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Aug 13, 2017, 08:31 PM
It's all about scale models!
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Build Log

VQ Models A-26 Invader (old version, electric conversion)


About a year ago, Dad and I went a Warbird fly-in down in Ocala, about an hour from here. We were surprised to see a really large A-26 Invader being set up, and were "all eyes."

So why the big reaction to the A-26? Sentimental reasons of course.

Back in the early 70's, Dad started an 83" A-20 Havoc, beginning with a very obscure kit briefly available at the time. It was cut styrofoam block, which he eventually covered with 1/64" ply. He opted for a very unorthodox power setup -- twin Wankel .30's with three bladed props.

We moved to Florida in '74 and it was finally completed here in Gainesville. It actually ended up painted as an RAF night fighter "Boston III", all black. First we tried a straight down the runway takeoff and landing -- at none other than the famous Gator Raceway, site of the Gatornationals drag racing event. Our club's runway was in the parking area of the raceway. That went "OK" and next two actual flights followed. The second ended with a crash landing that caused enough damage to retire the A-20.

Dad and I eventually got away from the hobby (first with me getting into competition F/F scale). But a few years ago Dad got back into RC (thanks to all the advances with electric and foamies) and I followed nearly three years ago. Anyway, that should explain our fascination with the huge black A-26.

Of course we gushed to the owner who wasted no time in telling us he had another, not quite as big, A-26 in the back of his van, NIB, and for sale. The price was $175. Dad went over with me saying "no, no, no!" We opened up the box, looked at the pre-fab parts and that turned to "yes, yes, yes!"

Thanks to the wonder of having the PayPal app on one's iPhone, the VQ Models 68" A-26 Invader was ours in a matter of minutes!

I'm now just getting around to starting this plane, intended for gas motors -- but I'll be converting to electric, as others have in the past. Hopefully I'll bring a new wrinkle or two to the process, and get some good info and advice from you readers in the process.

VQ has since come out with the A-26K Counter Insurgency Invader with Viet Nam Camo, which is set up for optional electric. But I'll have to figure out a few things for myself on this project and how far to go in terms of color and markings.
Last edited by MrSmoothie; Oct 24, 2017 at 12:42 PM.
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Aug 13, 2017, 09:12 PM
It's all about scale models!
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Electronic components


This is an ARF, but what they called an ARF ten years ago and what they call one now? Basically you get the airframe and suggestions. The rest is up to you. And frankly, I rather like that.

Don't get me wrong, I love all the foamies -- but there hasn't been one yet where I don't think about what I'd have done differently if I were King.

With this ARF, I get to make all the component and configuration decisions.

Dad had a recent takeoff accident with his FlightLine P-38 and he salvaged all the electronics -- then wondered aloud if they might work for the Invader? I did a quick comparison of the specs and thought some , if not all, could indeed work.

In particular, a rough check of dimensions indicated that the P-38 retracts would work just fine, as well as the 60A ESC's. I like that replacement retracts are easily available and not too expensive.

The servos should all work took, but I have a hesitancy about "used" servos. I have some new old stock HS-81 which look beefy enough and I'm heading in that direction.

I'm not so sure about the motors and would welcome input. The FliteLine motors are 3748 - 600kv and swing 12-7 three bladed props with 4s power. The same motor/prop combo is used on the F7F Tigercat as well.

I have no doubt that the motors are powerful enough for the Invader. My first idea was to get some Tigercat props which have the nice silver hub, same as the Invader.

This idea soured when I realized the A-26's nacelles are much closer to the fuselage -- the max prop diameter would be 11". APC makes an 11-8 three blade (but no pusher) as well as 11-7's (regular and pusher).

What little I know on the subject leads me to believe that the 11-8 might work but the motor might be too low KV. Going to a non-scale 4-blade prop is not an option. MotionRC doesn't publish all the specs on these motors, so it's hard to plug in all the details into a calculator to get an answer. Opinions?

Aside from the motors, one of the next big decisions will be how to handle the Lipos. After reviewing a few online articles/threads, some have used two Lipos, one in each nacelle, while others put them in the fuselage. There's plenty of room where the gas tank was supposed to go, and the plastic nacelle covers will be fairly easy to modify for access. The old version of this model did not provide any access to the fuselage (other than where the wing removes), but I could modify the cockpit canopy into a removable hatch if I went with fuselage mounted Lipos. CG would have to be a factor, and if tail heavy, an argument for putting them in the fuselage under the cockpit.
Last edited by MrSmoothie; Sep 09, 2017 at 04:51 PM.
Aug 13, 2017, 09:27 PM
It's all about scale models!
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How Scale?


I'm a scale modeler, through and through, and often sweat details that nobody else would care about (outside of a competition). And admittedly, this VQ Invader is a semi-scale -- what we used to call "standoff scale" in the old days.

That said, something is bugging me -- the model was provided with the optional "solid" nose made of fiberglass (and provision for 8 simulated .50 caliber machine guns) and all black USAF color scheme as seen in Korea. All that is fine. What's bugging me is this -- the model came with the wingtip gas tanks, as seen on the much later A-26K Insurgency "Nimrod". I've been rooting around on Google and see nothing to suggest that any Invader used the wingtip tanks prior the 1964 "K" version.

Yeah, the tip tanks look cool, and if I used them, probably nobody would "call me" on that detail. But it'd bug me!

I think I have two choices -- carve some balsa wingtips and finish as correct for Korea -- or use the tip tanks and repaint the upper surfaces to the Viet Nam "K" version camo. I think VQ's "K" color is a bit "overdone" and that I could do a better job. The bottom is already black, so I wouldn't have to repaint that.

Has anybody repainted a VQ model? What did you use and how did it adhere to their "preprinted shelf paper"? I generally use Tamiya acrylics and airbrush, but that might get a little costly for a plane this big -- latex house paint would be a lot less. But would it stick?

Other than time, carving new wingtips wouldn't be that big of a deal -- and since they were almost always painted an ID color (red, yellow, etc.) in Korea, there'd be no issue with matching the kit's black finish.
Aug 13, 2017, 09:38 PM
DFS#000178
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I've really wanted one of the original VQ A-26s for a while. I don't care for the Counter Invader as much. The original in that black trim is freaking gorgeous.

I had the limited prop size issue with my Royal B-25. I ended up going with 2 Turnigy G32 600kv with APC 12x10s on 2 4s 2000s, one in each nacelle.

Extremely aggressive pitch, but absolute buckets of power. I think we calculated it out to like a 70mph pitch speed.

Model weighs 13 pounds.

Royal B-25 (2 min 1 sec)
Last edited by Rampage; Aug 13, 2017 at 09:48 PM.
Aug 15, 2017, 01:46 AM
Ldm
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Mr Smoothie
I have owned quite a few VQ ( new and old ) and yes they can be easily painted.
I have used Model maters spray, I have used house water base latex , really did not seem to matter.
I would suggest reinforcing lighter balsa areas in critical areas like motor firewall ect, its just the nature of VQ to have some weak spots.
I am looking at the new camo A26 and the new Phoneix models 90" span A26 . Considering the ease of epower no real worries on losing an engine because of the obvious electric motor choice
Aug 15, 2017, 01:10 PM
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Hi LDM, thanks for the paint info. Sounds like Tamiya Acrylic would work fine (and probably better than latex) -- but it would take a lot of jars...

I can already see areas that require reinforcement, so I'm on board with you there -- especially where the retracts will attach.

I looked at the first flight video of the Phoenix Invader and have to say I was not impressed. Not sure if it was the model, the pilot, or the flight conditions that day. Usually twins that large look a lot better in flight.

I do like the "Special K" version camo -- but when I've seen closeups of the VQ rendering, I thought the "distressing" was overdone. I think I can do a much nicer job of it repainting this black one. But I'm still on the fence. I've got to figure out the power system first.

So far, I haven't had any answers or opinions on using the P-38 600kv motors, but with 11" dia. props instead of the 12x7's (due to less nacelle-to-fuse space). I reached out to Master Airscrew for their opinion on going to their 11x8 prop (all props 3 blades).

I know some guys cut down props, especially if they have a mill and can set up a jig. The real "K" had cut down prop blades so very squared off ends. Made me think it could be cool to use Tigercat props which have the correct hub, and cut them down to 11" diameter. Doable? Mistake?
Aug 16, 2017, 04:03 AM
Ldm
Ldm
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I wish I could help you with the props and power but I am trying to figure out the same thing with the Phoniex model A26.
I agree with your assessment on the looks and flight , but I figure with e-power I can be more majestic and I also feel the model in the video is under powered so the pilot has to fly above 3/4 throttle . Simple math when looking at the fuel and epower suggestions show all systems taxed to the max.
On the VQ one more word of warning -please please dont plan on removing the covering .
Many many have tried and end up scratching the model for good .
The sticky type covering is actually very strong and as a result it will pull the wood up ( large and small ) just enought to weaken and ruin the model .
On the new VQA26 , I have not seen the weathering close up , is it still overdone ?
Thanks
Lou
Aug 17, 2017, 08:31 AM
It's all about scale models!
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Hi LDM, I'm not sure if I've seen any recent photos of the Counter Invader that include close-ups. I kind of doubt it's any different than the one shown in this article:

http://www.vqmodel.com/NewVQModel/Bo...Invader-EP.pdf

In the close ups, you'll see that they made an attempt to weather/discolor around all the panel lines. It may look good from ten feet, but...

Lots of useful information in this article however -- things to do and things I want to do differently.

One thing I do NOT plan to do is attempt to remove the covering. It's either staying all black, or I would consider overpainting if I do the "K" version. It "is what it is" and I can see all kinds of trouble as you describe trying to remove the covering. Yikes.
Aug 17, 2017, 08:42 AM
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I've actually gotten started, but with an older kit like this, sometimes you really have to think things through as so much has changed in the last decade. I think the intended servos were huge based on the hardwood mounting blocks in the wings!

The FliteLine P-38 uses 9gm metal gear servos and that's what I'm re-using here. Plus the Invader has actual nylon-pinned hinges which offer far less resistance than the foamie hinges. I had to remove the hardwood blocks and then made new mounting blocks from basswood. I reused the FliteLine linkages.

Leaving for a long weekend, so there won't be any progress until next week.

Meanwhile I am still thinking about the power system. FliteLine offers a "high speed" option -- higher KV motor (880kv instead of 600) paired with a 12x8 two blade prop. I'm thinking that motor would work great with an 11x8 three blade prop using the "rule of thumb" going from 2 to 3 bladed prop. But it would be nice to use the original P-38 motors and save the money ($39 each).

As others have found, while the fuselage is huge, it's not super practical to locate the lipos there -- access is awkward. I think I'm headed for one lipo in each nacelle behind the firewall.

The FliteLine P-38 actually runs one Lipo to each motor -- with no parallel wiring. While that would sure be simple to do on the Invader, I think I like the safety of wiring the lipos in parallel and have that safety margin should one battery run low or fail.

My next actual step will be to make mounting plates for the repurposed P-38 main retracts and mount in the wing panels. I thought about making gear doors, but the vacuformed plastic panels are molded with a cutout for the retracts -- and with a black-bottom airplane, you would barely notice the doorless retracted gear. In other words, a lot of trouble for nothing.

The nose gear well is rather large, however, and I am planning on making gear doors in that location. I'll decide later if I want to servo actuate them, or use a single stiff spring, as FliteLine does very nicely in their F7F Tigercat. The spring holds the doors in correct open position, but the strut closes across the same spring to close the doors. I tried this system on an Alfa Models Beaufighter that I converted for retracts and it worked perfectly.
Aug 31, 2017, 06:42 PM
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Getting Underway...


Hi Guys, I'm back. I have good excuses for my absence -- the best one was a short vacation to Pensacola, where I spent nearly seven hours at the Naval Aviation Museum, which was outstanding, even better than I'd hoped for. If you haven't been, add it to your bucket list.

My other excuse is that my father saved the remains from his crashed Freewing 64mm A-10 -- I figured out that I could have an A-10 of my own for the cost of a new wing and fuselage. These two parts finally came back into stock while I was in Pensacola, and I ordered them immediately, and spent last weekend making a nice new A-10 out of the new and old parts. I had two successful maiden flights yesterday morning, and I'm very happy about that.

Now that my shop is freed up again, back to the A-26!

Prior to the Pensacola trip, I installed the aileron servos. Nothing special here, except that the original servo mounts (hardwood) were spaced for some kind of gigantic servo. I used 9mm metal gear servos from the P-38 parts stash -- I figured if they were strong enough for the P-38, they ought to work here. Linkages were also from the Lightning.

I'd already spent a lot of time looking at the main landing gear area, especially the mounts which were intended for a pneumatic retract system. One of my pet peeves with many trike scale foamies is that they always seem to make the gear struts too long. Most warbirds sat fairly close to the ground, and when they are up on stilts, they just don't look right. Plus, a longer strut is more prone to damage.

I decided to cut 0.75" off the top of the wire gear strut to bring it closer to scale length. Then I cut away the triangular balsa bracing from the hardwood mounts to make a clear area for a new mounting plate. I made that from 3/16" ply to go from ply bulkhead to bulkhead and against the inboard side which is also ply.

I liked the wheels provided in the kit -- more scale profile and size than the P-38 wheels (which are always too small, by the way). With a nylon spacer to keep the tire from hitting the plastic strut cover, they work fine.

The opening in the plastic was cut away first to the molded line (leaving the "lip") -- hoping the gear would clear. But this wasn't the case -- I had to trim another 3/16" or so off the inboard edge so the strut would clear, and a bit near the forward corner of the wheel opening. I had already decided I wasn't going to try and make main gear doors -- this would have been a lot of extra work, and with a black-bottomed nacelle, you would hardly see a difference in flight. I plan to paint the wheel wells flat black to further make them disappear (instead of the correct zinc chromate).

Now all I have to do is repeat the above on the other side. Hopefully that will take half the time.

One other thing: I've noticed on some models how the main gear cants out, since they were installed without regard for dihedral. I'm using a shim of 1/16" ply on the outboard side over my mounting plate. That way I can change it if it needs to be increased or decreased to get the correct vertical orientation.


IMG 9320 (0 min 17 sec)
Last edited by MrSmoothie; Sep 03, 2017 at 04:37 PM.
Sep 01, 2017, 03:34 AM
Ldm
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Great work , looks great !
Sep 01, 2017, 07:41 AM
It's all about scale models!
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Thanks LDM!

This weekend I intend to install the second main gear, and also the nose gear, and then depending on how that goes (and how much flying weather we have -- rain predicted) maybe attach the stab and rudder and install the servos.
Sep 01, 2017, 07:54 AM
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Motors / Props


As stated earlier, I hoped to use the motors salvaged from the FlightLine P-38.

The problem is that they are designed for 12x7 3 blade props, and the A-26 only has clearance for 11's. After much consideration and half-baked research, I decided to order the "upgrade" motors sold for the P-38, on this basis -- they are designed to be used with 12x8 TWO-blade props. Going by the "rule of thumb" so often stated (but not necessarily correct I realize), I should be able to go to 11x8 THREE-blade props with that motor.

FlightLine P-38 Lightning Motos
3748-600Kv Brushless Outrunner Motor (Stock scale power system) -- what I had, salvaged
3648-880Kv Brushless Outrunner Motor (Optional sport power system) -- what I've purchased

Consequently, I have ordered a pair of Master Airscrew 11x8 3-blade props. My plan is to set up a test stand and see how many amps I draw with a 4s Lipo.

Now that the latest version of the VQ Invader (A-26K) is optional gas or electric, they have specified power of about 800 watts per motor. I found a review article online by Dean Williams, who did an electric conversion coming just below that recommendation, and his plane flew fine. Once I get the amp reading, it'll be simple to calculate the watts and see if I'm in the ball park.

I realize I could have ordered any motor, but the upgrade P-38 motors were inexpensive ($40 each), and clearly intended for a particular size/pitch prop which I could use as a starting point for my change to 3 blades (which, for me, is just a requirement for a warbird like this!).

I've also seen how the FlightLine P-38 performs with the stock power system. I think with the upgrade, the slightly larger/heavier A-26 should handle well.

Of course, I won't do any motor mounting until I run this test, probably next week.

My current plan remains to install a 4s Lipo in each nacelle behind the firewall, with an access hatch on the bottom. I happened to receive a pair of 4s 4500 lipos yesterday for use in my 64mm A-10, and found that even that battery will fit in the available space. It's nice when you can use the same size lipo in more than one model, right?
Sep 02, 2017, 10:13 PM
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More work on the nacelles


Got the second retract installed, and trimmed the nacelle bottom plastic until the strut and wheel didn't hang up anywhere. I can see that I'll be able to close off a lot of the molded opening where the strut passes, but that will come much later.

I've already spent a good bit of time making adjustments to the plastic nacelle covers (top and bottom) and the mostly ply sub-structure so that they fit properly. And I still have more to do. This is the kind of "ARF" that provides an interesting challenge for guys like me who used to build everything -- or infuriate newer modelers who think an ARF should require a few screws to be installed and the plane be ready to fly.

Today I made battery trays from 1/8" ply and installed on balsa strip rails, using 5-minute epoxy. I made a semi-circular cutout at the tail end so wiring could pass more easily, and also cut slots on each side of the tray for a velcro strap. I'm thinking that the ESC will eventually mount to the reverse side of this tray.

As I mentioned, I intend to paint the wheel wells flat black so that they effectively "disappear" wheels up (as opposed to zinc chromate green), since I'm not doing wheel well doors. If VQ had provided the nacelle plastic "smooth" without the retract area recessed for cutting, I might have done hinged doors...

Anyway, the balsa in the well is very soft and just didn't look too finished to me. I can just imagine all the sand that will end up in the well. So I decided to line it. Typically, I might turn to .020 styrene sheet for this. Maybe it's a nod to Dad's A-20 project, which was a wire-cut foam "ARF" -- that he covered entirely with 1/64" ply -- but I made a trip to the art supply store and bought a sheet of 1/64" ply. First I made templates from thin chipboard (cardbard like on the back of a pad), and once I had that right, cut the actual pieces from the 1/64" ply and glued in place. Things look a lot more tidy now, and there's a much smoother paint-ready surface. I plan to airbrush with flat black acrylic. I have one nacelle lined, one to go.

Since I'm not going to install the motors or ESC's until I run a static test, the next step will be to modify the lower nacelle plastic to have a removable hatch to access the Lipo tray. I'm thinking I'll extend it aft a bit more so that the same hatch will provide access to the electric retract. It's a rare retract that you don't have to occasionally (or often) remove to repair or simply re-tighten the allen screws that fix the wire strut in place, so I want to be sure that can be done without too much difficulty. Once I determine the size of the hatch, I'll reinforce the edges on the inside with basswood strips.

But tomorrow and Monday (Labor Day) are looking like perfect early morning flying weather -- and that's what I plan to be doing! So no more shop until the afternoon.
Sep 06, 2017, 04:39 PM
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Motor / Prop Test


Well, I didn't get quite as much done in the shop over the long weekend as I'd planned -- the good news is that we had nearly ideal flying weather both Sunday and Monday morning and I made the most of it, flying 5 or 6 planes each day. I'm almost finished recharging all the lipos! And it's a good thing too, as Irma is heading our way, and it looks like that'll be the last flying I do for a while. If our power holds out, this will be an all-shop weekend for sure.

Both nacelles have the retracts installed, and the wells are lined with 1/64" ply. Battery trays are installed. I did not get around to cutting the battery hatches in the plastic -- I felt like I needed to look at that just a bit more before I started cutting plastic.

Meanwhile, I thought this was a good point to test the new motors I purchased. My Master Airscrew 11x8 3 blade props came yesterday. The new motors are the higher KV (880kv) "high performance" parts for the FlightLine P-38 and are intended to swing a 12x8 two bladed prop.

Today I screwed one of the motors to a piece of 2x4, and set up a 60A ESC (from the FlightLine P-38), AR400 Rx, and 4s 4500 lipo with my power analyzer.

The freshly charged battery was reading 15.2 to 15.35 volts. I drew between 52 and 52.5 amps. Even if I downrate the voltage to the specified 14.8 volts, I'm pulling 775 watts more or less, for a total of 1550. VQ now recommends 1500 watts total (for the current electric optional A-26K), and the 2013 build article (online) achieved about the same wattage as I did with his power combo (he used smaller 9x7 3 bladed props, of which I didn't like the look).

So I'm feeling good about my power setup and can proceed to mount the motors in the next few days. I really think the fuselage is going to proceed more quickly than the wing. At least that's what I'm telling myself.


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