CG Trimming after Tail Boom Repair

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A new weight and balance, after a tail boom repair, shows that several tens of pounds of trim weight needs to be added to a forward location in order to move the CG back into acceptable range. This fixes CG issue, but are there other concerns with doing this? Would be interested in experience of others.
Tom A

[Tim Taylor]

On Thursday, November 23, 2017 at 12:20:04 PM UTC-7, wrote:
> A new weight and balance, after a tail boom repair, shows that several tens of pounds of trim weight needs to be added to a forward location in order to move the CG back into acceptable range. This fixes CG issue, but are there other concerns with doing this? Would be interested in experience of others.
> Tom A

Please specify the glider type. We assume you mean that the c.g. needs to be moved forward into the correct range.

Some gliders have ballast weights that can be placed in the nose or near the front bulkheads, others will have lead epoxied into the nose.

[[email protected][_1_]]

You should investigate the potential of some ballast hidden somewhere in the tail. Or perhaps your CG calc's and/or measurements. A boom repair should not require that much ballast in the nose to get the empty airframe in CG range.

[Mike C]

On Thursday, November 23, 2017 at 12:20:04 PM UTC-7, wrote:
> A new weight and balance, after a tail boom repair, shows that several tens of pounds of trim weight needs to be added to a forward location in order to move the CG back into acceptable range. This fixes CG issue, but are there other concerns with doing this? Would be interested in experience of others.
> Tom A

Other than the max allowable weight of non lifting parts there should not be any other issues if the repair was solid. Added weight in a tail boom repair (long tail moment) takes several times the added weight when added to the shorter nose moment. Having to add so much weight forward of the cg though shows that a sloppy and probably excessive repair was made.

Mike

[[email protected]]

On Thursday, November 23, 2017 at 2:20:04 PM UTC-5, wrote:
> A new weight and balance, after a tail boom repair, shows that several tens of pounds of trim weight needs to be added to a forward location in order to move the CG back into acceptable range. This fixes CG issue, but are there other concerns with doing this? Would be interested in experience of others.
> Tom A

A properly done repair should not add more than 2 or 3 pounds at the tail skid. That would need about 10 in the nose. Many ships have some fixed ballast aft that can be removed to get back in range without lots of nose ballast.
What type of ship and where was it broken?
UH

[George Haeh]

The factory can add tail ballast to suit the first owner's weight and CG
preference. The factory documents will show how much, if any, ballast was
added.

[[email protected]]

On Thursday, November 23, 2017 at 11:20:04 AM UTC-8, wrote:
> A new weight and balance, after a tail boom repair, shows that several tens of pounds of trim weight needs to be added to a forward location in order to move the CG back into acceptable range. This fixes CG issue, but are there other concerns with doing this? Would be interested in experience of others.
> Tom A

Thanks for suggestions. The repair (and the weight and balance measurement) was done some time ago. The concern arises because of a new pilot with different weight and preferred CG location. Sounds like a reweighing is in order and also a check to see if there is already trim installed.
Tom

[AS]

>> A boom repair should not require that much ballast in the nose to get the empty airframe in CG range.<<

I have seen boom repairs just short of having 2x4s inside, so if it is one of those, that much lead in the nose may be indeed required.

Uli
'AS'

[Dan Marotta]

I think I see the problem...
https://www.dropbox.com/s/gy3qkujmyy7pt69/2017-11-24%2011.26.49.jpg?dl=0

On 11/23/2017 2:02 PM, Mike C wrote:
> On Thursday, November 23, 2017 at 12:20:04 PM UTC-7, wrote:
>> A new weight and balance, after a tail boom repair, shows that several tens of pounds of trim weight needs to be added to a forward location in order to move the CG back into acceptable range. This fixes CG issue, but are there other concerns with doing this? Would be interested in experience of others.
>> Tom A
> Other than the max allowable weight of non lifting parts there should not be any other issues if the repair was solid. Added weight in a tail boom repair (long tail moment) takes several times the added weight when added to the shorter nose moment. Having to add so much weight forward of the cg though shows that a sloppy and probably excessive repair was made.
>
> Mike
>

--
Dan, 5J

[Dan Marotta]

You mean like this?

https://www.dropbox.com/s/gy3qkujmyy7pt69/2017-11-24%2011.26.49.jpg?dl=0

On 11/24/2017 7:32 AM, AS wrote:
>>> A boom repair should not require that much ballast in the nose to get the empty airframe in CG range.<<
> I have seen boom repairs just short of having 2x4s inside, so if it is one of those, that much lead in the nose may be indeed required.
>
> Uli
> 'AS'

--
Dan, 5J

[Dan Marotta]

On Friday, November 24, 2017 at 7:32:29 AM UTC-7, AS wrote:
> >> A boom repair should not require that much ballast in the nose to get the empty airframe in CG range.<<
>
> I have seen boom repairs just short of having 2x4s inside, so if it is one of those, that much lead in the nose may be indeed required.
>
> Uli
> 'AS'

You mean like this?

https://www.dropbox.com/s/gy3qkujmyy7pt69/2017-11-24%2011.26.49.jpg?dl=0

[AS]

On Saturday, November 25, 2017 at 10:24:14 AM UTC-5, Dan Marotta wrote:
> On Friday, November 24, 2017 at 7:32:29 AM UTC-7, AS wrote:
> > >> A boom repair should not require that much ballast in the nose to get the empty airframe in CG range.<<
> >
> > I have seen boom repairs just short of having 2x4s inside, so if it is one of those, that much lead in the nose may be indeed required.
> >
> > Uli
> > 'AS'
>
> You mean like this?
>
> https://www.dropbox.com/s/gy3qkujmyy7pt69/2017-11-24%2011.26.49.jpg?dl=0

Yep - pretty much like that. Still, my vote for the top price for the most terrible repair would go to a Ka6e with a Bondo'ed on cuff over one side of the all-flying elevator after an off-field landing mishap. I wonder how much lead in the nose that one required - provided a W&B was even done after that 'repair'.
Uli
'AS'

[[email protected]]

My memory is a little hazy but I recall seeing Rudy Alleman's 301 Libelle at the 1981 15M nats in Minden with glassed on external longerons. I could have my facts wrong but apparently the tail boom had been broken a few times and he decided he didn't want to go thru that again.

Chip Bearden

[Eric Greenwell[_4_]]

wrote on 11/25/2017 5:53 PM:
> My memory is a little hazy but I recall seeing Rudy Alleman's 301 Libelle at the 1981 15M nats in Minden with glassed on external longerons. I could have my facts wrong but apparently the tail boom had been broken a few times and he decided he didn't want to go thru that again.

I've flown with Rudy since 1975, and there were no external longerons - ever!
Possibly, there were some applied after an accident to hold things in place in the
trailer until it could be taken to a repair place, but not for flying.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

[[email protected]]

I remember seeing Rudy's H-301 with the splints on the boom of his H-301 after he was forced to put it down in the canyon on the south end of Topaz Valley!
Remember examining the internals of his wing with Dick Schreder.............believe that was the last flight of that bird.
JJ

[Steve Leonard[_2_]]

On Sunday, November 26, 2017 at 3:38:54 PM UTC-6, wrote:
> I remember seeing Rudy's H-301 with the splints on the boom of his H-301 after he was forced to put it down in the canyon on the south end of Topaz Valley!
> Remember examining the internals of his wing with Dick Schreder.............believe that was the last flight of that bird.
> JJ

Last flight while Rudy owned it, maybe. It got repaired and I believe is based at Avenal, CA now. I think its old trailer is visible on Street View as you "drive" by the airport.

Steve Leonard

[[email protected]]

That makes sense! Eric & JJ: you were at that contest. I recall hearing that Rudy had landed on a road in a narrow canyon late in the contest somewhere down south of Minden (towards Bridgeport?). "Splints" sounds more accurate. I definitely saw them once but don't recall seeing them on the fuselage on the takeoff line, although it was a big contest.

Just checked the Soaring archives and Rudy took a DNC the last day so that's consistent with his not flying it that way. Thx for closing the loop on my memory after all these years!

Chip Bearden

[CindyB[_2_]]

On Monday, November 27, 2017 at 1:01:18 PM UTC-8, wrote:
> <snip> Rudy had landed on a road in a narrow canyon late in the contest somewhere down south of Minden (towards Bridgeport?).
>"Splints" sounds more accurate. I definitely saw them once but don't recall seeing them on the fuselage on the takeoff line,
>

I have been part of a recovery team for a glider that was badly pranged and boom shattered on an outlanding. Take a lot of photos BEFORE you move the parts. (Have authorization from local flight bureaucracy before disturbing the site.) I do strongly advise hauling along splints of whatever rigid and preferably LIGHT material you can carry. Aluminum conduit would be handy, pipe - PVC or metal, wood splints least favored. And a few rolls of duct tape. The internal push rods and cabling make removing the tail difficult in the field, and you are trying to minimize further damage. A few extra people, and a few feet of rope to sling the boom after splinting is necessary.. Sounds silly but a long blanket or sleeping bag can be used to sling the tail section, which can't be rolled until after repair.
Bothering to post these kinds of details is a way to pass along "skills" to the newer generation -- beyond where I can wave and point. My wish is to never have to use this knowledge again.

Cindy B
So Calif, USA