somegeek

My Feedback: (2)

SoonerAce - thanks for the balancing advice, will do!

To the rest of you asking about the CA on the wing joint... the manual said to use CA, so I used CA. The FG being applied later will be done with 30 minute epoxy.

somegeek

bruce88123

OK, but I am still surprised. Onward!

R T W

I would of used 30min epoxy on the wing joint we have had 2 LT40's fold there wings at
our club. Fiberglass tape will add a lot of strenth. Rest of build looks great. Carry on.

cwrr5

My Feedback: (32)

When in doubt, R.T.F.B. [sm=thumbup.gif]

somegeek

My Feedback: (2)

RTW - that sucks. Wonder if Sig should update the build manual then? Given those LT-40s had good proper surface to surface CA bonds, use of CA should not be an option if the wings folded. Every thread I've read regarding the LT-40 advised to "follow the manual and you should do great" with regards to the build...

Guess I can go back and run some beads of epoxy around the MADB joint to the spars in addition to the fiberglass being epoxied to the wing joint seam.

somegeek

bruce88123

How wide is the glass tape they provided for the wing joint? You could gain strength by going a little wider.

somegeek

My Feedback: (2)

The glass tape is 1" wide.

bruce88123

IMO if you were to use a wider tape, 2 or 3 inch (do not exceed fuselage width), you would add significant strength to the joint without a major weight penalty. Be sure to use 30 min epoxy to give enough working time and the strength. You could use the heat gun to thin the epoxy a little for great penetration. (do not thin chemically here)

Anyone have a disagreement with that suggestion?

cwrr5

My Feedback: (32)

Nope. Sounds right to me. [sm=thumbup.gif]

RTW, where on the wing did those break at? Was it in fact right in the center, or was the break a little further out? What was the plane doing when they snapped?
I am still suprised about the manual saying use CA, I'll have to look at mine someday. I wouldn't expect that in a Sig kit, usually they're very good. [sm=angry.gif]

somegeek

My Feedback: (2)

Manual page snapshot here regarding CA use on wing joint.

Either way I will fillet the joint corners and fill other areas with epoxy and use epoxy on the fiberglass tape. Prolly go with a 2-3" strip as suggested above.

somegeek

figment

I find that very strange. If I am not mistaken, and I very well could be, the manual for my LT-40 ARF used epoxy. But, that was 4 years ago, I may have just used epoxy on a recomendation. Also, the ARF came with 3" FG which I CAed. I hate using CA for that, and will only use epoxy in the future.

As far as manuals go, I also found it strange when I was building my LT-25 last month, that some of the descriptions and pictures incorrectly referred to the LT-40.

Anyhow, I am sure it will be fine.

Keep up the great work.

Patrick

bruce88123

Accessibility of the area with an ARF is much different that a kit and some differences can be expected. I don't like using CA around plywood myself. They must have confidence in this joint or they wouldn't be using it. I still recommend the wider tape though.

cwrr5

My Feedback: (32)

Never doubted you for a second somegeek.(but thanks for the picture) I still find that suprising, doesn't seem like there's a lot of surface area for the glue to adhere to, and the dihedral braces look a little on the "light side" to me. Maybe it's just because I build my planes like tanks. (jk!)

Whatever works - press on with pride!

bryris

I used 4" tape with 45 min epoxy.

The wing would stall long before it would snap with this setup....just barely enough room to clear the fuse, but it does.

somegeek

My Feedback: (2)

Moving along on the build...

Got the wing joint epoxied up and sheeted.

Fitted the ailerons and had a question that I didn't see addressed in the instructions(that I could see) - this gap:



Should it be wider or is it good? I have a touch of movement on the CA hinges if I need to widen the gap when I glue things up down the road...

I have the tip sanded at this point...



If I should need to widen that gap please comment - can sand off more of the aileron tip.

That CA hinge cutter w/ the guide is very nice! Made short order of the cuts once I got the guide adjusted.

Got the fuselage all glued up. Took some time to run a clean bead inside on every joint edge. The use of the following, highly advanced, not even on the market yet tool made it much easier to do to work the glue into the corners and such...



Easy to apply the Titebond II drop by drop with a toothpick and work it into cracks and push out any air.

Got to the step to start sanding the fuselage so I did a little sanding but pondered where I would mount my landing gear since I am going with a tail dragger setup. From what I've read on RCU... matching up the back edge of the front landing gear piece with the leading edge of the wing is the way to go?



I know I need to add some ply pieces to reinforce the mount and was planning to put a piece on the fuel tank area floor...



Is this the way to go for the front gear?

Got the horizontal stabilizer glued/pinned up tonight.



Still need to glass the wing joint - gotta clean up the seam and sand before I do that though. Think the dremel on med speed should take care of the high spots of epoxy. Gotta pick up some wider glass tomorrow.

Total build time: 40 hours

somegeek

somegeek

My Feedback: (2)

Added two pushrod braces...



They're lined up pretty well - the elevator rod can fall out of the tube on it's own. The rudder tube has slight friction but not enough to worry about.

Figure between the additional braces and the carbon fiber rods, I should see little flex to lose effective elevator control. Will prolly add some graphite to the rods if they get sticky at all.

Total build time: 40.5 hours

somegeek

bruce88123

Looking good and it appears that you are getting excellent glue joints. The extra supports are a good idea but be careful how much weight you add aft of the CG, it will all need to be balanced out and that will mean more wt up front. The aileron gap is OK as long as you don't put too much covering in the area and fill the gap. Gap could be larger and not hurt either. You'll be glad you used the wood glue when you get into the sanding, it goes so much easier.
Plywood gear reinforcement would have gone in easier if done sooner in the assy, before some of the other structure got in the way.
I'll let others advise on location/method as I have not done this mod on LT-40.

Keep up good work.

cwrr5

My Feedback: (32)

Looking good! The note on the landing gear picture should say "Leading edge" instead of trailing... but other than that - it's right on. 1/16 or 1/8 ply triangle shaped fuse doublers in at the point directly above the gear should do the trick(attached to fuselage sides and floor where gear mount). Don't worry about the gap in the inboard end of the ailerons, that's pretty much just asthetics and shouldn't make any noticeable difference in flight.

somegeek

My Feedback: (2)

Thanks for the input guys - updated that pic... guess I was a little tired when I put that label on there. DOH!

Think I'll widen that gap a touch for good measure.

Traded in the two rolls of silver and one of blue for three rolls of cub yellow. Kept one roll of blue for the control surfaces and some graphics.

Time for some sanding.

somegeek

somegeek

My Feedback: (2)

Got the bulk of the work done for the taildragger conversion today...

Closed up the stock hole for the gear mount. There was a ply piece on the top of die-cut sheet no 8 that was an exact fit for the width of this gap, just needed to cut the three lengths out of it.




For the tailwheel mount, I added a doubler. Since there is a second F8 piece, the angled piece was pre-cut, just needed to cut to length.




For the main gear mount, I epoxied in a piece of 1/4" ply to match the footprint of the main gear. Good bond with the fuselage doublers and F2. Also picked up some bolts and blind nuts for this mounting.




I altered the Sullivan tail wheel mount just a little. Cut off the top cap of the spring mount piece(using a dremel w/ a cutting wheel) and expoxied on a servo arm. Will run a connecting arm up and then into the back hole of the fuselage. Should look relatively clean when i get through with it.




Did some sanding and got the fuselage smoothed out with 120 today. Sure cleans up when you get that excess glue sanded off. Gonna run over it with putty and then 220 tomorrow.



Gotta fit the servo tray so I can position/install the pushrod holders for the tailwheel and then I can start pondering the fuselage covering.

Verified my covering iron's temps tonight and marked the 220ºF and 300ºF positions for the Ultracote I am using. Practiced covering a piece of scrap. That covering material is neat stuff. Need to do some more reading regarding covering techniques for corners. The covering covers the wood but doesn't hide rough surfaces... I'll be doing a little bit more putty work than I originally pondered. :P

Total build time: 47 hours

somegeek

cwrr5

My Feedback: (32)

Looks like it's coming along nicely! I like the tailwheel mount mod that you did.... but curious to see how well that's going to hold up over time.
That ply doubler is in the tank compt. right? (hard to tell in the picture - took me a few seconds to figure it out)

somegeek

My Feedback: (2)

Thanks!



In the pic above, I just cut off the top cap piece. The brass shaft that is just small enough to fit into the servo arm and the shaft has a few holes in it. Thinking the epoxy formed a good bond. Guess I'll find out over time.

Yep, it's in the tank area.

somegeek

Lowlevlflyer

My Feedback: (3)

You are just a little too far forward on your main gear placement, and I believe you have it turned around backwards. The straight edge should be to the front, with the swept edge to the rear, at least that's the way mine mount up. On my LT40, the front edge of the main gear is right up against the BACK of the fuselage former that is at the leading edge of the wing. This way, when the aircraft rotates up onto the mains on takeoff roll, the mains are directly under the leading edge of the wing, and when the aircraft is sitting at three point stance, the wheels are slightly in front of the leading edge. I've been flying mine like this from day one, and have had no problems with it. The ground handling is perfect, takeoff roll is well behaved, and the landing rollout is fine. No controllability problems at all.

somegeek

My Feedback: (2)

Thanks for the info Lowlevlflyer. Not questioning your experience, but most of the taildragger conversion threads I've read on RCU regarding the LT-40 suggested the placement I have an image of above. I have my gear mounted now... guess if I run into trouble down the road I can move my gear back a bit.

somegeek

Lowlevlflyer

My Feedback: (3)

After looking at your pics again, I dont think the 1/8" or so difference in where your mains are mounted and where mine are mounted will make any difference. CARRY ON!!