Giant scale OV-10A

[daveculp]

Finishing up version two of the main landing gear.  Here's a photo of the fit test.  I still have some painting to do on the main gear, of course.  The fit looks good.

I also installed a DF antenna at the nose gear - it's the loop type antenna that fits around the strut door.  I designed it so that it is pushed into the foam fuselage.  This is so that it can be easily removed in order to then remove the nose gear assembly.  The airplane is accumulating small dings already. 

 

[daveculp]

First test print for the new exhaust.  The original foam part weighs less than a gram (my scale doesn't go that low).  The new part, which is only a component of the whole piece, weighs 10 grams.  I printed this exhaust pipe as a separate piece because it's better for it to be open at both ends to drain properly while printing.  It also makes it easier to paint.

 

[Out2gtcha]

Dang, I cant see either one of the photos. usually the site will appear as a photo if the picture link is direct/embedded, but cant seem to get that one to work. Exhaust look good though! 

 

http://www.daveshangar.org/photos/OV-10A/exhaust.jpg

 

 

[daveculp]

New exhausts finished and installed.  I glued these in place, and on second thought I should have designed them with pegs to push into the foam.  That way they could be switched out with the original exhausts at any time.  These exhausts weigh 13 grams each, whereas the originals are less than 1 gram each.

 

[daveculp]

Progress on the 1/9 scale foamie OV-10A.  Antennas are all done now.  Oil cooler doors installed.  Here are some comparison shots with the 1/32 OV-10A.

 

 

 

 

Still haven't started on the cockpit interior, and I need to install pitot tube and clean up the landing light.  Also haven't installed the brakes on the main gear yet - I just need to paint them white and glue them on.

 

As for the propellers, I'm going to try to print up a set.

 

The original landing gear are still installed and are in the retracted position.  So, this model could be returned to flying status by removing the static display landing gear, the heavy bits - especially the external stores, and by re-installing the control horns and push rods on the controls.  For the next phase of construction the airplane will be made unflyable when I remove the original nose gear and all its supporting structure and servos.  This will be necessary to give it a full-depth cockpit. 

 

If I had wanted to build this as a static model from the start I would have removed all the landing gear and used seam filler a lot more liberally.  I also would apply six coats of Minwax Polycrylic, which I've learned from the foamie community is the approved solution for surface preparation and protection.

[daveculp]

Just testing the ability to link to videos here.  This is a short video of me putting the left main landing gear into the OV-10.

 

http://www.daveshangar.org/photos/OV-10A/Static-Display-Gear.mp4

 

Here a still capture from the above video:

 

 

In this shot you see the original propeller.  I'm working on a replacement propeller as this one is the wrong shape and size.  The correct propeller is bigger, has square tips, and is set to flat (zero) pitch.  In the background you see a spare fuselage in the original livery.  I'll be using this fuselage to design the new cockpit parts.

Edited December 19, 2020 by daveculp
grammer

[allthumbs]

Looks great Dave! 

 

You might have mentioned it earlier, but, with all of these mods, will the model still be flyable? Or do you intend for it to be static display?

 

Rich

[sky]

On 12/3/2020 at 10:47 PM, Out2gtcha said:

Dang, I cant see either one of the photos. usually the site will appear as a photo if the picture link is direct/embedded, but cant seem to get that one to work. Exhaust look good though! 

 

http://www.daveshangar.org/photos/OV-10A/exhaust.jpg

 

 

Oh wee, I am having the same issue. And I have had this in other forums as well, but there is a way to fix it. Btw, I'm using Chrome for a browser here.

Attention, a bit of tech mumbo jumbo ahead

 

/begin tech mumbo jumbo

The problem usually appears when you are visiting one website that is linking content on another website, as is the case here. We are at https://forum.largescaleplanes.com (note: it is "https" using SSL certificates), with the pictures being hosted on another site, http://www.daveshangar.org (note: it is "http" NOT using SSL certificates). Without going into too much detail, the two sites use different certificates (or one uses none) for security and that is usually the issue. Chrome being strict about security out of the box, decides the "non SSL" site is not secure and as such blocks the content.

Now, what to do?

Click on the lock in the address bar above, then click on "Site settings" in the small popup (at the bottom), then navigate to the bottom of the list showing up next and locate "Insecure content". That's the content with the anxiety issues, being afraid and not showing up. The default setting in Chrome is to "Block" that. Change that setting to "Allow", close the window and reload the page - the pics will now show up. Note that this is a site based setting, so it only affects forum.largescaleplanes.com, not all other sites globally. If you have the same issue in other forums, rinse and repeat.

 

Word of warning though. As this allows insecure content to show up, it might open the door for unwanted things, not only these pics to show up. So use at your own risk. Feel like in this day and age, we better put the warning sticker out there. Also doing that, you will see, that in the address bar it will show "Not secure" in front of forum.largescaleplanes.com after doing that, to let you know that you've tinkered with the security settings.

 

So if that is too much hassle, just right click on the empty pic placeholder and "open in a new tab" and the issues are gone as well.

/end tech mumbo jumbo

 

 

BLA!

That aside, this birdie is a monster. I have two 1/8 cars and they are already ginormous. Can't really get my head around the size of this "behemoth" ;). Awesome project.

[daveculp]

On 12/19/2020 at 4:19 PM, allthumbs said:

Looks great Dave! 

 

You might have mentioned it earlier, but, with all of these mods, will the model still be flyable? Or do you intend for it to be static display?

 

Rich

 

Hi Rich!   This a project in two phases.  Phase one is dressing up the airplane while keeping it flyable.  To return the airplane to flyable condition you'll need to:

 

1)  remove the static display landing gear

2)  extend the original landing gear

3)  remove the new external stores (they're too heavy)

4)  install the original props

5)  re-install the control horns and pushrods for the control surfaces

 

I don't intend to fly this airplane, but I wanted to design the dress-up parts in a way that could keep the airplane flyable in case someone wanted that.

 

Phase two is going to make the airplane permanently unflyable.  In this phase I'll cut out the original nose gear and its support structure and servos.  That's necessary to get enough room to make a full-depth cockpit.  

[daveculp]

On 12/20/2020 at 3:17 AM, sky said:

/begin tech mumbo jumbo

The problem usually appears when you are visiting one website that is linking content on another website, as is the case here. We are at https://forum.largescaleplanes.com (note: it is "https" using SSL certificates), with the pictures being hosted on another site, http://www.daveshangar.org (note: it is "http" NOT using SSL certificates). Without going into too much detail, the two sites use different certificates (or one uses none) for security and that is usually the issue.

...

/end tech mumbo jumbo

 

 

Thanks for the explanation!  I wasn't able to figure it out.  Normally I would use https as my protocol, but I originally set up Dave's Hangar as a place for my flight simulator models, and the integration with FlightGear Flight Simulator required http protocol.  I should check to see if that's still required.

[daveculp]

Two steps forward, one step back.  The OV-10 came crashing down one evening.  Fortunately it only fell about one inch before the external tank cushioned the fall.  The cause was a failure of the right main landing gear.  Here's a photo of the failure:

 

 

I hadn't expected this type of failure.  Fortunately I was able to bend the strut back into position, glue a spare piece of resin across the weak area, and just to be sure I also glued the strut to the gear doors.  Here's a photo of the repair:

 

 

 

I then opened up the mesh in my CAD app and added extra depth to this area.  I did the same to the left main gear.  While inspecting the left main gear I saw that the crash had also lead to a cracked strut:

 

 

 

The repair here is a bit trickier.  I opened up the crack with a grinding wheel and small saw, then I filled the area with CA and clamped it tight:

 

 

 

I hope this works.  To strengthen this area in the future I'll need to adjust my slicer settings - increasing wall thickness and/or infill percentage.

 

[daveculp]

Working on scale static display props for the Bronco.  Here's a photo of my first attempt at printing the right prop on my FDM printer.  I was hoping to print the prop in one piece, which would be convenient for me   Unfortunately the FDM print didn't turn out very well - the blades are just too thin, leading to ragged edges.  I then decided to try printing them in resin, which is a bit tricky since the blades barely fit within the build volume of my printer.  I did get one blade to print, sort of.  Some of it was mangled because of support failure (my fault), but the remainder shows me that this is the best way to print the props.  In the photo you can see the resin prop blade compared to the FDM prop.

 

 

 

The resin props will require a new hub, which I'm printing now.  The original spinner will (hopefully) fit onto the new hub.

 

 

[daveculp]

The attempted repair of the left main gear failed, so I've printed a new version.  The new one has the beefed-up area mentioned two posts above.  The original part was printed using the default Cura slicer settings, so for the new one I increased wall thickness to 4 and increased infill percentage to 40.  Here's a photo of the broken gear showing the internal structure.  You can see the walls are thin and the infill grid is mostly empty space.

 

[daveculp]

I've installed the new left main gear without finishing the painting.  I figure it's no use wasting time on it now if it might fail.  The problem with this testing is that the last gear unit took about three weeks to fail, so now I have to wait at least that long.  With all the external stores attached the weight on each main gear is 1.43 kg (3.15 lb).  This weight is without props, and without any cockpit enhancements, which together will add more weight.

 

I printed the gear standing in the upright orientation.  This is to minimize the surface deformities (any surface touching the supports is going to have deformities).  This means the "grain" of the piece is horizontal, i.e. the plastic layers are laid down horizontally.  This means the compressive strength is good, but the bending strength is not.  As you can see in the above post the breaks occurred in the horizontal plane.

 

 

[daveculp]

While the left main landing gear undergoes the slow-motion stress test I decided to finish the propellers.  Here's a photo of the new right prop compared with the non-scale prop that comes with the kit.

 

 

 

This prop is for static display only.  It uses the original spinner.  The prop installed:

 

 

 

 

For static display purposes the prop should be set to "flat pitch", which is not possible with an off-the-shelf prop.  Home-made decals are used for the data stencil, Hamilton Standard logo, and the red stripe.

 

The left prop is next.  For some reason I had trouble printing it - this is my third attempt at this 10.5 hour print.  I thought maybe the orientation of the blades was causing a problem with the separation from the FEP, so I flipped one blade around to  help the part/FEP separation happen.  Maybe that's what did the trick.  The part printed OK on the third attempt:

 

 

 

 

These blades barely fit in the Elegoo Mars build volume.  They don't fit in my curing box.  The turntable is unable to spin them all the way, but I think the curing result will be fine anyway:

 

 

 

Edited January 17, 2021 by daveculp