SeamusG

Time to fix the LT-40.

Things that are going to get tweaked during the rebuild:

[*]Engine upgrade from OS 46 FX to Evolution 52 NT (the 46 had real difficulty pulling the LT over to top of a loop)[*]Engine orientation changed so that the exhaust exits bottom center[*]Relocate the tank and throttle linkage to accommodate new engine location[*]Cowl will be built up[*]Tailwheel converted from servo controlled (HS-81) to rudder controlled piano wire[*]Elevator, rudder and ailerons to be rebuilt using rib-sheeted approach[*]Wing tips will be something different[/list]pic 1/5 - the Evo 52 is mounted rotated past 90 degrees to allow the exhaust to exit center stage
pic 6 - fuel tank needed to be lowered to accomodate new carb position
pic 7 - tank tray sitting on mock-up rails
pic 8 - mock-up rails.

LargeScale88

Can't wait to see you mods/rebuild! Its gonna be a sweet looking aircraft!!

Jason

SeamusG

Back to the stab &elevator.

The original plan provides for an open stab construction using 5/16" stock. The elevator is a solid piece of balsa tapered. The 5/16" stab stock was replaced with 3/16" stock and then sheeted with 1/16"stock. The elevator was constructed using a base of 1/16" sheeting 2" wide with a 3/16" x 1/2 used as a leading edge. The center was filled with 3/16" x 1 1/2" x 3" tapered from the leading edge to the trailing edge. Ribs were fashioned from 3/32" stock and CA'd to the base sheeting. Everything was then tapered from 1/4" at the leading edge to a "point" at the trailing edge. I used a piece of 1/4" hardwood held tight to the LE as a sanding stop. The TE was positioned close to the edge of the table. 80 grit on a GP sanding bar was used to taper everything. Another piece of 1/16" x 2 x 27 sheet was then glued to the top.

The LE of the elevator was shaped to a beveled, centered point.

Hope this stuff stays "straight" this time.

pic 1 - original plans reused
pic 2 - new 3/16" stock labeled per RCKen suggestion
pic 3 - stab framed - all pieces per plans except for thickness
pic 4 - frame was traced on backside of sheeting so that glue can be applied accurately
pic 5 - stab sheeted
pic 6/7 - base elevator
pic 8 - 1/8" &1/4"hardwood sanding guides - the 1/8"guide was removed to get a nice tapered edge
pic 9 - just about ready for the top sheet - still need to taper everything to a point
pic 10/11 - finished elevator & stab

btw - the overall combined weight of the stab &elevator is 3.8 oz.

I-fly-any-and-all

My Feedback: (1)

cool,a buddy of mine built the kit, each each aileron has its own servo, sheeted the tail, put elevator and rudder sero in tail, made plane a tial dragger, added a bomb drop and power is an o.s. 1.20 four stroke!

OzMo

My Feedback: (3)

Seamus.
Nice work on the tail feathers!
I love a good kit bashing!

SeamusG

Just trying to find a sense of humor.

The pics of the elevator were taken shortly after the elevator was removed from being weighted for 2 1/2 days (used Titebond with MinnFlyer's tip of wiping the glue off with a finger before joining the pieces). That was 2 days ago. Just sitting there on the bench the elevator has developed a "bend". The center is 3/16" out of alignment. I'm (im)patiently trying different approaches to straighten it. I'll probably need to replenish my 1/16" sheeting so that I can make another iteration of the elevator - this time limiting the glue used to thin CAfor the ribs and thick CAfor everything else.

SeamusG

3rd or 4th time is the charm.

The pic includes an edge shot of two nearly identical elevators. Both have 3/16 x 1/2 leading edges. Both have 12 3/32 ribs. Both have 3/16 x 1 1/2 x 3 center blocks. Both have 1/16 sheeting on both sides. Both have 90 degree angles sanded on their leading edges.

However, the one on the left is absolutely straight and the one on the right has a 1/2" bow in it.

The crooked one was glued with Titebond (except ribs were glued with thin CA on one side). After 2 1/2 days under a press it came out straight. Half day later is was bowed.

The straight one was glued exclusively with CA. 5 - 15 second CAfor the leading edge, the center block and the sheeting. The ribs were glued with thin CAto one sheet.

Time from beginning to end - straight (CA) - couple of hours. Bowed (Titebond) 3-4 days.

These things are 27" long. Who knows, shorter assemblies might be more resistent to warping. Thicker sheeting? That too. But for this spec of wood (3/16 inner with 1/16 sheeting) CAis my standard.

Now, I can return to my GPExtra 300Sbuild as it uses precisely the same dimension of wood for its stab, elevators, fin, rudder and ailerons.

BTW- the titebond elevator weighs 1.1 oz and the CAelevator weighs .7 oz

SeamusG

Progress so far includes building a sheeted fin with a fin post that extends thru the bottom of the fuse. This will be used to support a new tailwheel assembly. The fin post dimensions were transferred to the stab deck of the fuse. A hole was cut in the stab deck as well as the fuse bottom. A dry fit of the fin was made to make sure that things were close.

Just to make sure that the stab was aligned to the fuse I located and marked a centerline on the stab. A "T"pin was inserted at the front of the stabl. Another "T"pin was inserted at the top of the windshield. The distance between the windshield T-pin and the stab tips turned out to be 39 3/8". An adjustable clamp was used to secure the stab to the fuse. Distances were remeasured. A second T-pin was added at the back of the stab thru the fuse. To allow the test installation of the fin the front T-pin was replaced with 2 - one on each side of the centerline - allows the fin to be installed.

With the stab secured to the fuse, the fin post hole in the stab deck was transferred to the bottom of the stab. An X-acto #11 was used to cut the hole thru the stab.

With the holed stab back on the fuse the fin was dry fitted. Came out fairly well. There's some wiggle room - the slop will be taken up with a putty made of finishing resin &micro-balloons.

Next will be rounding the LEof the stab & fin. I'm thinking of adding bits of 1/8" balsa to the tips of the stab / elevator & fin / rudder. This is how the GPExtra S300 is detailed out.

Hinge slots for Dubro nylon pinned hinges will be cut per the plans.

I'll need to create a hole in the rudder bottom LEfor the tail wheel wire. The fin post will need to be slotted for a 1"long nylon bushing. I'm gonna insert & glue a brass tube to the inside of the bushing. The LGwire will run through the brass tube with a 90 degree bend at the top with the exposed wire inserted into the LEof the rudder.

Gonna have to dry fit the pieces a couple of times to make sure that all will go together nicely during the "pre-covering" assembly.

pic 1 - 3/16" framework is covered with 1/16" balsa sheet. Same for the tip up front as well as the new fin post.
pic 2 - dry fit of the fin / post after holes were cut in top and bottom of the fuse
pic 3 - stab centerline & front T-pin
pic 4/5 - if you look closely at the top center of the fuse just in front of the wing saddle you can see a centered T-pin
pic 6 - fuse top hole transferred to the stab bottom
pic 7/8 - dry fit of the stab &fin (with wiggle room for the fin post)
pic 9 - you can see that the front T-pin has been located beside the fin
pic 10 - rudder & elevator mocked up
pic 11 - with the wing - you can definitely see the dark amber Titebond around the wing ribs & shear strips

Haven't figured out what to do with the wing tips. Gonna make up new ailerons soon - thicker LEwill require use of 5/16" stock for the LE. Maybe a TE made out of 1/16" stock.

SeamusG

The downside of medium CAis that the resulting seam is difficult to sand. Ishaped the leading edge of the elevator & rudder with long "L" bracket with 80 grit on one edge and the whole thing clamped to the table. Took quite a while.

Now it's time to address the leading edges of the stab & fin (plus the tips as well). Rounding the leading edges will take some time and effort. So, I decided to add a piece of soft 5/16" x 5/16" stock to the leading edges and the tips (stab, fin, rudder & elevator). I used SIG-ment for the glue - fast drying and easy to sand. It will be easy to shape this stuff for covering.

pic 1 - Iuse scrap chunks of balsa and long T-pins to hold things together - here's one end of the stab
pic 2/3 - both leading edges have been glued up on the stab.
pic 4 - elevator tip
pic 5/6 - fin
pic 7/8 - just making sure that the base stab &fin remain flat

SeamusG

The fin LEoverhangs the fuse hole - it'll help stability.

pic 1/2 - fin &stab detail
pic 3 - the stab LEis forward of the notch in the fuse top
pic 4 - oops - used RCKen's suggestion to use a sharpie to mark wood intentory with dimensions
pic 5 - aceton did a decent job getting rid of the sharpie ink

SeamusG

pic 1/2 - rudder &elevator are hinged with Dubro nylon pinned hinges
pic 3 - ailerons are done - waiting for hinges

Gotta comeup with a new idea for the wing tips & finish the tailwheel bushing ...

Oh yea - for the calorie concious - the original light balsa ailerons each weighed in at .5 oz. The new ailerons weigh .8 oz each. Not gonna lose any sleep over this - those light balsa strips dented so darn easily ...

SeamusG

While removing the CAhinges from the wing trailing edges Ifound another problem - trailing edge is broken all the thru. Another challenge but better find it now rather than have the wing snap mid-flight.

SeamusG

Ifinished filling the trailing edge's previous CA & Robart hinge point "holes". Dowel segments were used for the hinge point holes and various thicknesses of "hard" balsa inserted with the grain going "into" the hole rather than the grain lengthwise with the trailing edge. Easier to use a tack hammer to persuade the pieces into the hole while the Titebond was expanding the piece beyond "snug".

I really spent some quality time aligning the hinge slots before cuttin' any wood - 4 hinges per plans (Dubro nylon pinned hinges). The "flop test" revealed that I finally got a decent hinge line.

Time for some kind of tip treatment. Measurements of the left wing tip were taken and a profile of the tip rib too.

pic 1/4 - hinge line nice-n-straight and tight. Both the trailing edges and the leading edges hinge slots were recessed just a bit to allow nearly a zero tolerance between the control surface and the trailing edge.
pic 5 - freezer paper works fine for tracing aroung pieces like the wing tip rib