CA-65 - Atomic_Sheep - Discussion Thread

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

Atomic_Sheep

Well-Known Member
Joined
Nov 6, 2008
Messages
201
Location
Melbourne, Australia
Hello,

Just starting a thread for the discussion of questions that I'll have along the way. Here is the first one:

I've got a cross brace member like the one in the image below. It's not at a 45 degree angle and I'm not sure whether to make the red distances the same or the green ones. At the moment I have the green ones as the same but logically from a structural stand point, the red ones should be.

This is me being perhaps too pedantic and it might not even matter all that much. FYI, the two red distances are 0.472 and 0.618.

CrossBrace.jpg
 

Matt G.

Well-Known Member
Joined
Nov 16, 2011
Messages
1,253
Location
Kansas, USA
I would make the green ones the same because that is how it is drawn in the plans. I'm not sure where you're getting that making the red distances the same is 'structurally better' because the gusset that is glued over the joint is what's going to be carrying the load, not the end joint of the member.
 

Atomic_Sheep

Well-Known Member
Joined
Nov 6, 2008
Messages
201
Location
Melbourne, Australia
Ah that makes sense thanks. The only reason that I thought making the red would be more structurally sound was because that would make the contact points the same size which to me for some reason means more structurally sound but I was totally missing the point about the gussets/corner blocks. Now it makes more sense to me. The only other thing that I'm not sure about is the fact that none of the corner blocks have dimensions attached, does that mean I should just eye ball them based on the plans and that should be good enough?
 

fly2kads

Well-Known Member
HBA Supporter
Joined
Jan 2, 2010
Messages
1,797
Location
Justin, TX
I'm with Matt...run the centerline of the members to the intersections of the joints, as that is what is shown on the plans, and don't worry about the relative dimensions of the mitered ends. Those will vary with the geometry of each cluster. As to the corner blocks, the sample here has dimensions for several of them, so you at least have some to work with. If dimensions are not given, you can usually assume that the exact size is not critical. You can take your own measurement off the plans, and if no scale for that section of the plans is given, compare to a known dimension. (For example, you conveniently have a 1.00" member nearby, so you can measure by taking the ratio of the block in question to that known 1" item.)
 

Matt G.

Well-Known Member
Joined
Nov 16, 2011
Messages
1,253
Location
Kansas, USA
Another reason to do it the way the plans are drawn that I hadn't thought of this morning is that the centerline of all members at an intersection pass through a single point so that they only carry axial loads. If they don't pass through a single point, some or all of the members will also have a bending moment on them, which may be significant, depending on the loads.
 

bmcj

Well-Known Member
HBA Supporter
Joined
Apr 10, 2007
Messages
13,776
Location
Fresno, California
Another reason to do it the way the plans are drawn that I hadn't thought of this morning is that the centerline of all members at an intersection pass through a single point so that they only carry axial loads. If they don't pass through a single point, some or all of the members will also have a bending moment on them, which may be significant, depending on the loads.
That's generally true in metal tubes... not sure about wood trusses though. Depending on the sizes of each member and the angle of the diagonal, he may not have that option. Being a well proven design, I would follow the plans in this case, according to your original interpretation.

I would make the green ones the same because that is how it is drawn in the plans.
I'm with Matt...run the centerline of the members to the intersections of the joints, as that is what is shown on the plans, and don't worry about the relative dimensions of the mitered ends.
 

Atomic_Sheep

Well-Known Member
Joined
Nov 6, 2008
Messages
201
Location
Melbourne, Australia
The reason I asked was because the plans aren't accurate enough to make that assessment. But many thanks ill go with the suggestions.

1.) On a different note, the plans have some brackets on them with the material description quoted as "Aluminium Extrusion". What is an extrusion?

2.) How would you connect the ailerons and the control stick as well as how would you make the connection between the control sticks. This is what the plans look like.

Connection.jpg

To me, the only logical solution is to use something like this a wire thimble:

https://www.google.com.au/search?q=wire+thimble&safe=off&hl=en-AU&gbv=2&tbm=isch&oq=wire+thimble&gs_l=img.3...5848.6335.0.6522.5.5.0.0.0.0.0.0..0.0.msedr...0...1ac.1.34.img..5.0.0.yDZeCuBXrgM

The plans say "3/16 Pin, 5/16 grip length washer and cotter pin"

I'm not sure how a cotter pin would help.
 
Last edited:

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
6,198
Location
US
1.) On a different note, the plans have some brackets on them with the material description quoted as "Aluminium Extrusion". What is an extrusion?
An extrusion is an aluminum piece formed by pushing molten aluminum through a two-dimensional "mask". Examples could include L's (also called "angle") , C's (often called "channel"), I beams, etc. They are usually sold in 6 to 8 foot lengths,and the full description should include the type and thickness of the aluminum as well as the dimensions of the "legs".
2.) How would you connect the ailerons and the control stick as well as how would you make the connection between the control sticks. This is what the plans look like.
I would think there would be a rigid link between the two sticks, with a hinge at both ends where they connect to the sticks.

Are the plans now on paper, and are you entering them into CAD?
 

Matt G.

Well-Known Member
Joined
Nov 16, 2011
Messages
1,253
Location
Kansas, USA
2.) How would you connect the ailerons and the control stick as well as how would you make the connection between the control sticks. This is what the plans look like.

View attachment 36910

To me, the only logical solution is to use something like this a wire thimble:

https://www.google.com.au/search?q=wire+thimble&safe=off&hl=en-AU&gbv=2&tbm=isch&oq=wire+thimble&gs_l=img.3...5848.6335.0.6522.5.5.0.0.0.0.0.0..0.0.msedr...0...1ac.1.34.img..5.0.0.yDZeCuBXrgM
That is a difficult question to answer without seeing the rest of the control system. How to the plans show the ailerons connecting to the control stick? I would assume that bellcrank on the bottom of the tube is what moves the ailerons, but...you're the guy holding the plans ;) Does it use push-pull tubes? Cables? Some Combination of them?

It looks like you'd need to use a push-pull tube with adjustable rod ends between the sticks because you can't push on a cable.

The plans say "3/16 Pin, 5/16 grip length washer and cotter pin"

I'm not sure how a cotter pin would help.
The cotter pin keeps the pin from working its way out.
 

Atomic_Sheep

Well-Known Member
Joined
Nov 6, 2008
Messages
201
Location
Melbourne, Australia
An extrusion is an aluminum piece formed by pushing molten aluminum through a two-dimensional "mask". Examples could include L's (also called "angle") , C's (often called "channel"), I beams, etc. They are usually sold in 6 to 8 foot lengths,and the full description should include the type and thickness of the aluminum as well as the dimensions of the "legs".
What a strange way to specify components. What are the chances of having something widely available in hardware stores or any stores for that matter that exists in the correct shape. I'm guessing you need to machine the pieces out from a solid block?

I would think there would be a rigid link between the two sticks, with a hinge at both ends where they connect to the sticks.
Ah good point.

Are the plans now on paper, and are you entering them into CAD?
That's correct. I'm building it up in CAD to see how all the pieces fit.

That is a difficult question to answer without seeing the rest of the control system. How to the plans show the ailerons connecting to the control stick? I would assume that bellcrank on the bottom of the tube is what moves the ailerons, but...you're the guy holding the plans ;) Does it use push-pull tubes? Cables? Some Combination of them?

It looks like you'd need to use a push-pull tube with adjustable rod ends between the sticks because you can't push on a cable.
Sounds like I need to look at the plans more closely. Will do.
 

Autodidact

Well-Known Member
Joined
Oct 21, 2009
Messages
4,513
Location
Oklahoma
It looks like you'd need to use a push-pull tube with adjustable rod ends between the sticks because you can't push on a cable.
Unless he has a closed loop cable for the ailerons. The pic in post #7 shows that connection between the sticks as inside the tube; it would be very difficult to bolt up a solid connection between the sticks, whereas a cable could be pulled out of the slot just enough to attach it.
 

Matt G.

Well-Known Member
Joined
Nov 16, 2011
Messages
1,253
Location
Kansas, USA
Unless he has a closed loop cable for the ailerons. The pic in post #7 shows that connection between the sticks as inside the tube; it would be very difficult to bolt up a solid connection between the sticks, whereas a cable could be pulled out of the slot just enough to attach it.
Is this thing a side-by-side or tandem? I was assuming it was tandem and that direction of movement was for the elevator and the bellcrank was for the ailerons, but now I see how it could be for a side-by-side with the bellcrank being used to actuate the elevator control.

At any rate, it's going to be just as hard, if not harder to get a cable in there as it would be a push-pull tube. We can't see what the ends of the tube look like, so I don't know what the access is like there. Either way, a means of adjustment would be necessary, and that would be somewhat easier with a push-pull tube. That could be pre-adjusted and installed, although it wouldn't be fun. It would be just about impossible to adjust a turnbuckle in there. I'm still curious what the plans have.

At any rate, not a particularly good control stick design, in my opinion.
 

Matt G.

Well-Known Member
Joined
Nov 16, 2011
Messages
1,253
Location
Kansas, USA
What a strange way to specify components. What are the chances of having something widely available in hardware stores or any stores for that matter that exists in the correct shape. I'm guessing you need to machine the pieces out from a solid block?
Extrusions are very typical for aircraft components. The whole point is so you don't have to machine it out of a solid block and waste 98% of the raw material stock.

Aircraft alloy extrusions are not something you can find at a hardware store. If you can tell us what alloy it is and what cross section and dimensions, we can probably make some suggestions as to where to find it.
 

Atomic_Sheep

Well-Known Member
Joined
Nov 6, 2008
Messages
201
Location
Melbourne, Australia
Unless he has a closed loop cable for the ailerons. The pic in post #7 shows that connection between the sticks as inside the tube; it would be very difficult to bolt up a solid connection between the sticks, whereas a cable could be pulled out of the slot just enough to attach it.
I have reviewed the plans, yes it looks like a closed loop cable.

Is this thing a side-by-side or tandem?
Side by side.

We can't see what the ends of the tube look like
This is what the whole system looks like. Very basic.

http://www.homebuiltairplanes.com/forums/member-project-logs/20439-ca-65-atomic_sheep-melbourne-australia.html

At any rate, not a particularly good control stick design, in my opinion.
It does seem very agricultural, but I haven't seen how other designs work so I can't imagine how to improve it.

Aircraft alloy extrusions are not something you can find at a hardware store. If you can tell us what alloy it is and what cross section and dimensions, we can probably make some suggestions as to where to find it.
So they are still purchased from somewhere rather than machined... interesting. Once I CAD those pieces up, I'll post them on here to see how they can be sourced.
 
Last edited:

Autodidact

Well-Known Member
Joined
Oct 21, 2009
Messages
4,513
Location
Oklahoma
At any rate, not a particularly good control stick design, in my opinion.
It looks, as the English would say, fiddly.

So they are still purchased from somewhere rather than machined... interesting. Once I cad those pieces up, I'll post them on here to see how they can sourced.
Should be readily available. Hopefully, anyway...:nervous:
 

Atomic_Sheep

Well-Known Member
Joined
Nov 6, 2008
Messages
201
Location
Melbourne, Australia
1.) Working away on the vertical stabiliser, horisontal stabiliser and wings and am trying to figure out what the profiles on the plans mean. Are the profiles for these surfaces the outer profiles at their respective stations i.e. that's what the final profile will be with flanges and covering or are the profiles supposed to mean just the ribs themselves?

2.) Also, how would you interpret these dimensions (namely 3.5" and 2.00"):

Dimensions.jpg

Would they be inclusive of the plywood cover or not? These are of the main wing spar.

3.) The spar looks like a pretty complex shape, does anyone have any good links on how to manufacture these? Are spars hand planed?
 
Last edited:

DangerZone

Well-Known Member
HBA Supporter
Joined
Sep 5, 2011
Messages
2,183
Location
Zagreb HR
1.) Working away on the vertical stabiliser, horisontal stabiliser and wings and am trying to figure out what the profiles on the plans mean. Are the profiles for these surfaces the outer profiles at their respective stations i.e. that's what the final profile will be with flanges and covering or are the profiles supposed to mean just the ribs themselves?

2.) Also, how would you interpret these dimensions (namely 3.5" and 2.00"):

View attachment 36981

Would they be inclusive of the plywood cover or not? These are of the main wing spar.

3.) The spar looks like a pretty complex shape, does anyone have any good links on how to manufacture these? Are spars hand planed?

1. Profiles usually have their perspective numbers which correspond to ribs on the side view plan.

2. Inclusive.

3. An electric planer simplifies work.


There are some pics Anton Cvjetkovic posted about the CA-65, they might allow a better perspective of the build.
 

Atomic_Sheep

Well-Known Member
Joined
Nov 6, 2008
Messages
201
Location
Melbourne, Australia
Hi guys, been a while since I touched this project but decided to do some more work on it. I'm reading through the construction manual and can't figure out what flanges and what a plywood web is. This is referring to elevator and rudder ribs. Here is the image provided.
Tail Assembly.jpg

I can provide a better resolution one if necessary.
 
Last edited:
Top