Interesting.
I was sure that my Nomad Mk II and Sherpa did not have exposed breather holes and I thought somewhere that I read that Thorn frames do not have them.
I copied this from the brochure I relied on when I ordered my Nomad Mk II frame and fork in 2013, I added underline for emphasis:
... ...
In order to do this, I contacted the finest frame
builder in Taiwan once again.
These people make the top end models of some very
famous American brands!
The first time Robin and I actually met them was at
Eurobike, our builders explained that they had to
send the frames with a little sticker saying “Made in
Taiwan” but it could easily be
removed and that is what the
American companies did. I told
them that they came very highly
recommended and that I
wanted our “hand-built in
Taiwan” decal applied beneath
the lacquer, where it couldn’t be
removed. There was a silence as
what I’d said was translated to
the others. Then they looked at
each other, nodded and then
their faces light up with a smile,
they all stood up and bowed and shook our hands. I
still get a warm feeling when I re-live that meeting
and I can attribute it to their willingness to make
certain that we get all the minor details that we want.
Such as having all the blow holes filled in. (These
small holes are necessary when manufacturing the
frame, to avoid exploding tubes!) yet they can let
water in. I believe that these holes are still present in
all the Americans’ frames!
That is from the Nomad Mk II brochure, Issue 20, Autumn 2012. I did a quick word search for moisture, did not find it, searched for water and found that.
Even though my Nomad Mk II had those holes filled in, I still used a rust inhibitor inside the accessible tubes in my Nomad, but there were not many. I think I only treated the seattube, top tube (both halves, it is an S&S frame), Downtube (both halves) and headtube. To access some of those tubes I had to remove a piece of tape inside the headtube that blocked off the top tube and downtube. I had never thought of using tape like that to prevent water ingress to those tubes, so I made sure I replaced the tape when done. The seattube and downtube both had water bottle cage bolt holes where water could get in from capillary action.
So, apparently either this was missed on that frame, or Thorn has changed their policy. Or, perhaps that feature was unique to only certain Thorn frames.