Yellow A-4 Skyhawk for P-60 Build Thread
 

Hi,

My wife went in and cleaned my little shop for me because it had basically turned into a storage for crashed planes and parts. Funny, after I walked in and saw the nice, clean space...I wanted to build something in there! I've got a couple of different projects going right now. One for me, and one for a customer. The A-4 is for a customer, but I thought I'd chronicle the build as I go in case anyone is interested.

By today's standards, this thing is tiny, but it's a good ol' bird and they fly great. This always was one of my all-time favorite DF birds.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

I am subscribing to this one. I have a Super Bee in a Falcon 120 for training but am looking for a second jet to build over the winter...

Please, pics asap!!! :D

Best regards,

Chris

p.s. I am considering the Starfire, A4, stingray, F-16 from yellow and the small F-5 from FB.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

I'm also going to follow. I'm rehabing an old Yellow A-4 with an OS 77/Dynamax that always flew well. I have also thought of building another for Golden West FD-3/67 power....I still have a couple of those!

Tom

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Hi,

Wow! You still have those GW's? Those were cool. In fact, those were the first turbines I ever saw fly. Bob at JetCat used to fly one of those in a Yellow A-4, too. I love this plane on turbine power, and with care it can be built at comparable weights, so the performance is superb. I had one with a Bee in it that would land slower than many of my DF powered ones. I'll have some pics up starting tomorrow.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Hi,

Got some work done today. The first pic is the stab. I glued the balsa tip on with Elmer's wood glue, both to the stab and to the elevator, which is just a piece of balsa aileron stock with the bevel already milled (like what you'd get from a hobby shop). After sanding the pre-glued balsa trailing-edge to match the stab, I tack-glued the elevator to the stab, then glued the tip block onto the elevator and tacked (with one drop of CA at the leading-edge). This way, I can sand it to shape, then break the elevator (with its new tip) free when the time comes.

The second pic is the wing tip block sanded to shape in basically the same fashion. The wing tip blocks have the angled cut already in them, you just have to line it up with the center of the aileron cutout. After final sanding, I'll continue that cut and remove the aileron for capping.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Hi,

The first pic shows the two main bulkheads, with the spars cut off (since I'm doing plug-in wings) and the doublers glued on to support the spar receivers. The second pic is just the other side of the first pic. The third pic shows the spar receivers installed, using a long spar from another plane to ensure that the receivers are aligned. You can see the notches cut into the bottom centers of the bulkheads to clear the lip (fiberglass roving) that runs the length of the bottom of the fuse.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Hi,

The first and second pics show the main bulkheads with the fixed-wing spars removed and fitted into the fuse. The second two pics show the stock inlets temporarily installed with the bottoms cut to make room for a DuBro 40 ounce main tank. The main issue with this bird is the lack of much room for fuel. I will most likely carry a centerline wet tank to extend flight times past four and one-half [full throttle] minutes.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Hi,

Next I started prepping the wing cores for the plug-in spars. I start with the existing slots and hog them out a little with a thin sander (piece of wood with some sticky-back sandpaper on it). I'll glue some 1/32" ply onto the insides walls of the slots. The first pic shows the hogged-out slot. You can see the stock width of the slot in the third pic.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

How did you find your main former point? By slipping your wings in the receiver and getting a mark on the fuse inside?? Looking good.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

I built a Yellow Blue Angel Arf with a Super Bee installed. Great combination, and flew great. I gave all the pipe dimensions to Tam, who built the pipe (He said it was the first Yellow A-4 pipe).

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Man I wish yellow still had that blue angle arf... it would be a perfect 90mm fan setup
a hot 4000 watts 90 mm would make that thing scream!

This will be a great build... shawn your always working on something cool.. nice
have a great 4th!

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

General,

Yes, I remember those ARFs. I wish we still made the camo one. The Bee was a great engine for this bird, that's for sure. That may have been Tam's first A-4 pipe, but this plane flew on turbine power years before the Bee was ever designed. I'm sure that's what Tam meant.... ;) Do you still have this plane?

Ron,

Thanks very much. Same to you and yours, of course!

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

I'm watching too Shuan. Glad to see your feeling better. Cheers

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Hi,

Thanks, John. Lots of cool memories flying that A-4 with your engine in it! Way better than any of my DF ones...

I got a little more work done on the wing spar system. The instructions call for some things I've learned are the hard or long way around a problem, so I'm using some shortcuts here.

The first pic shows the front spar slots capped with 1/32" ply from top to bottom skin.
The second pic shows the front spar trial fit into the 1/8" ply spar filler block, then the block itself before being epoxied to the spar. I used the stock spar that I cut off earlier to get the shape of the filler block. I held the cut off spar where it would have been, then traced the spar location onto it after putting the spar into the receiver. I cut and traced that onto a fresh piece of 1/8" ply which made the filler block.

The last pic shows how the spar and filler block will be glued into the spar slot later.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

build looks good amigo.[sm=thumbup.gif]

may i suggest reinforcing the top wingskin with CF veil or 2 oz CF cloth in an elliptical pattern prior to glassing. no matter how hard I tried to grease on a landing, the numerous firm landings i endured caused the retract plates to eventually transfer up through the top skin.

i flew mine with a P60, 50oz dubro and a uat. talk about a tight fit. i like the idea of using a smaller main tank and a drop tank. it'll give ya a little more room under the cockpit. I bet a P20 would be perfect!! not super fast but nice and light with a good turn of speed.

beware the high speed or approach turn stall....mmuuuaaaahhhhhhh :D pesky little buggar won't bother tellin ya when she's about to depart controlled flight. LOL turn a chunk of coal into a diamond if you're not ready. haaaa

keep up the good work
buck

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

buck-a-4

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Smitty,nice a-4.What is the dry weight?Do you think a Wren 44 gold would be enough?

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Hi,

There are already slots cut into the sides of the fuse where the wings go on. Basically, it's like you say...when I glue the formers in, I'll use the wings to position them.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Yeah,

One of the problems with this kit has always been the inconsistency with the foam they use in the cores. I've had some where the foam was a high-density bead and some where it was very soft. I've even had some of these (this is my eighth one) where one wing was one way and the other was the other way. On the dense ones, the gear plate being glued against the foam with a couple of dowels through it are plenty tough. On the lower density ones, they'll eventually punch through...not only with hard landings, but even with normal landings over time. Since I know this one will be a little heavy, I think I'm going to look at adding a reinforcement. As for that high-speed stall, this is the plane that taught me that there was such a thing as a high-speed stall! I'm pretty sure you were there, Buck.... :D

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Hi Shaun,can you tell me more about how you reinforce the landing gear plates with dowels. Where did you place the dowels?A few pictures would be greately appreciated.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Mark,

Actually, the dowel reinforcement is already in there. Basically, they drill 1/4" holes (4) and push a dowel down from the plate through the foam to the opposite skin and glued in. You can't really see them, but they're there. Actually, you CAN see them, but only after a very unfortunate incident.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

haaaa that seemed like ages ago!!! :D if you're high enough in the sky....it's fun to watch. not so much in the turn to final. LOL

the pix that Smitty posted shows the reinforcement i did after i punched the plates through. if i were to do it again i'd extend the CF over a larger area and then glass.

it's a great little airplane

good luck with 'er

cheers

btw "Mark5, Smitty,nice a-4.What is the dry weight?Do you think a Wren 44 gold would be enough?" i think it was near 15.5 dry and i think a wren 44 / P20 would be a great powerplant. nice and light with a great turn of speed.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Shawn,

I'd like to get your opinion on an idea. I still have the scale wing Yellow A-4 a buddy built 19 years ago(!) He made it with removable wings in a fashion VERY similar to your build. The capture channels bolted to the bulkhead developed significant play after a few dozen flights.....and maybe a hard landing or two! The bolts just enlarged the holes in the bulkhead and there was significant vertical flexing. We finally just permanently glued the wings to the fuselage and eliminated the plug in system.

When I build another, I plan to once again do what you are doing and add some triangle stock to the top of the capture channels. I plan to have the triangle stock overhang the capture channels and add a thin ply facing from the top of the channel to the bottom, basically encasing the channel to create a 360 degree support.

Overkill?

Tom

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

Hi,

I don't think it's overkill, but I think there might be better ways to accomplish what you're trying to. I think what I'd do instead (if I were concerned about it) is to make a 1/8" ply doubler to go around the spar receiver to 'capture' it. This is what I did when I built that twin P-120 powered Hornet. The main thing is that you have to sand the backs of the receivers with 60-grit paper, then epoxy them to the plywood when you bolt them on. Even when I didn't use the plywood capture, I never EVER had a spare receiver give way.

RE: Yellow A-4 Skyhawk for P-60 Build Thread
 

I planned to sand and glue the spar receivers as you describe.....I don't think that was done on the previous build. That's probably a significant factor in the receivers working loose.

Tom