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May 17, 2019, 08:05 PM
EB-66C Team Member
J Morgan's Avatar
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Build Log

A2D Skyshark at 1/8th scale


I had settled on my next build before leaving for SEFF. It was sort of a natural progression. I have a large Helldiver, I've built a couple of SBDs in the past, and had just finished my last build, the A-1H Skyraider.
By natural progression, I mean these all are a long line of Douglas designs in order. Well, sort of, there was a little known BTD Destroyer in between the Helldiver and the Spad. The US had ordered over 300 of the but then the war ended and it and a lot of other designs were cancelled. But the Navy did receive
about 28 of them before the cancellation. It actually had very good performance but just came too late to make it any further.
But Douglas wasn't too worried there as they already had the Spad on the drawing board.
So the Navy decided since jet engine development wasn't moving along fast enough that they needed an attack plane powered by turboprops. This is where the Skyshark came in. It was known as the Son of Spad since it was supposed to enter service and probably replace the Skyraider.
It did resemble the Spad in many ways, the vertical especially, but wound up being pretty much a completely different plane.
But it was powered by two Allison XT-40 turboprops linked to a common geared system that ran two counter rotation props. Long story short, the Allison turboprops continually had problems during development leading to a fatal crash on one prototype, meanwhile jet engines started catching up in their thrust and reliability. Probably a good thing as the Skyshark was a big heavy aircraft and no one was really sure just how suited they were for a carrier deck.
Allison's work and research with the XT-40 di lead to the highly successful turboprops that later were fitted to the C-130 and P-2 Neptune.
Only 12 aircraft were built and only 8 of them flew. There is one survivor and I have a lot of pics of it.
More on the build a little later.

J
Latest blog entry: A2D Skyshark at 1/8th scale
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May 17, 2019, 08:32 PM
Classic jets rule
AIR SALLY's Avatar
Cool been waiting for this one. What scale and specs are you shooting for.
May 17, 2019, 08:43 PM
Ken Stuhr
You RAT!
May 17, 2019, 09:19 PM
EB-66C Team Member
J Morgan's Avatar
Thread OP
Quote:
Originally Posted by AIR SALLY
Cool been waiting for this one. What scale and specs are you shooting for.
Rodger, you didn't read the title. 1/8th scale.
But that question leads to a complicated answer. I had made my mind up that I would keep it simple. Very light and forget about CR props, just run a decent sized 3 blade prop. It would have the look of a Skyshark and probably fly very well.
I told a few friends what I was planning and everyone said on no, got to go CR props. AXI makes a unit, VERY pricey and now discontinued ( wonder why?).
Himax makes several but the $$$ amounts are ridiculous. Besides, my luck we would have a nose over and trash the unit.
So when Ken posted that info on David Wigley's Westland Wyvern with the front prop free wheeling and flying at an AUW of 50 lbs, I thought that would be a good way to go. Make a simple adapter for the front and off you go.
But then I made the mistake of telling Wade.: He insisted we could make they CR unit and about as cheap as an adapter for the free wheeling prop.
Well, I know I can't! I have next to 0 metal working skills, even have trouble filing my nails with a metal emery board.
So I said if you can build it then fine, we'll go CR props.
Bottom line is he has the motors, Turnigy 4250-500kv and has ordered the metal, bearings, what not. So here we go down that deep dark rabbit hole.
We will be leaning heavily on Willsoman who has already built a unit and used it successfully in his Bugatti. In fact he did a tutorial that I will later post a link to, pretty interesting and shows the whole process.
The plane itself will be a 75" or so ws with the big deep fuse like its predecessor, the Spad.
I'll describe the build in a little more detail tomorrow. It's past my bedtime.

Ken,
RAT?

J
Latest blog entry: A2D Skyshark at 1/8th scale
May 17, 2019, 09:36 PM
Ken Stuhr
When I once beat my genius college roommate on an exam, that was his response. Seems only fitting when someone taps my secret build list...........
May 17, 2019, 09:38 PM
Ken Stuhr
All good and well about the gearbox..........NOW, what about scale propellers?
May 17, 2019, 10:16 PM
Pro Hoarder
turbonut's Avatar
Super cool john..I have a nice book on the Skyshark
Latest blog entry: In flight
May 17, 2019, 11:20 PM
Classic jets rule
AIR SALLY's Avatar
My bad....i saw this time
Got to love Wade...a true friend and a awesome scale modeler. go Wade the CR props will really set this apart.
May 18, 2019, 05:30 AM
EB-66C Team Member
J Morgan's Avatar
Thread OP
Ah, I see Ken. Sorry about that, wasn't intentional.
As far as scale props, I have not seen any available. The SS had big squared off tips, looks like about the best I can do is cut the tips off to give a little of that look. Right now I'm planning on using 16" three blade props but I'm open to changing if I need to.

Thanks Scott,
I only have one book on the SS, pic of it below. But I have a ton of pics from a walkaround a member of RCSB did on the only survivor.

AS,
Got to love Wade? Are you kidding? See what he gets me into? But he is a good friend.

Here is Willsonman's tutorial on the Flight Test site. Very good writeup and most probably will be our Bible while building up the CR motors. What am I saying? I'm not building up any motors, Wade is.

https://www.flitetest.com/articles/b...rotating-motor

J
Latest blog entry: A2D Skyshark at 1/8th scale
May 18, 2019, 08:54 AM
EB-66C Team Member
J Morgan's Avatar
Thread OP
OK, my original plan was to build a light weight plane with adequate power for a decent size 3 blade prop giving the look of the Skyshark.
Now, that's out the window with the dual heavy motors up front. Probably need two main batts too.
My old Skyraider that crashed in St. George was approx the same size. It had a heavier single motor( 50 mm) whereas this one has two 40 mm.
The two motors weigh about 22 oz together. Add about 3 lbs of batteries and we're already at almost 5 lbs w/o any airframe.
The old Spad weighed about 11 lbs with a 4 blade prop and 5s-5000 battery. I still think I can build this at around 12-13 lbs. If so it will fly incredibly.
But more important is to keep the weight as low as possible in order to use the old rotating retracts from the Skyraider. They are plastic cheapos but I have had great luck with them. I bought 4 sets figuring on replacing them often, I have had to replace one so far because a gust of wind caught the plane as Nut was doing a touch and go, slamming the wheel into the runway. 5 min later it was replaced. Robart gear would be $$$$ and HEAVY.
And I wasn't going to balsa skin this one but now I think I will just for additional strength. So I will be shooting for an airframe weight of > 6 lbs.
Here's all I've got so far. Used the overhead projector to make templates before I left for SEFF. I see the biggest problem will be mounting the dual motor and the custom made dual spinner, which might be difficult.
As you can see from the pic, it is a little over 6" in dia and 6.75" long. Oh brother.
Time to clear the bench and get started on the fuse.

J
Latest blog entry: A2D Skyshark at 1/8th scale
May 18, 2019, 09:00 AM
Parkcityflier
parkcityskier's Avatar
I remember seeing pictures in the early 50s of the Skyshark in flight and thought that it was really a cool looking airplane. There was a plastic model being offered of it during that time and I wish now that I had bought one and just put it away. Interesting, at that time, was that I was not aware of an airplane called the Skyraider, which would someday be such an important part of my life.

Jim
May 18, 2019, 09:55 AM
Ken Stuhr
If you're going to go to all the effort of this build/this size/etc, it should have scale, scratch built props! With all the 3D available these days, 2 opposite-handed blade masters should be fairly easy to acquire. Molds and subsequent layup with carbon cloth and epoxy is standard stuff too. Plenty of help available. The most interesting part would be sizing motor and gearbox for such monsters. I would think there's no need to match the huge pitch of the original, but the diameter and shape would be boffo!!!
May 18, 2019, 10:57 AM
EB-66C Team Member
J Morgan's Avatar
Thread OP
Hey Ken, RAT here!
Oh boy, scale three blade square tipped monsters. I admit that would be cool but would turn what started as a sort of look alike easy build into a full scale monster requiring yet more skills. I have a friend that can make them but given that he hasn't any free time as it is, would never ask him to do it. And the build has already gotten far more complicated with the CR props.
Plus, we get a nose over and trash the props, there we are. Waiting for more to be made. I'll probably be using MAS so I can get them right off the shelf.
May cut the tips square to help the look but that's about as far as I care to take it. I'm already dreading making the spinners.
Trying to establish the motor mount location before starting on the fuse. I'm close here I think but want Wade to take a look as he has the motors in hand.

J
Latest blog entry: A2D Skyshark at 1/8th scale
May 18, 2019, 06:36 PM
Registered User
p901P901's Avatar
Those are some big spinners. DAnG to find someone to print some. Know anyone?
May 18, 2019, 06:51 PM
Registered User
Terminater's Avatar
Just think after u finish this with the Counter Rotating props u could then make a Westland Wyvern with the same motor system


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