tail boom repair

I'm hunting for a first glider and have come across a few with repairs to a broken tail boom. In such a major repair, how do the shops insure that the tail group is realigned to its original position? Do they use jigs built to factory specs? Or rely on measurements? Or just eyeball it?

Is it customary for a buyer to measure a glider that has had such a repair, and if so, where does he find the specs? For instance, the distance between wing tip and tip of horizontal stabilizer?

Maybe this just worry-wart thinking, but I've had experience with out-of-alignment repairs on a tail dragger that caused it to fly slightly skewed - and a little slower. Is this an issue with these long-winged ships?

On Thursday, December 20, 2012 12:40:43 PM UTC-8, CTEX wrote:
I'm hunting for a first glider and have come across a few with repairs to a broken tail boom. In such a major repair, how do the shops insure that the tail group is realigned to its original position? Do they use jigs built to factory specs? Or rely on measurements? Or just eyeball it?



Is it customary for a buyer to measure a glider that has had such a repair, and if so, where does he find the specs? For instance, the distance between wing tip and tip of horizontal stabilizer?



Maybe this just worry-wart thinking, but I've had experience with out-of-alignment repairs on a tail dragger that caused it to fly slightly skewed - and a little slower. Is this an issue with these long-winged ships?

Yes. And you also want to pay close attention to the W&B. And yes a jig is used, often set up exactly off another glider if one is available. Quality of such repairs are all over the place. Improper alignment, improper composite repairs, improper W&B, etc. You either need to know/trust who did the repair and/or need a A&P glider repair expert who is experienced in this to pre-buy inspect the glider. Including doing a proper W&B measurement.

Darryl

Are you sure you want to know the answer ?

Follow Darryl's advice below.

Repair will vary considerably depending on the
make and location of the break. Many gliders
have long straight lines in the tailcone, and
for these it's easy to spot misalignment. But
you need someone competent to check this,
review the logs, and check the W&B !
That person is NOT your local RAS expert,
club expert, or local mechanic.
Do not skip this...

Hope that helps,
See ya, Dave

On Dec 20, 12:40*pm, CTEX wrote:
I'm hunting for a first glider and have come across a few with repairs to a broken tail boom. In such a major repair, how do the shops insure that the tail group is realigned to its original position? *Do they use jigs built to factory specs? *Or rely on measurements? Or just eyeball it?

Is it customary for a buyer to measure a glider that has had such a repair, and if so, where does he find the specs? For instance, the distance between wing tip and tip of horizontal stabilizer?

Maybe this just worry-wart thinking, but I've had experience with out-of-alignment repairs on a tail dragger that caused it to fly slightly skewed - and a little slower. Is this an issue with these long-winged ships?

Don't try to over-think this, though. I've seen measurable differences
in tip-to-fin distances even on pristine never-damaged (as opposed to
(NDH) gliders. I've also measured substantial profile differences
between right and left wings of Nationals-winning sailplanes that go
like stink and fly straight as arrows. Except for the latest
generation or so made in CNC-cut molds, even production sailplanes are
hand-built things with measurable differences ship-to-ship and even
across the plan of symmetry on the same ship.

As for a tailboom repair, it's not particularly difficult to jig it
out as straight as makes no difference. If it was done by a reputable
shop like JJ's, or inspected and blessed by a reputable glider fixer,
I wouldn't give it a second thought.

Thanks, Bob K.

Agree with the last post, but let me add one more thing...

If the repair was not properly documented (Form 337) and done by a
reputable licenced repair entity, you should walk away. Such a lack
of attention to a major repair indicates a willingness to shortcut a
host of minor issues, from trailer to towhook, that will come back to
bite you later.

You want to concentrate on flying the new ship with out any qualms, or
sudden maintenance surprises. Reward a seller of a well maintained
ship, and let the lessser ones got to an estate auction. You will do
yourself, your future aircraft, and the Sport a favor....

aerodyne

What Bob and Aerodyne said.

Have seen and have done boom repairs with string, straight edges, jigs, laser levels and a few with mostly highly calibrated eyeballs doing the leveling. A correctly aligned fuselage is what matters, not how it got there.

Like Bob, I have observed some amazingly non-symmetrical factory-fresh gliders that went like hell and flew straight. I have also seen some that were dogs but why they were so poor could not be measured; everything spec'd out fine.

The structural integrity is difficult to discern without destructive measures. Given that, if it was done by someone reputable, has held up for XXX worth of flying, and the exterior and interior surfaces look OK to the eye of someone who knows what they are looking at, I would not worry for my safety.

Documentation is another matter. One would expect to see a 337 for Std Airworthiness ships and a sign-off by an A&P for EXP. All should have a new W/B. Given that, some of the best GlassGuys were among the worst at doing the paperwork.

Thanks all. Your comments are a great help. And reassuring, too.

What I gather is that one should pay attention, but not go overboard on the subject. The point that these ships are essentially hand-make was something I hadn't considered, and it's helpful to keep that in mind.

On Friday, December 21, 2012 2:18:39 PM UTC-8, CTEX wrote:
Thanks all. Your comments are a great help. And reassuring, too.



What I gather is that one should pay attention, but not go overboard on the subject. The point that these ships are essentially hand-make was something I hadn't considered, and it's helpful to keep that in mind.

What you should gather is get somebody who really knows what they are doing to do an inspection.

Darryl

On Dec 21, 2:18*pm, CTEX wrote:
Thanks all. Your comments are a great help. And reassuring, too.

What I gather is that one should pay attention, but not go overboard on the subject. The point that these ships are essentially hand-make was something I hadn't considered, and it's helpful to keep that in mind.

Have Bob make you an HP-24 from scratch. You can even make your own
tail boom.

Brad
Tetra-15
N599GK

On Friday, December 21, 2012 6:31:48 PM UTC-8, Brad wrote:
On Dec 21, 2:18*pm, CTEX wrote:

Thanks all. Your comments are a great help. And reassuring, too.



What I gather is that one should pay attention, but not go overboard on the subject. The point that these ships are essentially hand-make was something I hadn't considered, and it's helpful to keep that in mind.



Have Bob make you an HP-24 from scratch. You can even make your own

tail boom.



Brad

Tetra-15

N599GK

I would get the exact repair location from 337 or log entry and inspect that area closely. Use a long straight edge like a 48" level, the top, bottom and both sides should be dead straight. Tram the wings using a 50' steel tape. Measure from a common point on each wing (say the outboard aileron cut-out to the probe mount on the vertical fin. These readings should be equal, but don't get excited if the differ a tad, 1/4" is great, 1/2" about average and 1" poor (I have seen 1" difference on a new ship straight from the factory). The tram can be easily adjusted on some ships, LS and Genesis by moving the aft lift fitting out on one side and in on the other, start with 1/4 turn. On other ships this can be done with thin shims under the lift fittings..............excess slop in the main wing pins can be removed by doing this also.
Cheers,
JJ