An unapproved modification

Not approved by Vans, but a minor change that makes fabrication easier.

Replace the 3/16 inch thick aluminum angle bracket that attaches the fuel tank to the fuselage with a 0.050 4130 steel bracket like the later RV-7s.



If you follow the original plans, you must open up the thick angle a few degrees - when I tried hammering into submission it just got damaged rather than bent.

The fuselage attachment with the three AN3 bolts and an internal angle/spacer remains exactly the same.

I noticed from internet picture postings that some builders actually installed the fuselage bracket in reverse so that they would have to lessen the 90 degree angle rather than increase it - a job that can be somewhat done in a vice. In my case the fuel vent outlet location got in the way.

In any case, a much easier solution to creating a 93 to 94 degree bracket.

Don't forget the later revision adding a slot for fuel tank ripping off in an accident. Follow the RV-7 plans and add the slot in the steel bracket and put the nutplate on the fuel tank bracket.

A bonus, you actually save 1/2 oz per side as well as being easier to create the precise angle needed.

just learning

Gil,
just curious if you think there will be any issue with corrosion from the steel in contact with the aluminum?

johnny stick said:

Gil,
just curious if you think there will be any issue with corrosion from the steel in contact with the aluminum?

Click to expand...

I'll epoxy prime the steel part, and the set up is identical in materials to the later RV-7s.

As far as I can tell from web pictures, Vans does not supply this RV-7 steel part powder coated.

Now it's actually fitted with the mounting holes, I'm fairly sure I got the two mounting surfaces to a much more accurate fit than I could have beating the h*** out of a 3/16 inch thick aluminum angle.

RV7 part number -GOT IT

Plans page 38 -available from the mothership. F-796A-L and -R.

Gil -
I have been trying to find that bracket in the RV 7 plans, and have not been able to. I also think it is the right way to go. Do you have the part number or a plans page number where I can find it? Thanks!

Sam

Sam Staton said:

Plans page 38 -available from the mothership. F-796A-L and -R.

Gil -
I have been trying to find that bracket in the RV 7 plans, and have not been able to. I also think it is the right way to go. Do you have the part number or a plans page number where I can find it? Thanks!

Sam

Click to expand...

Yes, the RV-7 part is F-796A on DWG 38.

However the fuel tank to fuselage gap is much greater on the -7 than the -6 due to the different wing attach method. The -7 part won't fit so I just made my own bracket up with 0.050 4130 steel.

The shape is basically the same as the specified 3/16 aluminum bracket, and the steel bent easily in a vice by hammering over a radiused oak form block. Just ensure that the final radius is greater than 0.156 inches.

This web link shows the larger -7 part, and that the hole in it precludes the possibility of trimming it down.

http://3.bp.blogspot.com/-kcSeYyaywxs/TuZKdAxyweI/AAAAAAAAC0A/B5iV61APtts/s1600/IMG_0278%5B1%5D.JPG

Dimensions

Gil -
I suspected as much. Do you have any rough dimensions to use? Thanks in advance.

Sam

Sam Staton said:

Gil -
I suspected as much. Do you have any rough dimensions to use? Thanks in advance.

Sam

Click to expand...

I just used the same dimensions as drawn in the RV-6 plans for the aluminum bracket on Dwg 46

Ends up being a 2 1/2 inch by 1 inch angle that is 3 7/8 inch long.

Dimensions w/pictures







The degrees are 82 & 70. The picture doesn't make that clear.
Hope this helps.

For the life of me, I couldn't figure out why people were hammering away at these angles - it's not precise, it's not very conducive to a nice finish on the part, and frankly it's not necessary. I'm kind of surprised, and also kind of not, that Van's recommends such an approach

I used a vise, supporting pieces of angle, and a length of square steel tubing. Set up the part in the vise along with a backing angle (with the flange facing away) such that the part cannot bend rearwards along the vise jaw. Clamp the square steel tubing to the part in two places, and bend as needed.

The whole process took only a few minutes and was extremely precise.

X marks the spot...

az_gila said:

Not approved by Vans, but a minor change that makes fabrication easier.

Replace the 3/16 inch thick aluminum angle bracket that attaches the fuel tank to the fuselage with a 0.050 4130 steel bracket like the later RV-7.

Click to expand...

Gil,
Great idea!
My late RV genius friend Arvil Porter figured that one out many years ago and well prior to the RV7's conception/inception/deception. When we built the RVX we knew we had to mate RV4 wings to a Six fuselage which has some minor differences. The steel bracket made it easy...
Arvil shared all of his ideas and mailed Van's several drawings including a copy of his "Heavy Weldment" drawings that he installed in all of his RV4's he built vastly improving the forward longeron/firewall strength.
Funny how they ended up in subsequent RV4 plans...

Great ideas like great memories never die...
V/R
Smokey