Savannah S Build Notes - TailFin

[IBob]

Pre-amble (Walk Slowly First?):

 

DIYer, no formal workshop background, greatly enjoying getting into my first build.

 

There is a goldmine of info on this site, plus a lot of knowledeable and helpful people to ask questions.

 

What I thought I could leave is a brief record of the bits I stumbled on.

 

My kit was manufactured December 2014.

 

Comments and suggestions welcomed.

 

Always.

 

The Tailfin:

 

1. First task here is to mount a couple of anchor nuts to the forward longeron, using A3 countersink rivets. There were no A3 countersink rivets in the kit, and talking with other Savannah builders, some got them in their kits, but most did not.

 

Some builders made their own by reworking a domed rivet.

 

I opted to drill out the anchor nut lugs, and use a4 countersink rivets.

 

2. Upper rudder hinge. The rivet gun as supplied is too 'fat' at the tip to properly set the rivets for this.

 

I ground down my hand riveter, have since also ground down the air riveter tip, on advice from here.

 

 

 

[IBob]

3. Consider which method you will use to mount the plastic tip before riveting skins to top rib: some builders sandwich a strip of aluminium between skin and rib to give fastening for the tip.

 

 

[IBob]

I spent a lot of time fitting the plastic tips. Although I'm sure I could do it in a lot less time now, I doubt I could do it quickly.

 

I AM VERY INTERESTED TO KNOW ANY TIPS AND TRICKS FOR THIS.

 

The Fin plastic tip is best fitted at the same time as the rudder tip so they can be aligned.

 

The tips all come untrimmed, that is they have to be individually trimmed so as to fit flush to the metalwork.

 

In the case of the Fin, I had to use the heat gun to get the tip to something like the shape of the metalwork: always an interesting exercise, and good that the others did not require it.

 

I then marked up my cut lines with masking tape.

 

For cutting, I started with some very sharp snips, but quickly gave that away when an offcut spontaneously snapped off.

 

After that I used multiple passes with a craft knife, and found that gave me a very accurate cut requiring almost no cleaning up. The knife also works extremely well for taking very narrow further cuts when adjusting the fit.

 

I took quite a lot off the the Fin tip to get down to the specified max measurement (though that will probably vary depending on what is delivered).

 

By contrast, I then took only enough off the Rudder to straighten and align the edges: any more and I would have been cutting further into the curves at the end.

 

I am using the 'petal' strips supplied for mounting. This requires a chamfer on the inner edge of the plastic, so that it fits over the rib metal and butts up with the skin. I found the hand deburring tool very good for this, used with care to avoid taking too much.

 

 

[eightyknots]

That is informative (i)Bob. Thank you.

 

 

[rmorton]

A quick question about the rivets for the fin, do the rims of the rivets stick up from the skin? It seems that they do, or should the hole be countersunk?

 

 

[IBob]

A quick question about the rivets for the fin, do the rims of the rivets stick up from the skin? It seems that they do, or should the hole be countersunk?

Which rivets are you referring to?

 

 

[rmorton]

Sorry my spell checker Rivnuts the seven for the inspection hatch

 

 

[IBob]

The inspection cover which is held in place by these is supposed to sit flush to the skin.

 

So I think they should be countersunk, though there is so little 'lip' this has to be done carefully to avoid going too far.

 

I countersunk mine a bit, but they are still slightly proud too.

 

Maybe Steve or Mark can give some guidance on this?

 

 

[rmorton]

Thanks Ibob, I wonder if the hole in the skin could be drilled out so the nut goes through altogether.

 

 

[IBob]

Thanks Ibob, I wonder if the hole in the skin could be drilled out so the nut goes through altogether.

Certainly you wouldn't want that happening.

Rivnuts need managing with care, especially in thin sheet metal like this. They can also rotate in use if overtightened (or corroded).

 

I have been putting mine in with a dab of Loctite 620. I have no idea if this actually improves the grip, but I figured it can do no harm.

 

 

[eightyknots]

Certainly you wouldn't want that happening.Rivnuts need managing with care, especially in thin sheet metal like this. They can also rotate in use if overtightened (or corroded).

I have been putting mine in with a dab of Loctite 620. I have no idea if this actually improves the grip, but I figured it can do no harm.

The use of Loctite sounds like a good precaution.

 

 

[MajorTom]

So I think they should be countersunk, though there is so little 'lip' this has to be done carefully to avoid going too far.

That is my opinion too. Maybe dimpling instead of coutersinking whould be better. Richard, you have your rivet squeeser. Why not buying a dimpling set? Schould fit into an envelope and no costoms...

 

 

[rmorton]

You read my mind (not difficult not much in it) I was looking for dimple sets and found a a very rough and ready set at Sonex aircraft for 10$ or so, it has to be worth a try. Looking at the tail skin if the rivet passes through it and is firmly held on just the rib it should still work and clamp the loose skin in place. Still a dimple would solve the problem.