primer weight?

[prkaye]

This is NOT to start a primer debate. I'm just curious if anyone has an idea how much fully-priming adds to the weight of a typical RV (not including the primer on the outside of the plane for painting). I guess if you knew the approximate weight per gallon of primer, and how many gallons of primer you used, this could be estimated.
Ball-park figures?

[TShort]

I'm guessing not much.
I have primed all interior structures of the tail (including the skins) and all the wing ribs, rear spars, etc. I have used about 2/3 of a kit of AKZO (two gallons per kit) with a significant amount of that waste (overspray and leftover at the end - probably 1/2 of what I have used).

The thing to keep in mind is that the majority of the weight in the liquid primer is solvent - let some dry sometime and see what is left. I bet in the amount I've used I've only added 2 lbs or so to the final weight of the plane.

YMMV.

Thomas

[RV6_flyer]

In A&P school, we had a project were we were to prep and prime an 0.032 piece of aluminum. You failed the project if its weight increased more than 1.5%. For 0.032 aluminum, you can expect a 1.5% weight increase when the primer is applied with a translucent appearance. (NOT a heavy coat.)

You can expect to increase the weight of your airplane 1.5% if you prime all the aluminum.

[TShort]

Well ...

1.5%, but only of the weight of the components primed.

That does not include wing spars, tanks, wheels, brakes, engine, etc etc etc.
So we're not talking 1.5% of the empty weight (which would still only be 15lbs or so), but 1.5% of the parts primed.

Thomas

[gmcjetpilot]

Originally Posted by prkaye

This is NOT to start a primer debate. I'm just curious if anyone has an idea how much fully-priming adds to the weight of a typical RV (not including the primer on the outside of the plane for painting). I guess if you knew the approximate weight per gallon of primer, and how many gallons of primer you used, this could be estimated.
Ball-park figures?

SWAG - 25 lbs at least. Depending on what "fully" means and how thick you apply it, added weight could be much higher. That is a lot of primer to prime ever square inch. But you can guess up to two gallons of primer attach to the structure, minus all the solvents and reducers that flash off. Primer is HEAVY. Good point.

That is why I don't prime every (internal) square inch. Rumor has it that Van does not prime the inside at all, or at least it was the case at one time. Also rumor has it the outside of the plane is NOT primed before painting, using only etch/alodine as a prep. I am sure clear coat paint jobs weigh more, verses single stage paints.

I recall a guy just reported 30lbs for his outside paint job. No detail on paint prep or type. It probably included the primer (wash?) / paint (solid) and may be a clear coat?

The area inside the plane, especially if you include every rib, frame and stringer individually primed, plus the sheet metal, could be quite hefty. One thing you have to define using a wash primer or a filler primer, that is much thicker. There are too may variables, but stand by 25 lbs. Why do it on alclad unless you are going on floats for salt water flying?

One thing for sure, add paint or primer inside or outside the structure it will add weight, and you can be sure the CG will GO aft, since most of the fuselage and the aft 2/3rds of the wing are aft of the CG.

[fehdxl]

I wonder if they primed the alclad parts of these...



... only humor intended.

-Jim

[RV7ator]

I weighed all empennage components of a 7 before and after priming with Akzo. It added two pounds. Not a particularly heavy coating but not translucent either if the object is to block oxygen penetration. I guesstimate a fully primed 7 would be ~15 pounds heavier than bare.

Another 7 was fully primed with Akzo. I used 1 1/2 kits. Put your thumb to the wind as to how much was overspray and solvent evaporation. 15 pounds added seems ballparky.

John Siebold
7 & 7

[chaskuss]

Originally Posted by prkaye

This is NOT to start a primer debate. I'm just curious if anyone has an idea how much fully-priming adds to the weight of a typical RV (not including the primer on the outside of the plane for painting). I guess if you knew the approximate weight per gallon of primer, and how many gallons of primer you used, this could be estimated.
Ball-park figures?

Phil,
Sterling states that their U1201/U1202 MilSpec epoxy primer weighes 0.01 pounds per square foot. That means that it takes 100 square feet of primed area to add one pound. This is based on applying the primer at 1 mil (.001") per the MilSpec.
You can determine the weight added by figuring out how many square feet of material needs priming.
Charlie Kuss

[chaskuss]

Originally Posted by gmcjetpilot

SWAG - 25 lbs at least. Depending on what "fully" means and how thick you apply it, added weight could be much higher. That is a lot of primer to prime ever square inch. But you can guess up to two gallons of primer attach to the structure, minus all the solvents and reducers that flash off. Primer is HEAVY. Good point.

snipped
I recall a guy just reported 30lbs for his outside paint job. No detail on paint prep or type. It probably included the primer (wash?) / paint (solid) and may be a clear coat?

The area inside the plane, especially if you include every rib, frame and stringer individually primed, plus the sheet metal, could be quite hefty. One thing you have to define using a wash primer or a filler primer, that is much thicker. There are too may variables, but stand by 25 lbs. Why do it on alclad unless you are going on floats for salt water flying?

One thing for sure, add paint or primer inside or outside the structure it will add weight, and you can be sure the CG will GO aft, since most of the fuselage and the aft 2/3rds of the wing are aft of the CG.

George,
Have you ever actually read the application instructions for the various brands of polyurathane paints? If you actually had, you'd know that they call for a 6 mil coating (2 coats) of finish paint. Assuming a MilSpec (1 mil) application of primer, that means the primer is only ONE SEVENTH of the weight of the complete paint job. Let's see, ... 30 pounds divided by 7 equals 4.29 pounds of primer on the exterior. If we assume that priming the interior will add twice that 4.29 pounds, that's quite a bit less than your guesstimate of 25 pounds. 25 pounds of primer sounds reasonable for a sea plane, but not most RVs.
I think you really are overstating what portion of the total weight can be attributed to the primer. If you live in Florida or New Zealand, you had better treat it like a sea plane, because it is. Down here, we have 4 year old RVs (always hangered) which have significant corrosion because the builder didn't use Alodine under the primer. FYI, MilSpec epoxy primers only stop 7 of the 8 types of corrosion. The only thing which stops filiform (the most insideous type) corrosion, is a chromate conversion process (aka Alodine, Iridite and several other brand names). Alodine will prevent 4 of the 8 types of corrosion. Most of this info is available on EAA Chapter 1000's web site.
Charlie Kuss

[az_gila]

I took Gary Sobek's A&P test requirements and did some maths...

0.032 Alum. 1 sq. ft. - 2024-T3 Alclad is 0.461 lbs.

1.5 % is 0.006915 lbs

If only one side is painted = 0.006915 lbs. per sq. ft. of primer max.

From the DETCO web site (U-1201 is MIL-P-23377 primer)

U-1201 and U-1201G Primer @ 1.0 mil - 0.0133 lbs per sq. ft.

This is about 3% for a single side being coated - 6% if you coat both sides, like a rib or bulkhead.

This web site from DETCO has a lot of interesting aircraft primer info. including finish paint weights....

http://www.detcosterling.com/slacgui...RAFT%20PRIMERS

It would seem Gary's number might be too low, and George's too high...

But... it's really easy to apply the AKZO primer too thick, so I bet you could reach George's number if you really laid it on to get a nice shade of green...
Remember 0.001 inches thick is the goal... use a micrometer on test samples if you are not sure what this looks like.

I vote for somewhere in the middle....

gil in Tucson