VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 10-29-2018, 12:04 PM
FinnFlyer FinnFlyer is offline
 
Join Date: Aug 2018
Location: Bell, FL
Posts: 41
Default F-463 and T-405

Can anyone give a valid engineering reason why those tank/fuselage angles:
1) Are 3/16" thick rather than 1/8"?
2) Has a 1" hole edge distance for a 1/4" bolt?

Started to make the F-463 and it will have to be bent to sit flush with both F-405 and the fuselage.

Too late to do anything with F-405 as it's already riveted/prosealed to the tank, but I'm very tempted to use a 1" x 2" 1/8" angle for F-463. That would allow a 1/2" plus edge distance for the 1/4" hole in both brackets and make it easier to bend F-463. (Holes in F-405 brackets not yet drilled.) Also tempted to have the fuselage-side angle flange point aft rather than forward as in the RV-8.

Finn

Last edited by FinnFlyer : 10-30-2018 at 08:52 AM. Reason: Changed 1.5 to 2
Reply With Quote
  #2  
Old 10-30-2018, 05:55 AM
fixnflyguy fixnflyguy is offline
 
Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 933
Default Many variations

There are many variations found in the field of RV-4's, but be sure you understand the slot mod not shown on all plans. That fitting handles wing twisting loads, but must be able to "slip apart" in the event of a wing separation in from an incident to prevent the inboard fuel tank rib from breaching the tank. The fitting on the fuselage also needs to be carefully contoured for the wing root fairing to clear it, so you need to have the fairings well planned at the time of fitting install. The angle is easy to bend as designed from the thick angle.
__________________
Bill E.
RV-4/N76WE
8A7 / Advance NC
Reply With Quote
  #3  
Old 10-30-2018, 08:44 AM
FinnFlyer FinnFlyer is offline
 
Join Date: Aug 2018
Location: Bell, FL
Posts: 41
Default

Thanks for the reply.

I'm aware of the slot and clearing the root fairing.
Thing is that the tip of F-405 is less than 7/8" from the fuselage. So a 1x2" angle would be quite adequate to ensure 1/2" edge clearance for the 1/4" bolt.
Looking at the drawing of the RV-8 posted here http://www.vansairforce.com/communit...d.php?t=165451 wound confirm that as acceptable.

Now, cutting a slot may be the reason for increasing thickness from 1/8" (ballpark engineering) to the 3/16". However, the lightening hole shown would seem to contradict that. Also the RV-8 has a bigger tank which should put heavier load on the brackets.

So here is where I need a second opinion:
With the 1/4" hole being just 1 3/8" from the fuselage can you think of any good reason for not using 1/8" angle instead of 3/16" angle?

Finn

Quote:
Originally Posted by fixnflyguy View Post
There are many variations found in the field of RV-4's, but be sure you understand the slot mod not shown on all plans. That fitting handles wing twisting loads, but must be able to "slip apart" in the event of a wing separation in from an incident to prevent the inboard fuel tank rib from breaching the tank. The fitting on the fuselage also needs to be carefully contoured for the wing root fairing to clear it, so you need to have the fairings well planned at the time of fitting install. The angle is easy to bend as designed from the thick angle.

Last edited by FinnFlyer : 10-30-2018 at 08:51 AM.
Reply With Quote
  #4  
Old 10-30-2018, 12:01 PM
fixnflyguy fixnflyguy is offline
 
Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 933
Default RV-4 plans revisions are few

I'm also going to "guess" VAN's would not make changes to the -4 plans unless there was safety issue,since production is low, and the majority of builds are utilizing the original call-outs. Doubtful that to your point, there is any reason you couldn't get by with the thinner material, however I don't recognize any great benefit, unless of course you don't have the original material.
__________________
Bill E.
RV-4/N76WE
8A7 / Advance NC
Reply With Quote
  #5  
Old 10-30-2018, 07:28 PM
FinnFlyer FinnFlyer is offline
 
Join Date: Aug 2018
Location: Bell, FL
Posts: 41
Default Saving weight

Thank you Bill.

Only advantage is less work compared to cutting/shaping the supplied 2 x 2 1/2 x 3/16 angle and lower weight. We spend significant work on cutting lightening holes in flap spars, brace, etc. to save weight. Those 3/16" angles are just offensive to me

Looking at drawings for more recent kits (RV-7, RV-8 and later) it's obvious that there are plenty of additional places to lighten the RV-4. (http://gikoncnsdr.blogspot.com/ Ramblings... point 9.)

Then there is the point of having to bend the 3/16" angle a bit.

Finn

Quote:
Originally Posted by fixnflyguy View Post
I'm also going to "guess" VAN's would not make changes to the -4 plans unless there was safety issue,since production is low, and the majority of builds are utilizing the original call-outs. Doubtful that to your point, there is any reason you couldn't get by with the thinner material, however I don't recognize any great benefit, unless of course you don't have the original material.
Reply With Quote
  #6  
Old 10-30-2018, 11:46 PM
Andy612's Avatar
Andy612 Andy612 is offline
 
Join Date: Jun 2012
Location: Whitehorse, Yukon Territory
Posts: 8
Default F-463 not so hard to bend

Just finished building new tanks for my already flying RV-4. Decided it was easier to just fabricate new F-463's rather than try to fit the new tanks' T-405's to the old existing F-463's. Bending open the 3/16" F-463 angle was easy for me using a vice and a piece of steel pipe I had lying around--can't remember exactly but it was 2 or 3" diameter. There's an EAA video showing a method used to open the angle here: http://www.eaavideo.org/detail/video...gle-adjustment
With the completed tanks in place all it took was a couple trips to the vice to get the correct angle--flush with both the T-405 and fuselage side skin. Then I match drilled to T-405 and temporarily bolted it in place there before match drilling the fuselage bolt holes. Then I removed it, and using a jigsaw and Scotch-Bright wheel, trimmed away a lot of the extra angle material for a "pleasing" shape , allowing sufficient edge distance around the 3 bolt holes. I could have bored a couple of lightening holes, too but didn't bother. My O-320 wood propped -4 needs all the weight in front of the spar that it can get.

My -4 also already has fiberglass fairings that cover the lower end of F-463 even though it is bolted to the lower longeron. If you want straight metal fairings, or have tight fitting fiberglass ones, then you might have to do something like this: http://gikonfuse.blogspot.com/ (click link and scroll down to Feb 15, 2007 "F-463 completed").

Probably could have got away with 1/8 angle instead of 3/16, but the plans called out 3/16 so that's what I ordered when I ordered all the tank parts. No point in not using it once I had already paid for it. Plus, the work involved would be very much the same, and the extra weight negligible.
__________________
Andy Muir
C-GJIP RV-4 160hp
Based at CYXY
Reply With Quote
  #7  
Old 10-31-2018, 09:15 AM
FinnFlyer FinnFlyer is offline
 
Join Date: Aug 2018
Location: Bell, FL
Posts: 41
Default

Thanks for the tip on bending angle. However, as much as I tried, I could not get the 3/16" angle to bend. Fortunately a friend let me use his mill to make it fit. (Tapered the 1" fuselage side flange about 0.05".)

I will be using flat fairings. Rather than G-IKON's solution, I intend to put the lower bolt through the skin into a 1/8" piece resting on the upper edge of the lower longeron. (On the RV-8 it goes through the skin and a rib flange.)

With a full tank (96 pounds) and less than a quarter of the weight transferred through the brackets at 6Gs (96 x 0.25 x 6) I don't see how the load on the brackets will exceed 150 pounds.

Granted, I don't know how much weight the tank skin/ribs can transfer from the rest of the wing, but I can't imagine it being very much.

A 3/16" bolt in 1/8" 6061T6 alu will handle more than 900 pounds (0.1875 x 0.125 x 40,000).

A 1/4" bolt in 1/8" 6061T6 alu will handle 1250 pounds (0.25 x 0.125 x 40,000).

No matter how I look at it, these brackets appear way, way over engineered.

Same goes for the F-444 brake anchors, also made from 3/16" alu angle. Other than providing extra wear surface for the bolts, they just do not make any sense.

However, point well taken on more forward weight needed with a wood prop.

Finn

Last edited by FinnFlyer : 10-31-2018 at 08:54 PM. Reason: Couldn't bend angle
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 03:25 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.