P-38 Lightning-Roddie style..

rsv1cox wrote:

Try the Golden Bees instead and check the weight.  You might even lose some.  

Bob  

The Golden Bee's are just slightly heavier than the product-configured engines.




There's also another important factor.. see the photo below..



Much of either engines' weight is concentrated near the center of the crankcase. Because of its' 8cc integral fuel tank; the Golden Bees' crankcase is approx. 7/16" (11mm) forward of the product engines' when mounted to the firewall.

Fuel-weight will be close to the same at 7.39cc's vs. 8cc's.. but the 7.39cc tank is positioned well-aft that of the 8cc integral tank on the Golden Bee. If the theoretical CG for this model falls on the wings' leading-edge at the nacelles.. then the external tanks will "straddle-it".. which would be ideal.

roddie wrote:

rsv1cox wrote:...The way that Jim did his was so much better.  I hope you kept a picture of Jim's...
Bob  

...Below is the link 944jim's BMH Mosquito-build. The fuel tank location seemed to be an issue..   I wonder how/if he found a solution.. Very cool paint/trim on that model!

https://www.coxengineforum.com/t10666-bhm-mosquito-in-ms-build?highlight=mosquito

I hate to crash the party, so I'll be brief.
First, Roddie...great model. I've been enjoying watching this one come together!
Second, Bob and Roddie...aw-shucks! I didn't think my attempt at that BHM kit made any impact. You two floored me by bringing it up out of context.
Third, yeah tank placement IS an issue. I had a pair of 2/3-1 oz tanks for it. I even went through great pains to remove the bottom vents in order to place the tanks on top of the wing. That was an excersize in futility!
I couldn't get the engines running at the same time. Once one engine got running, it would flood out before getting the other running. My son and I smoked a spinner trying my Hornet starter on this one. At one point I thought I ruined a basically new Norvel .074! Once the worst impacted engine was separated from the goobered tanks, it ran fine (phew!). The finish damage caused by ripping off the fuel tanks took a bit work to repair...just don't get too close to notice.
I will be making some 3/8 oz or 1/2 oz tanks, and mounting them UNDER the wing...just below the needle/venturi height. It may require taking advantage.of muffler pressure...but at least she shouldn't flood any more.
Bob, did you fly your Mossie yet?
Thanks, now back to our regularly scheduled P-38 news...

I just didn't like the way my bellcrank was positioned. The throw-ratios were off due to my not locking elevator-neutral when I drilled the bellcrank-pivot/hole-location. There's no clevis for adjustment when using two L-bends on the pushrod. I like the idea of one less failure-point in the controls.. but it has to be done correctly. What I had would not give equal up/down elevator deflection.   .. bogus.. I had to fix it.

A simple elevator "neutral-lock" using two craft-sticks and binder-clips allowed me to proceed in correcting the problem. The bellcrank mounting-screw is removed to expose the "eye" in the bushing. I then re-position the bellcrank (pushrod installed) with both arms equidistant from the boom/nacelle and use a small "awl" to mark the new hole-location for drilling.  



A more forward location yielded more needed "down" deflection.. and moving the pivot away from the boom increased the amount of available control-throw.



There's always more to this, than one can anticipate.

iDK, but I think having more “up” than “down” is a good thing, especially when you have gravity providing a bunch of “down” all the time.

rsv1cox wrote:

Unless your camera distorts, it looks like your control rod is bowed at the guide

Bob  

You're correct Bob. I didn't see the "bow" being an issue. If anything; the rod will have even less tendency to flex if slightly bowed. It could cause wear to the "fairlead" after a few-hundred flights... but if this airplane fly's that-many "missions"... it will have lived a fairly long-life.

Marleysky wrote:iDK, but I think having more “up” than “down”  is a good thing, especially when you have gravity providing a bunch of “down” all the time.  

Yes Rene.. that is true.. especially with my zero-incidence sheet-wing producing zero-lift. When flying "level"... there is a considerable amount of down-force acting on the model. With any luck; this model will turn with predictable-precision.. within the boundaries of an average line-length.

I have voiced my opinion on the usefulness of the 1/2A spring-style wheel-retainers before. Carl Goldberg models and Sig Manufacturing "had" offered these in the past.. but now; unfortunately.. you'll need to hunt for them. Bernie (Cox International) had sourced a NOS supply of them not too long ago.. and may still have some packages.



Hear me out.. these spring-collars are designed to fit 1/16" (.062"/1.6mm) piano-wire.. and provide a lightweight/reliable friction-collar that will assist in a myriad of modelling needs.

I am using these with this P-38 model. The elevator-pushrod is 1/16" piano-wire. It utilizes two "L-bends" which must be retained. Using a series of flat-washers with a spring-retainer; a linkage can be made to work with reasonable precision.

These photos will show where I have used these spring-retainers in the control-linkage of this model.



The above photo-example shows a 1/16" piano-wire pushrod being retained in a Sig 1/2A Nylon bellcrank. Take a close look..



The spring-retainer establishes a "clearance". That's basically the beauty of using it.

Here is where I use one on the elevator horn...



I'm just a novice flyer.. but I like to build precision into my flying models. It doesn't cost much...

Next-up was the nose-gear. I wasn't happy with what I initially designed. The nose-gear was designed around a "smaller-diameter" .045" piano-wire, having a double-wound coil to act as a "shock-absorber". The .045" dia. wire-size complicated using standard-size axle-bushings.. so I've upgraded the nose-gear strut to an .062" piano-wire assembly which will utilize a "single" shock-absorbing coil.



This should provide for a heavier-duty nose-gear.. without too-much of a weight-penalty. I'm not sure about wheels yet......... As I've said countless times before; wheels can help to finish-balance a model-airplane. I have several options open to this model. We'll see how she balances after she's got all her flying-clothes on..

Hey! Roddie,  I found a front tire for you........Fred Flintstone style.

rsv1cox wrote:Now that is funny Rene.  What's the back story if any?  Brit, Aussie, Kiwi?  

I like those spring retainers roddie.  

It’s a Woodyear tyre, made from roundwood. Used to support aircraft moving off the production line, whilst waiting for the real rubber tires to arrive.

(Nah! I just lifted the image from “woodworking for beginners “ Facebook page.)
https://www.facebook.com/groups/1761759164151923/permalink/1992964531031384/

Just for giggles.
My apologies to Roddie for hijacking his thread.

Nice build. I like your detailed pictures. Curious to see the paint job!!

Marleysky wrote:

This has been done before. I remember seeing a German WW1 Albatros in the aircraft museum in Brussels. That had original wooden wheels on it. This was because of the lack of raw materials.

Thanks for the comments guys. No worries about the "Woodyear" wheel Rene.. It never hearts to inject a little humor into a project.. especially where I tend to get OCD/anal with my methods.  

Actually... I just sourced some more wooden wheels.. but at 1.125" diameter; I think they're a skosh too small for this model.

Roddie... find a way to eliminate the BOW and resultant drag at the fair lead.... Trust me

fredvon4 wrote:Roddie... find a way to eliminate the BOW and resultant drag at the fair lead.... Trust me

I wasn't going to pay any attention to this.. but Phred scared me into it.. With my luck, I would have a control-system failure that could be traced-back to the bowed-pushrod.

A new/longer fairlead was the easiest fix.

I didn't want to cut the original fairlead off.. so I figured I'd try heating it with a soldering-iron to melt the glue (CA) which worked.



.. next came fashioning a new longer fairlead from a slightly larger safety-pin. I cut off the clasp and squeezed the two wire-legs together near-parallel using needle-nose pliers. I then clamped the part in the jaws of some small locking-pliers.. and proceeded to chisel-point the two legs using a sanding-block. I roughed-up the ends to better retain glue, using a riffler-file.



The locking-pliers were also used to drive the new fairlead into the balsa.. using my work-table as a back-stop.




I feel better having attended to this.. it was bugging me. Now I can hopefully pick up the pace.

I had left the holes in the blind-slat/wing.. because it afforded a place for a hanging-hook to keep the model up-high/safe from a balsa-chewing kitty..

You people following this build were probably wondering when and "if" I was ever going to plug them. Well.. today was the day.




I like this type of Elmers wood-filler. Last use was a couple years ago.. (this tube) The filler will harden in the nozzle with non-use.. but easy to clear-out.

rsv1cox wrote:We all feel better roddie.  Wouldn't want a small imperfection spoiling an otherwise perfect model.

Bob.  

You're too kind Robert.. Finish-work/painting is not my forte'.. and I assure you it will be far from perfect after that's done..

rsv1cox wrote:

I was hoping rocket pods or bomb/fuel tank hangars.  

............. you just gave me an idea Robert! I'm not planning on turning this airplane into a "Woonsocket Rocket".. ( .. only someone from Rhode Island might get that joke..) but some simulated-armament would be appropriate. I'll be spending some quality-time with Lynne this evening.. but check-back for some subtle additions soon...

rsv1cox wrote:

Hmmm............ Construct your existing fuel tanks into pods, feed engines from them.  Max cool.

That would be "Max cool" Bob! Balloon-tanks might work for replicating those. If it could be done in a non-complicated manner and provide consistent/reliable performance, I'd be all for it. What I'd "want".. would be a central-fill for both tanks.. having "tee'd" bleeders on both feed-lines for purging air from the system; sort of like bleeding air from hydraulic brake-lines. That sounds complicated... but it would be an interesting experiment. The bleeder-tubes would need to dump air/fuel into small recovery-vessels to avoid waste and preventing raw-fuel from being dumped onto the ground. The three open lines would be "capped/plugged" following the absence of air (bubbling) in the recovery-vessels.. which would result in a closed-system.

Fun to imagine.. but would it work?