HS 908 - Am I suffering new builder paranoia ?

[Spike]

I fabricated the second of the 908 attach brackets which anchor the front HS spar to the tail of the fuse. This one came out much better than the first. If your not familiar these brackets there is a picture below. The procedure is to precisely drill the middle hole on the top row and cleco that to the pre-punched hole in the spar. Then you align the bottom edge of both angles onto a common plane (immitating the fuse saddle) and then match drill the remaining holes into the spar.



I wasnt as precise in my hole drilling as I had wanted; one is about 1/32" off vertically. The end result is that the HS will not sit perfectly level on the fuse saddle. The measurements seem to indicate that one HS tip will be just a hare over 5/8" higher than the other. That is to say that I'm losing (or gaining) 5/8" over the 124.5" HS span, or roughly 3/10's of a degree.

One half of my brain says thats fine, drill the sucker and move on. The other half of my brain say stop cause its not perfect. Which side are you on?

-- John

[captain_john]

Spike, what drawing is that on?

CJ

[Spike]

That would be drawing number 3. Im assuming that Vans uses the same attach method of the front HS spar on most of its aircraft.

-- John

[captain_john]

Just looked at my drawing 3 plan. Nothing of the sort is shown there. In fact, it doesn't even describe ANY attachment points at all. All it eludes to is that SOMEDAY it will bolt to the fuse section. I will look at the fuse attachment one later, but that won't really be applicable to your dilemma.

Photograph a section of your plans for me to see how this ties in.

CJ

[Spike]

Heres a picture of the spar. As you can see the two L brackets are what attaches the spar to the fuse saddle. They are "drilled in assembly" to the fuse later in life. The problem is that one of them sits 1/32" lower than the other. To adjust them so that they sit on the same plane I have to angle them such that the spar is no longer parallell to the fuse saddle.




I just got off of the phone with a friend of mine who is building a 6A. He reminded me of the extra sheet stock and that this type of stuff was what it was used for. So, Ill take a 1/32" piece and make a shim to go under the low bracket and raise it up. Duh, why didnt I think of that? Guess thats what happens when its late out and your a new builder. Thank Poeboy!! (thats his login)

I test shimmed the bracket to see how this will work out:



Poof: both tips are within 3/16" of each other. Thats a gain of 1/32" over 24 inches. Thats good enough for me!! You guys rock!

--John

[captain_john]

Ummmm, YAH! Cool... what Poeboy said! Great idea! He DOES rock!

As I was reading the story, it is exactly what was going on in my head too.

BTW, this IS different to the -7's and -8's. The setup I have is different than this. I don't have "L" brackets. Instead, the rear bulkhead pieces have F-711c's which are called "Horizontal Stabilizer Attachment Bars". They bolt directly to the fuse during "final assembly".

Hmmmm, you are right though. One WOULD think they are all the same... or at least similar!

CJ

[txaviator]

I got so paranoid building mine last weekend (these same parts) that I :

1) Ordered another stick of angle to rebuild them JUST like I wanted them, and
2) Went and bought a new band saw to make life easier the next time around.

A new 12" stick of that alloy angle was only $5 from Van's, plus shipping. That's the route I took.

Gary Robertson