?

The one I use is a simple old Department of Commerce formula: .0725 x 4 over 3+(6/ARe).
2. ### Sizing white pine...

Hi Kevin, sorry about the "because I said so" answer earlier. Here is a better reason why I like white pine better. You are correct, AC 43.13-1B does list Northern White Pine as an approved wood for aircraft construction. It's scientific name is pinus strobus which is the same scientific name...
3. ### Sizing white pine...

Well, simplified, if the parts in question are in bending use, allowable stress (psi), Fbp = MY/I . If they are in column (as in cap strip in a trussed rib) use, allowable stress (psi), Fce = pi^2 E/(L/rho)^2. The column calc will be conservative if you don't use a restraint coefficient (4 for...
4. ### O-100-- interesting new engine

PROGRESS REPORT 9/14/18 While this IS exciting for all of us, we still have a ways to go. Accessory cases and rocker covers still need to be cast and approved for production and the new Gen2 cranks machined and tested. I have good news and bad news about that. First some GOOD news: while...
5. ### Wood for box spars?

20 to 23 feet is what my logger bucks the logs at. I take what he sends down and usually have to buck them further down wasting some wood at the ends. I also have to cut 30% of them down to 14 and 16 feet due to knots and other anomalies but I still end up with lots of 20s. Cub front spars are...
6. ### Wood for box spars?

Personal preference based on 42 years of working with Sitka spruce I guess.
7. ### Wood for box spars?

I've got a fair amount of nice 20 foot spruce boards in stock right now if you need it faster. I usually don't sell raw lumber but will help you this time. PM me your sizes if you want. You don't want doug fir anyway. Spruce or Hem fir is best.
8. ### Cracker Jack 2 LSA from Pete Plumb / Wood Wing Specialty

Silver varnish simply verifies the presence of varnish under the fittings. That statement probably needs to be qualified somewhat. According to the "old-school" woodworking practices, all of the wood in the structure has to be coated to prevent water absorption. That means there has to either...
9. ### Tail structure sizing

Oh, I see. I must admit my knowledge is limited to standard materials and construction. I have no idea how you'd ever figure Fbu, Ftu, Fcu on that stuff. Sorry I couldn't help. Good luck on your project.
10. ### Tail structure sizing

I wouldn't stress too much about this unless you are really cutting strength/weight to the minimums (like man-powered stuff or ultimate fuel economy, single-purpose stuff etc). If the aspect ratio of your tail is 3 to 3.5, the slope of the lift curve is going to be pretty shallow and max CL...
11. ### O-100-- interesting new engine

It's been a long, dark tunnel for me too Blane.c but because I'm the guy in the front with the map and the flashlight, the rest of you will have to continue to have faith in me until this engine emerges out of the darkness of development. I admit that I haven't been very good about reporting...
12. ### O-100-- interesting new engine

Yes, Applied Process with our new foundry and current machine shop. The tricky part is making them so they can't end up in a certified engine. I've been able to change all the parts we make a little so they won't work on a certified engine but there isn't much I can do with the arms but put our...