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Absolutely correct. Make sure the mold has cured fully. The suggested soak in the oven at 150F should do the job.
Attached are some photos of the finished product, including installation. The lead is clean and free of dirt and debris.
Note how neat and snug the casting fits in its site. It can’t slip out in any attitude of the aircraft.
Saturday, July 20, 2019 3:46 PMTo:
Re: [c-a] Weight and Balance - help with choosing additional nose ballast - or not
A safety note on steps 6-7 below. Make sure the plaster mold is THOROUGHLY dry. Other wise you risk a molten lead explosion from the moisture in the mold boiling to steam and throwing lead every where. Just had it happen with supposedly dry concrete. Prior to the lead pouring I would recommend baking the mold in an oven for an hour each at 150 F and then at 212 F. Wear a safety face shield or at least goggles.
I never dreamed that W&B would be such a complex issue. Thank you all for your input. Gives me a lot to think about – what with super stars like Mike Tooze and Marc Zeitlin adding comments.
Hey, I am the 187 lb pilot. That include all the clothing required to survive desert heat. I used to have a good BMI until my spinal cord began to collapse and I lost 1” in height. Now I am in the obese category – but I don’t believe it.
Mike, I will probably take the reverse approach since I have already produced a snug-fit, 12.1 lb lead ballast weight.. If 12.1 does not do a good job, I will cut of some of the top section and try again.
For those who might be interested in producing a snug-fit lead ballast, here is the process:
- Place a plastic bag in the space to occupy the lead weight and inject some two-part expanding foam.
- Remove the foam and trim to a best fit.
- Arrange the shaped foam in a position that would be suitable for pouring a mold.
- Wrap the foam in Saran Wrap and coat it with Plaster-of-Paris leaving the appropriate face open for casting.
- Remove the shaped foam from the Plaster-of-Paris.
- Place the Plaster-of-Paris mold, bottom down, in a bucket of sand.
- Melt recycled lead shot in an aluminum or stainless steel pot and skim off the gunk until the lead melt is shiny.
- Pour the melt into the Plaster-of-Paris mold.. There will be some outgassing of the mold. Watch out for spits and spurts.
- When cool. Break away the mold.
I am attaching some pictures of the process.
Thanks for all the input. I will report the results.
I assume from your spread sheet that you are the 187lb guy and we are discounting the heavy fellow.
Yes, you are with it. What you describe indicates to me that in trimming via nose down stick pressure that you do need to increase your ballast. (Down force produced by extra ballast is cheaper, drag wise, than extra down trim force with its associated drag.)
You could go for the 12.1 lb. but time is on your side, I would try, say, +6 or +8lb first. If you can't get the stick free trim condition then carry on to the +12.1lb etc. What you don't want is to run out of pitch authority in the landing configuration also if you have a problem landing in rain the more forward CoG will not help that. That's why I would advise an incremental approach.
You will feel so much more comfortable at your chosen a/s rather than have to 'fly it' all the time - and it will run more efficiently.
(Vance made a good point, if you have the space you could put in a larger capacity battery instead of some of the ballast. I recently swapped my 14Ahr m/c battery for a 21Ahr removing about 2lb of steel plate)
A point of interest that may or may not be relevant. Re. the lower weight pilot on the spread sheet.
When my daughter was flying G-EMMY all she wanted was 'hours' complaining that the a/s meant she flew longer stages.
I put the ballast such that either of us could safely fly without having to move the ballast.
This had the effect of maintaining my higher cruise a/s at neutral trim while she, at her lower front seat weight (w second set of pedals), flew at a considerably lower a/s but also, interestingly, at around neutral pitch trim. (She eventually gave me a GIB flight and I found myself leaning forward! - she was running leaned-out at 1900/2000 rpm! )
She now flies her 'light twins' long-haul for BA. And I have the Eze to myself. ;^)
Best with it Marc, - incrementally,
I was all set to remove some nose ballast, but your post has caused me some doubt. I generally cruise at around 165 kts TAS, and I run out of nose down trim and have to push on the stick. Does that mean that I need a little more nose ballast?
I have cast a 12..1 lb nose insert that will give me a CG of around 101 (see spreadsheet). Would you suggest that I test fly that configuration to see, if my nose trim is reduced? I like your explanation of how balance affects efficiency.
It is unlikely that a 230 lb pilot would fit in the cockpit of my LongEZ. A 230 lb pilot presents a forward CG (but still in the first flight box) issue with low fuel.
You are very right to reassess your W&B after a few (15) years.
However, you are now at a stage with your Long that you ought to be refining its performance.
I recently wrote on another point "".... Add(remove) ballast as necessary to achieve your minimum trim drag at the speed you choose to fly."
It is not simply to push your CoG back as far as safely possible. I worked all my carer in aerospace, a large part of that was in 'stability and control'. This included FBW systems that allowed reduce stability margins brought about by flying with rearward CoGs to attain more efficient flight. (mil and civil). Mainly for tailed aircraft this is the case but for a canard aircraft things are slightly different.. - the canard gives positive lift whereas a tailplane pushed down. So, by moving the CoG of a plane back if it is 'tailed' this reduces the down-thrust required from the tailplane , increasing efficiency (but reducing natural stability margins). But for a canard moving the CoG further back, incrementally, means less lift is needed from the canard - good to start with but if that means that the canard elevator is now required to produce 'down trim' to the extent of adding drag that is where the rearward CoG efficiency gain idea starts to fail.
But Forget All that, there is a much easier way. Following the quote above....
i.e What airspeed do you wish to fly with your required load? - Say, 160kts
Then run a test with your nominally safe ballast at a reasonable CoG.. Run at your chosen airspeed (160kt) and note the amount of trim you need to maintain 'stick free' straight and level flight.
If the trim is significantly 'down' and/or you need to augment the trim for level flight with more 'nose down stick' then this indicates that you need more nose ballast. If it is 'up' then you can reduce the nose ballast. (But keep within the given CoG limits)
After an iteration or two you will be flying with slight elevator trailing edge, TE, floating above the in-line position for minimum canard drag. Thus for that flight condition you have your main-plane and canard balanced for minimum trim drag.
For the Long and VE I have found that the faster the chosen airspeed the more down trim, stick nose down force, is needed to maintain level flight, so expect to increase ballast for increased 'chosen airspeed'.
Running you spread sheet as you go will keep you inside safe limits.
I hope this is of some help. OMV.
Best with it,
O-235 VE, Last winner of EuroCAFE, in our 38th yr.
After flying for 15 years on my last weight and balance determination, I enlisted the help of George Snyder and his certified, digital scales for a re-weigh. I am considering adding additional nose ballast, either 10 or 25 pounds.. I would like some advice on whether I should choose 0, 10, or 25 pounds of nose ballast. The nose already has 23.4 pounds of ballast installed.
I am attaching an Excel spreadsheet with the comparisons showing the effect on the CG for various scenarios of loading. I have indicated the position for the CG for each of the loadings, and color coded each as follows:
Green (in the first flight box),
Yellow (in the CG box, but aft of the first flight box)
Pink (in the CG box, but near the aft limit)
Red (dangerously aft of the CG box)
Question. Do I want to favor the nose ballast that places the CG in the first flight box.?
The CG box is shown at the bottom of the spreadsheet. You can play with the weights by just changing them.
Thanks in advance for your input.