The Sabre - I don't even know what it is anymore

Yusernaym

Well-known member
I didn't expect my next original plane to be a STOL bush style, but the competition is starting, so I'm putting the Stiletto's big sister on hold while I work on this. So far, I have one bad drawing and a few ideas. I'm planning on using full-sheet wings, giving me a 60" wingspan at 8 or 9 inches chord. I'll be using CA instead of hot glue to try to keep the weight down as far as possible. Given the weight of a sheet of foamboard and all of my electronics, I'll be going for a target weight of 650-700g before battery, which'll be a challenge at a 5 foot wingspan, but I think it's possible. Most of the fancy STOL features I mentioned in the thread that sparked the challenge will be out, with the possible exception of leading edge slats or vortex generators. I'll be trying to keep it simple, light enough to take a pack C without issue, and able to haul some weight as part of the challenge, hence the trading off of some weight for wing area. The concept sketches are pretty simple, with the only complication being the need to splice two sheets of foamboard together to get enough length in the fuselage, but it shouldn't be too bad. I hope to start prototyping soon, maybe making a test bed to try different angles of incidence using wedges below the wing.
 

Yusernaym

Well-known member
Side note, as someone who crashes her planes a lot during development, I've come to appreciate the Elmer's foamboard that I thought was a mistake. It's ridiculously durable, even more than ft maker foam, though there is the tradeoff of it being a pain to work with. The airframe of the current version of the Stiletto has, by my count, had four fairly high speed crashes, three nosedives and one whack into a tree. It's held up very well, looking a little wrinkled in a couple of places but otherwise perfect.
 

Yusernaym

Well-known member
20200924_101513_HDR.jpg

And here's the concept sketch I was talking about. It's not final by any means, but it should give you an idea of what it'll look like.
 

quorneng

Master member
That sketch is quite a reasonable STOL concept.
I appreciate you didn't ask for comments but I will give you mine anyway. Feel free to ignore it!
With really big, flaps you don't need to have the wing at a big incidence angle or have that much nose high attitude when sitting on the undercarriage. If you can make the flap in two sections so much the better. Include drooping ailerons then better still.

This is my most effective STOL if measured by the difference in speed it can achieve between no flap and full flap.
FlapDownR.JPG

The flaps occupy 2/3 of the span and 1/2 the wing chord. Both sections of the compound flap are worked by a single servo with their link rods in different servo arm holes.
FlapLink2.JPG

Took a bit of trial and error to set up.
Then of course having two counter rotating motors eliminates any motor torque effect which is an important consideration as the slower you fly the less effective the ailerons become.
Just saying.
 

Yusernaym

Well-known member
That sketch is quite a reasonable STOL concept.
I appreciate you didn't ask for comments but I will give you mine anyway. Feel free to ignore it!
With really big, flaps you don't need to have the wing at a big incidence angle or have that much nose high attitude when sitting on the undercarriage. If you can make the flap in two sections so much the better. Include drooping ailerons then better still.

This is my most effective STOL if measured by the difference in speed it can achieve between no flap and full flap.
View attachment 179808
The flaps occupy 2/3 of the span and 1/2 the wing chord. Both sections of the compound flap are worked by a single servo with their link rods in different servo arm holes.
View attachment 179809
Took a bit of trial and error to set up.
Then of course having two counter rotating motors eliminates any motor torque effect which is an important consideration as the slower you fly the less effective the ailerons become.
Just saying.
Thanks! I didn't mean to leave out asking for comments, I really appreciate when more experienced people give me advice. The wing incidence angle in the drawing was quite a bit higher than it'll end up being on the actual plane. I've actually considered adding a front motor to help with that, and keep the dna of my Stiletto delta, but I only have one C-Pack motor and esc, so I'm sticking with a single. I'm going to make the wing a solid single piece and add the control surfaces to the trailing edge, so I don't think your integral double flap approach would work, but it looks really good.
 

Yusernaym

Well-known member
20200924_112527_HDR.jpg

I had a break between classes so I made a quick scrap foam mockup of the wing profile, and figured out where the cuts should be. I'll start them a little further forward to keep the bottom more flat, but other than that it looks good. That spar mockup is very rough, just in there to take up space, but it showed me that I should probably have a double-layer spar for better rigidity. I also laid out some of the wiring, and found that while I had more than I thought, I'm still well short of having enough servos or extensions. This thing is going to have a lot of servos. Four in the wings, one for the elevator, one for the rudder, and one to steer the tail wheel (that'll be a 5g) Which brings us up to seven. Right now I'm at least two short, likely more as the 9gs I have are pretty old and I don't really trust them. I also only have two y splitters, which is enough for the ailerons and flaps, but I need one more for the rudder and tail wheel servos. The reason I'm splitting the rudder and tail wheel is to take the force of impacting the tail wheel off of the rudder, learning from my Edge 540, which tried to rip the rudder off on any landing. With all of those servos, I might want a separate BEC, but I don't have one right now and I'm trying not to spend too much on this build.
 

Timmy

Legendary member
That sketch is quite a reasonable STOL concept.
I appreciate you didn't ask for comments but I will give you mine anyway. Feel free to ignore it!
With really big, flaps you don't need to have the wing at a big incidence angle or have that much nose high attitude when sitting on the undercarriage. If you can make the flap in two sections so much the better. Include drooping ailerons then better still.

This is my most effective STOL if measured by the difference in speed it can achieve between no flap and full flap.
View attachment 179808
The flaps occupy 2/3 of the span and 1/2 the wing chord. Both sections of the compound flap are worked by a single servo with their link rods in different servo arm holes.
View attachment 179809
Took a bit of trial and error to set up.
Then of course having two counter rotating motors eliminates any motor torque effect which is an important consideration as the slower you fly the less effective the ailerons become.
Just saying.
woah ho ho! I've been looking for flap designs and yous is amazing! I
 

Timmy

Legendary member
View attachment 179810
I had a break between classes so I made a quick scrap foam mockup of the wing profile, and figured out where the cuts should be. I'll start them a little further forward to keep the bottom more flat, but other than that it looks good. That spar mockup is very rough, just in there to take up space, but it showed me that I should probably have a double-layer spar for better rigidity. I also laid out some of the wiring, and found that while I had more than I thought, I'm still well short of having enough servos or extensions. This thing is going to have a lot of servos. Four in the wings, one for the elevator, one for the rudder, and one to steer the tail wheel (that'll be a 5g) Which brings us up to seven. Right now I'm at least two short, likely more as the 9gs I have are pretty old and I don't really trust them. I also only have two y splitters, which is enough for the ailerons and flaps, but I need one more for the rudder and tail wheel servos. The reason I'm splitting the rudder and tail wheel is to take the force of impacting the tail wheel off of the rudder, learning from my Edge 540, which tried to rip the rudder off on any landing. With all of those servos, I might want a separate BEC, but I don't have one right now and I'm trying not to spend too much on this build.
that's a really thick wing!
 

Yusernaym

Well-known member
20200924_143702_HDR.jpg

We have the spar halves gluing and laid out on the wing. Next steps are going to be getting more servos, because I'm not going to use the old ones, cutting and test forming the curve of the wing, cutting and installing the wood for the wing attachment, and installing the wing servos. I have a plan for the fuselage, but it's not fully fleshed out yet with regards to tail servo locations and the tail wheel mounting.
 

Yusernaym

Well-known member
The wing is going to be attached using plywood plates that are glued to the spar and slide in to matching plywood on the fuselage side. There will be captive nuts on the wing side of these that will have bolts screwed through from the outside of the fuselage. I think I'll also use rubber bands for redundancy, but we'll wait until I have more of the plane built to make decisions like that.
 

Yusernaym

Well-known member
20200924_192108_HDR.jpg
20200924_200015_HDR.jpg

We've got a wing, and we have the sides of the fuselage. This is going to be a weird looking plane. I'm going to have to make the fuselage wider than I was planning for better wing support and less goofy looks. That means I'll have to figure something out to mount the firewall, as it's only about two inches wide and I need more than that. I've also decided to eschew the wood mounting system in favor of an easier solution - a whole bunch of rubber bands. I have switched back to hot glue because white gorilla glue takes approximately forever to cure and I don't have a ton of time to work. I'm going to accept the weight tradeoff for being able to finish my plane in a timely manner.
 

Yusernaym

Well-known member
So i weighed what I have so far, and we have a bit of a problem. We're at about 1kg, and I haven't installed servos, landing gear, or the tail stabilizers yet. I'm not sure what to do from here, honestly. I think I'll keep going and see how it turns out, but it's looking like it'll be a bit underpowered with the c-pack motor. I might have to step up to 4s and/or a higher pitch prop to get enough thrust out of this thing.
 

Yusernaym

Well-known member
I do need to keep reminding myself that it's going to be flying slow anyways, but I'm used to an Arrow that can go vertical almost as fast as it goes level, so it'll take some getting used to to fly something proportionally much less powerful.
 

Yusernaym

Well-known member
20200924_210731_HDR.jpg

Here's where we're at. For the amount of time I had today, I think I made good progress. I'm going to be making everything behind the wing narrower to give the prop a better chance of getting enough air, so it'll be widest in the middle of the fuselage, tapering to the nose and tail. This is a big plane. I knew that from the start, but adding the fuselage made a big difference in my perception of the size of this thing. I'm really looking forward to getting her finished and flying, even if she is underpowered, though I have a friend who might be able to lend me some electronics with a little more go if that's a problem.
 

Yusernaym

Well-known member
And I just remembered that I have some store credit at my hobby shop that would bring a second pack c down to a reasonable price, solving pretty much all of my problems at once. I would have twice the thrust and four more servos to work with, which would make things a little easier to figure out going forward, and having counter rotating props would keep the Stiletto family's signature feature going while solving the same problem it did there.
 

Apis

Member
That sketch is quite a reasonable STOL concept.
I appreciate you didn't ask for comments but I will give you mine anyway. Feel free to ignore it!
With really big, flaps you don't need to have the wing at a big incidence angle or have that much nose high attitude when sitting on the undercarriage. If you can make the flap in two sections so much the better. Include drooping ailerons then better still.

This is my most effective STOL if measured by the difference in speed it can achieve between no flap and full flap.
View attachment 179808
The flaps occupy 2/3 of the span and 1/2 the wing chord. Both sections of the compound flap are worked by a single servo with their link rods in different servo arm holes.
View attachment 179809
Took a bit of trial and error to set up.
Then of course having two counter rotating motors eliminates any motor torque effect which is an important consideration as the slower you fly the less effective the ailerons become.
Just saying.


I enjoy the look of that plane. Reminds me a bit of the Wingo. Do you have a design/build page on your plane?
 

quorneng

Master member
dH04000
Unfortunately the push/pull STOL is a bit of a 'Frankenstein'.
The compound flap wing was built in Depron as an experiment to be used on my Artec Wing Dragon. I wanted to see if the flaps would compensate for the smaller wing area, just 55% of the original wing, to give the same landing speed.
The actual build (in 2009!) of this wing is shown here.
In 2012 (it is really that old!) I decided to use the compound flap wing on a dedicated Depron fuselage incorporating two small push/pull motors. Unfortunately I did not describe that part of the build anywhere.
But it does fly
 

Yusernaym

Well-known member
Huge change in plans today. I have decided that locking myself into the inline twin motor setup was making the design process difficult, so I'll be making it a twin tractor, with the motors mounted on the wing. I think the wing will be solid mounted, both to keep it sturdy and make wiring easier. The redesigned fuselage will be mostly rectangular, rounded at the front, and keep the ample cargo capacity designed in from the beginning. Having the motors directly mounted on the wing should also help with takeoff performance, as they can just shove air at the flaps, and will allow me to set up differential thrust for reliable low-speed control.
 

Yusernaym

Well-known member
So, on the topic of dramatic changes to this plane, I had another idea. There's really nothing stopping me from making this a low wing, right? One of the reasons I abandoned the inline design was looks, and I think it would look interesting with a low or mid wing. I need some feedback before I commit to it, so do any of you have advice on whether or not I should make it a low wing?