13th Squadron SB2C Helldiver

[Niez13]

13th Squadron SB2C Helldiver

​

Plans: 13thsquadron.com

Here is the latest design off of the workbench, the Curtiss SB2C Helldiver at a 48" inch wingspan. It replaced the SBD Dauntless during the war but had mixed results with pilots saying it had a twitchy elevator. Although most people may think of the SBD when thinking of "WW2 Dive Bombers", the Helldiver is @willsonman // Joshua Orchard's favorite dive bomber/plane ever. We had a great time at the "Wings Over Edgewater" event and got to talk with Joshua Orchard about the design and history of the Helldiver. I let Joshua fly the Helldiver and take it home with him for further inspection. Hope all of you enjoy the design and let me know if you have any questions on the build!

Build Pictures: 13thsquadron.com

 

[Oldrover TJ]

Time to hide the Yamato!

 

[willsonman]

After taking this one home (very generous of you) I got to work making a power pod as I wanted to put my own motor and 4-blade prop on. A power pod assembly is a first for me in years but it was done is short order. I used a PETG printed front plate rather than a wood one.

The motor I had was from the Dynam B-26 at around 750kv and swings a 10.5x8x4 prop. On a normal 2200mAh pack it draws around 155W so a 30A ESC was totally fine here (less than 15A draw).

After a couple of smaller sorties at my local field the club guys and I had a conversation about the flight characteristics. It was constantly trying to fight me on power. Add a bit of power and she'd balloon up. Cut it and she would glide just fine. No issues. We initially thought there may be an incidence discrepancy since the semi-symmetrical airfoil works so well here. Then we spotted it. The elevator was indeed slightly up. We are talking only 2 or 3 mm of throw up. HOWEVER, this is a fairly short-nose-coupled aircraft so tail sensitivity is likely to be premium. I used the programming in my radio to adjust the center point of the servo throw (different from trim on OpenTX) and gave her another toss.

At this point I have to say that the issue is entirely gone. No bad tendencies at all. The 150-ish watts of power is plenty for how this airplane cruises. It takes a little bit of work to get altitude and if you try to go to fast she will bite you. When the foil stops flying the whole airplane does and it's pretty great. It forces you to be a better pilot and fly the airplane. Cruising at 1/2 throttle is straight and level and then applying throttle does what airplanes are supposed to... they gain altitude... not point the nose up to gain altitude, but as the airplane goes by it will just go higher. It's pretty awesome to fly something so small and so aerodynamically correct.

I had her out at a warbird event this past weekend and flew her many times. It was great to call up other attendees to give me a hand-launch and then they look at it fly and then they realize that it's something unusual. We then start the whole conversation about the history of the Helldiver and why it's great, and why it maybe wasn't. Everyone marveled at how well it flew and it just "looked the part" in the air. I've had about 12 flights on her now and still have yet to break the prop. SUPER light airplane helps on that.

I'd like to do retracts because I'm me but it's so light now that I think I would ruin it by adding them. The only bummer is that it really could use some sort of grip on the bottom for hand-launching. Have a look at the bottom of the EFlite RearBear. One of the best hand launch designs I've seen. I have one if you need a reference picture. I may just have to design something to print and cut a hole in the bottom for it.

 

[Niez13]

After taking this one home (very generous of you) I got to work making a power pod as I wanted to put my own motor and 4-blade prop on. A power pod assembly is a first for me in years but it was done is short order. I used a PETG printed front plate rather than a wood one.

The motor I had was from the Dynam B-26 at around 750kv and swings a 10.5x8x4 prop. On a normal 2200mAh pack it draws around 155W so a 30A ESC was totally fine here (less than 15A draw).

After a couple of smaller sorties at my local field the club guys and I had a conversation about the flight characteristics. It was constantly trying to fight me on power. Add a bit of power and she'd balloon up. Cut it and she would glide just fine. No issues. We initially thought there may be an incidence discrepancy since the semi-symmetrical airfoil works so well here. Then we spotted it. The elevator was indeed slightly up. We are talking only 2 or 3 mm of throw up. HOWEVER, this is a fairly short-nose-coupled aircraft so tail sensitivity is likely to be premium. I used the programming in my radio to adjust the center point of the servo throw (different from trim on OpenTX) and gave her another toss.

At this point I have to say that the issue is entirely gone. No bad tendencies at all. The 150-ish watts of power is plenty for how this airplane cruises. It takes a little bit of work to get altitude and if you try to go to fast she will bite you. When the foil stops flying the whole airplane does and it's pretty great. It forces you to be a better pilot and fly the airplane. Cruising at 1/2 throttle is straight and level and then applying throttle does what airplanes are supposed to... they gain altitude... not point the nose up to gain altitude, but as the airplane goes by it will just go higher. It's pretty awesome to fly something so small and so aerodynamically correct.

I had her out at a warbird event this past weekend and flew her many times. It was great to call up other attendees to give me a hand-launch and then they look at it fly and then they realize that it's something unusual. We then start the whole conversation about the history of the Helldiver and why it's great, and why it maybe wasn't. Everyone marveled at how well it flew and it just "looked the part" in the air. I've had about 12 flights on her now and still have yet to break the prop. SUPER light airplane helps on that.

I'd like to do retracts because I'm me but it's so light now that I think I would ruin it by adding them. The only bummer is that it really could use some sort of grip on the bottom for hand-launching. Have a look at the bottom of the EFlite RearBear. One of the best hand launch designs I've seen. I have one if you need a reference picture. I may just have to design something to print and cut a hole in the bottom for it.

Glad it's working out for you Josh! You have more flights on it than me now. My only question is when you were flying untrimmed, did it fly the same as when you flew it on my radio? Unfortunately, we can't really switch out the receivers again, and see if the elevator is trimmed up when I had my setup in it. Luckily, it sounds like its just a matter of if the elevator is centered or not but just curious.

I don't know if I can easily add that hand-launch piece to the design but maybe I can just add 4 or 5 formers in one spot to really strengthen that area. I never really have to worry about hand launching with my dad around .

 

[willsonman]

Glad it's working out for you Josh! You have more flights on it than me now. My only question is when you were flying untrimmed, did it fly the same as when you flew it on my radio? Unfortunately, we can't really switch out the receivers again, and see if the elevator is trimmed up when I had my setup in it. Luckily, it sounds like its just a matter of if the elevator is centered or not but just curious.

I don't know if I can easily add that hand-launch piece to the design but maybe I can just add 4 or 5 formers in one spot to really strengthen that area. I never really have to worry about hand launching with my dad around .

Yeah, it was just ever so slightly off when the servo was centered using my servo tester. I verified that my receiver was centering properly too and at first it was flying very similar to how it was in OH. That was the first flight. Then things got better from there on the second and subsequent flights. Getting the elevator exactly right is gonna be a tough trick but just make sure it's as dead flat as possible for your first flight and trim from there.

I still have yet to have a look at trying to make a grip. I've been occupied with a commissioned build I'm trying to wrap up. My hope is to get it at least into ground testing by the end of this week. I fought with Spektrum programming this weekend on that build and a random guy showing up to the field yesterday afternoon. For all the people that use spektrum and say that OpenTX is too complicated... It's just a different kind of complicated. Good grief my brain hurt yesterday.

ANYWAY, I do plan to get a grip done at some point. Until then, send you dad over here so I can fly this airplane more! LOL

 

[willsonman]

So, I have a half hour and drew up a handle based on the bottom of the fuselage and roughly what could be a landing skid. The part is 160mm long and the grip feels good in my hand. I ha e big hands.

I got the part printed in PETG overnight and I’m happy to say that the hot glue on high heat does nothing to the plastic.
A hole was cut along the bottom center line. I marked a line across the fuselage 1cm aft of the battery hatch. From there, another line 140mm aft of that line. From the center line I measured 5.5cm across the curvature of the fuselage on the fore and aft lines connecting them longways of the fuselage. Cut them out and the handle drops right in.

I scuffed the foam board and the plastic piece for the best adhesion I could. Hot glue is all mechanical adhesion anyway.
I’ve polished the prop nut in anticipation of a nicer font end. I’ve got the prop tips drying so hopefully the yellow and bling will set the font end off a bit more.

 

[Niez13]

So, I have a half hour and drew up a handle based on the bottom of the fuselage and roughly what could be a landing skid. The part is 160mm long and the grip feels good in my hand. I ha e big hands.
View attachment 202456
I got the part printed in PETG overnight and I’m happy to say that the hot glue on high heat does nothing to the plastic.
A hole was cut along the bottom center line. I marked a line across the fuselage 1cm aft of the battery hatch. From there, another line 140mm aft of that line. From the center line I measured 5.5cm across the curvature of the fuselage on the fore and aft lines connecting them longways of the fuselage. Cut them out and the handle drops right in.
View attachment 202457 View attachment 202458
I scuffed the foam board and the plastic piece for the best adhesion I could. Hot glue is all mechanical adhesion anyway.
I’ve polished the prop nut in anticipation of a nicer font end. I’ve got the prop tips drying so hopefully the yellow and bling will set the font end off a bit more.
View attachment 202459

A cut/hole in my plane! Had me worried there for a second lol. Cool to see the mods, and shiny prop nut. I just don't know if the yellow prop tips, or shiny prop nut will stand more!

 

[willsonman]

Pretty sure this look ticks all the boxes for me.

 

[CrshNBrn]

I'm having fun with this build as well. As mentioned by Willsonman, this plane has a checkered history, which makes it even more of an intriguing plane to build at the dining room table. Be sure to take note of the plan notes and be ready to adjust the skins to fit. Skin #5 in particular needed a little bit of help to fit correctly.

I think 13th Squadron also deserves a lot of credit for developing the best leading edge wing technique I've seen so far. As long as you keep the blue tape firmly attached and tight to both top and bottom sections, the leading edge almost disappears. However you can see what happens when the tape slips a bit. It has happened in the past, but as long as the gap isn't too big it can be filled with putty.

 

[Niez13]

I'm having fun with this build as well. As mentioned by Willsonman, this plane has a checkered history, which makes it even more of an intriguing plane to build at the dining room table. Be sure to take note of the plan notes and be ready to adjust the skins to fit. Skin #5 in particular needed a little bit of help to fit correctly.

I think 13th Squadron also deserves a lot of credit for developing the best leading edge wing technique I've seen so far. As long as you keep the blue tape firmly attached and tight to both top and bottom sections, the leading edge almost disappears. However you can see what happens when the tape slips a bit. It has happened in the past, but as long as the gap isn't too big it can be filled with putty.

Looking really good so far!!! How far off was skin 5 just curious?

Thanks for the kind words with the leading edge technique. Yeah the blue tape is crucial to making it clean. When it comes time for the maiden, just know that this airfoil technique creates very scale flying characteristics. @willsonman and I found that are higher throttle it tends to pitch up but still cruise flat at about 25-50% throttle. It wasn't because of the CG being off, it was simply from the lift created from the high lift, low drag style of wing. It will definitely be the most scale flying foamboard plane you've flown. Just something to remember when the maiden.

 

[SSgt Duramax]

Looking really good so far!!! How far off was skin 5 just curious?

Thanks for the kind words with the leading edge technique. Yeah the blue tape is crucial to making it clean. When it comes time for the maiden, just know that this airfoil technique creates very scale flying characteristics. @willsonman and I found that are higher throttle it tends to pitch up but still cruise flat at about 25-50% throttle. It wasn't because of the CG being off, it was simply from the lift created from the high lift, low drag style of wing. It will definitely be the most scale flying foamboard plane you've flown. Just something to remember when the maiden.

Awesome man! I am really enjoying my F6F. I am looking forward to adding another one of your models to my hangar here pretty soon. This may be one of them. I guess if I build this one I won't put a hoss motor in it. The F6F is getting upgraded to a 3536 1200kv with a 10x7 prop.

I am torn between this one, the stuka, and the black widow.

 

[Baron VonHelton]

I'm having fun with this build as well. As mentioned by Willsonman, this plane has a checkered history, which makes it even more of an intriguing plane to build at the dining room table. Be sure to take note of the plan notes and be ready to adjust the skins to fit. Skin #5 in particular needed a little bit of help to fit correctly.

I think 13th Squadron also deserves a lot of credit for developing the best leading edge wing technique I've seen so far. As long as you keep the blue tape firmly attached and tight to both top and bottom sections, the leading edge almost disappears. However you can see what happens when the tape slips a bit. It has happened in the past, but as long as the gap isn't too big it can be filled with putty.

To flare out your cowling, put a strip of foam under the little flaps. Or, maybe a ring of plastic.

 

[willsonman]

It's really more of a "rise" than a pitching up. Quite a nice change of pace from foam board airplanes I've flown in the past.

 

[CrshNBrn]

Awesome man! I am really enjoying my F6F. I am looking forward to adding another one of your models to my hangar here pretty soon. This may be one of them. I guess if I build this one I won't put a hoss motor in it. The F6F is getting upgraded to a 3536 1200kv with a 10x7 prop.

I am torn between this one, the stuka, and the black widow.

If I could put in my vote, try the Stuka. Its huge! Probably the toughest part is bending the landing gear wire. Its easy to fly and land.

 

[CrshNBrn]

Looking really good so far!!! How far off was skin 5 just curious?

Thanks for the kind words with the leading edge technique. Yeah the blue tape is crucial to making it clean. When it comes time for the maiden, just know that this airfoil technique creates very scale flying characteristics. @willsonman and I found that are higher throttle it tends to pitch up but still cruise flat at about 25-50% throttle. It wasn't because of the CG being off, it was simply from the lift created from the high lift, low drag style of wing. It will definitely be the most scale flying foamboard plane you've flown. Just something to remember when the maiden.

Thanks. I love all of your planes/plans. You folks are really fantastic designers and foamboard artists.

 

[CrshNBrn]

Thanks. I love all of your planes/plans. You folks are really fantastic designers and foamboard artists.

Just about a half inch for #5.

 

[Niez13]

Just about a half inch for #5.

On each side?

 

[Niez13]

Awesome man! I am really enjoying my F6F. I am looking forward to adding another one of your models to my hangar here pretty soon. This may be one of them. I guess if I build this one I won't put a hoss motor in it. The F6F is getting upgraded to a 3536 1200kv with a 10x7 prop.

I am torn between this one, the stuka, and the black widow.

I would go for which style of flying you want. The Helldiver flies very scale and is easy to build. The Stuka a beast that flies very slow and cruises around, but of course fast in a dive. The P-61 is my "go to" plane because it is so predictable and is very stabile but also agile.

Now the Stuka and P-61 are definitely the hardest builds of mine. The Stuka just has so much detail, but it is worth the time and effort. The P-61 is actually very easy to build, its just that the booms will probably be the tightest molding of foamboard you've had to do. Just have to take your time and let them sit over night rolled up with tape. The SB2C Helldiver is a relatively simple build that is very repeatable and has the least amount of parts to cut out of the three. Just depends on what you want.

 

[CrshNBrn]

On each side?

Yeah- both sides about 1/2 inch. I'm always hesitant to say plans are incorrect, as it's usually my building errors at fault, but I ran into the same issue with the cockpit skins tonight. I added about 3/4 inch to both sides of the cockpit skins and they seemed to fit better.

 

[Niez13]

Yeah- both sides about 1/2 inch. I'm always hesitant to say plans are incorrect, as it's usually my building errors at fault, but I ran into the same issue with the cockpit skins tonight. I added about 3/4 inch to both sides of the cockpit skins and they seemed to fit better.

Yeah that's interesting. It's questionable if its a plans error or build error but thanks for the info.