Author Topic: Rib Wood  (Read 197 times)

Offline okawbow

Rib Wood
« on: September 05, 2019, 09:53:04 AM »
I’m researching inexpensive wood for my upcoming LEXL build. I have worked with wood for 50 years, and have much experience selecting, cutting, surfacing, and gluing all types of wood.

I will be building on an extremely tight budget, and in the spirit of the original Legal Eagle builds, I want to save money as long as my material choices are adequate.

I was at a Menards lumber yesterday, and noticed a pile of premium, select, hemlock fir 2x4’s. Several had more than 10 grains per inch growth rings, and very straight, even grain. I selected one that only had one small knot, and seemed fairly light.

Today, I sawed and planed a sample for measuring and weighing to determine the density. The wood sawed and planed cleanly, and the scrap pieces seemed strong and not prone to splitting or cracking.

I microwaved the piece for 30 seconds at a time, (3 times) until the weight loss slowed down. I came up with 28.98 pounds per cubic foot density.

This wood seems stronger overall than the Sitka spruce I have on hand, that I use for stringed instruments. It is about 10% heavier. I’m considering using this for the ribs. Has anyone else used hemlock?

Offline Dan_

Re: Rib Wood
« Reply #1 on: September 05, 2019, 11:03:38 AM »
This guy did some testing but dint weigh the samples...  http://www.hainesengineering.com/rhaines/misc/sitka.htm

There is a good link to a NACA report you should read on his web page as well.  http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930091423_1993091423.pdf


“A superior pilot uses his superior judgment to avoid situations which require the use of his superior skills.”

– Frank Borman, Apollo 8 Commander

Offline okawbow

Re: Rib Wood
« Reply #2 on: September 05, 2019, 11:25:52 AM »
Thanks Dan
Based on the Government study, Westrn Hemlock averages just 8% heavier, and is 8% stronger than Sitka. With careful selection it can be used as a replacement for Sitka.

I would think it would be good for the ribs.

Offline Kamcoman77

Re: Rib Wood
« Reply #3 on: September 05, 2019, 12:43:42 PM »
Most of my non-aileron spruce ribs weigh 4.0 to 4.1 ounces. 8% extra makes them 4.3 to 4.4 ounces each. If I was going to use the hemlock, I think I would leave the vertical or front-to-back thickness of all rib sticks at 0.250" and sand the width down to 7/32" instead of 1/4"

Offline jrbirdman47

Re: Rib Wood
« Reply #4 on: September 05, 2019, 06:04:35 PM »
Using the above, it should make less than a half pound difference for the plane. Actually even less because the rib is not made up exclusively of cap strip, so probably 1/4 lb or less total. Interesting......


Offline Wayne Munich

Re: Rib Wood
« Reply #5 on: September 05, 2019, 06:54:27 PM »
I was planning On using CVG hemlock for my spar caps. !2ft spruce freight costs are ridicules.  I live in hemlock country and there is some really nice wood from the local boat wood suppliers