|May 13, 2008, 09:38 AM|
Fun-Build 2 - Guillow's B-24 Liberator conversion FLIES!!
I'm at it again...
Although still doing the minor finishing off items on my B-17 & DH-4
I thought I'd kick off this thread to get the ball rolling.
This one is going to be a real challenge to make fly well so I'm not going to rush it.
I had great success with the power system on my B-17 so that gets another run on this plane.
With the power availalble, it should be able to skull-drag the plane into the air so my focus will be on flight performance and ground handling (ROG & landing)
Most of the basics I've nutted out (I think) so this is what I'm planning for.
4x GWS brushed speed 350 (6V) motors (Now replaced by small brushless) http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5358&Product_Name=18-11_2000kv_Micro_Brushless_Outrunner_(10g)
GWS 4530 props (tba)(GWS 5043)
2000 ma/hr 2S Lipo (probably now 1200 2s Lipo)(Rhino 2350ma/hr 30C)
Retractable, steerable nose wheel (deleted - too heavy)
Retractable Main gear (deleted - too heavy)
Provision for my Edvr camera
This ship has a wing area of 189 square inches - that's not a lot at all.
For a 20 oz/ft wing loading, the AUFW has to be 26,25 oz.
With all the gear going in, it doesn't leave a lot left for an airframe.
(New target weight = 17oz)(actual airframe weight =17.8)
I could go for brushless motors but to be honest,I have all the gear for a brushed setup & I like the simplicity of the old brushed motors.(brushless motors used)
At present, I'm marking up the drawing with component sizes for the nosewheel.(deleted)
Looks like I will have a removable nose for the battery.(nose is interchangeable but battery hatch is on fuselage top)
If I do that right I can swap between a 'D' & a 'J' model.
Also I don't really need a separable wing. I'm lucky I have a ute in which I can transport up to three 48" span models at once.
Anyhow , back to the drawing board.
As well as this build I'm about to bash a GWS C-47 into a Heinkel He111.
This will get most of my time to start with but it allows me time to sort the technicals out on the B-24.
This hobby is so addictive -
(edit: 08 January 2009) (edit: Feb 2009)
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|May 13, 2008, 11:14 AM|
Right On Phil. Looking forward to the show. WOW 189 sq in . This sure is a challenge. With that weight goal would twin outrunners with two dummy props be more in line? Nahh you can do it and I think you are right, it will be fast, but hey the Lib's were faster than the Fort....
Go get em,
|May 13, 2008, 03:41 PM|
Godspeed Phil. I love the ambition of this project and I am sure that you have the skills to pull it off. One thought if you are going to be re-cutting the ribs from lighter wood?? would be to re-plot the airfoil to something that would be stable and high lift (e.g. Clark Y) and to think about a slightly wider cord as a way to increase the wing area. Of course this would deviate a bit from scale, but would give you more breathing room. Going to enjoy seeing this project unfold. I am also very excited about your idea for the C47-He111 conversion. Brilliant idea!
|May 13, 2008, 04:50 PM|
Phil, I have the kit and the same book (plus a couple of others) I have been looking at for about 3 years now and been too intimidated to start. This thread will be the bible for my (eventual) build. I've watched some of your other threads, this is very exciting. What Jim said.
|May 13, 2008, 07:47 PM|
Subscribed as well. I have the plans and that will be a bird for another day for me as I have the V-173 going as well as my Corsair. At some point in the future I also have a sterling Corsair and a P-61 Widow to do. But the first off the build table will probably be the 173. Good luck and lets see lots of pics
|May 13, 2008, 08:39 PM|
Good luck on this one. May the force be with you trying to come in at weight on this one. I can't imagine trying to do this plane at that size with everything you are adding to it. I'm anxiously watching to see how you handle the nose gear on this one if you go for scale location with it. Are you planning on having functioning rudders or just the steerable nose wheel?
|May 13, 2008, 09:48 PM|
The Liberator was a great plane, with a great history.
I just finished reading a book from Stephen E. Ambrose about a crew of an B-24.
Very nice book.
Good luck in your construction.
|May 14, 2008, 02:07 AM|
Cheers for joining in chaps.
Yes it sure is a challenge, definitely the hardest one yet.
Basically the principle is an aerial platform for the retracts system.
With the wings, I plan to sheet the LE to max thickness point, then run cap-strips over the remainder of the ribs & TE.
I did this on the Catalina with good results in appearance & weight.
The front end of the fuse will be sheeted but aft of the CG will be stringers.
If that looks crap, I'll sheet the lot.
Ryan - I plan on rudders functioning to help any yaw problems in flight.
I have a feeling this one will sway around a bit. Dunno why, just a feeling.
Rudders will have their own servo & a separate one for nosewheel steering.
Everything is intended to be as per Guillow's kit, including nosewheel location.
I have a retractable, steerable unit form Phillip Workshop which looks like it will do the job, it is fully adjustable in that I can reverse the actuator arm on retract and steering mechanisms. Pretty handy really.
Link is here.
All the gear gets mounted onto a plate & the plane is built around that.
Alex, I hear you on the Clark Y mod.
That is a wise call. I'll look into it & run it thru Profili & Motocalc to see the performance difference may be.
I have preference to do it as per Guillow's design - only so I can say I made another Guillows design actually fly.
But at the end of the day I would like a plane that is fun to fly - not a dog, so it would be good research.
The tail of this plane will be an excersise in engineering lightness.
I'm looking forward to the complexities of that bit.
I'm resigned even to building more than one empennage to experiment & prove concepts. Like I said - I won't rush this one.
To that end, I may even build more than one wing system too. I dunno, we'll see.
Anyway, I'll post again a bit later. there's not much to see now as it's all scratchings on paper.
|May 14, 2008, 07:42 AM|
Phil, you are probably right about the swaying. As short-coupled as it was, the 1/1 version apparently was very hard to keep on track at altitude. Pilots complained that it made formation flying (the backbone of American bomber strategy) very tiring and was blamed for much of the bomb scatter. Always thought it was ironic that although the Lib was faster, had longer legs, better bomb load, a higher rate of crew survival AND was produced in far greater numbers than the Fort, it was always the B-17 that got the good press. I think there is one flyable B-24 left vs a dozen or so B-17s.
As a colonial, of course, you would know that the LB-30 was Churchill's favorite transport, he preferred it over anything British.
|May 14, 2008, 03:05 PM|
You all of us worked into a frenzy over this project.. you will have to start it now! It will be interesting to see how you put it together. I understand the goal of trying to stick with the Guillow's plans.. There are much easier ways to go if you did not want to do a conversion.
I ran into the same rudder problem with the Dornier 17 I built a few years ago. I used an idea from 'ytseng' with a servo in the front of the fuse that is connected to a bell crank in the tail and then connected to both rudders. It seems very flimsy and I was worried about flutter.. but I must say that after 40+ flights by now it works great! The advantage is keeping the CG forward. This being said I would still opt for two very small servos in the rudder if you can get away with it with the width of the rudder and the CG. Let me know if you want to know more about this set up.
|May 14, 2008, 05:46 PM|
I'll be waiting to see how you go about hiding the rudder mechanism in that one. If I went just a little bigger then mine and got the horizontal stab just a bit thicker I could completely hide the mechanism in the stab with nothing protruding.
I find mine tracks well in a straight line (after it's in the air anyways) but for turns because of the short coupling you need to use a lot of rudder to get any kind of a decent looking turn out of it. Some of the later changes to the plane may have given it a less favorable reputation among the airmen which might be somewhat of why it never has quite the glory of the B17's and not as many have been kept in flying condition today. I think there are 2 still flying, not 1.
The later B24's and PB4Y-2's had a conventional tail instead of the split rudder to solve the problems. I think the plane really loses a lot of it's character in those versions. In later versions the payload rating was so high that they could only marginally climb so any advantage was probably lost in it turning into a really poor handling airplane. When the wing was damaged in flight it had a tendency to fold back along the fuselage making it impossible to bail out of the aircraft.
|May 14, 2008, 06:13 PM|
Joined Jun 2001
The Clark Y airfoil.
While I like a real Clark Y airfoil with its large philips entry it may not be appropriate for this wing. I think the Clark y is close to 12% thick and has a little more than 3.5% chamber. With the high aspect ratio wing and the rather small stab I would look to use another airfoil. I think the original ship had and airfoil that was over 16% thick. This gave the wing much of its structural strength and some of its high lift coefficient. With the small stab I would look for an airfoil that had 2% or less chamber. High chamber wings have large pitching moments that make for harsh stalls and are very speed sensitive when it comes to trimming. If you are going to redraw the airfoil I would look at a NACA2416 or QB2.5/16
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