2) Where? Edges, or the entire surfaces, or what?
3) What is this actually doing? Does the CA bond the internal structure together?
You can go CA-ing either just the edges, or the entire surface of the fin. The choice depends on what affect you are trying to achieve:
- Seal the surface of the balsa fin for smooth paint-ready finish.
- Structurally stiffen and strengthen the wood surfaces, plus #1.
- Seal the edges of balsa/plywood fins from delaminating and/or pitting.
Super-thin CA is great at penetrating the pores in wood and paper. That seals pores shut, smothes the exterior surfaces, and stiffens the part. The downsides are that it makes the fins a bit more brittle, and also removes the possibility of gluing the fins to the airframe with PVA/TiteBond type glues. You have to use CA or Epoxy to glue the fins after CA-ing them (not the end of the world), but may not be what you want.
In the context of the fins, for #1 or #2, sealing the entire surface of a large fin takes work, requires more CA, and will lead to a
LOT more sanding.
CA doesn't spread evenly, and cheaper CA brands generate tons of irritating smoke. Thus you either have to spray CA onto the fins outdoors, or pay 3x (triple) the price for Super Gold CA:
https://www.erockets.biz/search.php?Search=&search_query=ca
If strength (#2) is your primary goal, and a little extra weight is OK, the optimal outcome will be achieved by first papering the fin (search for threads on that), then either CA-ing the papered surface, or just the edges.
For example, when you want to make sure that your Screaming Eagle wings will never chip or break:
If you need strength (#2), but can't afford extra weight, like in the case of helicopter blades, then you only fill the grains (with primer, or wood filler), and CA on top:
Do I need to do multiple coats, or just one pass all over?
If you can manage to apply CA in one pass - well done!
For me, it usually takes multiple spray passes across the surface of the fin, then filling in more rough patches where the CA had been absorbed by the wood more than in the nearby areas.
Then you sand.
CA is hard, but it can be sanded. Just takes time, and patience.
There's also this for sealing the fins (and edges) without warping the balsa but I hear it smells nasty.
Have you tried it? Yes, how many coats did you use on fins to seal grains?
That looks similar to the Elmer's wood filler.
A few layers of application, followed by sanding, will definitely fill the wood grain in the fins, and add some strength. Not as much as CA would, but some.
The trouble with all water-soluble fillers (like eRocket's or Elmer's), is that water has a nasty tendency to warp balsa, basswood, and plywood.
For that reason, I avoid them on fins (but do use them on airframes):
HTH,
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