DamonTX

I've seen a few people in the other P-38 threads asking for a mid sized affordable P-38 or asking what the Marutaka is like. Well on and off for the past year I've been working on one so I thought I'd share the photos. If any of you are building or have built one, please add some pics and tips.

I'm especially interested in the radio set up. The plans provide no detail on this and I'm looking for some creative ideas on making a mechanically sound but relatively concealed elevator and rudder setup.

This plane will run on 2 .46AXs, will not have retracts. The modifications I've made are, lower boom hatches (behind the main gear), 4 flaps, inverted the engine mounts and made removeable cowls.

This P-38 will have 2 aileron, 2 rudder, 4 flap 2 throttle and 1 elevator servo (11 servos) with a Futaba 8UAF. Is this too much power to put through 1 receiver? Or is there a better way to route the flaps into one channel without using 3 Y harnesses and 2 extensions? I've considered putting separate receivers in each boom.

DamonTX

Get ready to spend a lot of time carving! Yep you pretty much get a box of wood, 3 stapled sheets of paper, plans and are basically told to whittle yourself a plane! Below is the hatch around the cockpit area (took about 5 hours of carving). I've also added two pictures of the modifications I've made, the lower boom hatch and removeable cowl.

Aruba_Maverick

Looks good DamonTX

Makes me want to finish mine on and off for the last 4 years.
I'll post some pictures later this week.

C Lim

dionysusbacchus

My Feedback: (25)

Damon, that's a great looking bird, you did an excellent job at sanding the contour. Many fail the balsa block test and come up with some ugly shapes, just look at the TF P-51 noses you see at the field! I am old school so I can give you my opinion, while it is my opinion it is backed up by aerodynamic principals. I never use servos in the wing tips unless it is absolutely necessary or it's a larger model. You should always keep the wing tips as light as possible, especially in a P-38. 11 servos is to much for this plane, the average servo is about 1 3/4oz so you have about 1 lb 3 1/4oz of servos on board! The Marutaka prototype had just 4 servos, that would be only 7 oz. Of course the bell-cranks weigh something but it won't come to 1lb! See the first picture. I know it sounds easier to install a servo instead of a bell-crank but it's not. It's just a rumor that bell-cranks have lots of slop in them, there is always a right way and a wrong way to do something. There is far more sloppy flying than sloppy bellcranks. I would use one servo for the ailerons at least

Also I have been working on plastic parts for the radiators and cockpit kit. For the cockpit kit I am just copying the original Royal version. Keep up the great work and keep us posted, I let you know when I finish the parts if you are interested.

Dion

scale dail

My Feedback: (8)

I have 2 of the old royal P-38's,one has been flying for years and the other is still under construction. the finished one wieghs 13lbs,powered by K&B .48's. 5 channels, no flaps. 6 servos, one for the ailerons with bellcrank in the wing under the cockpit. retract servo is in the pod in front of the windscreen. air tank is in the left boom. right boom has the extra strong elevator servo and a throttle servo straddling the retracted main gear strut.the left boom has a throttle and the rudder servo in the gear bay. the rest of the radio is under the cockpit.rudder linkage has two bellcranks.the 2 booms are attached to the tail in a ''U'' configuration. with the wing and pod separate. it fits in my Dakota in one piece on the way to the field.

TLH101

My Feedback: (90)

Just a heads up for you guys building these P-38s. There are 2 sets of glass cowls on E=bay that end today,(10/16). Just saw them, the item numbers are 5926390158 & 5926417897.
Hope some gets a good deal.

DamonTX

Dionysusbacchus ...Thanks for all the great info! I was worried about the servo weight and you've pretty much made me realize that I do need to rethink the whole setup. Well I'm gonna start by doing 1 rudder servo instead of two. Its a little late to do a belcrank for the ailerons so I think I'm going to spring for some digital/heavy duty minis. And I agree with you, if done properly, belcranks are not sloppy. My big regret right now is not doing the flaps with belcranks,,, will most likely go with heavy duy minis on those too.

Scale Dail...I hope mine comes out as well as yours. Did you cover with Monokote? Since the rudders are on one servo, are they coupled with a pushrod under the stab? Also, you must have quite a few extensions in there..is that anything to be worried about?

I came very close to building mine as one piece..thats why I originally made the hatch under the boom. But I wouldn't have been able to get to the tank or had access to the throttle pushrods in case I needed it.

TLH101... I looked everywhere for cowls!!!!!!! They look good and I'm thinking about placing a bid just in case I build another. After all that work on the cowls, I'd hate to get rid of it now.

scale dail

My Feedback: (8)

Mine is covered with K&B resin and light glass cloth,painted with K&B epoxy paint. that was 14 years ago. (K&B Superpoxy R.I.P.[])

TLH101

My Feedback: (90)

If you don't get them Precision Fiberglass lists them under the Royal P-38
http://www.precision-fiberglass-prod...dex.php?cat=23

JohnBuckner

My Feedback: (1)

Here is my Royal, ultimately lost in warbird racing. The gentleman holding the airplane is the project originator from around fifteen years ago who lost most of his eyesight sometime back and I finished out the project, yes he got to see (hear) his long time project fly. TT 61's and later full wave pipes, 14.5 lbs and fixed gear. Just acquired an old wing kit to get back into the multi engine warbird pylon circuit with next year.

John

DamonTX

Woah! With 2 TT .61s and at 14.5 lbs. it must've really moved. Is the new wingkit for that P-38 or another one.. or another racer? If you have any other pics of it please post. Thanks

JohnBuckner

My Feedback: (1)

It was resonably fast Damon but the weight and the associated high wing loading (around 45 ozs per square ft) spelled disaster when trying to fly the pylons. Stall speed is higher in a bank than level flight and much higher when pulling high 'G' now add that to the need for tight vertical turns at low altitude and the heavy wing loading and you can imagine what ultimately happened. The accellerated high speed stall and snap at thirty feet was spectacular.

The replacement that I was talking about is the Wing Engineering kit, not sure if they are still in business. Almost identical in size to the Royal/Marituka kit. Not quite as scale as the booms are built somewhat squared off and also uses a foam core wing. In Pheonix next year there will be three big warbird races starting in march and that is what i am going to build up this Wing kit for. Actually the multis historically have not been as competitive as the singles because of the higher wing loadings and they just won,t turn the poles as well as many singles but sure is cool. There have been some other multis racing this last year and that has encouraged me to build up another.


I,ll start that project after November as I am just finishing up floats for the four engine Cadet in my Avitar. This for the Lake Havasu float fly in nov. That airplane has 64 day and 2 night flights on wheels now and can,t wait to get it on the water.

John

Oh by the way only had maybe twenty flights on thye Royal but do recall it was a very nice flying ship even though heavy on two. Never had a flameout so can,t attest to single engine controlability .

khodges

My Feedback: (1)

I bought a completed Royal (AKA Marutaka) that had been in an attic for a number of years. It's disassembled right now against the day i drag it out and restore it. The finish is shot but the airframe is solid. What kind of power will it take to fly this thing? You are using .46's but mine had Enya .61's and I don't think they were original to this plane, they were upright, and the cowls had been cut and patched from previously inverted engines. I had the thought of using Saito .72's inverted. they would fit well within the cowls, which I also plan to make molds of and make fiberglass replacements for mine, also want to do retracts and add flaps. I'm also going to re-do the tail section and lighten the ass of this thing; but it is a gorgeous machine. Keep us posted on yours.

khodges

My Feedback: (1)

Look at a Kondor (KMP) P-38 ARF. Could you duplicate the flap setup like that one? They are true Fowler flaps and operate on either one or two servos(Can't remember for sure). The rudder setup you could do like the Aeromodelli Cesna 337. It uses a rod through the horizontal stab to tie the two rudders together, is almost hidden, and uses one servo to operate 2 rudders. My other thoughts for myproject are to use 2 throttle servos, tied together with a synchronizer on an auxiliary Tx channel to allow differentail throttle settings, tied to a rotary ciontrol on theTx. Turn the rotary to synch the engines or apply asymmetric thrust for maneuvers; and I'm going to figure out how to run the left engine backwards and counter-rotate the engines. If I can find the right Saito part(rear cylinder cam gear from inline twins), and if it matches the gear on the .72, I can do it.

TLH101

My Feedback: (90)

khodges,
Cowl are available from Precision Fiberglass:
http://www.precision-fiberglass-prod...dex.php?cat=23


"Doh" I see now I already posted this info. I thought I was in a different thread.

DamonTX

KHODGES--Sounds like you gotta fun project coming up. Yes I'm putting .46s in mine, I have a couple FXs lying around so I'll test those to see if they will run well together. Since John Buckner said something about 45oz per square foot of wing, I've ruled out retracts and have been hollowing out a lot of the parts. I don't know how to do fowler flaps but would love to see some on a plane like this one. My main goal is always to make the plane as absolutely mechanically sound as possible. Though I don't get to fly much, I try to make them so they could be flown for a very long time with little maintanance.

Since I started the post I've sheeted the rear of the fuse, used 3/32 instead of the supplied 1/8 to save a little weight. (Luckily I did that on the wing as well.) I've also installed the pushrod tubes from the CG to the rear of the fuse.

The biggest task thats been taking tons of time is building the area above the fuse over the wing. This is the most poorly designed part of the kit. The block they give you needs a lot of shaping and when sanded down doesn't cover everything so I've had to add more. The pics below are the finished left side and the starting point of sanding for the right side.

It's too late to do a rod through the stabilizer to control the other rudder. Take a look at the rudder pic. I was sorta thinking with my hands on how to control the second rudder. This isn't necessarily permanent, I just wanted to get some comments on it. Actually, I think having the rod back there is kinda ugly.

I'll be using two throttle servos as well. I have a 8UAF, I haven't looked into it yet but does it have the ability to use two channels for the throttle????

lrb75

My Feedback: (12)

I would go with smaller servos to save weight. Try Hitec HS85MG (3/4oz) for the ailerons and flaps and rudder servos. I have been using them for a while in a Royal B-25 on ailerons and they are holding up well. Use something like HS81s (1/2oz) for the throttles. I would use something more substantial for the elevator. I would also make sure both ends of the elevator are driven. I lost a 1/12 scale P38 because the sheet elevator flexed and it rolled everytime the elevator moved. Should save alot of weight.

DamonTX

Thanks for the advice... I especially like it because you recommended by favorite brand of servos, Hitec. I'll look into the 85s & 81s.

The elevator is a solid block of pretty dense balsa so there won't be any problems with flexing that thing. I have a Futaba 9202 that I was originally planning to use on it. However, I haven't tried digitals on anything yet and was thinking about looking into them as well.

lrb75

My Feedback: (12)

The 9202 would probably work fine. I have several 5945 digitals for a jet project but they haven't flown. I have some 5475 digitals in smaller sport planes and they are alittle slow but hold well. I would use one of the 5645MGs for the elevator if you have to try them out. Make sure you get the HS-85MG not the ones with the plastic gear sets.

DamonTX

I'm liking the 5245s for the ailerons and maybe the nosegear, 85MG for flaps and 81s for throttles. Since I may be going ahead with buying 2 .46AXs instead of using the older FX I have, I may have to use the 9202 for the rest. $$$$$$$ But then again, it won't be flying till probably April so I'll have time to recover. For the first time ever, my wife is getting a little concerned about this project! She dealt well with dropping 3K on the 1/3 Cub though!

khodges

My Feedback: (1)

You might be able to retrofit the rod in the tail, would involve making a groove in the underside of the horizontal stab, just forward of its rear edge (depends on what hinges you used for the elevator), bury a hollow tube and run a piano wire thru it attached to horns on the inside of each rudder, then attach your servo control to one or the other. Use filler to bring it back to proper shape. Also, regarding using 3/32 balsa--I experimented with weights of different materials for sheeting by cutting one square inch pieces of 1/8, 3/32 balsa and 1/64 ply, and measured them on a digital powder scale. I found that 3/32 balsa and 1/64 ply are within 5 grains of each other per square inch, with the ply being the heavier. This, for all intents and purposes, is the same weight. I intend to do a lot of 1/64 ply when I sheet certain parts on my project.

If your radio is similar to mine (9CAP), you can slave separate channels for ailerons, so why not throttles? I was going to use one of the stand -alone synchronizers, hook both throttle servos to it, and add a mix with one of the rotary switches on my radio. The idea is to have the rotary at its midpoint and the engines are in synch, if I turn the knob one way or the other, it increases one engine's speed and decreases the other's. This is just theory so far and I'm not sure I can actually do it, or if there's even any benefit to be had. I know that in combat, the -38 could not turn with the -109's and -190's, and the pilots developed the tactic of pulling back the throttle on the inside engine in a turn to allow them to turn tighter (it had a tendency to throw them into a spin, too).

I've played a little with carbon fiber and planned to use it in places where I had to remove material in order to mount retracts, and I plan on rebuilding the tails to thin the vert stabs and rudders a little, get them closer to scale. I took 4 rolls of film of "Porky II" , the P-38 L that belongs to Planes of Fame, when it was here at an airshow, and plan to detail as much as I can. I've thought of doing a larger scale, but The Royal is such a manageable size. Keep posting your progress. The -38 is such a gorgeous bird.

DamonTX

Alright my fellow twin-engine bretheren! Please give me some advice here. I ordered one Slimline straight pipe for inverted engines to see if it would work. As you can see from the picture, I'm going to have to cut away a lot of cowl to make it work. So much that there would be a gaping hole in the side and thats just ugly.

The only alternative I can think of is to order a 1/2" or so extension and put the stock mufflers on it. I measured it and it'd work but I really wanted to avoid it. Any suggestions???

LRB75...I just got the 5245s and have and have a 5475 on backorder for the elevator.

lrb75

My Feedback: (12)

Although my B-25 only has a HS-425 on elevator I would think about a better servo on the elevator like the 645 or 5645. The 9202 I think has a better gear train maybe not as much ultimate torque. All in all the linkage and the mechanical advantage that the servo has is most important. The original plane must have flown fine on the crappy servos they had almost 30 years ago when the plane was designed. Any standard servo should work. I saw you are thinking about fowler flaps. I have an article about fitting fowler flaps in a royal P-38 from I think RCSCALE Modeler. I also have the plans for fitting fowler flaps in a ziroli p-38. I'm building a scaled down ziroli now with this flap design. The Fowler set up sounded easy to do in the article but I'm afraid it might not be able to be retrofitted after the fact. I can try to find the article might take a few days. I can at least get you the issue number so you can get a back issue and take a look.

lrb75

My Feedback: (12)

About the mufflers you may find that side mounting the engines with pitts mufflers you wont have to cut as much. Plus the heads will be better cooled. Starting from stratch I personally would go with Saito 72s inverted, but you already have the engines. I know other people have mounted 2 stroke without butchering the cowls.

dionysusbacchus

My Feedback: (25)

That isn't a head on picture so I can't be sure about the room available in the cowl, but just cranking the engine over a few degrees looks like it will work. You might need to cut a hole in the firewall behind the engine so that you can have good airflow, or you could just cut the heck out of the bottom of the cowl!

Dion