Help with "built up TE`s" needed.

[Plumet]

I am new to building and really struggle with built up TE`s. The kind where a upper and lower balsa strip sandwich the ribs.
I always end up with the TE`s rear either too thick OR too thin. some say a chamfer should be used and some say just to lay the rear edge together with no chamfer.
I have yet to find a "how to" vid OR article with good pictures.
Can anyone help please?

 

[Joker 53150]

What size are you dealing with? If it's small enough you can take stock solid balsa and cut it down to size. Larger planes have the built-up pieces you mention, which can be a pain. Maybe go with slightly thicker/oversized sheeting for it so you can sand it down to final size without it becoming too weak?

 

[Hai-Lee]

I am new to building and really struggle with built up TE`s. The kind where a upper and lower balsa strip sandwich the ribs.
I always end up with the TE`s rear either too thick OR too thin. some say a chamfer should be used and some say just to lay the rear edge together with no chamfer.
I have yet to find a "how to" vid OR article with good pictures.
Can anyone help please?

I assume you are building a kit or at least to the plans. So I will state that where the two TE cover strips should normally glue together where they touch and normally not protrude past that point.

As for finish or profile of the TE section it should be squarish and never sanded round or similar because this introduces excess drag and turbulence which can cause problems long term especially in a speed model.

When sanding the TE you should always use a sanding block to avoid scalloping or rounding of the TE.

If my answer is off the mark provide a little more info or even a pic of the problem your are experiencing!

Have fun!

 

[Plumet]

Hai-lee, you are pretty much correct on all. the models are apx 60" wing span.
The thing is the plans are pretty basic and not produced great so the end view of the wing does not show much if any ot the TE build up.
Its weird, I can pretty much find most things on building but nothing with good details on this subject.

 

[Hai-Lee]

If the plans are poor, (I build from a lot of scanned and posted plans), it is always a good idea to draw out the problem area so that you get the assembly clearly in your head before applying glue.

Where you wish to extend the TE past the end of the ribs, (If pointed and not truncated), sand the mating surfaces of the TE strips, (slightly) to increase the contact area but as a rule never more than about 1mm of extension. This slight extension can stop the TE strips coming "Unglued" especially when building light and keeping the amount of glue used to a minimum.

Where extreme weight saving is not an issue a fillet of glue in the TE between the ribs can make the TE a lot stronger and more rigid.

Have fun!