Gross Weight Increase?

[doczee]

OK. These are all old posts. Anyone got any up-to-date facts or opinions on Wips mod? Thanks

[Steve Pierce]

It is a pain to install but not that big of a deal. It works, gets you a 2000 lb GW and have seen no issues in any of the 2000 lb GW Super Cubs I maintain.

[Bearhawk Builder]

What do you want to know? Just put one in at rebuild, easy to do at that point. It’s a simple kit with a rear spar reinforcement and fuselage ‘witness tube’. Expensive but makes sense to do while you’re there.

[The Kid]

I thought Whips gross weight increase STC allowed the user to use ANY floats he wanted; not just Whips?

[mvivion]

It’s now also approved on EDOs I believe. Talk to Wip.

MTV

[60below]

That's true, Mike. The only modification so I can use my Edos was to my wallet for the paperwork, but it's nice to have.

[jokerswe2008]

The 2000 lb gross weight increase STC belongs to Wipline. It is a big hassle to install unless you're re-covering the wings. It requires installing a cap strip on the rear spar at the lift strut attach bracket. It also requires welding or clamping a small diagonal tube to the rear seat front cross over tube at the door opening. On wheels it requires a 5/8" square tube on the upper gear legs.

It only allows for 2000 lb GW on Wipline floats or when on wheels.

Most guys just blow it off and fly like the planes have been for 50 years prior to the Wip STC. The Wip STC is more of a paperwork GW increase then actually making the plane safer.

Crash

There is actually some structural modifications. How did it work out for you?!
/AlaskaCubEU

[bob turner]

I haven't read the STC; I thought it was a 1/2" square tube. Hard to believe that tube adds anything structurally, but a friend did a heavy brake application on my Cub and the little Vee- thing broke! All of my gear legs now have a half inch square 4130 tube - mostly so the fabric doesn't pull it into an arc.

[Dave Calkins]

Installing the Wip upgross is not difficult, in my experience. I did one in the 90’s.

It involves a rear spar cap reinforcement and wing rib reinforcement gussets to alleviate crumpling of the rear spar, which is the failure mode for an overloaded wing, in multiple tests. The rear spar is upset from its vertical alignment at failure, and kindof twists, then crumples. Stabilizing it from twisting solves the issue in tested examples. That is why I guess Javrons simple sheet metal scheme works.

Also, a brace is added to the fuselage from near the aft lower door sill to the rear seat front cross tube. This brace stabilizes the fuselage in the door opening area from rear landing gear tube loads at higher weights. The kit I installed had a machined aluminum “channel” that bolts in place. A steel tube may be welded-in for an uncovered fuselage instead of the alu channel.

Also, the square tube is added to the gear leg “v” to further stabilze and integrate the gear leg loads.

1. the fabric on top of the wing is cut above the rear spar spanwise a couple of ribs inboard and outboard from the aft strut fittings.

2. wing rib attach bracketry is removed and thicker, larger gussets are riveted to the ribs.

3. a machined “cap” is placed on top of the rear spar and blind riveted to the spar.

4. wing top fabric is repaired.

5. bolt in the fuselage stabilizing brace at the rear door sill/rear seat front tube.

6. square tube is added to the gear leg v. Most new landing gear these days already have this tube.

The only “ pain” I found is matching the topcoat color on the fabric repair on top of the wing.

I think its good insurance, and it is nice to not break the law since you are gonna load that Cub anyway.

Pierce, what was the real pain?

Bob, that little fabric tacker shouldnt have failed from brake application, any other issues that go with it?

[mvivion]

One thing that some folks don’t consider is that a lot of folks here earn their living with airplanes. For many others, flying is a dream come true. In either case, a relatively minor “event” could conceivably result in the loss of flying privileges for some period of time.

Granted, that likelihood may be remote, but none of us needs that kind of hassle. So, the Half Ton Cub kit makes a great airplane even better, and affords some comfort if the worst were to happen. Cheap insurance, frankly.

If this kit were available when I owned a Super Cub, I’d have owned it a lot longer.

MTV

[Amy]

Hello from your friendly Wipaire rep (and Cub fan since long before)!

The gross weight increase kit has three main components: 1) Rear spar cap, 2) fuselage brace, and 3) gear reinforcement.

If you have purchased a new fuselage or landing gear in the past 10ish years, you probably have items 2 and 3 covered. Nevertheless, the kit includes the fuselage brace (both a weld-in and bolt-in option in case you are working on a covered airplane) and the gear reinforcement. I tell people to use these as conversation piece paperweights if you don't need them.

The rear spar cap is most easily installed when the wing is uncovered but many folks, including several members here, have done installs on covered airplanes. It just takes a bit more time.

Originally, the kit was only compatible on wheels and Wipline 2100 floats. EDO 2000 floats have subsequently been approved as well. I believe Aerocet established compatibility on their own with our mod and their 2200 floats; this type of approach would apply to any other floats - if the float manufacturer can substantiate the higher gross and has the paperwork for it, you can be covered by that. Specify at time of order what gear type you will be on and we can include the appropriate flight manual supplements. If you call later a paperwork fee may apply so tell me when you order the kit and save yourself a few bucks in the future.

There are some other requirements for the gross weight increase to apply as well. First, you have to start with a 1,750 lb. gross weight airplane. This can be a factory gross weight or an earlier fuselage modified to the 1,750 lb. gross weight. You will also need certain shock struts, cabane V, and bungees, plus the Pawnee 4-leaf, 1-hole tailspring. As with many Cub mods, there is flexibility for it to be the modified equivalent, and for the installer to determine compatibility of any previously installed modifications.

If you are ordering new wings, manufacturers like Dakota Cub can install the spar cap when they build up the wing for you.

I'm obviously a bit biased, but if you have the wing uncovered, I strongly recommend installing the gross weight kit. You won't have to cut into anything later, it's faster and easier to install at that point, and it helps resale if you ever part with your Cub. Plus, things never seem to get cheaper so spring for it when you have the opportunity.

Last but not least, you are eligible for a discount on the kit if you are buying it with Wipline 2100 floats.

If you have any questions or want any more info, feel free to give me a call directly at 651-414-6839.

--Amy

[Steve Pierce]

Pierce, what was the real pain?

Trying to drill the Piper rivets. Have since found how to use a Dremel tool for that job.

[mike mcs repair]

Trying to drill the Piper rivets.

yup!!

[skywagon8a]

Thanks Dave, that is the best explanation of how and why. I have wondered why and your post answers my questions.

[hotrod180]

…. the Half Ton Cub kit makes a great airplane even better,.....

HALF ton?

[mvivion]

HALF ton?

Oops.....the One Ton Cub. My bad

MTV

[StudentPilot479]

Unless you are on wheels - then it is the Almost One Ton Cub unless you will be burning 16.7 US gallons (or dropping an equivalent weight) before landing to get down to the 1900 lb MLW.

[cubpilot2]

I've gotten tired of potentially crowding the GW limit and am installing the GW kit on my 180 18A this winter.
Just got the kit from Amy.

Retiring in January and have plenty of time now; so all new fabric on wings and controls. (even though they really don't need it).

The ramp check Team was out in force this year at Lake Hood and reportedly using Gestapo tactics. Lots of people nervous, so this will lessen the concern.

[stewartb]

Congrats on retirement!

[mike mcs repair]

I've gotten tired of potentially crowding the GW limit and am installing the GW kit on my 180 18A this winter.
Just got the kit from Amy.

Retiring in January and have plenty of time now; so all new fabric on wings and controls. (even though they really don't need it).

The ramp check Team was out in force this year at Lake Hood and reportedly using Gestapo tactics. Lots of people nervous, so this will lessen the concern.

easy to install gross weight stuff in covered wings..... just ask

[cubpilot2]

easy to install gross weight stuff in covered wings..... just ask

Thanks Mike: Ive seen your description of doing that before and is an excellent approach.

I actually have a few other reasons/excuses for recovering the entire thing. One being age of some of the fabric; with wings at about 15 years, controls and fuselage is 28 years so its mostly just about age.

Plan to completely redo this thing to try and make it as nice as my recently restored 150 horse 18A.
The wife and I are planning to take one of the cubs "outside" (lower 48 ) to tour the country from end to end. (bucket list thing.) The 180 will do a better job in the higher elevations as we may be a bit heavy.

Beside that this cub has been in the family since 1991 and she's been a good girl. She deserves a little TLC. Plan to keep her around until its over.....