E/AB final weight?

[Will Kumley]

I know the performance numbers and finished weight listed on many of the kit planes are optimistic at best, but I'm curious if there is an average number this is off by? For example, the info for the Bede 4C shows an empty weight of 1250 lbs but I found one blog of a gentleman that built one and while it took some digging, it looks like his was closer to 1700 lbs when completed (although after re-reading it that may be the weight with 1 or 2 passengers in it). I understand a lot comes into play to get the final number but I'm curious if there is a standard above the advertised weight one could expect when shopping around for a kit.

 

[kyleb]

I know the performance numbers and finished weight listed on many of the kit planes are optimistic at best, but I'm curious if there is an average number this is off by? For example, the info for the Bede 4C shows an empty weight of 1250 lbs but I found one blog of a gentleman that built one and while it took some digging, it looks like his was closer to 1700 lbs when completed (although after re-reading it that may be the weight with 1 or 2 passengers in it). I understand a lot comes into play to get the final number but I'm curious if there is a standard above the advertised weight one could expect when shopping around for a kit.

Prototypes are usually a few percentage points lighter than lightly equipped finished kits. Why? Well, in Van's case, they really put the paint on thin and (at least in the old days) sent forth aircraft equipped to a "light VFR" standard. As an example, the prototype RV-6 weighed 970 pounds. Mine weighs about 60 pounds more. Van's lists the RV-10 as a 1575-1600 lb airplane. Mine is 1607 and has a couple of weight adding features, so it is relatively light given how it is equipped.

All that said, builder choices are what make most of the weight gain. Full interior? Thick paint? Extremely complex (multi battery, multi alternator, multi screen) electrical and avionics installs add weight. My priorities are biased towards light weight (better performance, better useful load etc) vs a plush interior. But if you want to ride around in Lexus like comfort, that's available at a weight penalty.

 

[Lndwarrior]

Most of the common kit planes have mountains of data on weights based on various engine choices.

Experimental aircraft (other than LSAs) can be "certified" at any weight the builder chooses, assuming proper weight and balance calculations.

I think you need to do some more research. Your comment that the weight numbers published by kit manufacturers is somehow unrealistic is simply not true. At least not when taken in context of the specific engine chosen by the builder.

 

[tsts4]

There's no standard. As mentioned above there's just too many variables involved between build choices and technique for a given kit. Best advice is to research the kit you're interested in and get a consensus as to the range of empty weights that finished airplanes are coming in at and generally how they are equipped at said weights. Forearmed with that info, you'll then be able to judge whether a given a plane is heavier or lighter than average.

Also, FWIW IMO the kit specs that the popular manufacturers (Vans, Zenith, GlasStar, Sling, Velocity, etc) publish today are pretty spot on. It hasn't always been that way but nowadays with pervasive social media it's hard to hide any glaring discrepancies.

 

[Capt. Geoffrey Thorpe]

All that said, builder choices are what make most of the weight gain

The T-18 was designed as an open cockpit, O-290 powered, VFR aircraft.

No problem finding one with full IFR panels, O-360 constant speed prop, gallons of bondo to hide all the rivets, leather covered everything, blah, blah, blah and an empty weight that exceeds John Thorp's intended gross weight.

 

[donjohnston]

I know the performance numbers and finished weight listed on many of the kit planes are optimistic at best, but I'm curious if there is an average number this is off by?

No. The kit manufacture could probably provide some information about this.

I know that my Velocity came in at 1,874 lbs. One of the factory built planes came in at 1,670 lbs. I know another builder's plane weighed close to 2,000 lbs. There is a tendency for builders to add weight by strengthening and reinforcing assemblies. I guess for piece of mind. Except (at least in the case of the Velocity) it's already over-engineered so there's absolutely no need to do that. The result of this is that many E/AB airplanes end up heavier than they need to be.

 

[Ed Haywood]

I just bought an EarthX TSO battery for my certified aircraft. If I was EAB, I would be all over that. 17 pounds weight savings over a Concorde RG-25.

How much does the paint weigh on a typical aircraft?

 

[Will Kumley]

No. The kit manufacture could probably provide some information about this.

I know that my Velocity came in at 1,874 lbs. One of the factory built planes came in at 1,670 lbs. I know another builder's plane weighed close to 2,000 lbs. There is a tendency for builders to add weight by strengthening and reinforcing assemblies. I guess for piece of mind. Except (at least in the case of the Velocity) it's already over-engineered so there's absolutely no need to do that. The result of this is that many E/AB airplanes end up heavier than they need to be.

One of the first planes I considered purchasing was a dragonfly. Online searching showed that it should have had a useful load around 600-700 pounds. The one we looked at was built heavy and had a useful load closer to 300 pounds. Lots of extra fiberglass resin and other heavy items got added during the build.

 

[Lndwarrior]

I just bought an EarthX TSO battery for my certified aircraft. If I was EAB, I would be all over that. 17 pounds weight savings over a Concorde RG-25.

How much does the paint weigh on a typical aircraft?

The nerds on Vans Air Force did some research on weight of paint. The consensus for one of their aircraft was in the range of 20 to 25 lbs.

On a light sport plane, such as my Zenith, that is a lot of weight. Since I had a heavy engine, I decided to polish my plane (with a partial vinyl wrap) to save the weight penalty of paint.

 

[tsts4]

I'm more of a drunk than a nerd, but the paint job (PPG Delfleet Essential) on my RV-10 weighs 25lbs. I know this because I was flying for 2 full years before it was painted and I reweighed it.

 

[Ed Haywood]

I'm more of a drunk than a nerd, but the paint job (PPG Delfleet Essential) on my RV-10 weighs 25lbs. I know this because I was flying for 2 full years before it was painted and I reweighed it.

Geez, the Delfleet paint job on my fabric aircraft probably weighs at least twice as much, since multiple coats of high fill primer are used to fill the weave and protect from UV.

 

[Lndwarrior]

I'm more of a drunk than a nerd, but the paint job (PPG Delfleet Essential) on my RV-10 weighs 25lbs. I know this because I was flying for 2 full years before it was painted and I reweighed it.

FYI - I meant "nerd" in the sense that the group over there is very precise and critical. That's where i go when I want to get detailed and precise information. There are a lot of really knowledgeable, experienced builders that make an effort to get the actual facts of all things builder related.

The only downside for me was when an repeat Zenith builder looked at my lycoming completed firewall forward and started asking why I did certain things. "Because that's the way the smart people on Van's do it!" I replied, smartly.

The response was, "Yeah, well most of their aircraft are acrobatic and need to keep together during G loading. You did not need to do this on your plane.".

All of a sudden I didn't feel so smart....

 

[tsts4]

I figured that’s what you meant but I’m still more drunk than expert by a wide margin. Anyway, there are best practices that are recommended to be followed regardless of whether a plane is capable of acro or not. The beauty of following the RV community is, as you noted, there’s a lot of savvy folks on almost any topic and it’s a huge. Typically FWF, as an example, is a weak spot in kit plans so being able to turn to the community for advice and examples is priceless.

Oh and roughly about 25-30% of the RVs out there aren’t aerobatic (9s/10s/12s).