Not too much progress tonight... got the stabilizer mounted on the fuselage...



Used epoxy and a few pins to hold it in place. Towards the back I put one pin up through the bottom of the top surface of the fuselage to pin it together back there. Epoxy seeped out just a touch at 95% of the edge so I think I got good coverage. Was thinking about dropping a few drops of CA into the joint where no seepage occurred. One thing to note, which is a no brainer(and I brainfarted on) is to note where your fin's footprint is so you put pin holes only where it will be covered up. I overshot the footprint and put a pin in a place that will not be covered by the fin. Heated up the exposed pin hole with the iron which relaxed the covering to mostly close the hole but I added a 2mmx2mm patch to seal it up.



One thing I noticed after everything dried and I took the pins out was that the right edge of the stabilizer is 4mm higher than the left. One thing that could have helped ensure a more precise mount was doing some clearance measurements in addition to the pre-fit. Sanding the platform on which the stabilizer sits to level it out relative to the base of the front of the fuselage sitting on the counter woulda helped get a level mount. I trusted my assembly of the pre-cut parts just a little too much.

I'm thinking about adding a list of things I learned during this build to the final posts to hopefully help someone else pondering this built.

Total build time: 65 hours

somegeek

It's hard to have idle time and not work on my plane...

Figured I'd install the elevator control hardware...

Mounted the control horn:



I used a dremel cutting wheel to clean up the ends of the machine screws(take off the point):



Used great planes metal clevises, 2-56 Dubro partial threaded rods and 1/8" carbon fiber pushrod material



Black Flash CA glue was used to secure the metal rods on the ends of the carbon fiber rods.



Was pretty cool to control a control surface with my radio for the first time.

Total build time: 67 hours

somegeek

somegeek that is a beautiful job i am going to build an LT-40 kit for my dad this winter and will use this thread for reference. He has always wanted to get into RC but just needs that little push. My brother is going to buy the engine and electronics and i'll supply the radio and plane. that way i'll have someone to fly with as well.

Geoff

Thanks, Flyboy76! Cool way to spend time with your dad.

That just made this thread worth doing - Glad it will help a bit with your build!

One item that I wanted to get an answer on and haven't gotten a reply is the pre-cut dihedral guage:



The dihedreal guage side is cut with a curve which messed up the angle of the W1 rib where the shorter end of the rib was less angled than the taller part of the rib so the W1 ribs were not totally flush against each other when joined. I am thinking this guage shoud be completely flat on that edge. Any input from the board elders?

Some food for thought so far...

Based on the tips recieved from message board members in this thread (special thanks to Bruce and Ken), other threads regarding building on this board and my observations/mistakes/"DOH!s"/etc., consider the following when building this kit...

- For gluing the main wing joint, use epoxy NOT CA - this includes the MADBs as well as the actual faces of rib 1 on each wing - use epoxy to mount the stabilizer as well as the fin

- For glassing the wing joint - use wider fiberglass vs the 1 inch strip that comes with the kit, more like 3 to 4 inches wide - 3/4 oz?

- During fuselage assembly, dope (fuel proof) the fuel tank area _before_ adding the tank floor or the windshield and also paint both sides of the tank floor and underside of windshield before installing.

- Add pushrod supports to F3 & F4 to prevent flex in pushrods. Flex in those plastic pushrods can cause a loss of effective control of control surfaces on the rear end... imagine not being able to effectively use your elevator in a fast dive. Using carbon fiber rods will go a step further to prevent flex.

- Paint any dark areas on the surfaces being covered or sand off markings before covering as it will show through on any lighter color covering

- Pickup more than a single box of T-pins - you'll use them - I wish I would have had 80 on hand vs the pack of 40 I used

- Wax paper and wood glue for most of the build made for an easier build regarding repositioning of parts as well as taking the parts off the wax paper and clean-up and less killed brain cells from that CA glue. Blech.

- Any surface features not sanded down/filled _will_ show through the covering, even rough grain - sand and sand again to assure a smooth finish. X minutes of extra sanding now will be worth it if you have this plane for a while

- Be careful with the iron pressure on edges when applying covering to not make indentions into the balsa.

- Denatured alcohol works great to clean up any epoxy on the covering. THink I need to use CA debonder to get the CA smears off the covering.

That's it so far.

somegeek

Somegeek I'm confused how you hooked your steering tail wheel to function with your rudder?All i see is a single servo going to the tail wheel.
compliments on your workmanship.

Thanks, ROBT4!

I still need to install the rudder pushrod on the other side of the servo horn. You install the control arms on opposite sides of the controlled item(tailwheel is installed on right side, rudder on left) as well so they will turn in the same direction when the servo turns.

somegeek

somegeek,

I'm an amateur builder and from my prospective you've really put together a nice looking LT 40 and a superb building thread. After just about completing my own LT 40, I would indeed agree with your build comments.

My horizontal stabilizer was just a tad off as well. I did the same thing as you took it for granted that things were lined up nice and level. I never checked the position totally with a ruler until the epoxy had set up and as a result I too was off about 4mm, DOH! Bring the ruler out prior to gluing, that could have easily been corrected with a sanding block.

I also covered my LT 40 in a lot of yellow and in some places where the part numbers were not totally sanded off they did show through the covering.

I found the dihedral gauge a bit confusing myself and did have to reposition my W1 ribs a bit to get a nice tight wood to wood fit between both wing halves.

Once again your build looks great and good luck with the maiden.

Regards
Mike

Thanks, Mike!

Kinda odd that both our builds are exactly 4mm off on the horizontal stabilizer. [sm=confused.gif]

somegeek

Somegeek
That seems like a pretty good setup for your tail dragger modification.Has that been used before or is that your idea?

I agree, that side should be flat, at the correct angle to set the dihedral. (I'll have to check mine when I get home).

"board elders"?!?!?

Does that mean Bruce and Ken? LOL!

The gear I used and placement was taken from other LT-40 conversion posts here on RCU, but I came up with modding the tailgear to mount a servo horn on for a balljoint mount. I can imagine that someone has done this before somewhere, but I came up with it in this instance.

somegeek

Good deal - seems if you want flat mounting faces, that would be the only logical solution regarding that guage being straight or curved.

I meant the wise folks of the board.

somegeek

Is he calling me OLD? 56, you decide. As for the guide, I have no personal experience with it so I am keeping my mouth shut for a change. I am surprised the sides are not flat though.

Mounted my Du-Bro Kwik Switch & Charging Jack unit last night...



The tray that the switch mounts in sits a touch higher than the ouside faceplate piece so I had to trim off about 1/16" so it would clear the fuselage doubler...



I have this setup as 'in' is on and 'out' is off. Someone mentioned on another thread that they would rather the battery accidentally turn on in transit and die vs someone bumping it before take off with a live engine and having no radio control. They also stated to put a clip on the switch shaft while in transit to prevent accidental powering on. Sounds good to me.

Didn't leave the switch mounted as I still need to add the window decals.

Total build time: 68 hours

somegeek

P.S. - busy with other stuff for the next two days so no plane work... [:@] DOH!

Got the tail and rudder sanded, trial fitted the hinges and ready for covering...



When capping the end of a long piece, it works nicely to tack a piece of covering on to the end and then stand it on end on a cutting board to trim it up with a straight edge razor to get it ready to cover...



Covered tip...



Before covering the stabilzer or the fin, I poked holes in the cross members so air can flow between the different covered areas... (saw this in the RCU thread linked above)...



Covered fin and rudder w/ hinges installed...



To drill the holes for the rudder servo horn mount, I put everything in place to see where the horn landed on the rudder and then marked the holes vs referencing the drawing. Figured this would yield the best placement...



Servo horn mounted on the rudder(angled due to control rod path of travel...



I epoxied the fin to the fuselage and got a nice consistent bead along all edges of the joint.



Control rod assembled and mounted on servo horn... (tape left in place after gluing of fin/fuselage joint)



Control rod mounted on rudder...



Really starting to look like a plane!



One question I had was regarding the placement of the Rx antenna given this taildragger setup. Was planning to drill a hole right below the Rx placement which is right in front of the main gear and then run it back along the bottom of the fuselage per the manual but I am wondering if there will be any issues caused by the main gear metal?

Total build time: 70 hours

somegeek

I am no expert, but I have a LT-25 tail dragger that has the antennae run along the bottom across the landing gear and I have had no issues. I remember worrying about that myself and then I forgot about it and flew it . Everything has worked out okay though.

Beautiful job you are doing BTW.

Patrick

I have a couple of taildraggers (Sig Hog Bipe and Sig Something Extra) that have the antenna ran like you are thinking about. Never had a problem with them this way.

Hope this helps

Ken

Thanks, Ken & Patrick.

somegeek

Wrapped the battery pack and receiver in foam and got them into place. Kind akward at first trying to get these into place but they go in nicely.



The hole in the firewall for the fuel tubes matches up well with the two bottom tubes on the tank, but the top one doesn't line up well when you have the tank against the back of the firewall so I altered the top brass tube so the fill hose is not bent sharply to exit the tank area...



Glued in the throttle tube and inserted the wire pushrod in place to help the tube keep it's form while the glue dries...



Mounted the engine - woohoo! Added a Hobbico exhaust deflector...



Put the fuel tank in place so I can glue in the rear tank brace (hooked up the fuel lines as well)...



Glued in the rear tank brace...



Added the windows earlier and installed the power switch



Total build time: 74 hours

somegeek

Somegeek-A really excellent build, you are a natural! Doing rubber bands or bolt on wing? I have bolt on and have never regretted it. BTW, I have the same plane and engine, but had to take the muffler deflector off. It seemed to cause dead-sticks in hot weather. Maiden flight is right around the corner!

I don't think the masking tape will be enough to hold the tank in. I recommend a hatch cover.

yel914 - thanks - getting there! Gonna do rubber bands initially as this is my first plane and want that 'flexibility' just in case. Will prolly switch to bolts down the road when my skills permit a more rigid setup.

bruce88123 - *PHEW* thanks - that was a close one... (plans to install hatch cover)

Mounted the throttle pushrod tonight...



Regarding the control arm on the carb, the brass body that inserts into the the carburetor control arm was tight when inserted and would not rotate very easily. I figured this might be an issue down the road if any dust or debris built up and might cause it to sieze, so I used a 1/16" bit to ream the hole out just a touch. The brass body rotates easily now but it's still a snug fit. If you are fitting this piece, do so without installing the retainer as it is not easily removable if you need to ream out the hole at all.



I used a needle heated with a lighter to poke the holes for the hatch screw. Also added the padding for the fuel tank. I installed a 12 oz tank (vs the stock 8 oz) so I had to use 1/2" foam rubber on one side and 1/4" foam rubber on the other and only a small piece on top(otherwise the hatch would not close).



Holes for the main gear...



Holes for the tailgear - you can see the hole I left when I had to move the gear back...



Tailgera installed...



Ailerons covered...



Total build time: 79 hours

somegeek

Ken,

That sounds like a great idea. Have you had any problems with the copies coming out at a different size even slightly?

Gene

somegeek,

I just finished my LT-40 not too long ago and I had also noticed that the dihedral gauge was a little odd looking. Knowing that I could cut another one from the pattern left in the scrap, I carefully sanded the corners of the gauge with a sanding bar until the dihedral and W-2 parts of the gauge were flat. I built the wing using the modified gauge and the dihedral in the wing was correct when checked using the DTG before and after I joined the wing together.

I used epoxy on the firewall and tail-feathers, but I also used CA when I joined the wing halves. In my build thread "Starting LT-40 Build" on post #6, Mindwarp states that he used the CA method 3 years ago and has had no problems to date. After reading the MajorTomski post (post #24) on your thread here, I am not worried about my wing at all. The parts fit when I dry fit the wing was even and tight. I flowed CA onto the FG tape after using spray adhesive to tack it down. It applied smooth and without bubbles.

It seems that we used all the same gear except that I left mine in a tricycle landing gear setup.

I too, routed my antennae out the bottom under the RX except that I drilled the hole slightly larger and used a piece of fuel tubing through the fuselage for a stress relief in addition to the one inside the plane. The T-pin I used toward the rear of the fuselage has a 90 degree bend so it would hook over former F-5 and then glued it in place with CA.

I also painted the engine and fuel compartment areas. I used SIG Butyrate Dope.

I don't know if you intend to beef up the area where the Fin mounts to the Horizontal Stab., but it seems to be widely agreed upon that triangle stock should be used in this area. I did not use as much as I as wish I had, but it seems to be quite strong. Definitely stronger than it would be without it.

I ended up changing the stock wheels to 3 1/4" on the nose and 3 1/2" on the main gear because I fly off of grass and the originals were a little too small, making it hard to get up enough speed to take off.

Your build and covering job looks top-notch by the way!!

Here's a some of pics to show a couple of the things that I did.

Gene