Empennage paint weight

Empennage paint weight

Hi I need some guidance. I'm building a 9 and trying to keep the weight down, have read all the posts and really appreciate the valuable info.

I have a question on how much my paint weights, I am using single stage with a primer under and have finished the all the empennage components.

Is there any numbers available on the unpainted weight of the empennage pieces either assembled or free standing. I wanted to match the unpainted weight to my painted pieces and see how my paint coverage is working out and how much weight I have added.

I will use a FP light prop with the O-320 engine. So I figure because I will be light way up front I don't any extra empennage weight that would need to be offset. I plan on buying the lightest good quality tailwheel to help.

Thanks for any numbers, looking forward to seeing how I'm doing with trying to keep the painting light.

Steve in NH

In my case. the Horizontal stab weighed 19.25 lbs assembled and the right elevator was 5.75 lbs and the left elevator was 6.31 lbs. This was completed, unprimed components from a stock Vans RV9A kit without hinge bolts.

I hope this is useful.

I am epoxy priming the inside and outside of all structure with a solvent resistant primer just like most major airframe OEM's do when they build aircraft and aircraft structural components. I am not trying to convince anyone to prime thier structure as it is a personal preference decision, but I do get tired of reading the comments on how heavy a primed RV will be.

The primer that I am using is Akzo Nobel 463-12-8. The material specification sheet reccomends an application thickness of 1.0-1.2 mills. A mil is .001" and is actually a pretty heavy coat of primer that gives a smooth totally opaque finish. The material data sheet states that once the primer cures and gasses off, the resulting dry film coating with a thickness of 1 mil (.001") will weigh .0093 Lbs per square foot. Maybe someone here will take the time to measure and do the math to determine how much weight will be added, but I doubt it ends up being remotely close to the 20-30 Lbs that I have seen stated here many times.

http://www.argosyinternational.com/sites/default/files/datasheet/AkzoNobel_463-12-8.pdf

My tail feathers weighed as follows:

HS - 19+ lbs
VS - 7.5 lbs
Rudder - 16 lbs
Elevators - 13.5

My numbers on the bathroom scales are

VS 9lbs
Rudder 11
HS elevators all assembled painted with trim tab installed 40lbs

Terry do you have a light in your rudder?

One last pass at this.
The weight of paint at 20 - 30 lbs is for the entire RV9 and includes primer. It is a very variable number depending on the paint system chosen and the skill of the painter.

The main point is that 2/3 to 3/4 of all the RV9 surface area is aft of the empty CG location (the CG is approx over the wing spar). The weight of the primer and paint becomes significant as you attempt to build a very light RV9.

For example a one lb reduction in the weight of the horizontal stab is equal to a approx 16 lb reduction in the prop. That is, if you change from a metal prop to a composite prop you need to reduce approx one lb in the tail area for the CG to remain unaffected.

The finished unprimed and unpainted weight of the Hor Stab is about 32 lbs. The finished primed and painted weight is about 40 lbs. The 8 lbs difference is reduced by the fiberglass tips, hinge bolts counter balance weights and trim system used as well as the primer/paint used. The weight of the finishes used on the empennage are small, but not insignificant.

Paint is one of the few choices a builder has in reducing an aft CG condition.

Two tips:
Consider reforming the counterbalance weights to move the lead as far forward as possible to reduce the moment arm of the weights by 1/4 to 1/2 inch.
Small potential but every little bit helps.

Always calculate the low fuel landing CG. Your CG moves aft as the tanks empty, it can easily move past the aft limit if you don't check.

William, thanks very much for the input. I had moved the elevator weight with an epoxy flow mix with lead shot in the forward nose of the glass tips, this required me to drill/remove a good amount of the standard weight to achieve the correct balance.

Your comment on the 16 lbs vs. 1 lb in the tail was timely, as I was wondering how to take up the lost 15 lbs by not using a CS metal prop and instead using a composite which is a weight reduction in a difficult place to compensate for. So I'm looking at who might have the lightest tail wheel to use.

Steve

Add couple grams

Steve make sure you prime those powder coated brackets. I can show you how they may look in several years if left unprimed. Not a pretty flaking sight

sibriggs said:

My numbers on the bathroom scales are

VS 9lbs
Rudder 11
HS elevators all assembled painted with trim tab installed 40lbs

Terry do you have a light in your rudder?

Click to expand...

Not an accurate method to weigh parts.

I weighed my rudder (same as the 9) without the top and bottom fiberglass. It does have the pivots installed. I got 8.48 pounds, bare, no external paint. I have CG if you want it, but you would have to hang yours from two different points to measure that.

BilL,

Did you calculate the CG of the wings, landing gear, fuselage, .........

If so how?

Thanks

Sibriggs,

Remember the 16 number is an approximation.
The Horizontal stab moment arm is close ( I eye-balled the CG position). However, the Prop moment arm could vary several inches depending on your engine mount, engine, prop extension and prop chosen. I used my prop Moment arm for the example. The 16 should be close but not exact.

whd721 said:

BilL,

Did you calculate the CG of the wings, landing gear, fuselage, .........

If so how?

Thanks

Click to expand...

No, I was just interested in the rudder for comparison to the 8 rudder. I did it two ways.

One, easy. Hang the part by a single point, then hang a plumb bob. visually align the plumb bob string with the hanging string (or wire) then take a picture and draw a line on the part. Then, in the same plane, hang from another point and the intersection is the CG.
Two. Establish a datum (usually along one edge) , weigh the part, then allowing it to pivot on the datum, calculate the moment arm - - - - well - - - use method one.

Both were used for my 9 (aka 7 tall) and 8, (aka - 7 short) rudders and both methods were as close as I could measure, maybe a 1/16th".

Engine Mount

First thanks for all the helpful info. I'm getting a real online education reading all these messages.

I need some recommendations on using the extended engine mount for my 9. To compensate for the light FP composite prop and keeping things as light as possible. Seems like most of the possible weight reductions are in the front of the CG, so except for saving about 1lb on the tailwheel, I'm focused on the engine location to keep the weight low and still have a good CG range.

With the IO320 engine and no CS prop and no prop governor there is 15-20 lbs less on the nose, would the standard mount give me the CG range or would moving the engine 2" forward be better?

Thoughts?

Steve