WOOD TESTING! WHICH WOOD IS STRONGEST? - Fisher Newsletter 12 08 24 2020

[@AzTrailRider57]

Wow, all this time I thought the Sitka Spruce was the golden standard. Years ago I was considering building a SkyPup and that was the holy grail wood.

[@fisherflyingproducts5747]

Yes. The results were very interesting to me as well. The more in-depth analysis is moving right along with an engineer and it looks good for the substitution.

[@Damorann]

The problem with "golden standards" like this is that the reasons behind why they were considered golden are often lost and then it's just the end result that's repeated. WWI planes were produced in the tens of thousands out of wood. I cannot believe they were all made of Sitka Spruce and yet they were successful designs. The WW2 Mosquito was birch, balsa and plywood. One has to always remember why the standard was created and look to see if they can't replicate the results with different materials. In this case, Canada has a huge amount of forest and a tremendous wood industry, so it always struck me as odd that not a single essence of wood here would be inappropriate for aircraft construction. Regionally sourced materials can be a huge criteria in selection and options that "cannot be replaced with anything else" just don't exist. As an engineer, I can say there will always be options. They may have downsides, but they are there and can work. Glad to see this Canadian company trying alternatives and maybe finding better ones ! I still have my hopes of flying one day. Who knows, maybe I'll be the lucky owner of one of their planes.

[@timketcham9139]

Thank you so much! I know that is a lot of work, both doing the test and especially documenting and relating the data.

[@garymitchell6897]

I used western hemlock when I build Dakota Hawk NZSOL.slightly heavier than spruce but stronger. Douglas fir is also good. Many friends have used it on their aircraft. Power companies in NZ use western Hemlock to make their ladders from as very strong straight grain and good insulation. Hope this helps. Cheers Gary Mitchell

[@crankhandle]

Hi gary I'm in nz too, were did you buy your western hemlock from?

[@salvatoremilitello8490]

Great information things like this are super important for anyone who builds

[@fisherflyingproducts5747]

Glad you think so!

[@stolaircraftsuyanto9728]

great video. thanks for sharing

[@garybucher6824]

How many grains per inch do you recommend for northern white pine?

[@pauls.2526]

Great video I appreciate it . What about processed bamboo for making ribs or eliminated bamboo for spars just putting it out there .

[@robertlafnear4865]

Wish you could have tested some of my Douglas Fir, Center cut, Clear, old growth that I'm giving a ton of thought to using for a Legal Eagle Spar and Wing ribs.......... would love to see some of my wood in comparison with the D.F. you tested.............. my trees are OLD, Tall, Small, knot free, tight grained,.... I'm almost ready to buy a small mill and use my Free wood for the build......... THANK YOU for posting this, I'll be doing some load testing myself for my project. WISH the guy using Tite Bond II would see your Rib build video and take note !

[@fisherflyingproducts5747]

Thanks for the comment.

[@riedjacobsen8620]

There is as wealth of information on wood characteristics from 1930s to 1960s from NACA, Forest Products Laboratory (FPL), EAA, and others that I have accumulated in my casual research. Over the next two weeks I will dig up the links to some of this research for those interested. Between weight, workability, and strength, Sitka spruce is the gold standard. But given the cost difference, some weight tradeoff might be worth a less material cost. If I recall, white pine and Douglas fir are the more acceptable alternatives.

[@fisherflyingproducts5747]

Thanks for the input. Every little bit helps.

[@machine7548]

I hope you take me seriously in asking, have you considered bamboo? Moso or the other humdreds of species. In most cases it grows to full maturity within 4 years and is considered very renewable. I have heard more than once of it having the tensile strength of greater than steel. I have long daydreamed of making a fisher with bamboo. My only questions are about moisture absorption and glue or epoxy adhesion. Even possibly rot risks. But once treated with a simple borax solution it may last forever. Descovering that some Japanese aircraft were originally made from bamboo set me on this rabbit trail.

[@machine7548]

Moso in particular may outperform sitka. I only wish I had the resources to test my theory.

[@fisherflyingproducts5747]

Interesting

[@seamuscashin2606]

you guys should get your hands on build and repair of wooden sailplanes by HANS JACKOBS baltic pine with vertical grain on spar booms for 18 metre spans was not in favor of spruce

[@fisherflyingproducts5747]

We have our hands full with our new Aria model. We have started building the company demo.

[@ioanekirarahu951]

I'll be watching it again, but since weight is such a critical factor in our aircraft construction, I'd be interested in data that specifically shows strength vs. weight in all the wood samples. Did I miss this? This is because my Dakota Hawk will not be my last wooden airplane project. I'm also interested in strength data, especially weight vs. strength for Ash.

[@fisherflyingproducts5747]

I did check the density of all the samples that I tested. I am finalizing the report of my findings. You will be able to compare the density/weight info with the tested strength.

[@riedjacobsen8620]

Ash is about 50% heavier than Sitka spruce. Ash has almost twice the compressive strength, but only 15% better modulus of elasticity. The show's up as being somewhat brittle.

[@carrollmcpherson4530]

Ditto.

[@chetorton7329]

I have concerns about substituting wood species in an existing design unless you are a structural engineer. For a plane that was designed for sitka spruce, substituting different species for some structural parts can change the way a load is distributed, making other parts more prone to failure. The previous structural testing results and safety record of the plane would no longer be valid.

[@fisherflyingproducts5747]

Chet, Thanks for your comment. This analysis was taken with a qualified engineer and computer analysis was completed within a built assembly both in a high wing monoplane and one of our biplanes. The difference in strength between eastern white pine and sitka spruce was found to be within 1%. Well within our design safety margins and also within the inherent strength of wood procured from the same species. This test was just the beginning of the analysis and was crude. We have since completed a much more thorough analysis.

[@BozeHollow]

This may be a stupid question, but what about carbon fiber? Note: I have zero knowledge of airplanes but I am trying to learn. You and I have spoken on the phone and exchanged emails recently. I am from Tennessee. BB

[@fisherflyingproducts5747]

Carbon fiber is wonderful"LY" expensive. We have entertained the thought of adding carbon fiber rods along the tension side of the spar caps.