I have a question about the mounting position of the T-405 tank attachment angle on the inside tank rib. The diagram shows the rear portion of the T-405 2? back. The drawing isn?t that clear as to where to take this measurement from. Is it from inside the rib or from the forward edge of the skin? Also, I am assuming the T-405 attaches to the fuselage at some point. Wouldn?t it be better to wait until you attach the wings to the fuse to make sure you have a tight fit or is it not that critical?
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T-405 Tank Attachment Angle
- Thread starter bmurrish
- Start date
Captain_John
Well Known Member
Bill,
Just do it. Nestle the bracket inside the flange of the rib and call it a day. The fuse attach bracket is infinately adjustable.
CAUTION: When you layout your rivets for this bracket, be careful to consider the penetration for the flop tube pick up! I had to use AN-426 rivets there, as my holes were in the way.
People, please correct me if my 411 is false. I think I am on the mark, but the next airplane I build will be the first one!
CJ
Just do it. Nestle the bracket inside the flange of the rib and call it a day. The fuse attach bracket is infinately adjustable.
CAUTION: When you layout your rivets for this bracket, be careful to consider the penetration for the flop tube pick up! I had to use AN-426 rivets there, as my holes were in the way.
People, please correct me if my 411 is false. I think I am on the mark, but the next airplane I build will be the first one!
CJAnother question about the T-405. I was test fitting it on the rib and it interferes with the top side leading edge hole that rivets the skin to the rib. Note: The rib does lay flat and the flange is 90 degrees
I thought I may have drilled it wrong but the rib and the skin are pre drilled. If you look at the pre drilled skin you will see that this hole in not aligned with the others making it sit closer to the ribs web.
I looked on the right wing tank that I have not touched and it is the same way. So question is, how do you do the rivet? Do you need to thin out the T-405 where that rivet is or is something wrong here?
I thought I may have drilled it wrong but the rib and the skin are pre drilled. If you look at the pre drilled skin you will see that this hole in not aligned with the others making it sit closer to the ribs web.
I looked on the right wing tank that I have not touched and it is the same way. So question is, how do you do the rivet? Do you need to thin out the T-405 where that rivet is or is something wrong here?
How To
Bill,
The 2" dimension is not terribly critical, but you should radius the T-405 edge to match the web-to-flange radius of the rib. Notch the T-405 where needed to clear shop heads of the skin/rib rivets. As depicted on the drawing, keep the angle's face parallel to the stiffener punched into the web. Be sure to locate the 1/8 rivet holes enough forward on the T-405 so that none of the rivet heads ride up on the angle's fillet radius, and far enough away from the rib flange to allow bucking bar and set clearance. After installing the rib, you must install the angle and stiffener plate with sealant before you can close the tank, so matching to the fuse is problematical. Besides, the mating part can flex fore and aft a bit for a tolerance taker-upper.
John Siebold
Boise, ID
Bill,
The 2" dimension is not terribly critical, but you should radius the T-405 edge to match the web-to-flange radius of the rib. Notch the T-405 where needed to clear shop heads of the skin/rib rivets. As depicted on the drawing, keep the angle's face parallel to the stiffener punched into the web. Be sure to locate the 1/8 rivet holes enough forward on the T-405 so that none of the rivet heads ride up on the angle's fillet radius, and far enough away from the rib flange to allow bucking bar and set clearance. After installing the rib, you must install the angle and stiffener plate with sealant before you can close the tank, so matching to the fuse is problematical. Besides, the mating part can flex fore and aft a bit for a tolerance taker-upper.
John Siebold
Boise, ID
Captain_John
Well Known Member
Bill, the holes that don't line up are like that for a reason. The very front of the nose rib has very short flanges. That is the reason for the indented hole alignment.
Also, I chose to rivet the 405 to the rib BEFORE riveting it to the skin. I made relief notches in the 405 so a no hole yoke *might* squeeze them. I am banking on the fact it will!
I will letcha know how it goes. I could find out as early as this coming weekend!
CJ
Also, I chose to rivet the 405 to the rib BEFORE riveting it to the skin. I made relief notches in the 405 so a no hole yoke *might* squeeze them. I am banking on the fact it will!
I will letcha know how it goes. I could find out as early as this coming weekend!
CJAha!
CJ's post gave me an idea. Use MK-319-BS pop rivets in the four holes obscured by the 405. You can fill the heads and no one will know the difference. (Pop rivets - exposed, where you can see them! - are required elsewhere on the aircraft, so it's not really heresy suggesting them.) Two things going on here. First, it is a gooey mess riveting on the 405 and doubler plate, and you have to use the corner of a bucking bar to reach into the rounded confines of the leading edge. Assembly on the bench would be nice. BUT, I can absolutely guarantee you that the very flat, very stiff angle will shape the rib nose just differently enough that the front rivet holes drilled without the angle will not line up. So, secondly, the poppers require a larger 7/64 hole, which should clean up the misalignment. Voila! You could cleco up the whole mess to see where you're headed before applying the sealant. The only downside I foresee is that you have to clean up the bit of sealant contaminated with drill chips, but no big deal since it's very accesssible.
John Siebold
CJ's post gave me an idea. Use MK-319-BS pop rivets in the four holes obscured by the 405. You can fill the heads and no one will know the difference. (Pop rivets - exposed, where you can see them! - are required elsewhere on the aircraft, so it's not really heresy suggesting them.) Two things going on here. First, it is a gooey mess riveting on the 405 and doubler plate, and you have to use the corner of a bucking bar to reach into the rounded confines of the leading edge. Assembly on the bench would be nice. BUT, I can absolutely guarantee you that the very flat, very stiff angle will shape the rib nose just differently enough that the front rivet holes drilled without the angle will not line up. So, secondly, the poppers require a larger 7/64 hole, which should clean up the misalignment. Voila! You could cleco up the whole mess to see where you're headed before applying the sealant. The only downside I foresee is that you have to clean up the bit of sealant contaminated with drill chips, but no big deal since it's very accesssible.
John Siebold
Captain_John
Well Known Member
John,
That makes a great "Plan B" if I can't fit the no hole into the cut out in the 405 (Which I am planning on being able to do).
Are the MK-319's structurual? ...not that it matters much, just wondering.
Maybe using the shop vac when you drill would minimize the shaving contamination?
CJ
That makes a great "Plan B" if I can't fit the no hole into the cut out in the 405 (Which I am planning on being able to do).
Are the MK-319's structurual? ...not that it matters much, just wondering.
Maybe using the shop vac when you drill would minimize the shaving contamination?
CJ
rv8bldr
Well Known Member
Doesn't really matter if those MK-319-BS rivets are structural as you will only use one of two, there are lots of solid rivets around them, and the rib is really being held in place by the Proseal. I put pop rivets in mine at that point as I couldn't get a bucking bar in there for the solid rivets. Don't worry about filling in the rivet, except maybe the bttom bit. The Proseal between the rib and the skin is what is holding back the fuel, so no fuel should ever touch one of these rivets anyway.
My $0.02.
My $0.02.
View From the Shop
Bill,
Others may be reading, so here's my report after clecoing the ready-to-seal/rivet the tank end ribs, and looking things over before mixing the sealant. I'm real wary of these corners because it's my second -7, and the neighbors are reminding me of the blue language emanating from the shop when I closed the first airplane's tanks.
You can seal and rivet the 405 (and the other reinforced end rib) on the bench, but prep the nose rivet holes for the pops before inserting the rib. Bench riveting the 405 and installing the rib should be accomplished in the same sealing session because there is indeed a very slight change in relationship between the rib flange and the 405/stiffener when on the bench verses matched with the skin. It won't fight you with uncured sealant, but if the sealant cures between 405 attachment and later rib installation, there may be hell to pay aligning the skin holes. The sealant isn't structural, but it's nearly stiff as your tires when cured. One other point. Remember to deepen the rivet clearance notches in the 405 to accommodate unpulled pops; they're a lot longer than bucked solids.
Or, install the rib with solid rivets, followed by the 405, again in the same session. No pops needed, and reaching in with a suitable bucking bar isn't all that tough. Just be ready with the right tools and a lot of toluene (the correct solvent for the sealant, not acetone).
John Siebold
Bill,
Others may be reading, so here's my report after clecoing the ready-to-seal/rivet the tank end ribs, and looking things over before mixing the sealant. I'm real wary of these corners because it's my second -7, and the neighbors are reminding me of the blue language emanating from the shop when I closed the first airplane's tanks.
You can seal and rivet the 405 (and the other reinforced end rib) on the bench, but prep the nose rivet holes for the pops before inserting the rib. Bench riveting the 405 and installing the rib should be accomplished in the same sealing session because there is indeed a very slight change in relationship between the rib flange and the 405/stiffener when on the bench verses matched with the skin. It won't fight you with uncured sealant, but if the sealant cures between 405 attachment and later rib installation, there may be hell to pay aligning the skin holes. The sealant isn't structural, but it's nearly stiff as your tires when cured. One other point. Remember to deepen the rivet clearance notches in the 405 to accommodate unpulled pops; they're a lot longer than bucked solids.
Or, install the rib with solid rivets, followed by the 405, again in the same session. No pops needed, and reaching in with a suitable bucking bar isn't all that tough. Just be ready with the right tools and a lot of toluene (the correct solvent for the sealant, not acetone).
John Siebold
Captain_John
Well Known Member
Here is a pic of my root rib with the stuff attached. Note how I notched the 405.
I agree with having the metal already prepped for whichever rivet is going to be installed.
Before I mud it all up, I am going to dry fit a rivet and squeezer to be sure it can be done with solid rivets.
CJ
I agree with having the metal already prepped for whichever rivet is going to be installed.
Before I mud it all up, I am going to dry fit a rivet and squeezer to be sure it can be done with solid rivets.
CJ
