BC12d being rebuilt in Souht Africa

[Theuns]

Hi everyone

I am new to this forum and discovered it purely by chance while searching for info on the BC12d's controll collomb setup.

I am hoping to tap into the vast know-how you Taylocrafters have as it is a very rare type here in South Africa.

The plane I am re-building is a 1946 model yet strangely on the spars there is a 1942 date stamp. Maybe production was halted during the war or it was old stock spars.

The aircraft had a slight "arrival" and the fuselage was basically written off.
When I removed the fabric I found a crack in the left rear spar about 6' out from the spar to fuselage atatchment.

It was approx 1/4 the way through ,cracked top to bottom crossgrain compression failure. By the looks of it , it was a very old crack and further investigation revealed a groundloop decades before......no inspection picked it up!

I am an fabric tech by trade and have learned to put many inspection holes in the wings.

I have rebuilt the wings, including splicing in a new piece of spar to repair the crack.

The fuselage is however a problem. I have the BC12d's owner manual but compared to the Piper PA-20/22's I usually rebuild , it is very spartan with the technical drawings and detail.
I am busy with the elevator and aileron control cables. The elevator is basically sorted, the aileron cabin "closed loop" setup is really confusing me.

The cable as you know runs from the yoke mound (the inverted U shaped welded tube structure) that pivots on the side of the fuselage front lower cabin tubes.
No problem so far, BUT the turn pulley that is mounted to a swivel joint about 4" above this pivot point is where the problem comes in.

The cable then goes from the swivel pulley to the sides of the cabin, then to the top of the front cabin, then back to the top rear cabin then joins in the middle of the cabin with turbucles, exactly as I can get the small drawing figured out.

Because the pivot of the collomb unit and the swivel pulley is not the same, the aileron loop gets tighter as the collomb is pushed forward, and goes slack when the colomb moves aft (up elevator)

This to me seems very wrong as I will not be able to have a constant tention in the aileron cable setup leading to either loose ailerons (flutter??) or damaged pulleys.

Am I missing something here?? Does anyone maybe have any advice if this is indeed the correct setup?

I will post pix of what I have done on the cabin setup tomorrow.

I apologize for such a long-winded first post, but I am fresh out of ideas here :-(

Thanx

Theuns van Vuuren

[Theuns]

Re: BC12d being rebuilt in Souht Africa

Just for interest here is the wing spar repair.

Theuns

[Dick Smith]

Re: BC12d being rebuilt in Souht Africa

Theuns, Welcome to the tribe....
Using the "advanced search" feature up in the upper right-hand corner of the forum page, I typed 2 words: aileron adjustment. One comment that showed up was:

You all have hit the major areas of trouble with stiff controls but it's almost certainly too much cable tension. If any A&P has had his hands on it and doesn't understand there is NO tension on a Taylorcraft, then you will have too much and the controls will be stiff. The aileron cables actually tighten up a bit as the elevator is moved. They should be adjusted to move freely at the point of the tightest tension and there will be a considerable amount of slack in the cables. The pulley guards keep the cables from coming off the pulleys so there isn't any danger of that happening. As far as aileron droop, yes there will be a little on the ground, but in flight they should be fine. If you tighten the cables to avoid the droop, then loosen them on the other side to make up the difference. You should be able to put the ailerons wherever you want them.

OK everybody - LOOSEN UP!

Jim Zangger

ps My dad took his Taylorcraft in for an annual and the A&E (at the time) actually tightened the rudder cables because there was no tension on them! All he did was move the pedals a little farther back. You can't get any more tension than the spring gives them anyway!
---------------------
I hope this gives you some understanding of the way these planes are setup...Try using that search feature and read through a lot of the comments. You will receive plenty of help...just ask for it. Again, welcome to the Tribe...we have a lot of fun helping each other. Dick

[Hank Jarrett]

Re: BC12d being rebuilt in Souht Africa

Lots of questions that could get confusing to address all at once. You will be able to get all the information you need here put her back together but I qould suggest you go at them one at a time.
Someone needs to post a photo of the control cable runs as it will take a book to describe it. One thing to consider is add a turnbuckle in the cross piece of the "H" to allow you to level the control wheels to each other. You also want to check the position of the rivet in the gear at the front of the wheel shaft. When you look at it you will see how it is to prevent you from turning the wheel too far. I would get the "front loop" right first on the ailerons circuit. That is the most confusing to most. As soon as we have some photos we can explain it.
The rudder cables and elevator cables can be straightened out after the ailerons are done. There are several ways to screw it up, and many of us are experts at it. We can guide you through and throw some more photos up in the confusing parts.
Welcome to the Tribe! You will find after the frustration wears off, working on a Taylorcraft is a BLAST!

Hank

[Theuns]

Re: BC12d being rebuilt in Souht Africa

Dick, Hank thanx allot guys.
I knew I was at the right place to get first hand info regarding the plane.

I am surprized that the cable loop was designed to have some slack in it. But it now makes sense to me.

I will post pix of the setup as I have it now , maybe this will clarify my poor discription.

In the meantime I am replacing all the fuselage stringers with new milled Ash ones, the previous owner used totally unsuitable wood and they were all warped or broken.

Theuns

[Hank Jarrett]

Re: BC12d being rebuilt in Souht Africa

Wow! Ash stringers. Yours will be the strongest in the Tribe! If you have problems getting the Ash (kind of hard to get around here) Douglas Fir is a great substitute for Spruce. A bit stronger and a bit heavier, but on stringers, not enough to worry about.

Hank

[Theuns]

Re: BC12d being rebuilt in Souht Africa

Well maybe not as strong as the other Taylorcraft I saw here on the forum that has steel tubing for stringers!

I usually use Saligna (a type of ucalyptis) as it is stronger than Spruce at close to the same weight but there was no stock.
For the stringers the Ash will be OK even if a tad heavier, there are only a few and this plane has an O-200 for power anyway.

Theuns

[Theuns]

Re: BC12d being rebuilt in Souht Africa

When I rebuilt the wings, I stripped every not/bolt, attatchement and bracket off.
Beadblasted them all , re-primed /painted and re-enstalled with the correct bolt torques.
The leading edge skins wer all replaced with new ones imported from the US

For spars with a 1942 datestamp on them, they looked remarkably good! Maybe the varnished they had back then was not so bad afterall :-)

Then re-covered with PolliFiber.

Theuns

[Hank Jarrett]

Re: BC12d being rebuilt in Souht Africa

The old spar material was fantastic. Much of it was slow growth Sitka Spruce with very tight, straight grain. The newer stuff is still pretty good but not as strong or stable as what was harvested in the 30s through 50s. Inspect old spars carefully, but all other things being equal, an OLD set of spars is better than a new set.

Hank

[Theuns]

Re: BC12d being rebuilt in Souht Africa

Guys, a question about the elevator trim cable -

The thin trim cable that goes (180 degrees) around the front trim handle pulley I see "bites" into the pulley quite well and I am happy with that.
The pulley that sits on the elevator that actuates the screwjack and belcrank for the tab is not serviceable and I need to make a new one.
I had inmind to turn a new pulley from nylon barstock or similar.

On the Piper trim screw jack , the pulley has a spiral groove cut into it so that the cable can go arond it 1,5 times (540 degrees). This jack does however actuate the whole stab and interlinked elevators so the forces are greater than on the Taylorcraft's tab.

How does the cable go around the rear elevator mounted pulley ? Just 1/2 rotation (180 deg) or also 1.5 rotations as per Piper?

I have completed the woodwork on the fuselage, now it is just varnishing with epoxy, a few little bits to do then I will be ready for fabric.
I had to re-design the inner part of the top cabin wood as the plane will not be getting it's top windows again.
You all know how it goes, once you start to change something on a plane it has a knock-on effect that comes back to bite you! LOL

<EDIT> I found some reference on the search standards about the rear pulley dimentions and as far as I can figure out from drawings it has only one groove, this would then mean only a 180 degree turn?? <EDIT>

Thanx

Theuns

[Robert Lees]

Re: BC12d being rebuilt in Souht Africa

Hello Theuns,

Yes, there is only the 180 degree turn on the aft pulley. No more required.

The thread below describes most trim problems and their solutions. In essence:

• Don't adjust trim unless the yoke is neutral
• Don't use grease anywhere near the cable; the cable must be dry to grip the V-section pulley.
• V-section pulleys (fore and aft) are important
• Use Rosin to aid grip.

http://vb.taylorcraft.org/showthread.php?49-Trim-common-problems

Hope that helps,
Rob

[Mark Julicher]

Re: BC12d being rebuilt in Souht Africa

Theuns,
I made a batch of new trim pulleys a few years ago. (the original material is phenolic) I still have some aft pulleys. I would be happy to mail one to you if you give me a mailing address (by private message of course) I will send a pulley to you to speed your project along.

Welcome to the Taylorcraft Tribe.

[Theuns]

Re: BC12d being rebuilt in Souht Africa

Rob, I will have a look at the link now, thanx

Mark thanx for the offer, I have an extra Phenollic pulley I will have milled to the correct size and shape.
Initially I thought of using Nylon, but maybe the Phenollic will grip the cable better.

Theuns

[Theuns]

Re: BC12d being rebuilt in Souht Africa

Guys, I have read up as much as I could regarding the trim cable and there are still a few things that bug me with this system :-(

I attach a few pix showing the cable routing and there are a few places where the cable goes through the "standoffs" and change direction rather steeply, is this normal for Taylorcraft??
Also the trim cable passes rather close to the top elevator cable in the rear section of the fuselage, it doesn't chafe yet, but seems like a potential hassle....or am I being to pedantic!?

There is also an alluminuim "cable guide block" that keeps the trim cable to the rear elevator pullye, but you can see how it does not line up well with the elevator in neutral position, it this "taylorcraft" or maybe an attempt by the previous owner?
I can forsee that it might damage the trim cable over time.

Last question, as you can see the elevator trim pulley fouls up against a piece of tube welded to the fin mound post. I can NOT see this as needing to be there atall. Even the manual does not show it ti be there. I just wanted to make sure before I cut it out.
There is no way it can remain there as no up elevator is obtainable with it inplace.

Any info will be very welcome.

Thanx

Theuns

[TimHicks]

Re: BC12d being rebuilt in Souht Africa

The trim cable angle on my '46 BC12D looks a lot like yours.