Tail Jig: Small, Simple?

[KatieB]

Question for the old-school builders who didn't have pre-punched skins.

I want to build a jig for skinning my -3's horizontal stab tomorrow. I am not crazy about building a floor-to-ceiling monstrosity of a wing/tail jig like Van suggests, since our temporary workshop is a fully-drywalled 2-car garage that I'm sharing with Ben's RV-8 in finishing. My jig will need to be mobile.

I like the small free-standing jig shown in Louise's RV-3 "Junior" album, and thinking of doing something like that. Anyone have any other good ideas, or things to avoid? Looking to stay simple, small, and cheap. In that order.

[Andy Hill]

Hi Katie...

Van's jig, as you say, is that large since it is also a wing jig.

However, if you want <<My jig will need to be mobile.>> I think you will be limited to welding up a metal one? Any wood construction relies on the floor and/or ceiling to provide the necessary rigidity. I can assure you the components mounted in the jig are placed under fairly high forces during the contruction process (straps etc.) and the slightest flexibility will see your construction warped

NB from Rob H

Unfortunately, I found a slight twist in the tip of the right side. After what felt like an endless debate, I've decided to redo the HS. I just would not feel comfortable with any twist, especially when I?m at 8,000 ft going 200mph. I guess this is to be expected, after all, it has been a steep learning curve

- I am sure Rob could expand, and others, even Vans might have said "use it", but it's a lot of effort to be wasted.

In general there are a few ways to better what Van's advises, but you really need to know exactly what/why you are doing.

Looking at the one's Russell did (in Lousie's album) my instinct is it is marginal. It relies very much on the long horizontal arms being on absolutely level floor - the slightest difference on floor level between the ends will be reflected in the HS. I would also add some cross braces at each end - that would make the jig more rigid, albeit not solve the floor level problem.

Just my 2c

Andy
RV-8 G-HILZ
RV-8tors
RV-3 coming on slowly

[Ironflight]

I concur with most all of what you said Andy - the jig is important if you want a straight structure with the -3 kit.

Originally Posted by Andy Hill

Looking at the one's Russell did (in Lousie's album) my instinct is it is marginal. It relies very much on the long horizontal arms being on absolutely level floor - the slightest difference on floor level between the ends will be reflected in the HS. I would also add some cross braces at each end - that would make the jig more rigid, albeit not solve the floor level problem.

In defense of "our" tail, Rus was building his fifth RV, so he probably knew that what he was doing would work. Which isn't to say that the pictures tell the whoel story.....

[Tony Spicer]

Katie,

Just tell Ben to move over a bit (and tell him I said hi). Here's what I used for the hs/vs.

http://picasaweb.google.com/tonyboyt...02280245081554

When Ben gets the -8 out of your garage you can move the uprights farher apart and you'll be ready for the wing.

Tony

[rocketbob]

When I built the HS for my Rocket it was going to be problemmatic to build the traditional tail jig since the ceiling is 12ft tall in my hangar. I had some 4" rectangular steel tubing laying around so I fabricated a box by welding it together on a flat table. I also put some "feet" on the jig by welding two legs perpendicular to the box so it would sit upright on the table. It worked out great because the box becomes your planar reference. So to align the center ribs all one has to do is lay straight edges across the box. Doing it this way is better than trying to use plumb bobs IMO.

[KatieB]

Well we were able to make a compromise to fit the 10' finished ceiling and the smallish space. I read your great responses this morning and yes, it would be silly to make a movable jig, since no floor is perfectly level. We built a jig with 4x4 uprights and cross-feet that are anchored to the cement floor. With those up and level, we built a cross member box with 3 of the straightest 2x6's Lowes had. Every dimension is level, square and immobile. Now i have to make the brackets to attach the elevator hinges. It's tall enough so that I can still run a line across the centers of the uprights and drop the plumb bob to check the squareness of the entire stab during the skinning process. Time will tell if it works as designed. (the steel is a great idea too, if we had steel and a welder... maybe for the wings.)

Tony, Ben says HI to you too. He probably wouldn't appreciate me telling him where to stick his -8. I've already told him that a workshop is no place for a car...

[rph142]

Katie,
Dont skimp on the brackets that attach the jig to the tip ribs either. Looking back I think my jig was plenty strong, but the 3/8" threaded rods that tied the ribs to the jig were probably too flexible. On my second HS I used the same rod, but shortened the distance between the upright and tip rib. The center support that located the root ribs must also be very rigid.

My first HS had a degree or two of twist between the two tips - easily visible by eye. Vans basically gave me their canned answer "you want to build as straight as possible but remember your not building a watch". In the end it only took 4 or 5 days to rebuild the entire HS. Now I know how guys finish these things in less than 2 years. Good luck.

[JonJay]

[quote=KatieB;495556] Now i have to make the brackets to attach the elevator hinges. QUOTE]

I believe Cleveland and Avery still sell these brackets premanufactured.

[KatieB]

Seeing as I have to make almost every part of this airplane, I don't think I could live with myself if I bought premade jig parts!

[Kiwi]

Originally Posted by KatieB

Question for the old-school builders who didn't have pre-punched skins.

I want to build a jig for skinning my -3's horizontal stab tomorrow. I am not crazy about building a floor-to-ceiling monstrosity of a wing/tail jig like Van suggests, since our temporary workshop is a fully-drywalled 2-car garage that I'm sharing with Ben's RV-8 in finishing. My jig will need to be mobile.

I like the small free-standing jig shown in Louise's RV-3 "Junior" album, and thinking of doing something like that. Anyone have any other good ideas, or things to avoid? Looking to stay simple, small, and cheap. In that order.

I built my "old-school" small tail RV-6 fin without a jig. I attached the rear spar (without the hinges) to a flat table purposely shimmed such that with the rear edges of the skin hard against the table, there was the proper overlap from the rear spar. Quite honestly with .032 thick skins, it naturally doesn't want to twist. These skins on a Cessna are .025 and their surfaces are bigger.

I screwed strips of wood to the table to hold the skin hard against the spar and liberally used skin edge clamps on the ribs at the "ends". I then used a rafter square to check it was sitting vertical and stood back and eye-balled it to check for any twist.

Once happy I used one of the time-honoured methods for drilling off the skin to the ribs and spars, and that is pretty much it.

Whatever you do, you use a method you are comfortable with.

Cheers,
Andrew.