Hi all, First post on here but have spent a lot of time reading over the years. I am considering scratch building the 2+2. But I am trying to figure out the difference in weight to the PA-14. I want to build it as light as possible and try to keep it as as cub like as I can and hopefully keep my fuel burn down. Can anyone explain the the gross increase on the 2+2 over the 14. I’m guessing it has to do with what wing is used….. I won’t be building the wood wing so I’ll have to choose from something else. Cheers
Wag Aero 2+2 gross weight.
- Thread starter j-kid
- Start date
Gross weight = max weight (people, fuel, gear). That is determined by several factors including wing, landing gear, fuselage, engine, prop, climb rate. I think you are talking empty weight = plane empty just needs fuel and pilot to fly. I think Javron has about the lightest wing for what you want. You will most likely get your best fuel burn running a 0360. Fuel burn/speed changes little if any with passengers and gear in my cub. I would build the plane to fit your mission. So what is your Mission?
DENNY
DENNY
RVBottomly
PATRON
Asotin County Washington (KLWS)
J-kid, I’m building one and I had the same question. The PA 14 has a max gross of 1850 while the Wag 2+2 says 2200. I spent a lot of time trying to account for the difference but couldn’t pin it down.
Marty57 here is also building one and has a valuable website chronicling his build. He said somewhere he ask an aeronautical engineer to look at the wings and he ended up being comfortable with the Wag GW.
I’m building a wood wing and I still might get an expert’s opinion.
Sent from my iPhone using SuperCub.Org
Marty57 here is also building one and has a valuable website chronicling his build. He said somewhere he ask an aeronautical engineer to look at the wings and he ended up being comfortable with the Wag GW.
I’m building a wood wing and I still might get an expert’s opinion.
Sent from my iPhone using SuperCub.Org
Ok thanks yes that’s my question..
Yes I looked at a lot of Marty’s blog. And also another guy I was talking to has a gross weight around 2900 but it has Pawnee type wing. If I could build it to the same weights as the plans that would be perfect for me. How realistic do you think Wag Aero’s empty weight of a bit over 1000lbs is?? I would want a wing with flaps.
Yes I looked at a lot of Marty’s blog. And also another guy I was talking to has a gross weight around 2900 but it has Pawnee type wing. If I could build it to the same weights as the plans that would be perfect for me. How realistic do you think Wag Aero’s empty weight of a bit over 1000lbs is?? I would want a wing with flaps.
No I am talking Gross weight… I will look into the Javron wing… I own a Rans s7s. I Want something that flys similar to the S7 with side by side seating and room for camping gear ect. I really don’t want fuel burn over 7gph hopefully. I have looked at the bearhawk for years but I think it’s just to big and thirsty for what I want.
BC12D-4-85
SPONSOR
Fairbanks, AK.
How was the GW of the 2+2 determined?
Gary
Gary
RVBottomly
PATRON
Asotin County Washington (KLWS)
That's the question. The original designer is long gone and I don't think WagAero has anyone who can say now. I don't know if static tests were ever done or if it was calculations, or what.
I'm half way through my build and I wonder about it a lot, especially after looking at what Javron and others did to beef up wings after some actual tests.
It is a lot of work, but I'm contemplating doing static tests on my own. I'd hate to break a wing, but on the other hand, I'd rather break a wing on the ground than in the air.
RVBottomly
PATRON
Asotin County Washington (KLWS)
I think around 1000# empty is very optimistic. It is similar to a PA 12 and most of those seem to fall into the 1100-1200 range. Flaps add pounds, of course. Bigger engine than the original O-235 adds weight. Etc.
7gph is likely optimistic too if you are running a big enough engine to make it worthwhile.
Also, you might want to look closer at the side-by-side aspect of the 2+2. I widened mine a bit, but it is still going to be snug for "modern-sized" people.
skywagon8a
MEMBER
SE Mass MA6
You are dreaming if you expect to regularly get 6-7 gph with the plane loaded. The consumption is related to the amount of power being used. Unless you build in drag reduction details your plane will be flying very slow at that consumption rate.
Keep in mind that specific fuel consumption (LSA of fuel per hp per hour) goes up as you reduce power. If you are running an engine at low power settings, the fuel efficiency goes down.
From a practical standpoint, an O-320 will burn close to 8 gallons an hour and an O-360 will be more in the 9-10 gph range. To expect better than that, you are fooling yourself. My O-235 burns about 6.5 per hour, I don’t see any way you can run an O-360 at 7 efficiently.
Sent from my iPhone using Tapatalk
From a practical standpoint, an O-320 will burn close to 8 gallons an hour and an O-360 will be more in the 9-10 gph range. To expect better than that, you are fooling yourself. My O-235 burns about 6.5 per hour, I don’t see any way you can run an O-360 at 7 efficiently.
Sent from my iPhone using Tapatalk
Several factors are involved with fuel burn in fix pitch aircraft like ours. The prop you have and speed you want to cruse at is very important I have a 160 hp 0320 fly with two 180 hp cubs similar to mine in wing and mods. They are both faster and burn less fuel with the same load. I did a long fly around with a 150 hp 0320 also set up like mine and I had a better fuel burn. I went out this weekend and just played around at 6 gal/hr because I was not in a hurry to go anywhere. Came back from Kotz once with a 185 I pushed up to 2650 RPM and he pulled everything back still got to fuel stop 1/2 hour before me and we had about the same fuel burn. Things to ask yourself, how fast do I want to fly? How short of strips do I want to use? What do I want for a climb rate? We need some 0360 fish spotters to add on what kind of fuel burn they are getting. People have a very hard time getting a cub in at 1000 lbs I would say a side by side is going to be hard below 1200. But not to worry they all fly fine. DENNY
Marty57
PATRON
Nipomo, Ca
A few points about the 2+2; I'm covering mine BTW so hope to be done soon. I had to modify my wood spar to clear the lift strut; I think I had to sand a curve about 3/16" deep over a 3" area of the front spar; the modification scared me. I consulted a friend; aero engineer; who ran the numbers for me. The mod reduced the strength of the spar to something like +/-10G's at 200 knots vs the original of +/-12 g's at 250 knots. Bottom line, the wing is overbuilt. I know that isn't the only factor in GW but the wing is definitely strong. Regarding fuselage size, I chose not to widen my fuselage because modifications to one dimension seems to have a cascading effect on way to many other unforeseen issues down the line. I handled the narrow fuselage by having my seats on sliding tracks. Unless I'm getting instruction from someone with the same short stance as me, sliding one seat back keeps the shoulders from touching, making it fit a lot better. Yes, it is narrow but how often will I really fly with someone else up front? I also added flaps to my wing, and I added the standard bow wing tip so that made changes to my wing; again everything is wood. The weight of my wing (uncovered, no cables, tank, or tank bay cover) was 64 lbs. That includes the modification I made to remove the cross brace in the fuel tank bay and put a 1/8" plywood shear plate under that tank bay; again after getting calculations done to support the change. All in all, my 2+2 wing is a lot different from the plans but it still seems to be very light and strong. I feel pretty good about the 2200lb gross weight in the plans but likely won't operate at that weight since I'm using a O290D2 so my HP is a bit limited. I attached my modified drawings for my wing.
Marty57
Attachments
Last edited:
Ok thanks for all the info.. I have only ever had a rotax so it takes a bit to get my head around the different engines. I realize there is no free lunch and I don’t mind putting a bit of fuel in if I’m loaded up and going somewhere. But I still hope to be able to fly around locally without feeling like I’m speeding all my money on fuel.
Thanks Marty that’s great info. I’ll look at it more closely on the weekend. Hopefully the wag aero plans will turn up soon. What sort of cruise speed do you expect to get? I plan to fly a lot with my wife but she is not very big, I am 6ft but I’m not very wide, from my measurements I think we will fit ok…. And it’s part of the reason I like it…. I don’t want something big.
RVBottomly
PATRON
Asotin County Washington (KLWS)
Run the W&B numbers, move it forward if necessary.
Quite a few have Rotax engines here. The main reason I don't look at them is the price. That, and horsepower is a little low for this application.
An O-320 dry is around 250, and am M74DM prop is another 32 lbs. 8 qts of oil another 16 lbs. figure another couple lbs for baffles, oil cooler, and 16 lbs for the exhaust.
Add all that up, then figure the weight of the 915 ready to go with all fluids, exhaust, baffles, radiator and prop. That will give you an idea where you stand.
Not a real fan of Rotax engines, but if you are out west and need to operate from high density altitudes, you can’t beat something with a turbocharger.
Sent from my iPhone using Tapatalk
Marty57
PATRON
Nipomo, Ca
I suspect the cruise will be like a 12, maybe 110. It's a bit faster than an 18 due to the different AOA of the wing attach points. The 18 gives you shorter take off but slower cruse, 12 and 14 a bit longer takeoff but higher cruse; it's all about tradeoffs.
Marty57
Good to know there is some rotax ones out there… I haven’t been able to find much info on Rotax powered Cubs.
It’s given me a heap to mull over… I need to sit down and run some numbers. I suspect that a 915 with a constant speed airmaster prop, having the turbo would preform similar to a 160hp lycoming, both operating at 3000ft on a warm day. Most of my operation is at around 2500 DA. 50% of the time with about 220lbs load 30% around 400lbs and 20% at 500lbs
Air strips are dirt around 2000ft with rising terrain to about 500ft agl
Thanks again
Air strips are dirt around 2000ft with rising terrain to about 500ft agl
Thanks again
RVBottomly
PATRON
Asotin County Washington (KLWS)
I suppose I should have been clearer. I don't know of any actual Cubs with Rotax engines. But some here have Rans or Kitfox airplanes with Rotax. Now I remember you said you have a Rans S7.
Long ago I was thinking a Wagabond project would love a Rotax.
brown bear
Registered User
emporia ks
dont kid yourself it still takes fuel to make horsepower
https://bydanjohnson.com/flying-the-rotax-915is-aircraft-engine-comparing-to-912is/
https://bydanjohnson.com/flying-the-rotax-915is-aircraft-engine-comparing-to-912is/
