• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

I pulled a Jeff and got a new project: ESM 71" SBD-5 Dauntless

willsonman

Builder Extraordinare
Mentor
#41
Well, I have a 5A BEC on the ESC and I've got a total of 7 servos currently on the system. They are not digital servos so the current draw is not that great. Once I have the retracts in I'll do a further evaluation to see how much current I am actually drawing and go from there.
 

willsonman

Builder Extraordinare
Mentor
#42
To ease back into building I took a little time to work on this project since it is a fairly straight forward list of things to do.

I had her out to the field on Wednesday evening to fly at my club meeting but she stayed grounded. The left aileron servo was acting up and the tail gear broke. I replaced the servo but the tail gear... The steel rod literally BROKE off at one point so I need to fabricate a new one with better quality steel.

I pulled out the fixed gear and started working on the retract installation. I cut the ends off one retract with a hack saw. Pretty easy since it is aluminum. These are pretty beefy so they did not want to go all the way down to the mounts. I built up the mount using some hard bass with medium CA. The screws I'll use will go well into the ply mounts so everything will be locked in. Reference photos show that the the scale oleos are at and angle and the wheel axle is at a further angle to be square with the ground. The retracts are 85-degree jobs and I am mounting them with an additional 5 degrees to get the scale look. Pictures will show this better once I get it done.

I need some metric drill bits to complete this so I'm on the hunt this afternoon at my local hardware store(s). You would think you could find something but it seems they are hard to come by.
 

willsonman

Builder Extraordinare
Mentor
#43
Ok, let's go over what's been done.

So, here is an up-close shot of the retract as it sits with the stock mounts. You can see the plate does not fit flush at all and in this position the top of the retract is flush with the top skin of the wing.
IMG_6265.JPG
Here is a comparison. I had to trim 4.5mm on each side to fit properly.
IMG_6266.JPG

With some built-up wood the retracts sit in a perfect position.
IMG_6267.JPG

I've got them both installed and I'm happy with the position.
IMG_6415.JPG
 

willsonman

Builder Extraordinare
Mentor
#44
Moving onto repair the tail gear... here is the main piece of steel. It broke clean off just above where the control arm sat. I heated this up to melt to solder down and use the same piece.
IMG_6419.JPG

So, I went slightly larger in diameter because it's what I had and figured the added strength would be good to. Had to enlarge a few pieces but no big deal. Used the old wire as a template and bent the new piece on my vice with a hammer. Roughed up the rod and the arm and used mechanical solder to secure it.
IMG_6417.JPG

I replaced the original wheel with something a little more narrow. It just seemed too wide and I was not a fan of the hub either. I've got a stash of them.
IMG_6418.JPG

She is all buttoned up. and there are just a few things I want to cover in another post.
 

willsonman

Builder Extraordinare
Mentor
#45
Ok, so let's observe a REAL Dauntless for a minute. As you can see below, the gear sits INSIDE of the wheels but they do NOT extend to 90 degrees. It is sort of pigeon-toed or something but that is how it works. You can clearly see on the left the the axle for the wheel sits at an angle less than 90 degrees. So, to accomplish this, proceed to the next image.
e60494f283e0401162a08b7b48895e2b.jpg

This sort of tells the whole story. I used 85-degree retracts, but the supports for the mounting also have another few degrees to get the oleos closer to the top of the wing. This allows the wheels to sit more flush with the bottom of the wing when retracted as well. Note that the oleo, when compressed will never allow the wheel to contact it as the top of the wheel will always remain the same distance from the oleo. I want to note that I did have to do a few hours of custom work for this. The retracts take a 6mm pin and the oldeos originally accepted a 5mm pin. I had to drill them out as well as drill and tap new set screws. The oleos were about 6mm too long so I had to cut the ends off, along with the original tapped holes for set screws. Further still, The axles needed to be bent so I used some 5mm rod I had and bent the angle to get the wheels to sit right on the ground to match the image. I had to then enlarge the hole in the oleo to accept the 5mm axles and those originally were 4mm.
IMG_6420.JPG
Here is a head-on shot and from a slight angle it's about right to match the picture above of the full scale version. The image parallax is terrible here. I assure you there is no toe-out of the wheels but slight toe-in.
IMG_6421.JPG

So, I ran the wires up to the wing root and put small holes there to snake the wires through and completed them with a y-adapter.
IMG_6422.JPG

To keep things tidy, I used a couple of plastic hold-downs I had in my box. These used to have nails in them that I removed. Sanded the bottom and a couple drops of CA hols the wires in place so nothing sags or snags.
IMG_6423.JPG

So, I think the only other thing here is that I would like to dress up the nose a tad. The majority of images I've found show no spinner. I'll try printing out my Corsair spinner and see how that looks. From there, I'll move back to the Corsair to wrap things up. If there is time, I'll come back here to work on the bomb drop.
 

willsonman

Builder Extraordinare
Mentor
#47
Thanks! I think it is strong enough for this big girl too. Time will tell but she has the makings of a good stand-off scale warbird now and I can start practicing my bomb runs again.
 

willsonman

Builder Extraordinare
Mentor
#48
Alright. So here is what I've been mulling around in my brain a bit. The image below is a sketch that outlines the basic idea. Servo uses a push rod to drive a short arm that swings the trapeze release to swing the bomb away from the prop arc. The issue all along has been that the hook or retention mechanism for the bomb being a means to not only secure the bomb to the underside, but to also function to release the bomb in a scale way.

The image as outlined is upside down from how it will sit in the wing. The hook at the rear of the trapeze should be at least at a 45-degree angle to hold the bomb up against the bottom of the wing. As the trapeze swings down (up in the diagram), the bomb will sway away from the fuselage by the retaining hook and gather momentum to swing down and fall away by wind resistance. That's the theory anyway. I think part of the factor I'm also play at is how to properly balance the bomb. If it is too nose-heavy it will just stay in the hook. If it is too tail heavy it will just tumble out and not fall realistically. So I need to figure out how these WWII bombs should be balanced, rather than my "good enough" approach that I've used in the past.

Any thoughts or comments on this design are quite welcome so chime in and let me know what you think.
Trapeze.jpg
 

willsonman

Builder Extraordinare
Mentor
#50
Update:

Took this one out to the field today. I did a taxi test and everything was tracking true. Charged packs installed and up we go. Flew just fine and I had a chance to really look at the flaps. It seems I do not have enough torque on the bottom flap servo to deploy them effectively. A new one will be installed. Landing was good... on approach. Smooth and had plenty of room for roll-out. The stock flat spots were not enough and the gear turned in. No damage done... which was a relief. Nothing ripped out and nothing bent. So I know this was the right direction to go. So, I need to grind down the flat spots further and really make sure they are good before this one makes a public appearance.
 

wilmracer

Posted a thousand or more times
Mentor
#51
Glad to hear she had another hop. That is a LOT of flap area for one servo. Not surprised it needs loads of torque.
 

willsonman

Builder Extraordinare
Mentor
#52
Yep. Swapped in a servo that should handle it better. Misting all afternoon yesterday so I did not get a real chance to test them out yet.
 

willsonman

Builder Extraordinare
Mentor
#53
As an update here, I have had two additional flights on this one. The first I noticed some weakness in the flat spots still so I ground them down further and the flight after I had no issues with the gear. So, I'm all set there.

I had replaced the bottom flap servo (single for three flaps) with a Turnigy digital one that was rated for much higher torque. Well, It died. Totally seized. So, I've been on the lookout for another one with MORE torque. This one is about as high of a rating as I can find on 5V and the price is great too. Just need to find it in stock. The airplane can still fly but my landings need to be a bit long.

Not sure I'll get to the bomb release before FFOH but she will come either way. She looks very scale in flight and is the total experience as a dive-bomber. She likes a lot of rudder coordination and you can clearly see the tail slip around if you don't do it.
 

PsyBorg

Fly Angry
Mentor
#56
If you still have trouble with the flap servos maybe look into steering servos for monster trucks. This is just an idea off the top of my head as I have not looked at numbers but I know they have serious torque to turn big ole 1/8th scale truck tires. Might be worth looking into if needed.
 

willsonman

Builder Extraordinare
Mentor
#57
The new servo arrived on Saturday afternoon. It was easily installed in 5 minutes. I took her out for another set of sorties yesterday and she did very well. I had to re-program some endpoints but that was no big deal. She flew just fine and slows down very comfortably for landings on my field (short runway). As I was disassembling to go home I noticed that the screws on the x-plate for the motor mount were loose. I pulled it all off at the field and tightened it all down again.

I'm still struggling with tracking. The left gear seems to want to toe-out a bit so I think I'll be pulling that pin out again so investigate. I also adjusted the tail gear as it was a bit right-biased. She tracked better after that but still need to address the main on the left side. Once that is sorted I'm sure she will be a constant joy to fly. The mains are very stout and hold up exceptionally well on my field.