Thorp Air Command - T18.net

Should the ailerons and stabilator be in the neutral positions at all times during the measurements while completeing the WB process?

NO, when you fly you would be changing control surface, won't make a hill of beans..........Aircraft needs to be level.

** admin posted for Bill Williams **

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Forum Administrator

Weighed my thorp last weekend, interesting topic. Plays with you head a bit.( A lot) Some people use the wing leading edge for the reference datum, some use the plans stations, in inches, (could be any where along the longertudanal axis.)as the datum. I used the 55inch datum ( wing leading edge).Its a good practical datum because using a plumb bob draped over the leading edge to the ground , chaulk line , jack point , chaulk line etc. Here in AU back in 1970 CASA (Civil aviation safty authourity ) dicided to reduce John Thorp Plan Max take off weight and limit C of G range for the Thorp. Now the Experimental category is in , the plans specs should be used. So therefore i have decided to do the flight test conservitavly and limited the weight to 750 kg max takoff weight and c of g range to 200 to 3000 mm.( wing L/E) see my attached spread sheet.( just add fuel and pax, baggage weight to the right hand box which auto calculates the weight and balace left hand box) This is reduce from John Thorp plan but still do.able.Sorry for the metric calculations but no brainer. What do you guys think? I will attach the spread sheet to my photo album. Carnt seem to attach it here. cheers

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James Ball

Lee. How can I up load the spreed sheet for w& b?

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James Ball

Hope this works

[file]THorpe_Weight__Balance.xls,131,,[/file]

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James Ball

I've been thinking about the weight of my Thorp...it comes in at a 983 lbs. Its not painted, it has an 0-290 engine and a wood prop. It seems to me that an airplane configured such as mine would weigh a little less that 983 lbs. I'm thinking the extra weight comes from the interior and panel instruments. It has an IFR capable panel with the standard 6 pack, lights/strobes. Would you guys tend to agree with that? The reason I ask is because if the extra weight isnt attributed to the interior and panel instruments, the only other thing I can think of is that my wing tanks weren't completely dry when I weighed it. Any thoughts?

I think that 983 is pretty close. Your airplane needs to go on a diet. I'm thinking the original builder was thinking 0-360/CS and didn't mind adding a few extra lbs.

here's where I think the weight is coming from;

1.) mid 70's era avionics dual com 11a(s), Nav 12/11 (plus glideslope receiver for the 12) ... + 10 lbs (see pic)





2.) Your Wing tanks are actual integrated 'tanks' rather than wet wings .. I bet that adds 10 - 15 lbs at least plus the plumbing, fuel pumps etc ...
3.) You have a very nice and complete interior, that adds up too. Also note custom cast rudder control assembly and brake pedals.
4.) The Blaupunkt speakers in the side panels (5 lbs at least)
5.) The FAR 121 quality transponder box and HUGE landing light in the tail cone 10 lbs (see pic)




Tail Cone Note, heavy Light and FAR 121 grade transponder.

6.) Unless you filled the wing tanks yourself at some point I doubt there was any residual fuel in there ... it sat for a long time.


Please don't take offense your airplane is a work of art (again see pic everyone ... it's a beaut!) but you are going to have fun trimming the fat.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

It is a beautiful interior ! [8D] Lee is right, all the 1960/70's avionics, plus that battery (looks to be a wet cell type, (about 20/25lbs) and the other components in the tail, can add up...really add up ! I know it would be a major undertaking, but redoing the panel with 2010 avionics would trim at least 20 + pounds, even more if you went all electric. The other added benefit would be extra leg room as the older radios in the lower "bent" portion of the panel could be eliminated and replaced with a very light weight MicroAir or Becker radio/transponder package. That combo would weight less than the VOR/CDI indicator ( I think ? ) Pretty close just by eyeballing it.

You have a great looking sky machine ! [;)] Most of the weight reduction items can be done over time ( R & R as the old units fail ) and as the budget allows.

RB
NX115RX

I had the same thougts on the panel Rich. I would really like to replace it with some of the new stuff out there, but I really want to fly it more than anything right now. I appreciate the input on the weight issues from everyone.

Ryan, here's another data point for ya. My Thorp with an O-290 and wood prop has an empty weight of 932. There are no gyros in the panel, VFR only with an Apollo 704 comm, 2.5#, and a King KT76A transponder for avionics. Removing the gyros and vacumn pump reduced my weight approx 20#, these were old gyros. I was able to save 8# when I replaced the generator with an alternator.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

Wow, I just wouldn't have guess the instruments weighed that much. I realize that stuff is heavy, but I never would have guessed gyros/pumps were 20 lbs heavy. I guess I need to be on the look out to trim weight everywhere I can. Thanks Bruce.

Another reason I went with an all electric panel. No vacuum pump, hoses, filter, regulator, clamps, etc. Plus I eliminate all the associated maint. with those items. I am SVFR only and have all the standard flight instruments (electric). When these steam powered gauges fail, I will probably replace them with some type of an EFIS set-up, which will reduce the weight even further. Rather than make an entire new panel (may do that anyway), they have the new EFIS units that fit right into the existing holes in your panel. [;)]

RB

I think we're talking about apples and oranges.

Bruce had two very large 60's era gyro's in his airplane which were indeed very heavy. I have an old DG like he pulled out at home and it is a lead brick. Ryan, I think you'd be doing good if you saved 10 lbs (probably more like 5 lbs) by replacing yours. Of course 10 lbs is nothing to shake a stick at but it's not going to be 20. Heck if it were 20 I'd pull mine out. Probably the reason The older style like Bruce had were replaced by the more compact units we're all familiar with today. Of course now those are becoming obsolete too thanks to electrics.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

For those still in the process of building, (like me now) the iPad is something to look at for a PFD/EFIS/MFD - they are working on putting accelerometers in the iPad, (they are already in the iPhone) as currently it it can not display accelerated attitudes, just pitch and roll - they are working on an algorithm to try and fix that - check out the "iCub".
The ipad is already a hit for charts, GPS/terrain and weather display. I'm cautiously optimistic it may ba a part of MLMIP (mid life mistress in pieces)

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Fraser MacPhee
N926WM
Serial #279-1
Angel Fire, NM (KAXX)

I think we are not too far off (very close) where the old flight bag will take the form of an ipad like device containing our geolocated sectionals, approach plates etc. and paper charts will go the way of the doe doe.

From the perspective of someone in the software industry I'm still very much a steam-powered gauge guy. I tell my coworkers quite often that if the airplane industry built airplanes in the same fashion as our industry builds software .. airplanes would be falling out of the sky!!

I agree with you though Frase like it or not ... iPad like devises are making a move off our laps and onto the panel. Bring your good luck charms when you fly in the clouds folks!

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Lee Walton
Houston, TX
N51863,N118LW
KEFD