kram

My Feedback: (7)

RV Man & I started building them in the same shop this week. We don't claim to have anywhere near the expertise of Samparfitt or Twinman, but we thought it would be fun to post pictures and progress notes as we build, then crash them.

Besides the obvious differences in scale detail and flaps, one of the first things we noticed was that, despite similar wingspans, the KMP is a "bigger" airframe: bigger nacelles and center pod, fuse is several inches longer. Which is closer to real scale???

KMP has a single, larger wingtube to connect the outboard wings, with no provisions for "warp" alignment. Dowels or pins will probably have to be fashioned.

Don't get confused about the pilot. It comes with the VQ kit, but I donated him to RV Man's KMP because NONE of my warbirds have pilots. These "Missing Airmen" commemorate the thousands of young aviators who gave their lives for causes in which they deeply believed.

Thanks, Samparfitt, for the detailed construction narrative. I printed it off and am using it for an auxillary construction manual.

mt

twinman

My Feedback: (2)

Cool idea!!!
DON"T EVEN JOKE ABOUT CRASHING!!! ARG!!
Twinman
PS Mine did not crash today.....uh make sure you loctite the screw on joints on the servo arm connectors for the flaps.......I forgot and landed with three flaps.....did not know until down.
Good Luck
Found this with reference to scale. Do not have your access to the two planes so we will wait to hear.
P-38 Specs

Wing span: 52 ft. 0 in (15.84 m) 12:49 PM 4/14/2000
Length: 37 ft. 10 in. (11.53 m)
Height: 12 ft. 10 in. (3.91 m)

SAPropbuster

My Feedback: (5)

I have one of the KMP P38's too and will be following your progress quite closely!

My calculations put the 38's @ 1/7.5 scale....good luck and DO NOT CRASH 'EM!!!

kram

My Feedback: (7)

Sorry about the delay. I'm suffering severe "job that pays for the hobby" interference this week, so as usual, RV Man is getting ahead of me (it's his shop) on the KMP. The upside to the delay is that I've gotten several EXCELLENT offers of advice and ongoing construction tips from people who have already built and flown the VQ, including one leading expert in the field (or dare I say THE leading expert in the field) who has requested anonymity, but whose advice is so valuable that I intend to highlight each pearl with a double asterisk ( ** ), so watch for those! So, where is RV Man gonna get help on the KMP?? Jump on in, guys. This is not intended to be a private thread.

The "wingspan to length" ratio of the real P-38 is about 1.37, our KMP about 1.40, our VQ about 1.48. My Yellow is closer to the KMP.

I've got the wings together. Although I do not intend to remove them for transport, I don't feel committed enough to epoxy them together YET.

** The support for the aluminum guide tubes on the inside of the wings seems flimsy, so it's good to slather some epoxy and micro-balloons or fiberglass strips to reinforce them. They can be easily accessed with the tips off.

** The set screw holes for the middle wingtubes on the inner wing panel are about 3-4" further inboard than the other holes and hard to see. Use the perfect light angle and iron the covering gently with a thumbnail to find them.

In this photo, I'm halfway into one of my favorite building tricks: Using a round fishing weight on a slick nylon string to thread servo leads through the wing. Alternatively, borrow a flexible fiberoptic bronchoscope, but few of us have access to that. You get an idea of how many hatches there are on the wing bottom. Samparfitt had an excellent suggestion to number, then remove those to avoid confusion

av8r4aa

My Feedback: (82)

VQ P-38
My friend who has one of these already flying reported that the outer aluminum rods are bending.
He is a machinist and is making some new ones out of unobtanium so that problem should be fixed.
I will add that he flys his plane in a aggressive manner. Maybe his style is a factor
Except for transport I would glue the whole VQ wing together if its mine.
The KMP outer wings are designed to use a J hook and some rubber bands to hold it on.
Of course it has 2 anti rotation dowells per wing. I am not real keen on that idea either.
I guess that I will just go out and buy a Hummer. Then I will not have to remove/replace the wings
Also with a Hummer, parking at the field is simplified!
Greg

kram

My Feedback: (7)

A coupla things are obvious from the KMP shot here: RV Man is ahead of me, and he got two left cowls. He is the ZEN MASTER with a spray gun, so he plans to re-paint it rather than try to send it back. In fact, I've heard some grumblings from that side of the shop about stripping and re-painting the whole thing. You can see the side-mounted OS 70 FS's. Neither of us is crazy enough about scale, or confident enough in the reliability of inverted glow engines, to go that route. RV Man reports that there was some minor misalignment in the way the booms fit to the inner wing and the stab, but nothing a little brutane (big pipe clamps, alignment blocks. and 30-minute epoxy) couldn't fix. He still hasn't told me how he plans to keep the ouboard wings from flapping around that single wing tube.

On the VQ, I hit my first minor speed bump. While hand-testing one of the Fowler flaps' motion (they seem a little stiff, even for a retract servo), a brass clevis arm snapped on an adjustment rod that basically controls the base of the flap. Red marks on the attachment points. It should be easy to fix, but the ease with which it snapped is unsettling, and I may replace them all. Overall, I'm very pleased with accuracy of the build and the alignment on the wings. Any little "off" would have made the wing tubes very difficult to install. They were easy. The covering material is new to me, but the craftmanship on it is immaculate. I hope and assume it's glow proof.

kram

My Feedback: (7)

RV Man is killin' me! He has the flap and aileron servos and linkages installed and the retracts in place. The brand of retracts that comes with the KMP is not stated, but they look and work like Spring Airs. Manufacturer's tolerances seem much sloppier than the SpringAir HD 102's that came with the VQ: there's a lot of slop and rattle to the mechanism. The gear wires are heavy duty but have only one-coil spring compared to the VQ's two. I got the 7/16" main oleo "upgrade" from VQ for about $85, so RV Man is drooling over those right now. The folks at Spring Air tell me that their 702 tri-gear set is a more versatile fit (with bushings) for a wire or oleo gear. If I decide to order those, I may pass the 102's off to the KMP. We'll do a side-by-side photo shoot and mechanical critique later.

As you can see, the KMP flap set-up is a lot simpler and less glamorous than the VQ's. Does that mean they'll be less effective, or less defective? Maybe both? There are no outboard flaps. The "flat box" housing for the inboard servos means he'll need a reversed servo or a servo reverser.

I replaced the broken clevis on my Fowler flap with a modicum of tweaking. The threads on the pushrod looked like 2-56, but must be some metric-almost, since the new clevis was tough to get on. No need for Loc-tite here! That dampened my enthusiasiam for a 4-clevis replacement. The other three "look all right" (famous last words before a last flight). Flap servos (JR 702's) are installed, but I don't like the wood they're screwed to. Too flimsy. Will bolster with scraps of light ply if it doesn't with mess with angle of the rod to the bellcrank. As you can see, the four Fowler flaps of the VQ down in unison is very glamorous.

kram

My Feedback: (7)

Just to combat rumors that this project is goin' to the dogs, we decided to publish photos of our Shop Supervisor:


And our Project Engineer:

kram

My Feedback: (7)

The VQ wing is servo'd up, adjusted and assembled and ready to fly. Total work time about 6 hours, including one very frustrating hour trying to get a reluctant ball link to snap onto a flap bellcrank. Finally had to invent a little homemade "C-tool" to press it on. The other three were easy, but there is NO WAY this baby is getting disassembled with any regularity! Overall, the fit and alignment of everything has been very impressive. It's hard to believe they could get it so right without trial-assembling each part. Little things like unwarped ailerons that line up perfectly with TE are just dead-on. And the detailed panel lines are understated, but meticulous. I've included a coupla shots of the battery hatch and tail feathers to give some idea of the lines.

OK, now I have to slap myself hard to break loose from the hypnosis of watching the flaps power up and down in unison!! Was there anything else to build? Oh, yeah. The fuselage: shown are the installation points for the rudder and elevator servos. I can't figure any way to avoid reversing an elevator servo without re-routing the pushrod guide-tube, which comes pre-glued. If I were advising the maker on future changes, I would suggest changing the guide-tube position to in-board on one of the elevator servos. Even a nut like me doesn't have a reverse JR 4131 just sittin' aroun' the shop, and I'm spooky about Y-reversers, so this will delay me a few days....On to engines, fuel tanks and center pod!

While I'm waiting for these pix to upload, let me ask those more experienced with this plane (or just flaps for that matter): How do you get intermediate flap positions when they're driven by retract servos? My JR 8103 seems to have no power over travel or intermediate positon of a flap servo (JR 703). They're either DOWN or UP.

kram

My Feedback: (7)

KMP construction is deviating from the instructions.

Now, folks, RV Man is no scale freak, but even he couldn't stand the aesthetics violation of the recommended elevator control system. They ask you to cut the tail off the centerpod and run pull-pull wires back from a single servo to the center of the elevator. Arrrg! The new plan is to run 4-40 Goldenrod from dual servos in the boom. He also plans to use the big Goldenrod on the rudder linkages to cut down on flop and slop perceived with the provided wire rods.

Also pictured is the KMP cowl after scale and engine cutouts are complete. The scale cutouts are done by the manufacturer on the VQ, by the builder on the KMP, and (as mentioned by Twinman on rcwarbirds) there is no seam on the VQ cowl. As we build these two birds side-by-side, it strikes me that the reason the VQ kit is so much more expensive is mostly about these details and attention to scale. My sense is that these details were expensive to produce, and in my estimation, a good value for the buyer, but whether it's worth the extra $$ to YOU, is a personal decision.

kram

My Feedback: (7)

DID I FORGET TO MENTION LOC-TITE !!??

Everything in the wing that has threads on it has Loc-tite. There are four little set screw deep in the base of the flaps that are installed at the factory, but do not have Loc-tite on them and should.

And tape or heat-shrink all internal servo connections.

mt

kram-RCU

Re: My struggles with one of the flap ball links:

** Go to VQ's website and find the link to "Twinman's Tool," an ingenious device that can be home made for just such problems.

I'm still not takin' this puppy apart very often!

twinman

My Feedback: (2)

I reply to av8r4aa and his aggressive buddy bending three aluminum rods with hardwood dowels inside per wing, I guess my concern about the tube mounts being glued enough inside the wing is silly. I will sleep better. Mine is a bit overpowered too, but I NEEDED IT!!
As for kram-RCU

"I'm still not takin' this puppy apart very often! " and the twinman tool. WELL!! You can't please everyone. OK I drive a Suburban and will not take the wings off either, but I can. I hate to be told I cannot do something!!
Twinman

kram

My Feedback: (7)

The spirit of RV Man's ill-fated Yellow will fly again!

He salvaged the Arrow pushrods with 4-40 connectors from the wreckage and found them ideal for the newly designed rudder and elevator controls. Also shown is the ample room in the booms for dual servo placement.

kram

My Feedback: (7)

Sorting out the Complexities of Gear Choices:

1) Fixed Wire Gear: Comes with the VQ, not KMP
2) KMP retracts: designed to be used with chromed wire struts. They look like Spring Airs, but kinda hard to believe Spring Air made something with that much slop. You can almost see it in the comparison photo.
3) Spring Air 102's: designed to be used with 3/16" wire struts. Came with the VQ kit (costs extra)
4) Spring Air 702's: designed to be used with a 3/8" strut or 3/16" wire (with provided bushing)
** 5) Heavy Duty Mains 7/16" oleos from VQ, Spring Air or Robart: has to be adapted through another bushing (provided) to the 3/16" wire to the upper unit (which if it's the 702's needs the other bushing to hold the wire.)
6) Heavy Duty Nose Offset oleos: ordered but not yet here from Robart.

To Summarize: My gear for the VQ will be 702 uppers-to bushing-to wire-to bushing-to 7/16" oleos.
for the KMP: 102 uppers-to 3/16" wire struts....add oleos later?

The retracts that came with the KMP kit are probably gonna get tossed, or used on a cheaper plane.

I know we've made things a lot more difficult than we had to, but any of you who have flown a P-38 off grass will surely understand.

kram

My Feedback: (7)

More Gear

kram

My Feedback: (7)

More Delays:

Due to my work schedule, I took the booms home for some tinkering and some time-under-wing of Big Sister Yellow. (Picture One)

The wood on the servo trays is really cheesy..seemed like guaranteed split 'n strip, so I reinforced with a little underside 1/16" birch ply (red tabs).

Engine mounts, rudders done.

Stangely, no marking or instructions in the manual for the critical firewall-to-spinner distance, so I asked for an upper level consult. Samparfitt said 5", Twinman said 5-1/8", so I'll take the Expert Average 5-1/16" I used my own hex-head #2 screws and homemade "vibration washers", and nyrod-reinforced screwholes for the cowls. I hate getting plastic/glass cowl damage from the screws. Easier to fix before than after.

kram

My Feedback: (7)

More Delays:

One would think that a feller with my experience and talent and brilliance would see the bumps in the road coming before my head hits the roof of the car!

I'm committed to side-mounted glow engines (Sorry, scale guys) Form follows function, esp. on P-38 engine reliability.

I didn't realize till I mounted them that the standard O.S. muffler for the FX .61 won't clear the firewall by a long way in that position. I'm not willing to carve away that much of the booms (right, scale guys?).

Fortunately, RV Man has some really cool-looking Pitts style mufflers on his B-17 from www.bissonmufflers.com. More phone calls, more waiting

kram

My Feedback: (7)

Flap Servos:

I asked Danny Snyder on the JR radio forum about getting intermediate positions out of flaps powered by a retract servo.

As I feared, he says there is NO WAY. It's a limitation imposed by the servo, not the radio.

I could change the setup to a strong, proportional (standard) servo with a very long arm like I use for my 3D stuff. Space in the servo well will be problematic and it would have to be low-profile.

Looks like RV Man's KMP will have fully adjustable flaps (albeit not scale), while my VQ will be stuck with either full UP or full DOWN. This will be a little discomforting on maiden, when I usually play around with flaps and elevator till I get what I like for landing...usually somewhere between full UP and full DOWN.

Any other ideas?

kram-RCU

I apologize for making the gear comparison so complicated. It reflects the initial confusion I had about gear after I bought this kit and the mental evolution since. In my brief experience with flying P-38's off grass, gear is one of the most important "technical challenges" of the aircraft, second only to engine reliability perhaps.

TO SUMMARIZE:
1) If you're flying off a very smooth surface and all your landings are going to be perfect, the easiest set-up is the Spring Air 702's with 3/8" oleos. Very easy to assemble, replace, whatever.

2) **If your field or your landings might be a little rough, I recommend beefing up to 7/16" oleos (or wire struts), which can be done with the 702's or the 102's.

Please remember this advice is offered by someone with exactly zero takeoffs and landings on this gear.

mt

kram

My Feedback: (7)

If you are a devout believer in the art of scale, it's time to avert your eyes.

Shown is the cowl cut-out for the side-mounted .61 FX. If you look very closely, you can see there's a subtle mismatch of the white (cowl-to-fuse), and the red (spinner-to-cowl). Not enough to bother me.

The spinner accomodates the three-blade MAS prop easily, but the combined thickness of the prop and the spinner makes the prop shaft a little too short. I haven't decided how to handle that yet. Not ready to spring for Tru-Turns yet.

Also shown is my Nyrod technique for vibe-proofing the cowl screws.

kram

My Feedback: (7)

The VQ booms are pretty much finished, from rudder horns to fueling nipples.

** Altho designed for disassembly, I plan to permanently glue the stab to the booms, once I line them up on the wing dowls.

Photos below show how nicely the servos fit in the booms and line up straight with the pushrods. Note how the elevator servo horn connector is upside down (red tab). This allows it to line up better with the pushrod and stay out of the way of the rudder pushrod. Tightening screw can be easily accessed through the wheel well.

** The firewall is coated with what looks like gray house paint with ?fuel resistance, so I'd recommend re-coating it with 30 min epoxy or Z-poxy.

I replaced the servo horn connecting hardware with some Dubro stuff that is more solid and user-friendly.

kram

My Feedback: (7)

Another brass clevis snapped under minimal stress! I was just prying it open to go on the elevator horn. That makes twice on this model, the first two times I've had it happen in...well, we won't say how many years of building. It's enough to really annoy me and to worry me about the integrity of the other hardware. And enough to get me on a soapbox:

The way I see it, there are three basic quality parameters for an ARF kit:

1) Design: Very well thought-out on the VQ. Somebody really put some thought into where things would fit and how they would interact. Example: There are two sets of throttle servo trays, one the stereotactic isomer of the other to allow for differences in engine/throttle position. Some of the mechanical stuff (like the flaps) is superior to anything I've ever seen on an ARF.

2) Build: Also fabulous on the VQ. Parts line up and glue joints are full and covering is neat. Well-crafted.

3) Materials: This is my main complaint is on this plane. I've had to reinforce all the servo trays, the hardware is cheap and fragile and sometimes inadequate. Quite frankly, I'm surprised. It seems like Items #1 and #2 would be the expensive part of an ARF, and putting a little higher quality ply in for servo trays would be a minimal cost.

The supplied throttle pushrods have Z-bends for the throttle linkage. There is NO WAY I can tolerate that much slop on a twin. Ball links were easy to solder.

kram

My Feedback: (7)

Work Schedule:

So far, I have invested about 6 hours for wing assembly, 12 hours for booms = total 18 hours. I expect it will take another 18 hours to finish.

RV Man has spent somewhat more time on the KMP, but he's also ahead of me. He has spent the last coupla days fitting the gear, and I hope to have photos of that soon.

The "Side-by-Side" nature of this project will suffer for the next coupla weeks: RV Man is off galavantin' around at some convention this week, then next week the LOML is forcing me to take a winter break and go play on the white sands and blue waters of the South Pacific. Sigh.

I hope while I'm gone, RV Man will give an accounting of his time investment and review his opinion of the Design/Build/Materials quality issues with respect to the KMP.

Towards the end, we will also give a rough accounting of the $ investment of the projects. Something we modelers rarely do, if for no other reason, it's scary!

Barring illness, financial ruin, or shark bites, we should be done by year's end. Maybe we'll take a road trip to Florida for maiden flights.

robert waldo

My Feedback: (1)

Hello, After building both P-38's do you think the VQ airplane is worth $139 more? The reason I ask is that I have the KMP airplane. This is wihtout question the worst Arf I have ever seen in 33 years. The booms and center pod are misalighned, the glass work is wavy and lumpy, gel coat or whatever it is is horrible, the tube spars are crooked, the verticals are canted inward, the balsa sheeting has popped loose on the wings, I don't consider the crappy retracts usable on something like this either so the fact that the VQ does'nt have them is not relevent. You can buy them from Vq for $639 bucks. Mr Kondor promised me another airplane, I don't mind spending a few bucks more rather than wasting $500+TAX.