JJ Colorado
Very Strong User
C/L ! Just beware of the dreaded figure 9.
One of my RC club has an area cut for C/L and I have a few planes to fly there. The new electric throttle controls / timers make solo launches a lot easier.
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Doc's D-Lite - A new thermal build at Aloft
- Thread starter Wayne
- Start date
One of my RC club has an area cut for C/L and I have a few planes to fly there. The new electric throttle controls / timers make solo launches a lot easier.
Hawaii Sloper
Very Strong User
Love the keyed parts on the rudder. That will make building for newer modelers (and experienced ones) easier and less stressful!
Konrad
Very Strong User
What I like is how much weight has been removed from the new wing. Also the quality of the laser cut is much improved. Does Doc (Ed )have any reason for keeping with the flat plate vertical fin. And has he looked at the problem I contacted you about the rudder geometry. As engineers we tend to look for way to drop out variables. I think Doc and I got this wrong. I'd like to make sure this doesn't get into production. I also mentioned Dr Drela's surface engagement system.
I don't recall what issue you had brought up??
We like the flat plate to keep things simple and the price low. We can look at a foiled tail in the future, but it does add complexity, and would there be enough benefit for that?
Doc keeps wanting to add complexity and I keep wanting to keep it simple. My thought is don't force the builders into anything complex, they can always do a complex mod on their build if they like, but always start with simple. For example on the tail we are going with normal push/pull rods and control horns, not pull strings with return springs, or crazy internal linkages. KISS
We like the flat plate to keep things simple and the price low. We can look at a foiled tail in the future, but it does add complexity, and would there be enough benefit for that?
Doc keeps wanting to add complexity and I keep wanting to keep it simple. My thought is don't force the builders into anything complex, they can always do a complex mod on their build if they like, but always start with simple. For example on the tail we are going with normal push/pull rods and control horns, not pull strings with return springs, or crazy internal linkages. KISS
Konrad
Very Strong User
You guys don't use the contact us part of your site?
(I go over this with the guys on my next visit)
As this is an aircraft for the builder and F3J REF flier I'd think adding features that don't add much if anything to the complexity of a build would make the kit more desirable. A fleshed out tail will add more strength and or lightness and maybe even more authority. The only downside I see is in the up front engineering. But from the end customer's point of view, with this target customer, a built out tail is a desired feature.
I don't think KISS is the best principle for this level of model, competition or builder. But this is your's and Doc's project.
(I go over this with the guys on my next visit)
As this is an aircraft for the builder and F3J REF flier I'd think adding features that don't add much if anything to the complexity of a build would make the kit more desirable. A fleshed out tail will add more strength and or lightness and maybe even more authority. The only downside I see is in the up front engineering. But from the end customer's point of view, with this target customer, a built out tail is a desired feature.
I don't think KISS is the best principle for this level of model, competition or builder. But this is your's and Doc's project.
JJ Colorado
Very Strong User
Could just add an optional set of 1/16 inch balsa riblets that could optionally be glued to the vertical stab to provide a little airfoil shape priot to covering. That way you can make a slab stab, or optionally build the slab stab (to get it straight, then add the tiny bit of airfoil to it after the glue is set. For the rudder itself ou can simply sand that part to shape.
Konrad, we can add options to the build instructions showing more complex methods.
Do you really think there is a great advantage of having pull string and a spring on the tail of a plane like this? I personally do not as I this plane will be coming in at an appropriate weight for its airfoil already. But here is the great thing, if you want to do that, then do it!
Do you really think there is a great advantage of having pull string and a spring on the tail of a plane like this? I personally do not as I this plane will be coming in at an appropriate weight for its airfoil already. But here is the great thing, if you want to do that, then do it!
Very true.
JJ Colorado
Very Strong User
I doubt pull spring systems would be good in something more than 2.5m.
Looks like you are planning to compete with the 3.5m Yellow Jacket.
Looks like you are planning to compete with the 3.5m Yellow Jacket.
Konrad
Very Strong User
I do like Pull Pull but they aren't worth the extra work. That would be a builder option. I've actually used them to good effect on ships larger that 4meter and some full size models.
I'm thinking of taking the material budget in the current structure and using it to make a "thicker" vertical stab. Fleshing out the vertical will allow the geometry to add a whole lot of stiffness allowing the designer to actually lower the amount of material to maintain the same stiffness of the flat sheet fin. No need to add any rib material. What I'm thinking is a total redesign of the fin not an add on feature. If designed from the outset this would allow for just as easy a build as the flat plate. But this isn't my design.
But what I am concerned with was some of the discutions I had with Ed. I think he and I were a bit too eager to drop some variable in our control discussions.
Like I said this is best discussed face to face.
We are building up the second prototype right now. Many refinements since the first version. If it meets our goals, she will be ready to go into production, with one exception, waiting for some changes to our fiberglass fuselage. (our manufacturer is out for a bit with a hand surgery.) Our goal is to keep the price very reasonable.
We will probably offer a 2 or 2.5 meter cousin later on.
We will probably offer a 2 or 2.5 meter cousin later on.
Any chances on getting a wing and tail kit to use any fuselage I want?
Konrad
Very Strong User
Saw this and Doc on my last visit. Gotta say I'm liking the revisions I'm seeing in the second prototype. I have to say I'm not on the design team so these observations are just mine based on a cursory look at the plans, build and informal discussions with the primary designer, Doc.
I like the LE sheeting and subsequent design features. The airfoil is based on some Dr. Drela (not the Doc referred to in the title) airfoil. I'm not an aerodynamicist so I don't recall which one. But it is one designed for wood construction with an emphasis on controlling the separation bubble. Dr Drela notes that the LE sheeting needs to be brought back at least to the 40% chord so that the transition from the sheeting to the open structure doesn't cause premature separation of the airflow. Along those lines Doc has added a drag spar (Red thing in the drawing) at the aft end of the top sheeting to control the pop up we so often see with unsupported sheeting. Sheeting pop up would be worse than the classic separation bubble issue with the sheeting stoping at the apex of the airfoil (on top of the spars). This drag spar is a pain to build with! But the end result is well worth the effort.
Something that I don't think has been discussed enough is the added structural strength/stiffness the aft LE sheeting provides. You can think of this as an added arch in conjunction with the 'D' tube front wing. Doc has used this in the justification for going with a thinner than "normal" built up balsa wing. I've forgotten the advertised thickness of the airfoil. But it is thin for a wooden wing and near that of most composite wings. (This is key to the plane's performance).
Some other design features not obviously apparent at a glance is that Doc is using what he calls a "Starburst" pattern. The idea is to try to get some of the ribs to align with the torsional forces that might be seen on the fin and stab. These forces are usually addressed with intercostals diagonals going between the ribs. This starburst pattern is trying to make the allocated structure (weight) do more than one thing at a time.
P.S.
@Wayne , did I pass the pop quiz for structures, material properties and aerodynamics?
I like the LE sheeting and subsequent design features. The airfoil is based on some Dr. Drela (not the Doc referred to in the title) airfoil. I'm not an aerodynamicist so I don't recall which one. But it is one designed for wood construction with an emphasis on controlling the separation bubble. Dr Drela notes that the LE sheeting needs to be brought back at least to the 40% chord so that the transition from the sheeting to the open structure doesn't cause premature separation of the airflow. Along those lines Doc has added a drag spar (Red thing in the drawing) at the aft end of the top sheeting to control the pop up we so often see with unsupported sheeting. Sheeting pop up would be worse than the classic separation bubble issue with the sheeting stoping at the apex of the airfoil (on top of the spars). This drag spar is a pain to build with! But the end result is well worth the effort.
Something that I don't think has been discussed enough is the added structural strength/stiffness the aft LE sheeting provides. You can think of this as an added arch in conjunction with the 'D' tube front wing. Doc has used this in the justification for going with a thinner than "normal" built up balsa wing. I've forgotten the advertised thickness of the airfoil. But it is thin for a wooden wing and near that of most composite wings. (This is key to the plane's performance).
Some other design features not obviously apparent at a glance is that Doc is using what he calls a "Starburst" pattern. The idea is to try to get some of the ribs to align with the torsional forces that might be seen on the fin and stab. These forces are usually addressed with intercostals diagonals going between the ribs. This starburst pattern is trying to make the allocated structure (weight) do more than one thing at a time.
P.S.
@Wayne , did I pass the pop quiz for structures, material properties and aerodynamics?
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Konrad
Very Strong User
This is more a discussion of the limitation of some CAD programs. First I need to be clear that there are huge differences between CAD (Computer Aided Design) and CAD (Computer Aided Drawing) programs. I'm sure that is clear as mud!
As a former machinist and manufacturing engineer I was comfortable with some of the earlier CAD/CAM programs (Computer Aided Design/Computer Aided Machining [Manufacturing]). Today much of what I see in hobby grade CAD (Computer Aided Design) really are just powerful CAD (Computer Aided Drawing) programs. This is fine as most Hobby CNC machines really only work in 2D. And as engineering hobbyists we aren't asked to do a full blown analysis of the Form Fit and Function of the design. (Well, not unless you are trying to sell me some BS.)
When I was last at Aloft I saw this fin and was asking why the radius for the ribs were inconsistent? As one of the last generation of machinists taught on manual machines I like to see the print call out standard radius as it helps with the selection of the cutter to be used. (This is just my eye, with the XY table of a laser cutter this is not a concern.)
Talking with @RafaelAvila I learned that he had to use the brute strength method to generate the radius, as the CAD program he was using has some limitations.
Normally when I draw a corner I just let the lines intersect I then come back and ask the program to add a radius I've defined earlier. And as if by magic, the corner has the radius I defined. I was usually doing this in the 3D model. In a 2D rendition or drawing these left over artifacts often are still in the vector defined code. As such the laser cut file will see these and cut them. I believe Ralael had to draw this with spline of bezier curve tool (brute force) to avoid the unseen cut lines.
This is just me, but I like to see parts without the delicate points. (See this post and attached drawing) I just get a bad feeling whenever these break off during the build.
Please give the guys at Aloft your feedback during the prototype stage. If there is good reason and it isn't too difficult I'm sure the crew would love to add the feature or your input into the design.
FWIW, All my drawing where done in an antiquated CAD (Computer Aided Drawing) called Canvas 8. For this forum all my drawing are free hand. I haven't set any constraints as I would, if making real engineering drawings. It is best to think of these as sketches at best. (I like to call these cartoons)
As a former machinist and manufacturing engineer I was comfortable with some of the earlier CAD/CAM programs (Computer Aided Design/Computer Aided Machining [Manufacturing]). Today much of what I see in hobby grade CAD (Computer Aided Design) really are just powerful CAD (Computer Aided Drawing) programs. This is fine as most Hobby CNC machines really only work in 2D. And as engineering hobbyists we aren't asked to do a full blown analysis of the Form Fit and Function of the design. (Well, not unless you are trying to sell me some BS.)
When I was last at Aloft I saw this fin and was asking why the radius for the ribs were inconsistent? As one of the last generation of machinists taught on manual machines I like to see the print call out standard radius as it helps with the selection of the cutter to be used. (This is just my eye, with the XY table of a laser cutter this is not a concern.)
Talking with @RafaelAvila I learned that he had to use the brute strength method to generate the radius, as the CAD program he was using has some limitations.
Normally when I draw a corner I just let the lines intersect I then come back and ask the program to add a radius I've defined earlier. And as if by magic, the corner has the radius I defined. I was usually doing this in the 3D model. In a 2D rendition or drawing these left over artifacts often are still in the vector defined code. As such the laser cut file will see these and cut them. I believe Ralael had to draw this with spline of bezier curve tool (brute force) to avoid the unseen cut lines.
This is just me, but I like to see parts without the delicate points. (See this post and attached drawing) I just get a bad feeling whenever these break off during the build.
Please give the guys at Aloft your feedback during the prototype stage. If there is good reason and it isn't too difficult I'm sure the crew would love to add the feature or your input into the design.
FWIW, All my drawing where done in an antiquated CAD (Computer Aided Drawing) called Canvas 8. For this forum all my drawing are free hand. I haven't set any constraints as I would, if making real engineering drawings. It is best to think of these as sketches at best. (I like to call these cartoons)
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Konrad
Very Strong User
This goes under personal preference.
Why use a round carbon leading edge?
It is my experience that these carbon rods are troublesome. They are brittle and very difficult to repair. In the raw form the covering doesn't attach well. In this application the top sheet might not bond well. I see no advantage to the carbon leading edge, other than maybe as an assembly aid or cost.
I'd like to see a LE much like these. I also think the wooden LE if done correctly is much more durable for the reasons given here
Why use a round carbon leading edge?
It is my experience that these carbon rods are troublesome. They are brittle and very difficult to repair. In the raw form the covering doesn't attach well. In this application the top sheet might not bond well. I see no advantage to the carbon leading edge, other than maybe as an assembly aid or cost.
I'd like to see a LE much like these. I also think the wooden LE if done correctly is much more durable for the reasons given here
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Konrad
Very Strong User
In my discussions with Aloft on Friday I learned that there was some misunderstand as to what I was trying to say about a fleshed out set of stabilizers and more advanced builds. When one moves up to this class of glider it is assumed that one has some experience with wood gliders. If this is true, the KISS principle when it comes to construction is often not the best philosophy.
We have learned that the new fuselage is to have at least a 25 mm (1 inch) longer nose to help with the balance. As some of you know I don't like long nose gliders out of concern for directional stability and mass coupling. This adds to the pilot work load and adds to the recovery time from a stall, particularly in a turn such as coring a thermal.
I'm of the opinion that a flat plate sheet balsa is not the best allocation of the mass budget. I don't have too much concern about the effectiveness of a flat plate verses an airfoiled surface. After all many full sized general aviation planes has flat plate tails. So do many high performance aircraft such as Leo Loudenslager's Laser. A surface that has some added thickness can be much stiffer/stronger than a flat plate for the same amount of material.
The benefit of adding a bit of complexity in the design can be seen in the tail surfaces of this Chrysalis lite from DJ Aerotech. These fleshed out surfaces actually were no more difficult to build than the current flat plate design with ribs.
Now I'm not advocating for one method over another as to how to get this thicker structure. But adding ribs to the existing flat plate structure to my mind is counter productive when it comes to taking weight out of the tail. I think the design needs to have this lightness designed into the structure from the beginning. We (I) do see a huge improvement in the loss of tail mass with these pieced flat plate tails from the originals with lightening holes. (BTW; I'd like to see a 'D' tube set of tail feathers)
Let Aloft know that if you are going to go through the effort to build those wings that you would, or would not, be willing to spend another 10 minutes assembling a lighter set of tail feathers.
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