maxiemac

I had a re-think on how to assemble this wing because I wasn't confident that the tabs front and rear of the wing ribs would give me a wing that conformed to the required incidence angle, washout and dihedral, so I took a different tack - in a previous post I said one constant I saw was the leading edge notches that support the longeron backer behind the leading edge - so on that basis I set up the leading edge longerons of both inboard and outboard wing leading edge backers parallel to the building board by cutting support blocks 35mm high to place between each rib (pic 6) - the inboard wing was pinned to the bench and the outboard wing was then assembled (pinned but not glued) to achieve 3.5 degrees at the wing root (pic 2), 3 degrees at the wing tip (pic 3) you can just see the tip of WR19 in line with the measure gauge I made.

So it appears I may have got the basics about right - by marrying the inboard wind section to the outboard section I can see the whole wing is in alignment long before I build nacelles and other stuff - I really didn't want any surprises trying to marry and then have to modify any or all of these 3 items at a later time - now here is the boring bit - the following numbers show the variations of the rear wing rib tab alignments - starting at WR19 I measured the tab height above the bench top thru to WR4A and the following numbers are the measurements I made - WR19 18mm, WR18 18.5mm, WR17 17mm, WR16 17.5mm, WR15 16.5mm, WR14 17.5mm, WR13 16mm, WR12 17mm, WR11 15mm, WR10 14.5mm, WR9 13.5mm, WR8 13mm, WR7 12mm, WR6 10mm, WR5 8.5mm and WR4A 9mm.

And the front tabs were only marginally better - as previously stated these are all over the place, how can a wing build true with such drawing variations that follows thru into the cut kit - hence my rethink - in pic 6 you may just be able to see the black cotton string line from WR4A thru to WR19 I used to confirm the straightness of the leading edge which was double checked with a laser before assembling the other parts behind it - pic 1 shows how it looks at the moment before gluing - however, now I'm reasonably satisfied this wing will build true there are a few more mods to do - the top and bottom front and rear main spars need their cutouts realigned to fit the spars between WR4A and WR10 - the top and bottom notches are in the wrong places, they're too far back - aaaagggghhhh another fix to do.

Now all this has to be taken apart and the port side wing ribs modified so hopefully that wing will build true as well - when all is done I'll take pics of them and post as I did with the fuz formers - but I'm not sure how many others are following this thread and could easily put this model in the 'too hard basket' - cheers - maxiemac

maxiemac

Proof of Concept - as said earlier I wasn't happy with the wing rib tabs accuracy to build this wing according to the instructions - using this method no wing rib tab touches the work top - the outboard wing is now assembled but not yet glued (except for the bottom rear spar) - still more work to do on the ribs for the spars mainly due to having to use bent balsa sticks supplied in the cut kit plus it is difficult to get the spar tapers perfect.

With this setup 3.5 degrees wing incidence and 3 degrees wing tip washout has been achieved - the 3 pics show what it looks like now - I'll finish the rib recesses for the spars, disassemble the lot and make the changes to the starboard wing ribs etc - I made ply doublers for WR19 (end of the wing) and WR16 (hinge point for the aileron) for added strength - yes there is a kink in the inboard and outboard wing spars at the join but both assemblies were done over the plan, the important part is, the leading edge is straight - I'll just have to manage the wing joiner installation with ply wedges.

In another post I'll show the setup steps to get to this point - cheers - maxiemac

maxiemac

I did some investigating to see why the front and rear main spars were not straight and found more Palmer Plan drawing errors - pic 1 confirms the inboard wing section was assembled over the plan, ditto pic 2 for the outboard section.

Pic 3 shows the two main spars out of alignment - pic 4 shows the inboard wing clamped to the fuz with a 1/4" gap between the rear spar and the aft wedge in the fuz - pic 5 shows both inboard and outboard wing sections directly over the plans - so I think both drawings are wrong.

Anyone wanting to build this model from Palmer Plans and/or use a PCK cut kit would be well advised to do what you see above, line up the two drawings before assembly making sure to keep the wing leading edges in a straight line from WF1 across WF4 and WF4A plus WF19 at right angles to that, then alter each drawing so it gives you a straight line for both forward and aft inner and outer spars to ensure the spars are in a straight line, then draw new spar cutout positions for each rib so they all line up.

It will make a big difference when it comes time to fit the SIG wing joiner - I'm now faced with prospect of taking my own medicine and redrawing plus disassembling my wings and re-cutting all spar cutouts and reassembly - alternately my easier option is to shim the supports for the SIG wing joiner and put up with what I've got.

I would be interested to know if any other prior builders of this Palmer Plans model ran into the problems I've outlined in this thread and hear from you - but more work for me to fix these ????? - cheers maxiemac

maxiemac

I decided to take my own medicine and disassembled both inner wings (pic 1) then had both wing drawings copied for the port wing and reverse copied for the starboard wing - both port wing drawings were placed on the bench to adjust them so both front and aft spars were in a straight line and marked the drawings accordingly (pic 2). PS: I put up the wrong pic - the one I should have used shows lines drawn on the inner wing drawing to get the realignment of the main spars - you can see a gap of 1/8" at the trailing edge to achieve this.

The reassembly first step was to set out the support blocks for the leading edge backer (pic 3) followed by pinning down the leading edge backer and lining up the leading edges of both outer and inner wing panels with a string line (pic 4) and confirmed the alignment with the laser beam.

I also chose to replace the balsa inner wing main spars with 1/4" x 1/4" laminated spruce - these parts carry the nacelles, engines, undercarriage and outer wing loading - it seemed to me to be a better option than using balsa. (pics 8 & 10)

The bottom front spar was placed in position and checked with a straight edge (pic6) followed by setting the end ribs in place (pic 5), after that placing the rest of the wing ribs and CA'ing them and checking for squareness to the leading edge and to the work bench with set squares (pic 7).

After setting up all wing ribs I found the wing joiner slots in WR 5 & 6 were out of alignment with WR4A & WR4 (pics 8 & 9) - after some mods the wing joiner was trial fitted and is now correctly aligned - next steps are to backfill the wing rib slots that had to be altered for the main spars (they were all over the place) and to CA all parts and hopefully end up with a straight wing with correct inboard and outboard incidence angles. - cheers - maxiemac

maxiemac

More Wing Joining - the plan shows to use lite ply sheer web behind the wing joiner but to me that wood type is a bit too compressible at a stress point so I replaced the lite ply with same thickness 5 ply (pic 1) that's harder and more rigid - the 4 holes to mount the wing joiner channel were drilled (pics 2 & 3) only to find the holes through the ply web butted right up against the undersides of the main spars (pic 3) - no room for washers and nuts, what to do?

I'm not a fan of gouging wood in main spars that carry wing flight loads, undercarriage movements and so on - 2 more holes were drilled and countersunk into the centre of the joiner channel thanks to a tip I found on giantscaletwins website making a total of 6 mounting bolts - the 2 centre ones will have lock nuts and washers fitted whilst the 4 perimeter bolts will be epoxied at the same time as the whole assembly is epoxied in place.

Before this is done another way might be to fix spruce vertically behind the 4 joiner channel holes and use longer bolts that extend into the space in front of the front spars and just glue the sheer webs around the bolt/nut protusions - I' still thinking on that.

Pic 4 shows the extra keying between aluminium and ply I hope to get by dremeling with a round router the metal surfaces prior to gluing - pic 5 shows the assembly ready to glue in place with 3/16" square spruce to be epoxied top and bottom of each horizontal wing joiner surface - hopefully also strengthening the wing joint. - cheers - maxiemac

christophe31

HI,
i m really impressed about the job you done on this short kit, i'm in the beginning of my build too, where are you know? any progress?
rgds
christophe

maxiemac

Hello Christophe31 - thank you for your contact - I haven't touched this model since last August - I have side tracked myself by putting together 3 ARF trainers for new pilots I have been instructing a well as putting together a couple of ARF's for myself including a Bucker Jungmeister and a nearly finished 38% Corby Starlet.

When I've done that l'll get back to the Aero Commander - it's been sitting unloved on the bench for too long - your nice comment will inspire me to re-start this build - cheers - maxiemac.

Patto

maxiemac

Hello Patto - just the nudge I need - I haven't touched this project since my last post August '15 - I've got a miniCRAFT 66" Christen Eagle sitting on another bench I haven't touched in 4 months - I need to get re motivated and get on with both these projects, plus I have at least 6 more to do - just need to live long enough to do them

Ok Ok I've been told, I'll try and make an effort, but first I'll need to re read my own posts to try and remember where I was up to - cheers - maxiemac

Patto

I have just finished a build (Hostetler Skymaster) and am looking for my next project. I'd really like to do a Twin Commander, but this one is just a little too small. Two .90 four strokes? I'm thinking 35-55cc gas engines on my next project. So, I'm thinking either scaling the Palmer plans for this airplane up to 147" (1/4 scale) or looking for a different twin.

My question is do you think there is enough detail in the plans for me to accomplish this? I'm comfortable with cutting the pieces by hand and such (although I would much prefer a laser-cut kit!!!) as long as there is enough detail in the plans. I'm also worried about making the cowls by hand since there would be no fiberglass option out there that would fit perfectly.

jetfixr

My Feedback: (13)

maxiemac

Hello Patto - I agree with jetfxr, I found the plans are not accurate enough hence the kit that Kitcutters supply is not accurate, I did a lot of fuselage reshaping as shown here in previous posts - I don't think upsizing the plans for a kit to cut would be very much use - the bigger Aerocommander jetfxr mentions is a fiberglass moulded kit - I thought of getting one but it was out of my price range plus the cost of freight to me would have been huge - if I had my time again I would have saved up and bought Giant Scale Twins Aerocommander- cheers - maxiemac

PS: jetfxr - your project has been on hold longer than mine -

Patto

I saw the fiberglass kit. It's really nice, but I'm wanting to do a balsa build. Palmer seems to be the best despite the issues. I'm pretty determined to make this happen!

Now the question is where to put the build thread...

maxiemac

Use the forum as shown above but give it your title identifying the Shrike but make it a bit different to those other Aero Commander threads as shown in this 'Twin & Multi Engine RC Aircraft' forum - us other Aero Commander Shrike builders can then watch with interest to see how you're going - we can discuss back and forth as needed.

Upsize the Palmer plans to what you want and maybe have a close study of what you've seen in this thread so you will know where which formers need altering because you will certainly find out where the formers are wrong as you build it.

Take particular note of the line up of the fuselage stringers - they do not line up in the cut kit made from the Palmer plan - line them up appropriately by stacking your ply formers and mark the cutout in the correct places before you cut them so they flow instead of jumping all over the place - check out page 1 starting at post 5 thru 21 to see what fixes you will be doing.

By the way the cabin internal roof line on the cabin plans are the wrong shape, it's raised in the centre but should be a flat curved roof line for the 500S Shrike - the raised centre section appears to me to be of a very early Shrike - have a look at page 2 post 28 to see what I mean and then look at page 3 post 45 pic 7 to see the actual roof line shape at the cabin rear, but it flows like that thru to the front where it meets the overhead panel with all the engine starting gear and other switches etc.

good luck - cheers - maxiemac

Patto

I'll watch for those issues, thank you! And, I'll be going through your whole build thread.

While I don't see a need to recreate the wheel, I think having two build threads on this design is a good idea. I'd like to see more folks build one of these. Maybe we'll inspire them.

I'm also hoping that you'll decide you can't let me finish mine first and get yours going again... 😁

I'll get mine going in the next couple weeks. Stay tuned...