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How to make a plane wing out of 6 mm think wood.

#1
Hello everyone. I was looking on ways I can build a wing for an rc airplane that I plan to build out of wood and I stumbled on the problem of getting lightweight material I need to create it (AKA foam). Do you have any advice on how to create a 10 cm wide, rectangular wing with 6 mm thick wood? videos and guides would be appreciated
 

Hai-Lee

Old and Bold RC PILOT
#2
A wing with a cord of 100mm using 5mm wood would require some tools which I am not sure you would have access to because the Wing would obviously need to be lightweight and 5mm wood is basically very heavy.

You could use the wood as a spar or spars and fill the voids with some loose papermache or similar.

More details or information from you will be required for a better answer.
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
#3
Mario,

First off, welcome to the forum!

What kind of wood? Are we talking Balsa? Bass-wood? Oak?

You can make a solid-core wooden balsa wing, but it would be an arduous exercise to plane-then-sand the plank down to an airfoil. careful precision would not be required, but it would be a lot of wood to remove. Basswood is suitable for spars, perhaps a limited number of ribs, but not much else. Other soft and hardwoods would likely be wholly unsuited to anything but small hardpoints due to their density.

If you can get access to any sort of thin-film-material (Mylar, cellophane wrapping paper . . . ) and a bit of spray adhesive, you can build a ribbed wing frame (wing ribs with spar and stringers) spray the adhesive on the ribs, then cover with the film. If the thin-film material shrinks under heat, all the better -- block the finished wing up with the desired warp (wingtip trailing edge slightly twisted up gives a bit of washout for a gentler stall behavior) then shrink the plastic to remove wrinkles and set in the desired warp.
 
#5
I can get cloth and wrapping paper

Mario,

First off, welcome to the forum!

What kind of wood? Are we talking Balsa? Bass-wood? Oak?

You can make a solid-core wooden balsa wing, but it would be an arduous exercise to plane-then-sand the plank down to an airfoil. careful precision would not be required, but it would be a lot of wood to remove. Basswood is suitable for spars, perhaps a limited number of ribs, but not much else. Other soft and hardwoods would likely be wholly unsuited to anything but small hardpoints due to their density.

If you can get access to any sort of thin-film-material (Mylar, cellophane wrapping paper . . . ) and a bit of spray adhesive, you can build a ribbed wing frame (wing ribs with spar and stringers) spray the adhesive on the ribs, then cover with the film. If the thin-film material shrinks under heat, all the better -- block the finished wing up with the desired warp (wingtip trailing edge slightly twisted up gives a bit of washout for a gentler stall behavior) then shrink the plastic to remove wrinkles and set in the desired warp.
As I stated in my post below, I am designing this plane to be a cargo plane designed to lift pretty heavy things inside of it.
 
#7
A wing with a cord of 100mm using 5mm wood would require some tools which I am not sure you would have access to because the Wing would obviously need to be lightweight and 5mm wood is basically very heavy.

You could use the wood as a spar or spars and fill the voids with some loose papermache or similar.

More details or information from you will be required for a better answer.

Please look at reply below.
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
Mentor
#9
That's a lot of weight.

Running some numbers . . .

For a takeoff speed of 10mph (~16kph) a 6% airfoil (6mm high, 10cm cord) on a weightless airframe (AUW is 10#, so we ignore the airframe weight, which will probably be closer to 2-5 lbs) . . . looking at a clean efficient airfoils in that range the coefficient of lift tops off just below 1 . . . Using the Lift Formula, solved for area, your wing will need to be at least 12' long (3.6m) to give you the wing area you need.

A solid core 10x0.6cm cross section will not get you where you want to go.

Bumping up to a 10x1.2cm opens up a few nicer airfoils, and can get Cl up to around 1.2, but even those top out at 10' long (3m).

You need far more surface for that kind of payload -- the cord is simply too narrow. You need to look at cutting ribs from the balsa sheet *at least* twice as long (20cm or more) from 2-4 cm balsa, assemble the ribs supported by spars and stringers, then covering the hollow gaps with either a plastic covering material or thinner balsa sheeting.

For an airfoil shape, I'd recommend looking at the Clark-Y airfoil -- This should give you a fair amount of lift at a 20cm cord, and a good amount of lift at 30cm cord. It's also flat bottomed, which makes it easy to cut.

As for assembly concepts, look here:

http://www.rc-airplane-advisor.com/balsa-wood-building-sequence.html

This covers building from plans, but he demonstrates laying out the ribs, spars and stringers, then sheeting the leading and trailing edges -- you can sheet the entire wing in 1-2mm balsa, but placing ribs at ~5cm intervals and covering with a plastic material is much lighter.

Keep in mind, even at 30cm, you're still looking at needing a 1.5m wing to get the area you need for a ~15lb AUW. This will be a fairly long wing, and your spars will likely need to be a harder wood -- like basswood -- to transfer the forces from the 10lb payload weight out onto the wing.
 
#10
Ok... you made me rethink my 10lbs payload

Ok then.... what about 3 or 6 pounds instead? I think I got way too ambitious for my own good. The wing length from the body to one end of each wing would be 60cm.
 
#11
Ok then is this good specs for the wing design?

That's a lot of weight.

Running some numbers . . .

For a takeoff speed of 10mph (~16kph) a 6% airfoil (6mm high, 10cm cord) on a weightless airframe (AUW is 10#, so we ignore the airframe weight, which will probably be closer to 2-5 lbs) . . . looking at a clean efficient airfoils in that range the coefficient of lift tops off just below 1 . . . Using the Lift Formula, solved for area, your wing will need to be at least 12' long (3.6m) to give you the wing area you need.

A solid core 10x0.6cm cross section will not get you where you want to go.

Bumping up to a 10x1.2cm opens up a few nicer airfoils, and can get Cl up to around 1.2, but even those top out at 10' long (3m).

You need far more surface for that kind of payload -- the cord is simply too narrow. You need to look at cutting ribs from the balsa sheet *at least* twice as long (20cm or more) from 2-4 cm balsa, assemble the ribs supported by spars and stringers, then covering the hollow gaps with either a plastic covering material or thinner balsa sheeting.

For an airfoil shape, I'd recommend looking at the Clark-Y airfoil -- This should give you a fair amount of lift at a 20cm cord, and a good amount of lift at 30cm cord. It's also flat bottomed, which makes it easy to cut.

As for assembly concepts, look here:

http://www.rc-airplane-advisor.com/balsa-wood-building-sequence.html

This covers building from plans, but he demonstrates laying out the ribs, spars and stringers, then sheeting the leading and trailing edges -- you can sheet the entire wing in 1-2mm balsa, but placing ribs at ~5cm intervals and covering with a plastic material is much lighter.

Keep in mind, even at 30cm, you're still looking at needing a 1.5m wing to get the area you need for a ~15lb AUW. This will be a fairly long wing, and your spars will likely need to be a harder wood -- like basswood -- to transfer the forces from the 10lb payload weight out onto the wing.
Front of the wing: 3cm
Back of wing: 1cm
 

Craftydan

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#12
A couple of points for advise . . .

- there's an engineering principal that has served me well when starting many a project: Necessity is the mother of invention.

If you haven't carefully considered what you want to accomplish and why, any requirements you make are pointless . . . 10lb? 6lb? 3lb? Of what? To go where? Why? How little is too little? How much is enough? To succeed, you need to know what good enough and not good enough will be. It's the end goal that drives a successful design.

It's true in general, but most of the great plane designs took this seriously -- start with the goal then design the plane around that.

We can help you think through how to get to where you want to go, but until you know where that is, our recommendations may not lead you to something you'd consider success. More details about your goal will help us, help you.


- I take it the 0.6m wing-half limit is based on the length of the boards? Something else? Board length might be an issue with a solid core wing, but it's fairly trivial issue with a built-up wing. You might need to go with a panelized wing design (the overall wing is made in several panels which are connected together after each is assembled) to get the span your goals need. Building with a panelized design is a touch more complicated, but not bad.


- I'm not following you with the 3cm/1cm spec. Are you talking about a cross-section shaped like a tapered rectangle, with the front being 3cm high and the back 1cm high, 10cm wide?
 
#13
CLarification.

A couple of points for advise . . .

- there's an engineering principal that has served me well when starting many a project: Necessity is the mother of invention.

If you haven't carefully considered what you want to accomplish and why, any requirements you make are pointless . . . 10lb? 6lb? 3lb? Of what? To go where? Why? How little is too little? How much is enough? To succeed, you need to know what good enough and not good enough will be. It's the end goal that drives a successful design.

It's true in general, but most of the great plane designs took this seriously -- start with the goal then design the plane around that.

We can help you think through how to get to where you want to go, but until you know where that is, our recommendations may not lead you to something you'd consider success. More details about your goal will help us, help you.


- I take it the 0.6m wing-half limit is based on the length of the boards? Something else? Board length might be an issue with a solid core wing, but it's fairly trivial issue with a built-up wing. You might need to go with a panelized wing design (the overall wing is made in several panels which are connected together after each is assembled) to get the span your goals need. Building with a panelized design is a touch more complicated, but not bad.


- I'm not following you with the 3cm/1cm spec. Are you talking about a cross-section shaped like a tapered rectangle, with the front being 3cm high and the back 1cm high, 10cm wide?
For the purpose of building my plane, I plan to make a cargo plane to fly about 12 km out to sea to fly over an offshore key and back as shown in this picture. The reason I choose a cargo plane design is because I want to be able to put equipment like an fpv camera, gyroscope and extra batteries inside of it to make the round trip. The ability to carry a load up to 3 pounds easily ( Finalized the weight) is going to be used for A, carry the weight of the extra batteries and B, to fly various objects inside of the plane when I am just flying it around.

The 3 to 1 specification describes the cross section of the wing from a left side view. 3 cm for the front, 1 cm at the back according to the Clark-Y airfoil you suggested that I should build for a wing design and the 0.6 m length is mostly made as estimation of the correct length for a roughly 1m length body. Id the length is wrong, I would have to use that Equation you give me to determine the correct length of an aircraft going 10mph during takeoff to redesign the wing length.

Length of journey posted below.
Flight path.jpg
 

Craftydan

Hostage Taker of Quads
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#14
Thanks for the detail. That does help.

Crocus Bay beach to Prickly Pear cay and back . . . looks like a pretty ride. 24-30km round trip . . .

My 2-5lb rough guess for airframe weight actually included the electronics (motors, servos, RX gear, and modest battery), and if all you want to do is fly that route FPV with a flight stabilizer onboard, I think you'll be surprised how little that gear weighs. with a cruising airspeed around 20-30mph (30-50-ish kph) -- reasonable but not zippy -- you're looking at needing at least an hour of flight time. Probably more if you wanted time to loiter around a bit once you got there, with reserve left to get you home. Might also want to look into prevailing winds. A constant headwind will become a tailwind on return, but a cross wind will fight you going both ways, forcing you to waste energy to maintain course -- if that's the case, more time needs to get tacked on.

Doable, but a bit of a challenge. I've seen videos of a Bixler put up over an hour of powered flight with an oversized battery pack, but it was on a ridge, so he was likely stealing some lift even if he wasn't trying to.

One thing I'd suggest you look into is the components you want in your payload. most online stores will list the actual weight of the part that goes on the plane, so you can spec out most of the parts and us a spreadsheet to get a running tab for a weight budget. With that you can play tradeoffs between price, capability and weight to get what you need. Most 2.4GHz control radios have a 1-2km range, so that's out.

Look into "LRS control" systems. Most are at a lower frequency and higher power, and yu'll need ot look into your local laws to see what kind of a license you need to use that gear -- here in the US you need an Amateur Radio Operator's license, and the same may be true for you.

Also, even high power 5.8GHz FPV gear isn't much good past 2km, so I'd recommend looking into lower frequency gear. 900MHz and 1.2/1.3 GHz bands have good range, just make sure they won't interfere with your chosen LRS. One thing to be aware of, the lower the frequency, the smaller the available bandwidth -- 5.8G drops off in range pretty fast, but the picture is fantastic from the available bandwidth . . . The picture quality will suffer a bit as you go down in frequency, but even then, most pilots are more than happy with the results.

To directly answer your question analytically sizing your fuselage length and tail surfaces isn't super complex, but it's more than what I would go into for a post like this but we can hit some rules of thumb that'll get you "close enough".

Borrowing from Dave Thornburg's "Old Buzzards Soring Book":

- Size the fuselage on the cord of your wing -- leading edge to nose tip plan about 1-1.25 the cord widths (to give you a good space up front to balance the plane), and gap between the wing and the tailfeathers plan about 1.8-2.5 cord widths (to give the tail enough length in back to stabilize the wing).

- For your tailfeathers those are sized on the main wing area. Horizontal should be about 24-27% (about 1/4) the area of the wing, and Vertical should be 4-7% of main wing area, depending on how much dihedral you put in.

- Dihedral. Even for an aileron plane, you want at least some. 1-2" of rise per foot of half-span at the wingtip should be good (5-10 degrees per side). too much more than this and the plane will start to develop dutch roll, and too little the plane will have trouble staying level in roll.

- Keep in mind, for stability, the tail is pushing down not lifting up.

This is just starting to scratch the surface, so go look, think about it, and we'll chat more later.
 

Craftydan

Hostage Taker of Quads
Staff member
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#16
Liamnmave,

I'd agree for most anyone in North America . . . but notice all that water? Anguilla might be a bit limited in their variety of building materials available, and insulation foam would likely be near the top of that list. The whole premise of the OP was foam was hard to find.

Count your blessings it's readily available . . . I know I do.
 

agentkbl

Illegal Squid Fighting?
#17
you could angle the wood in the middle and spin it really fast... that would make it able to lift ten lbs.

Just kidding. but make sure to post the video of that flight. it looks like a beautiful route.
 
#18
Thanks for the advice.

Thanks for the detail. That does help.

Crocus Bay beach to Prickly Pear cay and back . . . looks like a pretty ride. 24-30km round trip . . .

My 2-5lb rough guess for airframe weight actually included the electronics (motors, servos, RX gear, and modest battery), and if all you want to do is fly that route FPV with a flight stabilizer onboard, I think you'll be surprised how little that gear weighs. with a cruising airspeed around 20-30mph (30-50-ish kph) -- reasonable but not zippy -- you're looking at needing at least an hour of flight time. Probably more if you wanted time to loiter around a bit once you got there, with reserve left to get you home. Might also want to look into prevailing winds. A constant headwind will become a tailwind on return, but a cross wind will fight you going both ways, forcing you to waste energy to maintain course -- if that's the case, more time needs to get tacked on.

Doable, but a bit of a challenge. I've seen videos of a Bixler put up over an hour of powered flight with an oversized battery pack, but it was on a ridge, so he was likely stealing some lift even if he wasn't trying to.

One thing I'd suggest you look into is the components you want in your payload. most online stores will list the actual weight of the part that goes on the plane, so you can spec out most of the parts and us a spreadsheet to get a running tab for a weight budget. With that you can play tradeoffs between price, capability and weight to get what you need. Most 2.4GHz control radios have a 1-2km range, so that's out.

Look into "LRS control" systems. Most are at a lower frequency and higher power, and yu'll need ot look into your local laws to see what kind of a license you need to use that gear -- here in the US you need an Amateur Radio Operator's license, and the same may be true for you.

Also, even high power 5.8GHz FPV gear isn't much good past 2km, so I'd recommend looking into lower frequency gear. 900MHz and 1.2/1.3 GHz bands have good range, just make sure they won't interfere with your chosen LRS. One thing to be aware of, the lower the frequency, the smaller the available bandwidth -- 5.8G drops off in range pretty fast, but the picture is fantastic from the available bandwidth . . . The picture quality will suffer a bit as you go down in frequency, but even then, most pilots are more than happy with the results.

To directly answer your question analytically sizing your fuselage length and tail surfaces isn't super complex, but it's more than what I would go into for a post like this but we can hit some rules of thumb that'll get you "close enough".

Borrowing from Dave Thornburg's "Old Buzzards Soring Book":

- Size the fuselage on the cord of your wing -- leading edge to nose tip plan about 1-1.25 the cord widths (to give you a good space up front to balance the plane), and gap between the wing and the tailfeathers plan about 1.8-2.5 cord widths (to give the tail enough length in back to stabilize the wing).

- For your tailfeathers those are sized on the main wing area. Horizontal should be about 24-27% (about 1/4) the area of the wing, and Vertical should be 4-7% of main wing area, depending on how much dihedral you put in.

- Dihedral. Even for an aileron plane, you want at least some. 1-2" of rise per foot of half-span at the wingtip should be good (5-10 degrees per side). too much more than this and the plane will start to develop dutch roll, and too little the plane will have trouble staying level in roll.

- Keep in mind, for stability, the tail is pushing down not lifting up.

This is just starting to scratch the surface, so go look, think about it, and we'll chat more later.
Thanks for the information you gave me about how the plane should be built. Also I have managed to make a 3d model of what the plane should look like. (without the motor compartments on the wings)
https://www.dropbox.com/s/lq9rbhx01j0zxyc/3d cargo plane.skp?dl=0 Anything I need to fix on this model?
 
#19
Model finished and dimensions are here

you could angle the wood in the middle and spin it really fast... that would make it able to lift ten lbs.



Just kidding. but make sure to post the video of that flight. it looks like a beautiful route.

I will. But as of now. I have finished the model for my plane on Sketch up. This files have dimensions also but I need to make them more orderly later on.

https://www.dropbox.com/s/lq9rbhx01j0zxyc/3d cargo plane.skp?dl=0
 

Tench745

Well-known member
#20
I have to ask, why do you want to fly 12 km to a far off island with the ability to carry more weight than your plane needs to? To be blunt, the lack of specifics from the get go and the large payload in an offshore location makes this sounds like it's intended for drug trafficking. No accusation intended, but perhaps consider your explanations more carefully in future?
If you do get it flying we'll all want to see it of course. :)