HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Oct 03, 2012, 10:01 PM
Oh no, not again!
jhspring's Avatar
United States, LA, Carencro
Joined Dec 2005
5,277 Posts
Discussion
Reviving the Lib

So a little background. Back in '08 I build Fahim's B-24, painting it as a Navy PB4Y-1. Original build thread is here: http://www.rcgroups.com/forums/showt...ht=wowplan+b24

I finally got around to maidening it in '10. It flew perfectly, however my ignorance of multi's bit me and the the landing was rather ignominious. Repairs were easy, but there have been snags. The parking lot where I originally flew the plane is really too small for something this big and it has also gotten progressively more busy, to the point where I seldom even take my parkfliers there.

And the Lib does NOT like grass. I have made a dozen attempts at the club (grass) field and nothing works. Even getting a rolling start from the run-up pads, as I do with many of my taildraggers, is no help. When she hits the grass that nose digs in so hard I have prop strikes. With that high thrust line, adding power pitches the plane forward as it rotates around the mains, and that little, semi-recessed nosewheel just locks up. If I had a re-do, I would use much different nose retracts.

So the PB4Y has been a hangar queen for the last couple of years. Well, I don't really have space for HQ's, it looks lovely in the air, and I am having a blast with my HK Lanc, so figured it was time to bring the old dear back to life.

The objectives are first to find a way to get it airborne on grass, secondly, to re-wire the wing so it has a single connector, i.e. is easily removable. The Lib takes up most of the loadspace in my Merc and I need more than one plane at the field. Thirdly, I have decided to add flaps. My plane is a porker, right on 5 lbs, which is a full pound more than Fahim's prototype. I plan to land it gear down, so if I can slow it down some and land it on the mains, that would be a good thing.

To address the grass issue, I have built a launch dolly. 3" wheels for the grass, plane sits a little nose high, which should get it in the air more easily. Taxis okay, and when I pick the plane up by hand, the dolly falls free every time. Of course, who knows what will happen at the field .

SWMBO calls, more tomorrow.
Jeff
jhspring is offline Find More Posts by jhspring
Reply With Quote
Sign up now
to remove ads between posts
Old Oct 04, 2012, 12:37 AM
What's 3D?
trumps's Avatar
Australia, WA, Ellenbrook
Joined Feb 2008
3,316 Posts
great to see you are back onto her, she is a great looking plane and deserves another chance!

Craig
trumps is offline Find More Posts by trumps
Reply With Quote
Old Oct 04, 2012, 07:13 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
12,996 Posts
How about considering a bungee assist for take-off ?, or even bungee the trolley ?. There has been a few threads on portable runways, but I can't remember anything that looked particularly suitable.

There's always take along a lawnmower when you go flying

I have no choice but to fly off grass, so go for a larger scale models just to get the bigger wheels.

Nice looking B-24.
eflightray is offline Find More Posts by eflightray
Reply With Quote
Old Oct 04, 2012, 07:59 AM
Oh no, not again!
jhspring's Avatar
United States, LA, Carencro
Joined Dec 2005
5,277 Posts
Quote:
Originally Posted by eflightray View Post
How about considering a bungee assist for take-off ?, or even bungee the trolley ?. There has been a few threads on portable runways, but I can't remember anything that looked particularly suitable.

There's always take along a lawnmower when you go flying

I have no choice but to fly off grass, so go for a larger scale models just to get the bigger wheels.

Nice looking B-24.
Thanks Craig, Ray. Bungee is an option, a lot of the EDF guys at the club use them. The Lib is pretty porky, 5 lbs is a lot to get into the air. Truthfully, I am a little afraid of bungees, my few attempts haven't been particularly successful. I feel a lot more in control when I am running the left stick.

The guys at the club are pretty good and with the proliferation of electrics, we usually scalp a strip of grass in the middle of the runway. It helps but...

The Lib nose retract was modified from an (Eflite, I think) F16 nose gear, reversed so the wheel retracts forward. It is too lightweight for the job, really and I haven't been willing to tackle the major surgery required to replace it with a HD unit.Things are pretty tight in the nose.

I have made surprisingly good progress with the flaps, waiting on a care package from Grayson. Hope to be airworthy again next week.

Regards,
Jeff
jhspring is offline Find More Posts by jhspring
Reply With Quote
Old Oct 04, 2012, 09:38 AM
Registered User
D-Rock's Avatar
Phoenix, AZ
Joined Oct 2004
1,882 Posts
HI Jeff, great to see you are working on the Lib again! Sadly with other projects, mine has been set on the shelf for a bit. You did a great job on yours and look forward to seeing her redone with flaps.

D-Rock
D-Rock is online now Find More Posts by D-Rock
Reply With Quote
Old Oct 04, 2012, 11:14 AM
Registered User
owlsabie's Avatar
South Africa
Joined Feb 2009
2,713 Posts
Hey there Jeff! Looking forward to following along on this one I've promised myself one of these one day . . .
owlsabie is offline Find More Posts by owlsabie
Reply With Quote
Old Oct 04, 2012, 12:31 PM
Oh no, not again!
jhspring's Avatar
United States, LA, Carencro
Joined Dec 2005
5,277 Posts
D-Rock, I'm not surprised at your Lib sitting. You pretty much have your hands full designing these days.

Hey Owl. Well anything to keep me from finishing the Blenheim. Actually, been thinking about this for some time and the Lanc has been the push to get me to do it. One flap is done and bread-boarded up, just needs glue and paint. The other shouldn't take long now I have worked out the actuator geometry.

I have 3 planes in the car, hope to fly this aft. Try to post some more pics tonight or tomorrow. Jeff
jhspring is offline Find More Posts by jhspring
Reply With Quote
Old Oct 04, 2012, 02:39 PM
Registered User
Lawrence, Kansas
Joined Dec 2001
588 Posts
Long ago, there was an outfit that sold Sureflite .40-size foamies with conversion kits for electric power. I bought the P-39, and discovered that part of the conversion involved a mod that prevented installation of the nose gear, which in turn meant the mains were pretty useless. They claimed they hand launched theirs, but hand launching a low wing, 50 or 55" span, underpowered scale model left something to be desired. I built a dolly (trolly?) for it and had many successful takeoffs. One warning I was given, and I'll pass on to you, is to make sure that IF the dolly does NOT fall away, it does not adversely affect your CG. I don't even know if mine would fly with the dolly, but I took the precaution of adding some weights to the front of the dolly so the combo CG was still in a safe range.

I have a free-castoring tailwheel on mine and it steers fine with rudder, I guess the prop blast over the rudder does the job even at fairly low speeds. I have heard of people putting a 2nd receiver in the dolly just for steering, but mine does not seem to need it.

Cool Lib, good luck getting it in the air.

- - Dave
DaveA is offline Find More Posts by DaveA
Reply With Quote
Old Oct 04, 2012, 09:26 PM
Oh no, not again!
jhspring's Avatar
United States, LA, Carencro
Joined Dec 2005
5,277 Posts
Thanks for the tips Dave. At the club field I have lots of space. If I can't get off the ground in 600 feet or so, I probably don't want to. I just want my dolly to track straight and not run big circles.

Regards,
Jeff
jhspring is offline Find More Posts by jhspring
Reply With Quote
Old Oct 04, 2012, 09:39 PM
Oh no, not again!
jhspring's Avatar
United States, LA, Carencro
Joined Dec 2005
5,277 Posts
Surprises

When I got the Lib down and powered it up, the starboard inner refused to turn. A little experimenting revealed that the ESC had given up the ghost. This is the second time this has happened. I put it to bed with all 4 turning and next start-up an ESC has gone bad. I always thought these things were bullet-proof unless you overheated or overamped them.

It's problematic, b/c the original powerplants were those HK cheap combos of a no-name bell outrunner and a Mag 8 18A esc. I found a Mag 8 the first time this happened but nobody makes them any more. I had a TowerPro 15A I put in and everything works, but it seems that at low throttle settings, like on the bench, I am getting much more thrust from the starboard inner than the other 3. My test meter is my hand held behind the wing

I posed the question in the power forum and a couple of experienced guys recommended not flying in this condition, so I ordered a pair of 18A esc's from Grayson, which just came in tonight. I will replace both inners, so that if there is a difference in power (timing?) or throttle curves, it will be symmetrical. That also gives me a spare for the outboards. The problem with all this is that since I never figured on replacing esc's, everything is soldered in, and in fairly tight quarters. I have to be pretty careful not to melt my plane.

Bit of a nuisance, but not critical. On the plus side, with the improvement in lipos over the last few years I can now get a 20C 3S5000 in there which should give as long legs as the real Lib.

Regards,
Jeff
jhspring is offline Find More Posts by jhspring
Reply With Quote
Old Oct 04, 2012, 10:00 PM
Oh no, not again!
jhspring's Avatar
United States, LA, Carencro
Joined Dec 2005
5,277 Posts
Flaps

Okay, I am going to want to slow this beast down for landing. Like I said, it's a porker. The real Lib had Fowler flaps, for which I have the drawings and if I were at all CAD literate, I would replicate. That not being the case, I have some pseudo-fowler hinges from HK that will suffice. I also scored the last piece of 1.5" wide aileron stock my LHS had. Fahim lists the stock WA as 419 sq in. My flaps are 16 in by 1.5 in, so 48 sq in total, call it 12%, which should make them worthwhile. I am assuming that a slotted flap will count as a separate section of wing, even though I am not getting any rearward translation with these hinges.

I started trying to cut a well out of the TE, and at some point realized it was just too thin and cut the whole piece out. Lined the front of the flap bay with 3/32" balsa. Used 10 thou fiberglass sheet from the Composites Store to replace the missing wing surface. Strong, smooth, doesn't warp in the Louisiana humidity and the piece I used weighed 18 gm/wing, exactly the same as the piece of wing I removed. The rest is largely straightforward, except I have never done these before, so there was a lot of cutting and fitting. I have both servos facing the same direction to avoid the use of a bulky reversing Y. I believe I can hid the servo arms under the removable section of the inner nacelle. Once all the hinges were in, I couldn't figure out where to put the flap horn, until I remembered Kieth Sparks C130 thread. I cut one arm off a 2-56 metal clevis, bent a piece of 2/56 rod into a U, cut a slot in the flap LE for it to fit, and then CA's the staple-shaped pivot flush to the flap LE. Works like a charm. Very short arm, steep angle, operates in the opposite direction of regular flaps (push-open, pull-close).

Starboard side is breadboarded, everything needs to be glued down, but I want to use lightweight filler to round the inner surface of the wing to promote smooth airflow. More pics as I progress.

Regards,
Jeff
jhspring is offline Find More Posts by jhspring
Reply With Quote
Old Oct 05, 2012, 10:55 AM
Registered User
Beaumont, TX
Joined Feb 2007
1,333 Posts
Way OT but, the similar threads list at the bottom is a hoot!
Pete Miller is offline Find More Posts by Pete Miller
Reply With Quote
Old Oct 05, 2012, 11:55 AM
Registered User
Joined Aug 2006
416 Posts
@Pete: I just saw some of those "related" threads myself, and as a confirmed political lefty, they are a hoot!
I can't wait to see how the flaps affect landing performance.
phoran is offline Find More Posts by phoran
Reply With Quote
Old Oct 05, 2012, 01:57 PM
Oh no, not again!
jhspring's Avatar
United States, LA, Carencro
Joined Dec 2005
5,277 Posts
ROFL. I couldn't figure out what you loonies were talking about til I scrolled to the bottom. Gawd, who knew what was in the thread title was so politically loaded. Jeff
jhspring is offline Find More Posts by jhspring
Reply With Quote
Old Oct 10, 2012, 04:26 PM
Oh no, not again!
jhspring's Avatar
United States, LA, Carencro
Joined Dec 2005
5,277 Posts
Nearly there

Okay, been working on the Lib in dribs and drabs. Put the new esc's in. In the process realized that the double-sided tape I had used to secure the motor leads had dried out and let go, which means it wasn't such a good idea in the first place. Made wire clamps from 10 thou plastic sheet and secured them to the firewall with a socket-head servo screw. Decided I had best do that for all 4 motors.

Flap installation turned out to be fairly straight forward. Those HK hinges are easy to use and the flap can be snapped in and out, nice for testing and fitting. Servo linkage fit (just) under the removable nacelle and the whole came out pretty neat.

Made up the new wiring harness. Thought I had a bad servo for a bit, turned out to be a bad Y-connector. I needed an 8-pin connector this time, +.-, L Ail, R Ail, Flap, Gear, Throttle, so 7 active pins. B/c of the way I wired it initially, the Ubec is in the wing, and power comes from that side. I used duplicate +/- leads to the rx, so nothing should get hot even if flaps, gear and ailerons are all working at the same time. Rx side is simpler, only need signal leads for the individual channels.Hooked it up, everything operates as advertised.

Leaving town for a few days, managed to slap a coat of Deep Sea Blue on the upper surface. I thought I had a ton of that from my days of painting destroyers in Measure 21, but I was down to my last bottle. Enough for 30/30. Props on and power tests when I get back, maybe get to fly the beast next week. Fingers crossed.

Regards,
Jeff
jhspring is offline Find More Posts by jhspring
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Lib-Dems take a hammering in local elections leccyflyer Life, The Universe, and Politics 20 May 06, 2012 07:09 AM
Discussion Debating libs 7oneWo1f Life, The Universe, and Politics 18 Mar 30, 2012 12:22 AM
Discussion 808 taken a bath i and way way to revive? fishycomics Aerial Photography 1 Mar 23, 2012 07:36 AM
Discussion Lib media bemoans retirement of RINO Olympia Snowe D B Cooper Life, The Universe, and Politics 34 Mar 05, 2012 03:38 PM
Discussion Lib feeds on Lib... Mathews and Huffington rcjetpilot Life, The Universe, and Politics 1 Nov 01, 2010 08:27 PM