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Cowl Pins

SteveHRV7

Member
Has anyone installed their cowl pins from inside the cockpit? I just ordered a cowl from Sam James for my 7a and he recommended installing the cowl pin from inside the cockpit to avoid an external cowl pin lock (looks bad) and to prevent the pin inadvertently backing out into the prop. Pictures would be great if you have any. Thanks!
 
Dick Flunker inserts his pins from the back. They go into the air intake vents. Works well.

I have mine through the front with no "external locks". I used the original method show on Van's plans back in the 80s. The forward end of the pins snap into the inside cowling inlets. Never had one come out in 17 years.
 
A Lockheed Technical Fellow & Design Engineer friend of mine has his such that when you push on the front of the NACA vent, it pivots into the plane and you can reach in & pull the cowl pin. You'd never know from the outside that the NACA vent is spring-loaded :) Rosie
 
Pins

There is a gentleman (can't recall his name) that has a builders assistance shop at Lockhart,TX. He puts his pins inside the NACA vent also. Looks sharp
 
Has anyone installed their cowl pins from inside the cockpit? I just ordered a cowl from Sam James for my 7a and he recommended installing the cowl pin from inside the cockpit to avoid an external cowl pin lock (looks bad) and to prevent the pin inadvertently backing out into the prop. Pictures would be great if you have any. Thanks!

Steve,
Danny King (here on the forums) has done this on his RV-8. Very slick, and he says it helps with re-installing the cowl as the lower cowl is the first engaged by the pins when they slide in from the rear. You can PM him here on the forums. I'm sure he can provide pictures and descriptions.

Best,
 
Very Easy To Do

I had done this in my RV7 and found it to be much easier and cleaner than putting the pins in from the outside front then having to fabricate something that looked descent to cover it up. I showed what I had done to Mike Bullock and he did it as well and documented it on Rivetbangers here: http://www.rivetbangers.com/forums/viewtopic.php?t=3072

Mike bent his guide tubes where mine were fairly straight. When you purchase the knobs, be sure there is plenty of material left in it to drill because you will be drilling past the screw hole to fit the hinge pin.

Doing this is so easy that everyone should be doing it.
 
Yah Yah Good Stuff

I just did this a couple of weeks ago. Instead of drawer knobs like Mike Bullock used, I took a piece of 1/2" aluminum rod and cut it 1.5 inches long. Tapped #2-56 into the center to make a Tee-Handle on the end of the hinge pin. Used a 2-56 thread die to thread the hinge pin (hard stuff, use Boelube & go slow). I ordered thinwall stainless tubing with a 3/32 ID from McMaster Carr, and ran that from just forward of the firewall, aft to the rib adjacent the subpanel. It curves a little around the NACA vents, but no problem. Proseal was used to tack down the stainless tubing against the fuselage skin under the NACA duct. It IS IMPORTANT to have the aftmost eyelet on the cowl hinge be fastened to the lower cowl as mentioned previously. I also fabricated tiny brackets to guide the stainless tubing to point directly into that eyelet so minimal fiddling is required when pushing the pins in place.

Overall, it came out great and I am very happy with the result.

One "safety feature" of this design modification that might not be obvious is that you never fully remove the hinge pins (the front 10" stays engaged in the stainless tubing when "fully retracted", and they lay in your seat - so it would be almost impossible for you to "forget" to put them in. You know, like maybe you're putting your cowl back together and you just get the upper cowl camlocs on the firewall installed when your cellphone rings and you're called away for 25 minutes?

Let's see, hmm now, where was I? If your hinge pins are on the bench and normally install from the front it is ALMOST conceivable that you MIGHT forget to put them in on a really bad day.

I will post some photos of the final configuration when I get home tonight.
 
I put mine from outside (where VANs shows) and it gets covered by a nice fairing that I made from fiberglass. The piece is about 1.5 tall/wide and it wraps around the air inlet and goes back about 2.5"

Let me know if you can not visualize it and I will take a picture and will send it. I am pretty sure the same thing can be made from aluminum, though some metal shrinking/stretching will be needed to form it really nice can then polishing it would look sharp.

The issue I can foresee putting it from inside is user friendliness of it.
 
The issue I can foresee putting it from inside is user friendliness of it.

Seems like it would be fairly easy to me, just hang the lower half on the firewall like this photo (borrowed from RB link)

IMG_9436.JPG


Then start the pin in the first eyelet, remember the bottom needs to have the first eyelet, see above post 7, set the top half on, and push the pin all the way in.
 
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For a tightly fitted cowl, some times I need to push the two halves together with one hand and push the pin with the other. This is specially the case at the beginning, but it is not much of an issue. After all, we want to have some thing for our spouse to do, right?
 
There are some great ideas here. I insert my pins from inside the cockpit, but unlike a few others, I didn't make provisions for making it easy! Doh! My pins are a royal pain to get in.

I like the idea of running a guide tube from the NACA ducts forward, but how do you secure the pins once fully inserted? Anyone care to elaborate with their ideas?
 
If you join the James Aircraft group on yahoo there are several examples of how others have done this. I am doing it on my RV-7A.

Jay Erickson, 7A finishing
Grassy Meadows Skyranch UT47
 
Resurrecting this thread from the bowels of the ship.

I have the cowl pins (piano wires) that insert from the cockpit forward into the cowl halves. I like it a lot and it sure does make things nice and smooth on the cowling. I know Danny King was an influence on this build so the fact it ended up with the hidden cowl pins doesn't surprise me. On an un-related note I know Danny would fly this bird every year at annual and he would do amazing yet graceful aerobatics with it.

So back to the cowl side pins. I have noticed that over the course of a couple of hours in the air the pins tend to migrate aft/out and in the case of the left one it comes out far enough to potentially interfere with the throttle quadrant.

While sitting in the pilot's seat the cowl pin knobs can't be seen but they can be touched so as part of my run-up check list I reach down on each side and make sure the knobs are fully engaged.

When the pins move aft in the air it takes too much force to press them back in the guides so I have to wait until back on the ground when the cowl isn't pressurized. If I were to try and force the wires they would just buckle. I don't like the idea of the cowl being disengaged at the sides up on the front end of the cowl for 4 or 5 inches either.

I need to come up with a retainer of some sort to keep the pins in place. It shouldn't take much to keep them in place during vibration. The round metal knob on each of them doesn't really have anywhere for a safety device as it isn't drilled, and is thick and round. I considered bending up some thin spring-steel strap to make a spring-loaded release that stays engaged across the knob but that got real complicated in a hurry based on the location and lack of mounting area for the retainer.

Has anybody had similar issues where the cockpit-side cowl pins come out a few inches in flight due to vibration? If so what type of solution did you come up with?
 
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+1 been done a lot. :D

Personally I like having all the connectors for the cowl outside and not having to deal with the cockpit. The idea of putting them in the NACA scoop on side of fuselage is OK.

The old saying is so true. STICK WITH THE PLANS and finish the plane.
 
I have the cowl pins (piano wires) ...

Maybe I'm being anal, but wanted to point out that piano hinge pins are not "piano wires," which are the wires of various gauges that are struck by the hammers in the piano to make the sound. I've used piano wires for other purposes too. If you actually did mean piano wire here then perhaps a bit more detail would be helpful, i.e. why use that as opposed to the hinge pin... more flex?

Regardless I'm grateful you resurrected this thread. Most (all?) of the prior images are no longer available. Perhaps people will provide more recent images of this aspect of the build?

Thanks.
 
Maybe I'm being anal, but wanted to point out that piano hinge pins are not "piano wires," which are the wires of various gauges that are struck by the hammers in the piano to make the sound. I've used piano wires for other purposes too. If you actually did mean piano wire here then perhaps a bit more detail would be helpful, i.e. why use that as opposed to the hinge pin... more flex?
Thanks.
Yes you are being a little picky. This is a slang term. Aircraft hinges use actual aircraft AN or MS part numbers, with specs, including the pin. Van supplies aircraft hinges. The hinge pins were never made for a musical instrument. I don't know of anyone who thought hinge pins were intended for a musical instrument or went to the music store to by "piano wire" for their hinge. It is just a slang term for hinge pin.

You say you used actual piano wire in an airplane? Please tell me where you used real piano wire for a piano in an aircraft? Where did you buy it? Grainger and Hobby Lobby sell "Piano Wire" or "Music Wire", but again these are not for musical instruments either. It is just slang term people know has fine or small diameter solid steel wire (that is not wire copper wire for electrical wiring). Don't use hobby or hardware store hardware for your planes primary or secondary structure.

You know all the control cables and planes with external flying wires (like biplanes)sing very use very specialized wires made to aircraft standards. Now that is not to say some have not used something from the farm and tractor store, but in most cases it is aircraft grade or should be.

It really is not necessary to deviate, as aircraft hinges and pins, cables, flying wires of various diameters are readily available for their intended purpose and have strict specs and surface finishes. Do not use non aircraft parts for structural items.
 
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