29’s-31’s and a long , flat prop for a 7GCBC ?

Gillie

Gillie

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Sep 15, 2019
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Roundup , MT
Hi , I have a 73 Bellanca GCBC and also have a short , narrow , one way in , one way out dirt strip @3500’.
Im wanting to put 29” or 31” tires and a 80” seaplane prop on her . Has anybody here done likewise ? If so could you please school me about the process as far as STC’s , 337’s and or field approvals . I have seen similar setups on 7GCBC’s that have put the bigger tires on the stock Citabria spring gear , not Scout gear . I would like to go that route if possible . Any advise about wheels and brakes would also be a big help .
Are VG’s a realistic way to lower stall speed and get improved slow speed handling ? I see lots of pros and cons .
Thanks !
Gillie
 
Hi Gillie. There's nothing worse than a new thread with no replies! Your questions are so specific that I'm guessing there aren't many people out there with the specific experience needed to give you a really good answer. In that case, IMHO, you might want to call the factory and speak with Dale, he's the most well versed guy out there and he might even be able to refer you to someone that is already flying the configuration you're interested in.

Good luck!
 
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He ought to be able to get a comment on the VGs. I have no experience with VGs on Citabrias so cannot help.

I have flown every variant on the Super Cub, and Micros on the C-180. I can perceive no advantage, but proponents tell me I have no "feel" for airplanes. I teach these same folks slow flight and stalls, and they are often surprised at what I show them. On the other hand, I make it a point to not operate out of any strip where big tires and long props are the difference between success and failure. No cojones.
 
Hi Gillie,

How short of a strip we talking?

I've got a 69 7GCBC rolling on 31s with stock gear. Alaska bush wheels are STC'd for these planes. I like both the 29s and 31s. depends on what you want to run over. I don't care to run over things or land on too rough of places, so I was looking for 29s, but found these 31s in like new condition for a good price so I went that route.
I have a seaplane prop for it when its on floats, but I run a 74-52(I think) on wheels. I have flown on wheels with both props and I decided on the 74 because a) its way cheaper and easier to find, therefore I care less about rock dings and normal off airport wear and tear, b) more prop clearance so it'll hopefully be less likely to be dinged, c) faster cruise. The performance is great I think. I don't measure my takeoff and landings (I know, not a true Alaskan Pilot thing to do!) I do have 160hp spinning the club, so that helps. Both these props are on the type cert, so just logbook entry. The seaplane prop is 1A175GMA80-46. If you are just seeking to eek a little more out, you can take your prop to a prop shop and have them flatten it. There may be other STC'd props out there.
I believe that Alaska Airframes, bushwheel wheels and double puck brakes are direct replacement approved, just logbook entry. You will want to upgrade your axles. I believe scout axles are direct replacement as well. I have c-180 aluminum solid axles on my plane.
My plane has VG's. You have to really try to get it to break at stall. If you just ease into, it'll just start to sink much like a cub. I have no idea how much they actually shorten takeoff and landing distance, but they do make the stall way more benign. I'm rebuilding the wings right now. I would likely not put them back on, but the wife told me I am so, vg's it is. Maybe someone here has gone from no vgs to vgs and they may be able to tell you if they are worth it.

I think pretty much all your asking for is approved, and easy to do. Call Airframes and they should be able to take care off all the landing gear bits.
The props are just logbook entry.

If you never want to do acro, there is a leading edge cuff. Crosswinds I believe? Made in Alaska of course. I have seen them, but have no data on it.

I am of firm belief that one of the best performance gainers is weight. Adding a bunch of stuff to improve performance adds weight that it needs to overcome. Look to see where you can shed weight. firewall battery? Ditching panel fillers that aren't working, or used? toss the carpet? Just a couple ideas

Good luck
 

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Bartman said:
@Tangogawd Awesome reply! Thanks!
Click to expand...
Thanks much for the replies fellas , Tangogawd , you answered all my questions , thanks for taking the time and posting the pic ( great lookin bird ). To answer your question , the strip is 900x35 with high ground on 3 sides . I can get in . But have only just completed the strip and get out OK at temps below 35deg F and half fuel by myself (180lbs dressed ). My abort point is at the halfway mark , departure is down hill but staying in ground effect much further than the end of the strip is difficult as the ground is rough , broken type creek bottom with high ground /trees on on both sides .
I figgured that the bigger tires would give me a more favorible AOA and needed ground clearance for a longer prop .
prop on her now is a Seninich 74/52 . Stock Lyc O320 A2B 150 hp .
 
That is tight. I want a video of this approach and takeoff!

The bigger tires will help greatly with takeoff AOA. 31s will give more than 29s, and they will be more cushion if you have to "drop" it in.

let us know what you end up doing
 
Are you sure this isn't Super Cub territory?

On the VGs, a very smart aerodynamicist has posted that they keep the flow attached longer during the stall, but let go more abruptly.
Another aerodynamicist who teaches at UCSD says that VGs are to correct mistakes.

Here is my experience with Cub VGs - during Covid, I sent a student up with another instructor with the idea that they would explore stalls. They came back and said that they could not stall the aircraft.

So I took it up. It does stall! Without warning, the left wing drops. Power on, it is worse. Full power it enters a spin! Like, right now!

In defense of the VGs, the aircraft is mis-rigged, to compensate for mismatched ailerons - common in Cubs.

We have another 160 Cub with VGs that has relatively benign stall characteristics - I cannot tell if the VGs have any effect, but a full power full flap stall is preceded by a standard buffet, and then the nose gently pitches down. That's the way most Cubs behave.

And by standard buffet, i don't mean the kind with unlimited roast beef.
 
Thanks again guys . I’ll see what I can do about some video and I will be sure to let you all know what I end up doing .
I’ll most likely have a few or more questions and really appreciate the info / opinions.
 
I agree with Bob on the VGs. I can not comment to the 7gcbc, because I haven't flown the 2 setups, but I think they are worthless on a cub. Many guys tell me otherwise, but I have flown cubs in AK bush and really couldn't tell you if they do much for working the plane. I have also flown cessnas in both configurations. I 'feel' that it has more effect on the cessna wing. But I am still not installing them on my C-180.

I was thinking the same about this being 'cub' territory, but GCBC if kept light should continue to work.
 
I have use of a 1500x50‘ strip on my neighbors place that I would use to drop off or pick up back seat passengers and fuel up for extended flights . Will not use my strip for those purposes .
I can’t see where VG’s could hurt but I cant stand the thought of trying to get them clean after flying thru a swarm of grasshoppers .
 
On the 180 - my buddy had a nice later Cessna, and I loved flying it (not as much as I loved the early '59 with Horton leading edges). So he put the Sportsman kit on. I don't remember flying just the sportsman; I think he had the Micro VGs put on at the same time. I asked the mechanics to get the Sportsman template, but they just used the stock template and glued them on.
After that I was never comfortable below 70 on approach. A good Cessna with a cuff can approach at 60.
Talked to a couple of VG experts. They agreed that the combination was not good.
I do love the 180. The Decathlon turned out a better choice for me, although not as much fun in the pattern.
 
Gillie, VGs wont hurt. I don't operate into places that I would NEED that little bit 3 kts slower speed. Just don't care to. I also ski fly in the winter, and VGs with wing covers is a major pain in the.....

I plan on doing a sportsman cuff on the 180 in the fall. Mostly because the leading edges are beat to hell and the sportsman is cheaper than reskinning. I have many friends with sportsman and VGs and they swear by it. But I wont be installing VGs.

The 180 is the 'working' and hauling plane. The 7gcbc is the the fun plane!
 
Once somebody spends $3-4 grand on a mod, they have to love it. They become fervent.
 
I had aero straight skis but never ran them. I'm too far from the runway and there is too much out dirt in between so I got rid if them. I need some sort of wheel ski. I'd like to see a set of Trick skis and/or Summit skis. I want to check them out before dropping that much money.

I run Schneider 4000 penetration skis on the C180
 
Tangogawd , question if I may ......is the stock gear that you are running your 31’s on steel or the newer aluminum ?
Also , I read a post from last year where you mentioned that you had a couple pair of Scout gear . Still have a pair and might they be for sale ?
Thanks
Gillie
 
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