[delusional]

Apologies for newbie question. I see no tolerances on Vans drawings. Is there some other document that gives guidance? Something in Part 43, maybe? Also, a radius is clearly shown on the corners but I see no dimension for it. There must be some rule-of-thumb, or some other digit...

Naturally, my very first part, the stabilizer bracket, came out .020 under at the wide end. Should I make it over or just cheat the hole in .020 in final assembly?

 

[tc1234c]

Usually these dimensions are not critical. As far as I can remember (I could be wrong) the only tolerance on the plan is the on the trailing edge. Even in this case the tolerance is stated as within 0.1" (not following the ASME dimension and tolerance standard).

 

[C-GRVT]

it's a good question

I'm building a non prepunched 6A, so can only speak from that experience (where everything on the plans are dimensioned).
You will have to use your judgment. Some dimensions are mandatory for strength, such as edge distances (with very occasional exceptions). Some are mandatory for fit, such as the location and alignment of stabilizer and elevator brackets and rod ends, or the reinforcing angles on the front stabilizer spars, which if made oversize won't fit, and if undersize, won't allow proper edge distance on the attach bolts through the longerons. For these types of things, my "tolerance" is to make the part as close to specification as can be achieved.
Other dimensions are more tolerant of variance. Where the lightening holes go in the battery box, or how large they are, is an obvious example where the builder has lots of discretion.
For the airframe construction, I have found that following the plans as exactly as I can has served me in good stead.
When you get to systems, including firewall penetrations, etc., you will find a lot more room, and perhaps need, for variance.
I am not sure what bracket came out .020 undersize, but if it fits, if edge distances can all be maintained, in other words, if it is functional and meets accepted aircraft construction techniques, I would think it is a good aircraft part.

Bill Brooks
Ottawa, Canada
RV-6A finishing kit

 

[delusional]

That sounds reasonable. In this case I think I'll just adjust the location of the holes slightly to accomodate the specified edge distance. But it would be nice to have some sort of more general guidance from Vans. Every time I make a part it is bound to be measurably off a bit so a choice has to be made in each case...

 

[apkp777]

You won't find many "tolerances" listed in Van's plans. However, AC 43.13 will have them. Also, a set of A&P text books will also have much of what you need. Of course you can always use your best judgment. Clearly if it looks bad, likely it is. Also, if you have any doubt about a particular then you can ask here. There are 2 or 3 opinions available from each person on this site.

As far as your .020 undersized bracket. It will be fine. You will be able to "cheat" that on final assembly. I believe I had a similar size issue and it was not a problem moving the attach fasteners over a fraction.