Ryan Murphy
Registered User
Charlie,
very similar indeed. Looking forward to going through your build.
Thank you,
Ryan
very similar indeed. Looking forward to going through your build.
Thank you,
Ryan
New build with lots of mods
- Thread starter Ryan Murphy
- Start date
skywagon8a
MEMBER
SE Mass MA6
Ryan, In what part of the World are you located? I can't quite make out your licence plate.
Ryan Murphy
Registered User
Removable rear seat cross bar question
All,
I would like to permanently remove the rear seat cross bar. From what I understand, it is required for flight. Anyone have any experience with such a modification?
the masking tape is my idea for substitute bracing.
All,
I would like to permanently remove the rear seat cross bar. From what I understand, it is required for flight. Anyone have any experience with such a modification?
the masking tape is my idea for substitute bracing.
Attachments
Ryan Murphy
Registered User
N1PA,
I’m in Prescott,AZ. Need to update my profile.
Ryan
I’m in Prescott,AZ. Need to update my profile.
Ryan
Paul Heinrich
PARTNER
Illinois & Wisconsin
I’m pretty sure that the upper crossbar is the only thing that keeps the sides from folding in or out. I wouldn’t mess with the geometry of such a critical structure.
And how would you support the rear seat if you do change it to your suggested geometry?
Why would you want to permanently remove it anyway?
And how would you support the rear seat if you do change it to your suggested geometry?
Why would you want to permanently remove it anyway?
mike mcs repair
Registered User
chugiak AK
the original cross bar was paper thin folded into a square tube like the compression members in wings early on... not much strength there...
you are best to just weld in a cross bar, then cut at edges 3/4 through about 1 1/2" or 2" from sides (remember left side has fuel lines behind panel and needs longer stub...) then you weld on a cap to center section, and drill and pin outer stubs... you can weld pins in, or use removable pins....
you are best to just weld in a cross bar, then cut at edges 3/4 through about 1 1/2" or 2" from sides (remember left side has fuel lines behind panel and needs longer stub...) then you weld on a cap to center section, and drill and pin outer stubs... you can weld pins in, or use removable pins....
Without the bar in place it is pretty easy to move the side of the fuselage in and out. I have had dogs get under it and lift it up when flying, plane did not fall out of the sky but for rough backcountry work I would want it in place. I don't think bars in place of the tape would really do the job, and they take up a lot of space. While we are on that section of the fuselage, a few questions. Why did you want to remove the bar? It is normally the support for the rear seat back. Are you going flat floor or raised floor? Are you doing extended baggage? Do you plan to sleep in the plane? I would recommend you look at the Willow mountain door mod at airframes. Consider making the bottom of the door flush to the floor for sliding heavy stuff in and out. I don't think I have ever heard anyone say the baggage door was too big.
DENNY
DENNY
Ryan Murphy
Registered User
Thanks guys.
Yes, flat floor, mounting directly to lower longeron “similar to Willow Mountain”with extended baggage. My hope was to have a sling style rear seat similar to a carbon cub.
Thanks again for the suggestions
Ryan
Yes, flat floor, mounting directly to lower longeron “similar to Willow Mountain”with extended baggage. My hope was to have a sling style rear seat similar to a carbon cub.
Thanks again for the suggestions
Ryan
Ryan Murphy
Registered User
Update:
Tail wheel pretty much complete. Added a bump stop, additional tubing and gussets. I was working on TW steering; however, the complexity is getting a bit out of control. TW will free castor for now.
Routed cables and temporarily installed pulleys. Elevator and rudder cables will be mounted under the fuselage. Baggage floor will be mounted to lower longerons.
Tail wheel pretty much complete. Added a bump stop, additional tubing and gussets. I was working on TW steering; however, the complexity is getting a bit out of control. TW will free castor for now.
Routed cables and temporarily installed pulleys. Elevator and rudder cables will be mounted under the fuselage. Baggage floor will be mounted to lower longerons.
Attachments
Last edited:
Ryan Murphy
Registered User
The main gear and tail wheel added a bit of weight. Now that they are close to complete, I am switching gears and going on a diet. Without sacrificing too many luxuries, the new goal is weight savings.
Working on carbon fiber parts now. Building a seat and laying up panels and floor boards.
Sent from my iPad using SuperCub.Org mobile app
Working on carbon fiber parts now. Building a seat and laying up panels and floor boards.
Sent from my iPad using SuperCub.Org mobile app
Attachments
Ryan Murphy
Registered User
Attachments
Ryan Murphy
Registered User
Attachments
courierguy
MEMBER
Inkom, Idaho
I have a flying buddy in Prescott, if you ever see A to Z Crane (his outfit) working in town, and a short stocky guy at the controls, go up and tell him (Terry) there's a big pool of hydraulic oil underneath his machine, and it's just gushing out. Crane joke....
FWIW I have conventional cub style gear on my Rans S-7S, and it's shock struts use both 1380HD shock cords and the Fox airshocks. The shocks have been idiot proof, when I think to check the pressure I find it's the same as last time, and that may have been several months. Mine came with a special small volume/high pressure pump. Tiny and light, I don't fly with it because I don't feel the need. I think I'm running 125 psi.
Ryan Murphy
Registered User
Small world. I met Terry a few months ago while helping frame a friends house. He was the one flying the trusses.
Sent from my iPad using SuperCub.Org
Sent from my iPad using SuperCub.Org
Diablo Rojo
Registered User
This build is awesome, i like the gear and am going to have to steal some of your ideas, nice work
labrador_cub
Registered User
Wabush,NL
someone correct me if I'm wrong but didn't piper do exactly this when they built the PA14? I remember that being a point of interest talking about how they upped the gross weight from the PA12 while not adding any tubes but in fact effectively removing structure by changing the rear seat. I know My wag fuselage has no mention of a tube there, in fact after just flicking through my plans twice I cant find anything on the rear seat...
skywagon8a
MEMBER
SE Mass MA6
It's more likely the cross tube is required for landing. Holding the fuselage in shape due to landing impact loads. Imagine where the loads go with the landing gear pushing back and upward along with the wings pushing down. Wouldn't that tube keep the fuselage sides from pushing outward?
labrador_cub
Registered User
Wabush,NL
I can see what your saying and I agree a downward motion on the rear spar carry through will cause the upper longerons to bow out in the rear seat area, but honestly I cant see much movement be transferred through the rear door post tubes, they are relatively small and in order for them to go down the 1 inch tubes and cathedral that go to the next station back would have to push that point rearward to allow a downward movement, similar to how the front spar carry through on a pa18 stays in place just fine with just the tubes going to the firewall and panel location where as the earlier pa12 and 14 have them and the 2 additional larger 1" tubes going right to the gear fitting.
also I located my page with the seat drawings, I remembered after I removed it from my plans book because wag had it between 2 of the main fuselage pages and it was in the way flicking back and forth. but indeed the upper rear seat tube is non structural in the wag plans at least, been trying to dig up what was originally in the pa14. in fact the way wag has the plans drawn the rear seat would fall out if that location bowed out just 1/2" so I'm guessing there's little to no defection. that or a lot of back seat passengers had a rough landing after they ell into the baggage area! FWIW I also plan on this tube being non structural in my plane.
Edit: I should also mention Ryan I really like this build! your doing good work and we must think kinda alike because your tail wheel suspension is almost exactly what I had in my head for mine! keep up the out of box thinking as charlie said I too like seeing it!
also I located my page with the seat drawings, I remembered after I removed it from my plans book because wag had it between 2 of the main fuselage pages and it was in the way flicking back and forth. but indeed the upper rear seat tube is non structural in the wag plans at least, been trying to dig up what was originally in the pa14. in fact the way wag has the plans drawn the rear seat would fall out if that location bowed out just 1/2" so I'm guessing there's little to no defection. that or a lot of back seat passengers had a rough landing after they ell into the baggage area! FWIW I also plan on this tube being non structural in my plane.
Edit: I should also mention Ryan I really like this build! your doing good work and we must think kinda alike because your tail wheel suspension is almost exactly what I had in my head for mine! keep up the out of box thinking as charlie said I too like seeing it!
Last edited:
skywagon8a
MEMBER
SE Mass MA6
Both Ryan and Labrador_Cub,
Unless you are engineers with an understanding of tubular structures, I would be very careful before removing a tube which Piper originally had in their design. Just one of those tubes being removed can change the load paths of the entire structure. Piper's engineers didn't put extra tubes in there if they weren't needed. Keep in mind, Piper was very conservative. If they could save a few pennies by leaving out an unnecessary tube they would. A small tube doesn't necessarily carry a load, it may just be holding a load carrying tube in alignment so that it doesn't buckle.
I'm not certain how much engineering Wag did for their drawings. I was under the impression they just copied Piper's. If there s a tube missing on their drawings, I would be suspicious they just missed drawing it in. All that is necessary to make drawings is a draftsman and a printing press. At the time Wag began printing these drawings, there were often questions about the airworthiness of the items they sold. Buyer beware.
A missed tube may have unseen consequences. Perhaps by not being there, a crack or break will form in a location which you would not suspect?
I have witnessed an extended rudder balance arm failing a flutter test on a sheet metal rudder. The fix...... add one 1/8" rivet on each side. Just one rivet !
Unless you are engineers with an understanding of tubular structures, I would be very careful before removing a tube which Piper originally had in their design. Just one of those tubes being removed can change the load paths of the entire structure. Piper's engineers didn't put extra tubes in there if they weren't needed. Keep in mind, Piper was very conservative. If they could save a few pennies by leaving out an unnecessary tube they would. A small tube doesn't necessarily carry a load, it may just be holding a load carrying tube in alignment so that it doesn't buckle.
I'm not certain how much engineering Wag did for their drawings. I was under the impression they just copied Piper's. If there s a tube missing on their drawings, I would be suspicious they just missed drawing it in. All that is necessary to make drawings is a draftsman and a printing press. At the time Wag began printing these drawings, there were often questions about the airworthiness of the items they sold. Buyer beware.
A missed tube may have unseen consequences. Perhaps by not being there, a crack or break will form in a location which you would not suspect?
I have witnessed an extended rudder balance arm failing a flutter test on a sheet metal rudder. The fix...... add one 1/8" rivet on each side. Just one rivet !
Re: removal of the cross tube. When I built my old PA-12 I got field approval for removable rear seat tubes. My FAA guy was helpful and insisted the tubes be placarded to be installed for flight. I asked why and was told the sides will bulge out with tail loads. The demonstration (I never did it) was to load the plane heavily on the ground with the tubes out and then try to place the tubes. I was told the pins wouldn't align. That same flex would happen as I landed or taxied over rough ground. I was pleased to have the tubes removable for ease of loading but can't think of any time I'd need them out for flight.
In my new Cub the upper longerons are on top and it's fairly easy to make them bow by applying a load to the tail. Mike and I agreed that's something to watch and probably brace with a clamp-in tube in the future.
In my new Cub the upper longerons are on top and it's fairly easy to make them bow by applying a load to the tail. Mike and I agreed that's something to watch and probably brace with a clamp-in tube in the future.
Ryan Murphy
Registered User
Rear seat crossbar
Thank you all so much for the compliments, comments and advice! I have decided to leave the removable, rear seat crossbar unmolested and intact. I do really like the Carbon Cub sling style rear seat, It’s just not gonna happen on this build. The sides of the fuselage in the area of the rear seat cross tube make a long and unsupported span. I agree, something needs to be there to prevent deflection.
Again, thank you all for the help
Ryan
Thank you all so much for the compliments, comments and advice! I have decided to leave the removable, rear seat crossbar unmolested and intact. I do really like the Carbon Cub sling style rear seat, It’s just not gonna happen on this build. The sides of the fuselage in the area of the rear seat cross tube make a long and unsupported span. I agree, something needs to be there to prevent deflection.
Again, thank you all for the help
Ryan
courierguy
MEMBER
Inkom, Idaho
The newer versions of the Rans S-7S have no cross bar behind the passenger seat, where my 13 year old model does. When I noticed that, I thought of SC's I had seen with that bar being removable. I believe they trussed the cabin sides in a way to handle the expected loads, to transfer the forces up into the upper and lower crossover tubes. or something like that. Point being, they re-engineered things back there, just didn't remove it.
They touted it as "opening up the baggage compartment," or words to that effect. I didn't like it, I like having a distinct rear baggage area, with the stuff in there not being able to slide forward or get mixed up with the junk on what I call my forward cargo deck. That's an aircraft ply platform I made that pins into the hardware that normally secures the passenger seat, and goes in or comes out in seconds. Between the two, I have a bit over 5' of baggage area, and I even plywooded the bulkhead below the hor tube to further keep things separate. MOST importantly for me, my Montague bike's rear tire is nicely supported by that horizontal crossbar, it jams in there just perfect, between it and the upper crossover tube, and losing that tube would mean I'd have to "re-engineer" how I carry my bike.
I remember at JC several years ago, various personages were taking my folding hot rod ebike for a spin, and after Joe Dory finally came back with it (with what we call the ebike grin, they're fun) Jim Richmond from Cub Crafters took a ride next. When he got back, talk of how it would fit in a Cub came up, in particular the new at the time X Cub. Turns out, it wouldn't, due to the non folding front seat. This of course made my day, making my lowly S-7S superior in one respect to the X Cub, it also queered my idea of buying one, I put my checkbook away. Just kidding there.... Unless you have big ass doors/door like the S-7S does, that folding pilot seat is a must in my book, I was quite surprised to find that all SC seats didn't fold, as stock.
They touted it as "opening up the baggage compartment," or words to that effect. I didn't like it, I like having a distinct rear baggage area, with the stuff in there not being able to slide forward or get mixed up with the junk on what I call my forward cargo deck. That's an aircraft ply platform I made that pins into the hardware that normally secures the passenger seat, and goes in or comes out in seconds. Between the two, I have a bit over 5' of baggage area, and I even plywooded the bulkhead below the hor tube to further keep things separate. MOST importantly for me, my Montague bike's rear tire is nicely supported by that horizontal crossbar, it jams in there just perfect, between it and the upper crossover tube, and losing that tube would mean I'd have to "re-engineer" how I carry my bike.
I remember at JC several years ago, various personages were taking my folding hot rod ebike for a spin, and after Joe Dory finally came back with it (with what we call the ebike grin, they're fun) Jim Richmond from Cub Crafters took a ride next. When he got back, talk of how it would fit in a Cub came up, in particular the new at the time X Cub. Turns out, it wouldn't, due to the non folding front seat. This of course made my day, making my lowly S-7S superior in one respect to the X Cub, it also queered my idea of buying one, I put my checkbook away. Just kidding there.... Unless you have big ass doors/door like the S-7S does, that folding pilot seat is a must in my book, I was quite surprised to find that all SC seats didn't fold, as stock.
