SeamusG

I'm doing a crash-rebuild thread for my LT-40. Rather than ask this question in context of my specific thread, I thought I'd ask for any / all suggestions for fixing a trailing edge in preparation for installing new hinges.

Background - my LT-40 wing has been hinged 3 times previously. During the original build it got Robart hinge pins - first time for me. Somewhere along the line I figured that a tail dragger with a bolt down wing made sense. Since I wasn't impressed with the Robart hinge pins (way too tight - control surfaces needed some force to move them up or down) I replaced them with CAhinges (hey - it's a trainer). Hinging is my most unfavorite activity I ended up with a few dry hinges. So, I cut the CAhinges and re-hinged with CAagain - this time using a 1/16" hole in the center to help wicking. Everything was cool until a battery failure that resulted in a new fin/rudder, stab/elevator and ailerons.

So much for background.

I'm gonna use my favorite hinge - Dubro nylon pinned hinges. Last night I cut out the CA hinges. Some holes are nice-n-tight. Some holes are loose-n-sloppy. Since there are 16 slots and 10 holes in the trailing edge. I only need 8 slots (4 per aileron) I need to:

[*]fill slots that won't be reused[*]fill slots that are way to big to be used for Dubro hinges[*]fill holes from the Robart hinges (actually - just finished gluing 3/16" dowel pieces into the 10 hinge holes)[/list]I was thinking of doing my "Norm Abrahms" imitation and fabricate 1/8" balsa biscuits to be inserted and glued into precut slots. My problem is cutting 1/8" slots through the trailing edge that is 1/2" thick.

Long winded - I apologize ...

So how would you attack this problem?

huck1199

I guess that you don't want to move the hinges in the aileron so you can't just move the TE hinges over 3/4".  I have a slot tool that I rarely use but it is good for enlarging existing slots using the thick blades.  It has enough depth to cut 1/2".  The unused slots can be filled with light wood putty.  The LT40 has nice large stock to work with.  An arf would be un-repairable.  If you don't have a sloting tool or can't borrow one just cut with a sharp #11.   It is a painfull job, I have done this several times repairing planes for others.

ChuckW

If you have a mini table saw or something similar it would be easy to cut a 1/8 groove in the trailing edge and glue new wood into it. You might also be able to drill a series of holes close together and remove the meterial in between for a uniform slot and then fill it?

Is the covering still on the plane? If not, it might be easy enough to cut out the entire trailing edge and replace it. I've done that a couple times.

SeamusG

TFF

Because it is a trainer and you can have a bunch of leeway on what you do, why not cap it with a 1/8" thick strip of balsa. Covers the holes and adds some structure. Depends how much craftsmanship you want to put in. You could cut off all but an 1/8" and then a piece of wood added to the same size removed. New meat to help with hinging either way. I would be covering it up with monokote, but I am lazy.

TedMo

You do have a messy situation however,I know if you really want to repair it you will have to open those hinge slots evenly so that you can fill them in with perhaps 3/16" balsa to enable you to insert new hinges. This will then be good as new. By the way in order to cut neat slits for ca hinges get some small jig saw blades that ARE JUST ABOUT SAME THICKNESS AS HINGE.That works great

Gray Beard

My Feedback: (-1)

Just filling them without removing the old ones I would use light spackling paste pushed into the holes, sand and then add a couple drops of thin CA. The thin CA makes the Spackle harder then wood and will adhere to the wood edge. It has to set up before you use the CA or it will expand and be very hard to sand flush. Do a test on some scrap and see how you like it.

SeamusG

Hey Gene - how ya doin'? Your young protege dazzle ya with his flying skills?

About filling holes - those damn round holes left behind when I removed the Robart hinge points are a weak point! There were filled with lite filler & CA'd. The trailing edge broke through precisely at the innermost hole. That's why dowels were used to file the round ones. Heck, even a trainer can generate "some" strain on the wings.

I ended up squaring up the holes and making them consistent with various drill bits, X-acto blades & saw blades and then "hard" pieces of balsa of various widths were cut-n-shaped to fit. An emery board worked nicely for 1/16" sheeting. These were then driven down into holes filled with Titebond II (which pushed out the back all over the work surface).

Let's see if RCU will accept THIS post ...

Oh - one of my favorite saws is a couple of hack saw blades fixed together.