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FTFC'18 WWII Curtiss-Wright XP-55 Ascender

#41
Thanks... good information. I was going to aim for 1/3 cord, kind of like CG. But now.. maybe I'll do it right.
I should probably clarify that I meant 1/4 MEAN (average) aerodynamic chord, not root chord. It ends up being at around 1/3 root chord for wings due to the sweep, depending on angle. That's why I linked to the wing CG calculator. Much easier to calculate that using the site then do it by hand every time :).

I am looking forward to both of your canard builds, really seeing some awesome aircraft surface for this challenge!
 

rockyboy

Skill Collector
Mentor
#42
Thank you for the clarification - and yeah, I'm super excited about all the awesome designs people are tackling! :applause:
 

localfiend

I like 3D printers...
Mentor
#43
Sorry, been out of it and didn't see your shinden canard question.

A bit less than half of the canard moves. This is a mini version, but same ratio.



And here's an abused FT Vector with full flying canard slapped in. This actually worked really well, needed a bigger servo than 5g though, which is why it's apart.

 

HilldaFlyer

Well-known member
#44
Thanks my friend

A bit less than half of the canard moves. This is a mini version, but same ratio.
Ok - moving half a canard is cheating... :rolleyes:

And here's an abused FT Vector with full flying canard slapped in. This actually worked really well, needed a bigger servo than 5g though, which is why it's apart.
Oh, I see how you did that now. Great - I was trying to come up with a way to twist the dowel. Very clever!

So, is the dowel just poked through the foam board or do you have some sort of gift card or ply to stabilize the foam?
 

LitterBug

Troll Spammer
#45
So, is the dowel just poked through the foam board or do you have some sort of gift card or ply to stabilize the foam?
I'm going to be using some tubing or a 3D printed hole to have the skewer pivot in. I'll hot-glue those in to the fuselage so the pivot holes don't get sloppy.

Cheers!
LitterBug
 

HilldaFlyer

Well-known member
#46
I'm going to be using some tubing or a 3D printed hole to have the skewer pivot in. I'll hot-glue those in to the fuselage so the pivot holes don't get sloppy.

Cheers!
LitterBug
Sounds good. I haven't decided what I'm going to do yet... but while at work daydreaming about building today, I thought what I'd do is to build a FT-style prototype, you know, the easy build using FT techniques and if it all works out do a more elaborate build with more advance techniques to capture more scale aspects that make this such an eye catching aircraft.

I've got the outline traced. Trying to decide if the prototype will have square or octagon fuselage. Easy vs. hard???
Probably square.
 

LitterBug

Troll Spammer
#47
By tubing, I meant a soda straw or coffee stirrer... Could also use the centers from some old props that have been mangled. Gotta keep it in the FT budget and made from stuff laying around!

Cheers!
LitterBug
 

HilldaFlyer

Well-known member
#48
By tubing, I meant a soda straw or coffee stirrer... Could also use the centers from some old props that have been mangled. Gotta keep it in the FT budget and made from stuff laying around!

Cheers!
LitterBug
Yeah, I was thinking straw of some sort. Good call.
So tell me if the connection between the canard and dowel is strong enough. I'm always afraid that something of this configuration will start slipping over time - so like I said earlier, I tend to over engineer. I've had control horns and servos come loose during flight, and that's no fun (for the plane) but I always get a chuckle out of it since I rarely loose a lot of $ in a crash.
 

localfiend

I like 3D printers...
Mentor
#49
Ok - moving half a canard is cheating... :rolleyes:



Oh, I see how you did that now. Great - I was trying to come up with a way to twist the dowel. Very clever!

So, is the dowel just poked through the foam board or do you have some sort of gift card or ply to stabilize the foam?
Heh, it moves more than the full scale version does. :D

The vector bbq skewer is just poked through the foam. Didn't much care as it was just a proof of concept.

Bracing would be good. You could also use wire with bends on either end to better hold each side in tandem on a bigger plane.
 

HilldaFlyer

Well-known member
#50
I Spent the day cleaning the build area. I got home from FlightFest 2017 and left almost directly on a 3 week cross country road trip. Not complaining, just saying I dumped all the FF stuff and went away. Golly, it took a day to put all the stuff back.

During this past week I have been working on the plans in the evening.


Here is the wing so far. For the simplistic FT-Style I’m going to omit the wing extension elevons. I have increased the size of the inboard elevons to make up the difference, but I know a lot of roll motion is produced from the wing tip. If you have a beef with that, let me know. I can make the elevons wider and longer if needed, but I believe these will suffice.

Just to let you know what I’m thinking, for the more scale model, I am going to do one of two things to control the outboard elevon. One option is to put a single servo to drive both control surfaces underneath the vertical stabilizers (which, by the way, will not have rudder control surfaces). I’ll then use two control linkages from one servo to both control surfaces. More likely, however, I think the better approach, although will add weight, is to install an additional servo for the outboard control surface. This kind of configuration will allow me to make it an elevon or aileron as desired.

 
#51
I think you will be good omitting the wing extension control surfaces... ...ex-cons?
The inboard surface is far enough away from the CG that you will have plenty of leverage.

I would go with two servos as well. I think elevons would be the best way to go. Especially with that wing sweep. Stalls are going to be quick and deadly. Although, those winglets will help.

Looks good so far, keep it up!

Edit:
Looking at the wing layout again, omitting the ex-cons would actually help with stability. If you were to put the inboard elevons with a nose up attitude and leave the ex-cons stationary, you will have a "v" shaped drag at the tips which is far aft of the CG.

Edit: Edit:
Oops, never mind. I totally misread that. I thought you meant omitting the ex-con all together and using one servo for both inboard ailerons. Thats what I get for staying up WAY past my bed time. I was well beyond Three Mile Island and fast approaching Chernobyl by that point.

Sorry about that.
 
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HilldaFlyer

Well-known member
#52
Wing Prototype

Printed out the wing plan and slapped a wing together with hot glue. Here are some photos.


Wing cut out.


Peel paper from the inside 4 cm from trailing edge following the line of the elevon hinge. The masking tape is used to stabilize the paper for peeling. I’m using Ross foam board and since it doesn’t peel that easily, tape helps hold it together while peeling.


The trailing edge was beveled along the elevon hinge line. I used a hot wire cutter to make the bevel, but you can use sandpaper.


The leading edge was beveled to 1 cm from the edge. I creased the bottom panel at 2 cm from the leading edge and the top panel had creases about every cm like the plans show. This many creases was a little tricky, but it made for a real nice curve.

Glue the spar to the bottom panel along the marked line. (no photo).


The leading edge along the wing tip was glued together with hot glue. I put a small bead of glue between the wing panels, waited for it to cool a bit and then squeezed it toward the leading edge. Let the glue cool to a point that it won’t burn and then keep pinching the edges together.


The spar was glued to the top panel and then the trailing edge of the top panel was glued to the bottom panel. Nice looking wing with sharp trailing edge.



Things Learned

Top panel was short on the trailing edge by 1 cm at the root and 0.5 cm at the vertical stabilizer.
The top and bottom panels are separated at the point I would like to make a hinge.
The wing tip is too thin to add another servo and control surface. Hopefully it won’t need it.
Need to move the fold lines to be parallel to spar.

 
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#54
Wow, that's a great airfoil! Smooth!
If the rest of your build looks like this, you are going to have one clean air frame.

High speed, low drag!

What are your thoughts on the power plant?
 

HilldaFlyer

Well-known member
#55
Wow, that's a great airfoil! Smooth!
If the rest of your build looks like this, you are going to have one clean air frame.

High speed, low drag!

What are your thoughts on the power plant?
Well - thank you. Compared to your build... this is really amateurish, but we won't compare. I have to admit the wing looks a lot better than I expected... but the fuselage won't look nearly as sexy as yours... I'll post below and you'll see what I mean.
 

HilldaFlyer

Well-known member
#56
Last night I had a frenzy of activity.

Built another wing after making adjustments to the plans.

Cut out the wing. Crease along the crease lines. Score cut the leading edge. Bevel the leading edge to 1 cm from the leading edge. Sand the bevel to make it smooth. Bevel the trailing edge to about 4 cm (the plans have been marked at the point where the elevons hinge). I used a hot wire cutting tool (shown above, along with the strip of foam that I removed). This can be done with a sanding block (shown) but it is way more messy. The wing tip is beveled to 1.5 cm but should be more, as I discovered when gluing.


Glue the spar into place (for this quick prototype I used hot glue, but I will use Gorilla glue in the real deal).


I am going to practice using Gorilla Glue on this prototype, so the leading edges of the wing tip were tacked together with masking tape. This only shows the first to pieces. Spread the trailing edges apart from each other until the leading edges meet and tape them together.


Cover the entire slot with tape. and the wing will look like this. Run a bead of Gorilla Glue along the leading edge and the taped together portion of the wing tip. Using a toothpick, spread Gorilla Glue along the rest of the tip edge.


Use tape to hold the edges together. It will look something like this. Now run a bead of Gorilla Glue along the spar. Smear Gorilla Glue along both top and bottom panels of the beveled areas. I use a playing card.


Use masking tape to hold the wing tip trailing edges together.


I used weight to hold the rest of the trailing edge together. I placed the whole mess on wax paper.

Give it about 30 minutes to cure and remove the tape. If you let the Gorilla Glue cure completely, then you have glued tape to the wing and it is really, really hard to get off.

 

HilldaFlyer

Well-known member
#57
Box Fuselage

Here is the first pass at the square fuselage… I’m envious of all the other builds with roundish fuselages. So here goes a square body, nothing like a hard body.


Cut it out The notches will hold the shelf.


This is the center shelf. It will stabilize the fuselage when the wing slots and canopy are cut away. It also will form the foundation for the canard hinge. The wings will be fitted with risers that connect to the shelf for alignment.


Fold it together. I have yet to cut out the fuselage top, which will have rounded foam turtledeck.



And here is how the wing will attach. Yeah, it is held together with tape for now. I have some adjustments to make on the nose. You see - I don’t do 3D designs (yet), so I plan in Illustrator, pring, build and adjust the plans. The first prototype is fairly clunky.

I’m going to use the box fuselage for the prototype to make sure it flies, but in the meantime, I’m going to see what I can do about getting the fuselage to be rounder.

What are your thoughts on the power plant?


Power Plant. That is a good question. I don’t know what kind of FT size motor class this fits but I’m thinking NTM 2836 1800 kv with 2200 3S. This setup with a 7x5 prop pushes 2 lb thrust at 30 amps. I’m not going for speed, although it will look fast. The next setup under consideration is NTM 3536 1800 kv on 3300 mAh 4S using 7x6 will pull 60 A and deliver 3 lb 4 oz of thrust.

 

PsyBorg

Wake up! Time to fly!
#58
Lookin good mate.

The round fuselages are not hard to do as much as they can be tedious and finicky. I have been messing around with methods for bending round things from flat foam. It takes a bit of practice for sure. Sticking to what you know and what you know works is always best. so nothing wrong with square.

To quote Huey Lewis and his nose...

 

HilldaFlyer

Well-known member
#59
Ok, going to be hip for now. I've done octagons previously. I'm thinking that for ease of build, square and octagon are fine, more curve than that ends up being too complicated for the average FT builder (what do you think?)
 
#60
Square, octagon or round, you can tell when someone puts the time in. Something I learned very quick in art, a good artist can express more with one line than others can using all of the lines in the world.

Judging from the looks of that wing, I am sure this thing is going to look great.

The first setup there sounds pretty equivalent to a c-pack, but that 4 cell setup sounds like it will be a monster! I think you are going to need a liiiiittle more tape to hold that wing on! :p

Seriously though, it's looking good brother, keep it up!