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SA300 Wt/Bal
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dusterdan



Joined: 11 Feb 2006
Posts: 80

PostPosted: Sun Nov 14, 2010 8:43 pm    Post subject: SA300 Wt/Bal Reply with quote

I just completed a new wt/bal on N1468 following a long term refurbishment effort. It previously totaled 1298#. I removed heavy gyros front and rear, replaced the wobble pump and associated plumbing to the rear pit with a forward mounted Dukes pump, replumbed and rewired everything else, and installed lighter mags,starter, and alternator as part of the IO360 major o/h. Also installed a smaller 26gal main fuel tank with all alum lines aft of the firewall replacing the old heavy insulated automotive type lines. HB Special T/W installed as well. Added a 760 com / transponder & encoder mounted behind the front seat back. Probably added weight doing fiberglass repair work on the nosebowl as well. Bottom line, it just came in at 1235# with 70# on the T/W and included engine oil. This is with a Hartzell aerobatic prop and a 19in mount. I need to verify measurements from datum to determine the empty CG. Seems like a lot of work and expense for 63# but as you have read here previously, if you are building one, every little bit helps. Also possibly added 35+ HP with LYCON 10.5 to 1 pistons, porting and polishing, SS crossover exhaust, and performance cam. May not get to fly it until spring if this cold weather lasts. Only one way to further reduce weight and that would be to recover and repaint but that may be passed on to some future owner.
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Dan Benkert, N1468
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jsh



Joined: 19 Dec 2005
Posts: 354
Location: Burnet, TX

PostPosted: Mon Nov 15, 2010 2:38 am    Post subject: Reply with quote

that still seems a little heavier than what I would guess, based on what mine is and they seem somewhat comparable. I will say that 65 lbs, in my experience is a big deal....one of the surprising things when I started flying mine and carrying pax was how much small/moderate weight increases affected performance. I like your weight on tailwheel....mine is 65 lbs.
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dusterdan



Joined: 11 Feb 2006
Posts: 80

PostPosted: Mon Nov 15, 2010 3:40 am    Post subject: SA300 Wt/Bal Reply with quote

I could get down more by giving up the smoke system and inverted oil system but those are just too much fun to forego,
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Dan Benkert, N1468
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frank



Joined: 02 Dec 2005
Posts: 456
Location: Lynn Haven, FL

PostPosted: Mon Nov 15, 2010 10:49 am    Post subject: Reply with quote

Dan,
I'm not sure of the origin but have used the ratio of 1 HP gained for every 5 lbs of weight removed. So, 65 lbs is equivalent to 13 additional HP !!! And yes, there is another way to save weight in the plane by reducing the weight in the back seat. I looked back at earlier annual FAA physicals and found that I was adding a pound per year to the back seat. Not much until you add up the years as well!

Further gains can be made with a composite prop, smaller (Oddysey??) battery, tiny ELT (I have one if needed - 121.5), Aviation Products Tailwheel (have one of those as well), and cleaning out all those miscellaneous items that seem to accumulate in the headrest luggage compartment, etc, etc.

And yes, these birds are weight sensitive. Our Acroduster, fully loaded with 2 bodies and underwear/shoes/toothbrushes and tools for XC to contests was a true slug until we had burned off a portion of our 25 gallons of Avgas.

I recall an IAC contest at which Kevin and I were sharing the plane with a plan to carry only the minimum fuel needed for each sequence in the box - anything more would degrade performance on a very hot and muggy day in Atlanta. We were both flying Sportsman and he was responsible to add the necessary nominal amount of fuel between his sequence and mine. There was a sly smile on his face as I came to the plane for my turn in the box. Yep, he had topped it off completely and on purpose to handicap dear old dad. Turns out that extra handicap was not needed as I was fully capable of over-rotating spins and flying outside the box regardless of the fuel on board. The point is I could truly notice the extra and unneeded weight of the addt'l fuel.
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Starduster History



Joined: 30 Nov 2006
Posts: 736
Location: St. Helens, Oregon

PostPosted: Mon Nov 15, 2010 12:12 pm    Post subject: W&Bs On older Airplanes Reply with quote

Dan My first question would be, how accurate was the original W&B? Your airplane is over 40 yrs old and is one of the earliest built Stardusters still flying that I am aware of and if you are using the original W&B numbers might not be all that accurate. Your airplane was built by J H Parker Jr in Torrance Ca back in the late 60s around 1968 and was owned by Lee and Sharon Dorance for many years. it was also ground looped by her that required gear rebuild and at that time was moved back. I only point this out as when most are rebuilt generally they gain weight. Even my airplane has gained almost 100# lbs in 20 yrs! How can that be? their were a lot of reasons that I wont go into, But gee that doesn't weigh much, however a whole lot of little things that do not weigh much can when added together, do make a difference.

Most like women gain weight over the years and like frank said its not just the gals! So your weight reduction might be more substantial than you think. You are one of few that have really tried to lower the empty weight and I applaud you. Most just live with it. like jsh said a few pounds can make a lot of difference. As I am always amazed when I fly mine with little fuel something I don't do often and by myself how well it performs.

Most of these airplanes (Starduster Toos) powered with a four cyl lycoming and with a center section fuel tank, radios xponder and the normal creature comforts weigh between 1200#lbs and 1300# lbs empty. the C/S prop can add another 30# lbs

Back in the good old days the 70s many of these airplanes had really bad aft C/G conditions especially with two heavy people pilot passenger and min fuel!
And many had some shall we say some rather creative weight and balances worked to insure certification.

Such as weights altered, mostly tail weights also it was not uncommon to also change some of the arms for not only the passenger and the pilot but the arm from the datum to the tail wheel! It is quite amazing what several less inches can do to a marginal C/G! I probably have at least two dozen W&Bs from other Stardusters that I have collected over the years and many of them exhibit some massaging of the numbers.

My advise to those that own older Stardusters or are going to buy one is to do a current W&B to verify the numbers.

Example: RM 611 lbs x 7.63 = a moment of 4661.93
LM 612 lbs x 7.63= moment 4669.56
TW 83 lbs x 183.5 = moment 15230.50

EW total 1306 lbs Weight times arm= moment 24561.99 Divide these two numbers and you have 18.8

Equals 18.8 E/W C/G and the limits are from 18" to 27"

The 7.63 "number is the distance the wheels are aft of the Datum :IE gear moved back!

The 183.5" is the distance from the Datum to the contact point of the tail wheel in level flight attitude. and is the correct way to conduct a W&B on a tail wheel airplane. I have seen these as short as 178.0 and unless the person shortened the fuselage this is not a correct number!

the following are arms that were supplied by Jim Osborne at one time owner of Starduser and he was an aeronautical Engineer that had worked at one time or the other for many of the aircraft and Aerospace companies in California He was also the spark plug and advocate of the Acroduster Too.

Current arm numbers from datum firewall:

Pilot 70.0 Inches aft
Passenger 42.0 " "
Fuel Wing 19.0 " "
Fuel Main 9.0 " "
Baggage 90.0 " "

I have also seen the above numbers mysteriously become shorter by several inches.

There are certainly other ways to conduct W&Bs and can work equally as well as for instance the one supplied by the FAA in their home built document packet, But one still has to have the correct weight and arms otherwise you may have a really good W&B but just because the paperwork says so does not mean that the nose will come down when the airplane stalls!

As always this is only my opinion. Dave
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Dave Baxter
Starduster History


Last edited by Starduster History on Tue Nov 23, 2010 11:14 am; edited 2 times in total
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Marl



Joined: 01 Dec 2005
Posts: 509
Location: Georgia, Albany/Dawson (16J)

PostPosted: Mon Nov 15, 2010 12:13 pm    Post subject: Reply with quote

frank wrote:
There was a sly smile on his face as I came to the plane for my turn in the box. Yep, he had topped it off completely and on purpose to handicap dear old dad.


Frank-----

I can't believe Kevin woulda done something like that to you!!

HA!! That's FUNNY!!! Laughing


.
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Marl Halbrook
Albany, Ga
Starduster Too N88GG
BK-13005
http://websites.expercraft.com/halbrook/ (Starduster Too Recover)
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frank



Joined: 02 Dec 2005
Posts: 456
Location: Lynn Haven, FL

PostPosted: Mon Nov 15, 2010 2:42 pm    Post subject: Reply with quote

Marl,
Yes, he denied it but I knew that smile when I saw it.

The rest of the story that day was - we raced to convert it back to 2 seat for departure immediately after his last sequence, topped off and headed South between two areas of severe WX, racing sunset to get home just before end of civil twilight. All the other competitors were stuck at Tara for another day or two waiting for the WX to clear. We missed the awards ceremony and did not get our results until the next week - he beat me of course.

Dave,
"but just because the paperwork says so does not mean that the nose will come down when the airplane stalls!" So true. We watched our CG gradually creep aft (while still in paperwork limits) until we needed to assist the nose with downward elevator going into a spin. (My excuse for over rotating!). Therefore we went thru our own weight saving and move-the-CG-fwd exercise. Another factor in achieving a "normal" stall is the relative angle of incidence of the upper and lower wings. Most biplanes are rigged so the upper wing stalls first allowing the nose to drop at stall. Ours was rigged the same on upper and lower so it would theoretically fly identically inverted. (Hmmm - think for a moment about recovering from an inverted spin if the rear wing is stalled and not the front - a bit more challenging!!!)

And, FWIW (Dan) - you can save about 5 lbs per main tire by going with lightweight (non-trainer) 6.00 x 6 "8 ply rating*" version. They cost 1/2 as much as the beefier version but only last 1/2 as many landings. (*) means there are not actually 8 ply in the tire - when you see cord they are paper thin so change at the very first sign of any cord. Checking a skidded and blown-out example I count only 4 visible plies.
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dusterdan



Joined: 11 Feb 2006
Posts: 80

PostPosted: Thu Nov 18, 2010 6:57 pm    Post subject: wt/bal Reply with quote

Thanks guys for all the input. Frank, I have used Oddysey batts for years. Best starting punch I have found for the higher compression engines. I also have the light tires because most of my landings are on my sod strip. Dave, the previous wt & bal was done when the IO360 was installed following the last ground loop. Bill Clouse did the structural repairs and engine install was done at a well known Compton area shop. It seems consistant with where I'm at now. I had a troubling 10# split between the mains, then noticed 1 of the 4 rubber feet was missing from the scales. The split is now a more acceptable 2#. Also used a digital level to fine tune the 2d attempt and found that I was .5 deg tail low the first time. Doesn't sound like much but it increased the mains total 5# and decreased the T/W the same which is even better. If I fill the main tank I'm within limits for acro, but could not carry an adult up front and remain there. Filling both tanks and carrying a small amount of baggage will also be fine. Now the big question, can we define 1700# as an acro gross wt and something higher as a max cross country gross weight? I know the radial engine TOOs are flying well above the plans number. BTW, part of the slightly higher than expected weight might be in the gear structure. Bill Clouse told me he put the strongest gear he could build on it following the last ground loop by one of the previous owners.
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Dan Benkert, N1468
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Starduster History



Joined: 30 Nov 2006
Posts: 736
Location: St. Helens, Oregon

PostPosted: Tue Nov 23, 2010 11:22 am    Post subject: Weight & Balance Reply with quote

To all I apologize for the mistake on the W&B arm Numbers for the main tank and the wing tank in my previous post! This was a mistake and was caught by one our sharp eyed builders and I thank him for catching it as it was mistakenly reversed in the post I made on this subject. I have made the corrections to that post. Main should be 9" aft of the datum and wing should be 19" aft of the datum! Gee this is the first mistake I ever made? Dave
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Dave Baxter
Starduster History
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John Singer



Joined: 03 Dec 2005
Posts: 131
Location: New London, NH

PostPosted: Tue Nov 23, 2010 3:21 pm    Post subject: Reply with quote

Dusterdan

Do you want to sell the wobble pump ? If so How much ?

johnsinger912@comcast.net
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frank



Joined: 02 Dec 2005
Posts: 456
Location: Lynn Haven, FL

PostPosted: Tue Nov 23, 2010 3:42 pm    Post subject: Reply with quote

Mistake??? Dave the best explanation was given by the guy who "never" made a mistake: Actually he thought he had made one but said he was mistaken!
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dusterdan



Joined: 11 Feb 2006
Posts: 80

PostPosted: Thu Nov 25, 2010 4:36 pm    Post subject: SA300 Wt/Bal Reply with quote

Following usually good advise from Dave led to discovery of an abundance of mostly small errors on the previous wt & bal report. I believe these led to a cumulative error giving an unacceptable result that was fixed with a simple adjustment of the tail weight to 56#. There is no way that was ever possible given how much I reduced the gross weight and it sits now at 68#. The arms for everything except the main fuel were longer than what Dave provided in his post. Distance to the mains measured 9.1 vice previous 9.5 and the big mistake was distance to the tail is 180.5 vice the previously stated 184.7. This gives an empty CG of 18.79 . I haven't run every situation but a 230# pilot and a full main tank sits at 25.1 and a burn down to 10gal still sits at 25.7. both are within the 27.0 aft limit I have unless that is also incorrect. My advise to any owner would be to check the math and measurements several times before you do any radical corrections to fix what may have never been a problem at all.
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Greg



Joined: 18 Dec 2005
Posts: 96
Location: Columbus MS

PostPosted: Thu Dec 16, 2010 8:08 pm    Post subject: Reply with quote

So I finally had some time to play with the weight and balance today, and found several surprises. Despite switching to a lighter Odyssey battery, a lighter 'homebuilder's special' tailwheel, and removing a 32# weight attached to the front of the engine, my empty weight went up 55# to 1193. Still, it sounds like that is a reasonably light weight, so ok. However, when I measured the actual distance to the tailwheel, it was 183, not 178 used in the original calculations. Unfortunately, that has put me in a situation where it is easy to get c.g. too far aft, so I am going to have to put the '32# deadweight' back onto the front of the engine. Not very elegant, but it does help keep c.g. not so far aft. I also noticed that the original w/b used 7.5" to the main wheels, instead of the 7.63" mentioned by Dave above. I'll recheck that also. Not a huge change, but it does make a difference on the c.g.
Has anyone else had to use a weight up front? My empty weight will still only be 1225, but it just seems kinda goofy...
Also, thanks Dave, for all your info! it's nice to know the spin may actually be recoverable now, once I get my aft c.g. straightened out!
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RDavidson



Joined: 16 Dec 2010
Posts: 127
Location: Pueblo, Colorado

PostPosted: Fri Dec 17, 2010 7:39 pm    Post subject: weights Reply with quote

Greg,

A lot of people have used weights, installed anywhere and everywhere forward of the firewall.

I called Saber MFG in Granbury Texas, and they built me a 20# weight that is installed on the front of the prop with the prop bolts going through it. I'll try to attach a picture.

I had a small engine and a fat pilot. I wanted to take fat friends with me too! So now my Duster can carry two 250 pounders!

I have changed a lot of stuff on my aircraft, so I won't know until I finish a weight and balance if I really still need the 20#s on the prop.

I know that Mark Landoll makes a harmonic balancer that fits on the starter wheel that adds about 13#s and has some engine performance benefits for about $500. I believe he also makes a weighted ring that goes in the same place, don't know the price on that. He doesn't have a web site, but you can google him and find his number.


Good luck,
Ron
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RDavidson



Joined: 16 Dec 2010
Posts: 127
Location: Pueblo, Colorado

PostPosted: Fri Dec 17, 2010 7:50 pm    Post subject: weight pic Reply with quote



The spinner bulkhead actually fits underneath the weight, and the spinner will cover them both.
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