How do you make your cowls from PETG? You mentioned a head gun and a mold/plug of some sort. Could you give more info on how you do this? I am putting together several JKA FW's and would like to spiff em' up a little. Also, any other tips or improvements on the JKA kits that you have tried? Thanks in advance!

There's a "How-to" on pop bottle cowls here:
http://www.rccombat.com/sections/wor...le%20Cowls.htm

Stuff I normally do to JKA planes (rubber-banded-on wings):

WING

1) Use either 1/8" 'glass rod or 3/16" hardwood dowels for the spars and glued in with ProBond polyurethane glue.

2) Use 1 layer of 1" wide strapping tape in one piece around the entire wing starting and finishing on the top in the center. Always spray a coat of spray adhesive on the foam before taping.

3) Use 2 layers of 2" wide strapping tape over the spars over-lapped by 1/8" to 1/4", top and bottom.

4) 1/4" x 12" hardwood dowel TE from the center on each side. 1/4" sqare balsa TE from the dowel to the tip.

5) Balsa ailerons with torque rods, the bearings glued to the hardwood dowel TE.

6) 1 strip of 2" wide strapping tape laid over 1 strip of 1" wide strapping tape on the LE.

7) Two popsicle sticks imbedded in the bottom of the LE, touching at the center for rubber band crush protection.

8) 6" of the center section 'glassed with 2oz. cloth and epoxy (over the torque rods and strapping tape).

I build the FUSELAGE as described here:
http://www.jkaerotech.com/P47bs.htm

With the following exceptions:
1) Replace the kit's light plywood firewall with 5-ply 1/4" Birch plywood.

2) Slot(s) for the fuel tank cut into the fuselage and the assembled tank tank is glued in place with ProBond polyurethane glue while the fuselage halves are glued together with 5 minute epoxy.

3) The 2mm Coro doublers are glued to the firewall with ProBond polyurethane glue, and the remainder attached with spray adhesive as per the instructions.

4) 1/4" hardwood dowels for rubber band hold downs glued in with ProBond polyurethane glue (the rear dowel positioned high enough to clear the torque rods).

The wing and fuselage also get covered with either TowerKote or EconoKote iron-on covering instead of packing tape. Be sure to spray on a light cote of spray adhesive and let it dry for 1 hour or more before covering, and use a low-temp iron.

I usually use Rustolium gloss colors sprayed onto the covering after scuffing the covering with fine Steel Wool. For the Fw-190, there are several combinations of Rustolium colors that look pretty good:

"Standard Day Fighter" scheme: (AKA- RLM 74/75/76)
Gloss Smoke Gray and Gloss Charcoal Gray over Gloss Harbor Blue undersides.

"Eastern Front" scheme: (AKA- RLM 70/71/76)
Gloss Hunter Green and Gloss Dark Hunter Green over Gloss Harbor Blue.

"Tropical" scheme: (AKA- RLM 79/80/65)
Gloss Sand with spots of Gloss Dark Hunter Green over Gloss Harbor Blue.

HTH,
D

Please post some pics when you get your Wurgers done!

Thanks for the speedy reply Demon!

One part I want to make sure I understand, you wrap the entire wing (not just the center) with 1" strapping tape? Does this add much weight?

Also, that PETG stuff looks pretty easy to deal with, have you ever tried making a petg cover to wrap over the LE of the wing? That would be pretty tough in a mid-air I bet! Any thoughts?

Sorry, I should have been more descriptive.

The attached image shows what I meant by "the entire wing", which should have read "all the way around". Also shown is the location of the strip of 1" strapping tape on the LE.

I never tried to make an LE "cover" from PETG. Neat idea, but it would be pretty heavy.

I don't build my wings to have a ridgid LE. The LE shown has some give that allows this wing to absorb and disipate impact energy. In short, they bounce off of almost anything they hit. In fact, the only impacts that have penetrated this type of LE are direct engine strikes. I'm not about to waste my time/effort/money trying to engineer an LE that can go through an engine without damage.

Some combat pilots approach this problem by attempting to build an LE that is (supposedly) stronger than anything it might hit. The problem with this theory is that someone always comes up with something that is stronger and the LE eventually fails.

As long as it bounces, it can hit steel and still survive.

HTH,
D

The attached image is to clarify where the 2" wide strapping tape goes. The bottom of the wing also gets 2 strips of 2" as per the top of the wing.

D

Oh, and one more thing:

Try Manco strapping tape available from WalMart. It is the thickest and toughest of the strapping tapes I've found (FAR stronger than 3M strapping tape).

D

Darin,

I am working on a JKA P-47N, and I am going to make modifications simular to yours, but I have a question or two for you.

I notice you use balsa for the TE except the center, why the dowl in the middle? I was going to use balsa for the whole TE.

What size aileron stock do you use, and where do you get it?

I noticed that the instructions for the P-47 wing don't result in a wing that is 1/12+10%, it's closer to 5%. Do you cut the wing a bit longer to get the extra span and area? I am currently leaning that way. But I was wondering about the wing chord. I assume it's also at 1/12+5%, but I haven't found numbers for the fullscale P-47N wing chord so I can't be sure of my measurments. What did you do for the wing size?

Thanks

"I notice you use balsa for the TE except the center, why the dowl in the middle? I was going to use balsa for the whole TE."

The dowel TE is for rubber band chrush protection. I used 1/4" balsa TEs before, and the balsa eventually fails, crushing th aft 2" - 3" of the wing. I also tried using 1/4" dowels from the center to just outboard of the torque rod bearing, but that failed at the dowel/balsa joint. Using a 1/4" dowel from the center out to the location of the first CA hinge results in a TE that does not crush at all without much of a weight penaly.

"What size aileron stock do you use, and where do you get it?"

For 'regular', straight strip ailerons (such as the Zero, P-51 and Fw-190), I use 1" x 1/4" aileron stock from Tower Hobbies (because I buy stuff like that en mass). Any local shop should also have it.

For the curved ailerons on the P-47, I use 3/16" sheet balsa cut to the shape required using the kit aileron as a pattern and extending the root lines to get the desired span. You could sand the 3/16" sheet to a point at its TE, but I just round off the rear edge and leave it flat.

"I noticed that the instructions for the P-47 wing don't result in a wing that is 1/12+10%, it's closer to 5%. Do you cut the wing a bit longer to get the extra span and area?"

The P-47D's span at 1/12th +10% is 44 13/16". The P-47N's span at 1/12th +10% is 46 3/4".

The kit provides enough material on the wing panels to cut the panels to any size from exacly 1/12th to +10% for any version of the Jug.

On my first Jug (the Razor Back P-47D in my RCCA site signiture), I built it to 40.5" (1/12th). On my latest, I went with the P-47N with a span of 46.75". The 'new'one is just being finished and I haven't flown it yet, so I can't comment on the difference in flight performance yet. I should have it flown within the next week or so (depending on the weather).

"But I was wondering about the wing chord. I assume it's also at 1/12+5%, but I haven't found numbers for the fullscale P-47N wing chord so I can't be sure of my measurments. What did you do for the wing size?"

The measurment I have from a factory 3-view is 9' 2 1/32" for the P-47N's overall root chord. That translates to about 10" @ +10% (including ailerons). The drawing for the wingtip supplied with the kit is perfect for the tip dimentions and shape.

HTH,
D

Thanks for the info, Darin, that helped.

Do you know where I can get a decent 3-view of the P-47N? I've been looking around, and most all the 3-veiws I see are the "D" version.

Thanks

My pleasure Kirk.

Here's a 3-view of a P-47N that matches the factory drawing:


D

Darin,
You da man! Thanks for the 3-view. That's really cool

I noticed you said you cover your planes with towercote or econocote. I was flipping though catalogs last night getting ready to order parts, but I noticed that the cool military flats are only availble in normal monokote. I know you said you paint the covering. My question is, do you find any particular color is good for painting? White seems obvious, but I know that in the plastic films, the lighter colors are noticeably heavier than the darker ones.

Thanks

Kirk,

I use white for most projects because paint covers it very easily (I don't use a primer coat at all). And, any white trim areas can simply be masked off.

The only exceptions to that are for schemes that have large areas of a color that the covering is available in.

For example, I have a Zero in the works that has a completely orange underside (Operational Training Unit colors).

For this, I'm covering it with Orange TowerKote and painting the topsides with Rustolium gloss Dark Hunter Green.

D

I flew my 46.75" P-47N yesterday (good timing because we had about a foot of snow fall here today). It flys as fast or faster than the Razorback.

With its lighter wing loading, it is nearly impossible to get it to Deep Stall. At full throttle with a MA 10x4 prop on the .25FX and the recomended throws, it won't stall at all (it just mushes to a lower AOA and keeps going). Even with massive overthrow on the elevator, I couldn't get it to tip stall at any speed (even coming out of full tilt boogie vertical dives).

Full details on this model forthcoming in RC Excellence magazine....

D

Darin,
How much did it weigh, RTF, and with what servos?
I'm still working on mine, along with too many other projects. I'm a very slow builder, that's for sure.
Kirk

This one was built box-stock. All up weight is 3lbs.4oz. with 3 Tower TS-35 servos, full-size Airtronics reciever, 700mAh Sanyo NiCd battery pack and an OS.25FX.

I hear ya on the "too many projects". Gozer and I just cut 18 wings Saturday - 14 of those are now awaiting my attention as well as the 7 fuselages that go with them. But hey, once those are done, I won't "have to" build any combat planes for a couple years!

D

You have overlooked the terrifying fact that you will be flying in heats against me, Demon.

Hmmmmmmmmmm...
As I understand it, your scale planes also follow the JKA style of construction. After your first few midairs, you'll realize that NOTHING is terrifying to a superball pilot.

D

Hey Demon,
I'm thinking of switching over to econokote/towerkote to cover my next model. Any tips applying them directly over foam (aside from using low temp). I've never used low temp films before, do they shrink up well? Do you prep the foam before application? Your planes look really clean with that covering (tape has too many visible seams).

Low-temp covering goes on just like regular covering. If anything, the low-temp stuff shrinks more and is generally easier to work with.

Be sure to spray on a light coat of spray adhesive and let it dry for at least 1 hour before covering, and use a low-temp iron.

As with covering any solid surface, start in the middle and work toward the edges. Other than that, just follow the covering manufacturer's instructions.

D

im bringing this back to the top for reference purposes.

It's a great thread.

Btw, I'll add that after flying combat for a few years since that thread started, I went away from low-temp heat-shrink for covering a while back. I now juse use clear or white packing tape instead. The tape is about the same weight or lighter, and it's a lot stronger, espeically at resisting prop cuts. I get my tape from uline.com, but I don't mind buying a case at a time. Other guys get their from places like fastpack.com (I think that's the url).

I do still use the soda-bottle cowls though. It's the way to go, the cowls are strong, light, and easy to make, and the plugs aren't hard to do either.

It'd be alot better thread if that all knowing, world beater would post to it too.

Oh, I guess I just did. Great reference thread Demon, if you can sticky the thing to the top, it'd probably be an idea.

Hey I used this thread to build my JKA 47. The mods worked great unfortunately I cant get Dan at JKA to scale up to 48" for 2548.

i would personally like some more detail on building the trailing edge/aileron part. maybe some pictures? i would love a build-along from demon or someone utilizing his construction methods.