g_boxwood

Good evening gentlemen (Europe time ),

I finally started this plane that has been waiting around for some time now.

I post about it 'cause it will be a testbed for a few new things for me, so I'm sure I'll need some advise here and there.

I already have a question!

I don't like to cover such a large bird with Monokote film so I'll end up glassing the fuse and... what about the wings? They're open frame, what can I use so that I'll be able to paint them?

Is SIG KOVERALL an option?

or any other 'fabric' covering?

Thank you,

jooNorway

My BigLift II got a glassed fuselage too.
The wings got GlossTex, which didn`t need any painting.
I have never used Koverall (yet) but it sure works. But since weight isn`t an issue on a BigLift I prefer covering with glue on... no need for Balsarite.

g_boxwood

Thank you for the infos,

I'll stick with OraTEX wich is a fabric covering by Oracover, it doesn't need any painting as it is glossy by nature but I'll paint it to match the fuse (it's a multi-color scheme which I don's want to do with coverings).

What servos did you use?

jooNorway

Mine got Hitec HS-605`s for all rudders in the wing, but I think these servoes are discontinued by now.
625 and 635 for the elev and rudder if I am not wrong. 605 for the tow-release. Receiver; MPX DS-IPD 9 synth, never failed
Moki 30ccm gasser up front.
Durable plane which have served well for some years!

wrob

Anybody know where I can find a Big Lift II in the USA? I'd like to buy one.

g_boxwood

Did you check with Multiplex USA?

I see they dont' feature the BL on their products... give them a call and see if they could import it for you.

Or check the Graupner TAXI 2400 which is almost the same (a little bit better).

MPX USA dealers:

http://www.multiplexusa.com/WTB_files/wtb.htm

g_boxwood

I've been working onto this project on & off in the past few months and I thought I could share what has been done so far.

First let me say that I'm not fond of kits so you can guess by yourself how much I do love ARFs... nonetheless I didn't want to invest any additional time and resources other than those provided in the package (something I paid for) in working out all the things I didn't like.

I just replaced a few hardware items (the tailgear unit and the control horns) and I just added a little bit of mine in the assembly process. Nothing more than that.

As I said I paid for it the way it came...

The assembly starts with the wings and they consist of 2 panels each, the inboard constant chord panel and the outboard one.

Inboard Wing Panel

The first thing to do deals with the wing strut anchor plate: the Big Lift design doesn't employ any wing tube! The wings stay where they belongs thanks to the wing struts, a few steel alignment pins (that slide into brass tubes glued to the fuse) and some heavy duty rubber bands.

Check out the following picture:



the wooden block on the left is what actually supports the 4 self-tapping screws that hold the anchor plate in place; next to it is the custom triangle stock I added to support the balsa strip that goes flush with the anchor plate itself.



The funny thing about it is that another balsa strip is required to properly seal the area around the anchor plate otherwise the covering material wouldn't have anything to stick to: I added another triangle stock to support the second balsa strip (no mention about it nor it is included)...



... and I then added the second strip:



Don't skip this extra step or there won't be any support for the covering material!

g_boxwood

Outboard Wing Panels

The OWP simply require the modeler to add the wing tip blocks: I used aliphatic glue for the job and I then sanded them to shape with the ailerons in place.



The rest of the assembly involves both the inboard and outboard panels.

First I wanted to enlarge the holes in the ribs so I could install some paper tubes to route the servo wires.



I used a Dremel tool fitted with a snake extension:



I then planned how to mount the wing servos: each 645MG is secured to a 2mm thick G10 hatch with hardwood blocks epoxied in place:



The sheeting is then removed and an inner 1/16" birch-ply frame is epoxied to the sheeting from the inside (see previous pics):



Four hardwood blocks are then added at the corners to better support the screws that hold the hatch in place (see following pics).

g_boxwood

Next the 2 panels are joined together with 30' epoxy and a 1/8" lite-ply brace:





Please note that the original design calls for the wingtip block to extend past the the fixed portion of the wing: I didn't like it and I cut the block adding it to the aileron:

g_boxwood

Wing Control Surfaces

I started with sanding the control surfaces to match the wing section (they didn't on their own as they're stock):



Next I chose where to install the flap hinges and control horns:



As I said I replaced the original horns with Robart's Super Horns as I felt them to be more suitable for a project of this size.

I wanted both the flap hinges and the horns to bite onto harder wood and to spread the loads onto a wider surface so I embossed the control surfaces (both the tops and the bottoms) and added 1/16" birch-ply plates:





Everything is then sanded again to match the wing section once more:

g_boxwood

The same applies to the wing TE:



Bottom view:





I also added a lite-ply stiffener sandwiched between the reinforcement plates:

g_boxwood

Both the wing and control surface are then sanded together once more for a precise and definite match:



The wing panels are then checked for simmetry and the fixed portion plates are drilled for the flap hinges: do not drill the moving surfaces yet, wait until they have been covered!



One last fancy 'corrective' job is to fill the aileron hinge slots with some scrap balsa as they were cut really too wide (both the TE and the aileron stock):



Don't forget to add the balsa blocks supporting those hinges...

g_boxwood

Final wing prep deals with filling and sanding...

I also painted the wood with Graupner BALSA-FIX...



... and I started covering the wings with white OraTEX:





I really liked that covering material (first time) while I felt something was wrong with the BALSA-FIX: it turned out extremely thick and slimy out of 2 new bottles and I had to thin it a lot to get it to a paintable viscosity... maybe I got 2 old never-opened bottles...

g_boxwood

In the past few days I hinged the wing control surfaces and I checked the linkages and throws: everything seemed fine so I'll move up to the fuse next.

jooNorway

Kudos for great and precise job! I like the way you do the building

g_boxwood

Thank you joo!!

g_boxwood

I need your advise!

As I told you I'll be using my BL to drop R/C skydivers and I'll be starting with dropping one from its drop box.

I'd like to locate this drop box inside the fuse but it interferes with the steel plate the wing struts connect to. So I can mount the drop box onto the outside or inside the fuse but a less closer to the CG than it is possible with the outside mounting.

Let's sum up with the 3 mounting options

1. EXTERBAL drop box right behind the main gear = let's say neutral to the CG



2. EXTERNAL drop box over the main gear = slightly negative pitching moment?



3. INTERNAL drop box right behind the wing struts attachment bracket = positive pitching moment



Do you think the trimming may deal with this last option?

The CG is located right in front of the long hole

Thank you for your advises!

g_boxwood

The Fuselage

I gathered some thoughts about the fuse and I started with no hesitation.

One note: my tail came with very badly cut openings for the stab and the fin! The corners are also rounded in a asymmetric way...



The tailgear unit that comes with the kit is flimsy, over-complicated to assemble and lasts half a landing: throw it away!

I chose a Graupner tailgear assembly and I removed the sheeting to install the 5 mm birch-ply plate:





I also elected to install the rudder+steering servo directly in the tail:

g_boxwood

As I said I'll be flying my BL to drop R/C Skydivers: I needed to fit a drop box and I wanted it to be recessed inside the fuse rather than being bolted on externally.

The only available position was not as close to the CG as I wanted but after a word with a fellow modeler who owns a BL we decided that it was not a problem.

I took the alumimun drop box I had and made a lite-ply version to bury inside the fuse:





I also added a lite-ply floor all around the box for added strength:



I then checked the ground clearance and it turned out more than adequate:

g_boxwood

I then turned to the main gear plate and I added two half-bulkheads (4mm birch-ply):

Cuba59

hello,
how just to build your own BL

[link=http://www.rcuniverse.com/forum/m_10032217/anchors_10032217/mpage_1/key_/anchor/tm.htm#10032217]E-BigLift in RCUniverse[/link]