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Spruce substitue opinion

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Old 12-07-2012, 06:13 AM
  #1
chip_MG
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Default Spruce substitue opinion

Hey all you builders..

I like to build from plans mainly and am about to start a new project, a 1/4 scale swift taylor craft..
Here's the deal, I am going to use Poplar for the Fuse longrons also the spars ect in the build.. Anybody use this wood for thier projects before?? Spruce as everyone knows is not available but poplar is at home depot and lowes.. I allready have ripped up some every nice 1/4 Sq ect,

Any thoughts??

Thanks all,

Happy landings to ya..
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Old 12-07-2012, 07:29 AM
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Default RE: Spruce substitue opinion

If you have a lumber source available that lets you select the boards, I think you will find that you can find pine boards that you can rip (if you have a decent table saw) to size and that they will be nearly as good as the spruce ones are. I have done this many times and find the results to be very satisfactory. Just select those boards with good close grain orientation with knots far enough apart to allow the needed length. Yes, there will be some waste but IMHO, well worth it.
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Old 12-07-2012, 07:42 AM
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Default RE: Spruce substitue opinion

Thanks Rodeny,

I have use pine in the past on a Skybolt bi-plane and that one is still flying..

What type of pine have you use , The "select pine" at home depot is pretty good

Thanks for the reply
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Old 12-07-2012, 08:23 AM
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Default RE: Spruce substitue opinion

Although people have built planes from poplar it is a weak structural wood. Not really good for all the effort you are about to do. Straight grained pine is good, but if you go look at staircase rails, and other trim, you can find spruce or other better candidates like fir. You want tight close grain in long runs. Large sweeping grain is not strong.
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Old 12-07-2012, 08:51 AM
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Default RE: Spruce substitue opinion

Aircraft spruce has spruce last i looked.

For spars, i have really started to like a hard balsa laminated with uni-directional carbon fiber on both sides. This provides an amazingly strong wing spar for about the same weight as a hardwood.
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Old 12-07-2012, 11:15 AM
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Default RE: Spruce substitue opinion

My aviation reference books also list fir, hemlock, and white pine as potential sources of aircraft wood. Must be straight grained and the more rings the better. The references also listed cypress, basswood, and poplar as potential sources. Local availability is important. I use the first three because they are locally available. Frequently I can find suitable wood as 2X3, 2X4, and 1X4 from the local hardware store that I cut up on my table saw.
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Old 12-07-2012, 01:07 PM
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Default RE: Spruce substitue opinion

Spruce is indeed available...

http://www.aircraftspruce.com/catalo...s/capstrip.php

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Old 12-07-2012, 01:14 PM
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Default RE: Spruce substitue opinion


Quote:
ORIGINAL: Hemikiller

Spruce is indeed available...

http://www.aircraftspruce.com/catalo...s/capstrip.php

What he said...

Bob
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Old 12-07-2012, 04:51 PM
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Default RE: Spruce substitue opinion

I get my spruce at Home Depot in the fence area. 1"x6"x6' or 8' select pieces with the least imperfections and rip them down on the table saw.
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Old 12-07-2012, 05:10 PM
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Default RE: Spruce substitue opinion

I had a neighbor who made Mandolins. He had a source for some very nice stuca Spruce. It was near San Francisco. I tried to talk him out of a board, but he wouldn't part with what he had, but promised to pick me up one on his next trip "in a few weeks". Well then next I knew, the moving van was taking him and his wood away. And he never told me his source.

Bass wood is a good substitute. They use it in window shutters.I had a ton of wood shutters in my house. As we removed them, I stripped the larger pieces of wood from them. After being in the sun for 12 years, they were nice and dry, and light. I built a number of wings using wood ripped from them and they were very strong and no heaver than a balsa wing. I replaced a broken wing on an ARF I had and the replacement weighed less than the original wing. Look at a cabinet shop or shutter shop. You may be able to talk them out of some wood.
Don
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Old 12-07-2012, 06:17 PM
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Default RE: Spruce substitue opinion

Hemlock is sometimes grouped and sold with other species as hem fir in the construction industry. I noted some hem fir a few years ago that was light, straight grained and absent of moisture and laid in several sections in the back of the water heater closet to ensure it staying dry. I've ripped several spars from it and found it very suitable. It is pitch free, takes glue well, is light and adequately strong with straight grain.

If one went looking for the better hem fir offerings, they would likely be allusive. I've used a great deal of it but the cache found on that one occasion was indeed superior to the general mix. I do not know which of the several species that are grouped into hem fir that my find was. Whatever it is, it is very suitable for airplane spars.
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Old 12-07-2012, 06:20 PM
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Default RE: Spruce substitue opinion

Poplar is a good choice (540 on the Janka hardness scale). It is harder than Eastern White Pine (380), Basswood (410), White Pine (420), and Hemlock (500).

I've used it for spars and leading edges without any problems. We overbuild our models anyway.

Bob
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Old 12-07-2012, 06:31 PM
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Default RE: Spruce substitue opinion

Go out to the local airport and ask the local fbo if anyone local repairs cubs,aeroncas, etc. the last j3 my dad and i recovered we put in new spars. The old spars had enough wood to make 100 model planes. I should have saved them.
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Old 12-07-2012, 08:19 PM
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Default RE: Spruce substitue opinion

I have been using popular from Lowe's for years. I have yet to have any failure from stress. Just my 2 cents. Im doing a project right now for myself that Im using popular.
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Old 12-07-2012, 11:30 PM
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Default RE: Spruce substitue opinion

Douglas Fir is a good enough substitute for spruce to have been approved by the FAA as such, several years ago. The scarcity of spruce is nothing new.
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Old 12-08-2012, 12:18 AM
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Default RE: Spruce substitue opinion

If you don't fold a wing every now and then...you're probably building too heavy.....
For planes with 50 inches of span [and under] carrying 5 pounds [or less] and capable of 100 mph speeds, hard balsa has served me well over the years in built up wings that have 1.25" [or thicker] airfoils.
For 1/4 scale..I have no clue. I'd seek the advice of someone who HAD seen spar failure at that scale and who might also have the credential to inspect large models.
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Old 12-08-2012, 01:29 AM
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Default RE: Spruce substitue opinion

I'm surprized nobody suggested Western Red Cedar. Not as strong as spruce, but a bit lighter.

Jeff
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Old 12-08-2012, 06:18 AM
  #18
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Default RE: Spruce substitue opinion

Thanks from you all,


I figured some real builders would respond with some real world experience here, not what they heard someone else say..

Makes me glad to see that there are still you guys out there how actually have the requeist skills to build your own planes like I do. Not many in my area that I know of..

Some of the folks I know thought that using pine was a real bad chioce, but that was coming from the ARF crowd most of which have trouble even assembeling thier own ARF's

I enjoy building as much as flying myself.. I think there are only a couple of guys in my club that build at all..

I have used pine for serveral builds but was looking at the poplar because its mostly clear and fast to pick at the lumber stores.. The 1/4 Sq's I ripped up on my band saw look great to me, seem to be very strong..

Well thanks again,

Happy landings too ya from Texas,,[:@]
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Old 12-08-2012, 07:05 AM
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Default RE: Spruce substitue opinion

Chip;I also build from plans and use poplar from HD & lowes,I do all my own cutting,bench top bandsaw-scrollsaw.I have never used spruce,poplar is just as dense but just a touch heavier but big warbirds dont care,keep up the GOOD work.GEO.
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Old 12-08-2012, 09:57 AM
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Default RE: Spruce substitue opinion

Here is a picture of a C47 I built. The wing panels, and wing center are all popular stringers and spars. 136" span. Only balsa in them are the ribs from 1/3rd of each wing panel to the tips and the hinge areas. Everything else is 1/8th ply and popular. I buy bulk and rip to my own specifications.

Never had a wing problem in 15 years of building this way. 30lb airplane with two engines. Id say thats a pretty good stresser

Spruce and all the other FAA aproved woods are just fine if your gonna be puttin your own butt inside one lol, but for our models, the best is not always the.....best....

WBG
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Old 12-08-2012, 10:26 AM
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Default RE: Spruce substitue opinion

Is it Spell Check that puts the "u" in "poplar"?
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Old 12-08-2012, 01:30 PM
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Default RE: Spruce substitue opinion

Chip, I recently bought some poplar from a small localy owned sawmill and they cut into 3/8x1/2x6' strips and the quality of the cut looked like it had been plained to demision, they used a fine tooth band saw. The owner told me that poplar is almost as hard as spruce, the grain is straight and tight without knots. I have since built the wing 68" span and with sheer webbing it seems to be very strong.
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Old 12-08-2012, 01:32 PM
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Default RE: Spruce substitue opinion


Quote:
ORIGINAL: retransit

We overbuild our models anyway.

Bob
BINGO!!!
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Old 12-08-2012, 04:16 PM
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Default RE: Spruce substitue opinion

A lot of wood varieties tend to be different in different geographical areas. For example the poplar I can get around here is punky and low in fibrous strength. It's just about the last thing I'd use as a substitute for aircraft grade sitka spruce. Meanwhile I can find some pretty good and very straight grain hemlock quite easily that is far more suitable as a spruce replacement. Our west coast pine is a far cry from the eastern white pine. The western pine has a stronger grain to it and the growth rings are more prominent. But it's always been tough to find long pieces that are clear of knots.

First off a wood used for spars should be resilitent. That is it should spring back to nearly straight after being bent quite far. On that aspect our western poplar fails miserably. It compresses along the inside of the bend badly and doesn't come back to its original size so the stick remains bent like a bad ski. That's the first test I'd try. SOME bend is to be expected. But it should mostly relax back to a nearly straight condition. Try this with YOUR poplar in YOUR area and compare it to how hard balsa flexes and returns to straight.

Speaking of hard balsa if you find some really heavy balsa that is nicely straight grained this can produce a darn nice spar and main longeron stock. I'm talking seriously heavy so it's like spruce. So heavy that it feels like it won't float in water.... Balsa of that sort is very fibrous and surprisingly strong yet flexes well. Spars made from this sort of heavy balsa might need to be a little larger in section but for fuselage longerons this very hard balsa can sub in for spruce very neatly.
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Old 12-08-2012, 05:52 PM
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Default RE: Spruce substitue opinion

The reason for the knots are the branches. Tall growth (165 ft.) Poplar has no branches for the first 80-100 feet. That's the reason it is virtually knot free.

Bob
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