How much snow will bend an RV wing?

pboyce · #1 12-24-2005, 05:41 PM

In the Dec 05 issue of EAA Sport Aviation, there was an article and photos regarding the potential damage the weight of heavy snowfall can do to wings. Is this much of a concern for RV's? Anybody ever heard of an RV wing being damaged by heavy snowfall?

Paul

Bryan Wood · #2 12-24-2005, 09:19 PM

I don't have any idea about your question, but did come accross this picture a while back and thought it was pretty neat. Our planes should be at least as strong a Mooney.

Regards,
Bryan 9A

osxuser · #3 12-25-2005, 12:49 AM

I doubt a RV wing is anywhere near as strong as a Mooney wing. While the Mooney aircraft itself isn't designed for high G manuvers, the wing is EXTREMELY strong. The hanger talk always goes back to the story of "when" Mooney aircraft was purchased by (I think U.S. Steel?) they decided to put the wing in a test jig to determine the strengh. It is said the jig broke somewhere around 12G's (at the 1960's M20 gross).

This is believable for two reasons:

1. The wing is build out of a single piece milled spar, no carry-through like RV's have.

2. They still use the exact same wing today on the much higher gross Bravo models. These carry over twice the fuel that the early models did, as well as having an engine that weight close to twice the amount (Turbo 540 vs. O-360)

The Mooney is an extremely efficient and strong airplane, and should not be taken lightly. It's interesting to note that a M20J 200HP top speed is advertised as 201mph (170ish Knots). That is with FOUR seats, an RV 7 will get you 10 extra MPH if your lucky, but thats with only two. Dan would know, he used to have one, they are great airplanes

Kevin Horton · #4 12-25-2005, 06:27 AM

Well, the wing is designed for a -3g flight load, at the aerobatic gross weight, if I recall correctly (short-wing RVs). So, if the aerobatic gross weight was 1550 lb, the wing should be able to support 4650 lb if it is properly distributed. I think we need to subtract the weight of the wing itself from that amount, but it is still quite a large number. Let's say 4500 lb of snow is OK.

The short-wing RVs had a 110 sq. ft gross wing area with the old wing tips. The gross wing area includes the area in the fuselage between the leading and trailing edges, so the actual wing area available for snow accumulation is a bit less. This varies with the RV model, but lets say the wing area for the snow is 100 sq. ft. It should be able to support about 45 lb/sq. ft of snow.

Liquid water has a density of about 62.4 lb/ft^3, so it would take about 8.5 inches of water to equal 45 lb/sq. ft. Fresh snow has a density about 10% of water, so we are good for about 7 feet of light, fresh snow, but the density increases as it settles. I've seen references that it may settle to about 30% the density of water, which would equate to a bit over 2 ft of snow depth for 45 lb/sq. ft. But, if it ever rains, the density would go way up, and the loads would increase greatly.

Personally, if it was my RV, I would get the snow off as soon as possible after a major snow fall. I wouldn't let it get more than one foot deep on the aircraft. I would also be sure to get any significant accumulation off if it looked like it might rain.

Note: The above calculation only considered the wings. We have no idea how much snow the rest of the aircraft can support. The canopy, cowling, tail, fuselage or landing gear might be the weak link here.

gmcjetpilot · #5 12-25-2005, 08:25 PM

Quote:

Originally Posted by Kevin Horton

Well, the wing is designed for a -3g flight load, ...............aerobatic gross weight was 1550 lb, ........able to support 4650 lb if it is properly distributed. The short-wing RVs had a 110 sq. ft gross wing area............wing area for the snow is 100 sq. ft. It should be able to support about 45 lb/sq. ft of snow.

Liquid ... water density ... 62.4 lb/ft^3, ... about 8.5 inches of water ... 45 lb/sq. ft. Fresh snow ... density ... 10% of water, so we are good for about 7 feet of light, fresh snow, but .......settle to about 30% the density ...... for 45 lb/sq. ft. But, if it rains, density would go way up, ... loads would increase greatly.

Wow excellent, math is fun. I think you forgot to carry the 2.

U da man Kevin, I feel sorry for your calculator though. G Merry Christmas

rv72004 · #6 12-25-2005, 10:12 PM

Thats why tail draggers are better.
Wax the wing and the snow just slides off.

n468ac · #7 12-26-2005, 08:33 AM

Quote:

Originally Posted by rv72004

Thats why tail draggers are better.
Wax the wing and the snow just slides off.

LOL ... with our lastest snow all the tail draggers that were tied down had more snow than the tied down tri-gears. My guess is the snow piles up on the wing because of the angle.

aadamson · #8 12-26-2005, 08:51 AM

Didn't think it mattered. Get a "little" snow on a tri-gear and it instantly becomes a tail dragger anyway (really shows how little weight on the tail is needed to raise the nose). Unless of course there is a nose ring that is tied down, but in all my years, I've never seen one used. Even tho most Cessnas have em.

Alan