Spar Plate heat treating question, etc.

In reading through the preview plans of the "3" I noticed that the four 1/4 inch steel "straps" that help tie the spar halves together are supposed to be heated treated to 125,000 psi. On another drawing sheet it also provides a Rockwell numbering range of 26-29 I believe, or something close to that (don't have the plans in front of me so proceeding via memory which isn't what it used to be ).

Anyway, since this a/c wasn't built by me I am attempting to make sure it is airworthy prior to the first flight, and am therefore interested in determining if the original owner complied with this note or not. I discussed this with an aero engineer friend and he said one method measures the hardness but the other test method requires a sacrificial piece to destroy.

My question therefore is: What are you all doing re. this testing requirement on your birds?

Additionally, I just replaced the fuel sender on our fuselage tank, and found that the gauge reads 3/4's when I hold the float in the fully raised position. Is there an easy procedure to figure out how to calibrate this to make it more accurate. I imagine I will need to add a resistor to one of the wires to get make it more accurate...

Thanks for your inputs...

Doug Lomheim
OK City, OK
RV-3 Restoration

https://www.dropbox.com/s/vbnwr2iiioujoxx/Spar 14 inch plate.jpg

Center-Section Straps

When I got my RV-3B kits in April of this year, those parts came pre-drilled. I presume they are heat-treated too but I haven't tested them and don't plan to.

You might be able to find someone who can do a hardness test on them. It puts a tiny indentation in them, quite similar to the mark of a center-punch. It is the standard method of testing parts for heat-treatment and does not sacrifice the part, which remains useable. A heat-treatment shop should be able to do this.

You can contact Van's with your serial number and ask them if they have a record of these parts. This would be the easiest thing to do.

If you wish to replace them, I'll bet that Van's can sell you these, undrilled, and you could have a machinist match-drill them to these. If he does a very good job they ought to fit. If he doesn't, though, you wouldn't want to force it - and with the tight fit and close-tolerance bolts, it will be hard to tell if it's merely tight or if you're forcing it. Or perhaps new pre-drilled parts will fit. I don't know how long they've been drilling them with the same jig.

I'd email Van's if I had this concern. Failing that, I'd find someone with a hardness tester.

Dave

Floats will hit the top of the tank before they are full, due to the wing dihedral.

BobTurner said:

Floats will hit the top of the tank before they are full, due to the wing dihedral.

Click to expand...

Wing dihedral doesn't affect the fuselage tank.

Gauge should read "full" in the full "up" position. Calibration is done by bending the float wire.

On the spar plates, if they came from Van's drilled, they have been heat treated.
I've only run across one instance where the plates had been lost and the builder had to make new ones. Fortunately he had access to a heat treating facility, so it turned out to be not a big deal.

Fuselage Tank Calibration and hardness test

Mel said:

...Gauge should read "full" in the full "up" position. Calibration is done by bending the float wire.QUOTE]

Thanks for all the replies...bending the wire makes perfect sense and is a lot easier than messing with attempting to figure out a resistor to calibrate it...

Doug

Click to expand...

RV3 spar splice plates

I have seen several sets of RV3/4 spar splice plates from Vans, some as old as 1982, and they all have nicely rounded corners, with the bolt-holes very symmetrically and accurately pilot-drilled. I would be concerned that the part shown in the photo did not originate from Vans. The heat-treat requirement for those parts is clearly specified in all RV3/4 plans, however, so if the original builder neglected to do it, they would have been grossly negligent.

- Steven
700+ RV3 hours
(two more last weekend!)

Spar Plate Rockwell Tested and press fit pins...

I took my 1/4 inch plate to a local company here in OKC and for only $60 (ouch) they performed a Rockwell test on it. It came in at "42" so it appears that the original builder did have the pieces heat treated after he drilled the holes...

On another note, are any of you using tapered pins vs. bolts on your RV-3 Spar installations? The original builder used these but I couldn't find anywhere in the plans that it called for anything except AN bolts...

Doug
RV-3 Restoration

https://www.dropbox.com/s/rhx2x93c35ygf3f/Spar tapered bolts.jpg

https://www.dropbox.com/s/f35iz4mz9oyli96/Tapered Spar Pins.JPG

taper pins on RV3 center spar

Very early RV3 blueprints called out "Use High Strength Bolts or Taper Pins 100,000 PSI Shear minimum" for the wing spar center section. Later plans called for "NAS 1305-25" and "NAS 1304-25" bolts, the taper pin option being removed (I used the later plans for my build). There was never a hardware part number called out for the taper pins, only the strength rating.

- Steven
700+ RV3 hours
(one more last Saturday!)

highflight42x said:

Very early RV3 blueprints called out "Use High Strength Bolts or Taper Pins 100,000 PSI Shear minimum" for the wing spar center section. Later plans called for "NAS 1305-25" and "NAS 1304-25" bolts, the taper pin option being removed (I used the later plans for my build). There was never a hardware part number called out for the taper pins, only the strength rating.
- Steven
700+ RV3 hours
(one more last Saturday!)

Click to expand...

Thanks for the inforamation Steve. Since that is way this one came and it appears to have the required hardness, I'm just going to continue in the spirit of "IRAN" and put it back together as I took it apart...

Doug

Want to check heat treatment of steel parts?

This is a day late and a dollar short but for future thread seakers... If you are unsure if your parts have the proper heat treatment because you dont know if the parts originated from Vans or were manufactured by the Builder.. It would be wise to Have them checked. The Test equipment usually only leaves a very small pin head size dimple in the part and is none distructive. A source of this testing can be done cheap or free in most cases if you take it to a college or trade school in Machining technologies. It takes just a few seconds to set the scale on the tester, clamp the part in and release the leaver. I double checked My splice plates and all were at or a little harder than what was called out for in the plans. It was done free at the college Machining tech. and only took about 20 min. 15 of which was just talking about the project( something I do too well). Now I feel so much better, NO WORRIES...