Cowl wrestling match

[n3480h]

I've been fighting my cowl for what seems like weeks. The hinge wires were all but impossible to get into the hinges, so I drilled and re-riveted the top sections of hinges. Fits better, but still requires a lot of force to get the hinge wires in, in spite of replacing the original wires with wires that are about .020" smaller in diameter. Also extended the nose for the F1 hub on the 2180, because the original engine I had planned to use is a 1915. The F1 hub protrudes farther. So, I got the cowl clamped in position and found that the GPASC 1819 carb's mixture adjustment disk protrudes below the bottom of the cowl (in the cutout opening) by about 1/2". I guess its not a big problem because when I switch out the 1915 for the 2180 engine, I plan to use the SU carb setup Gaston has on his Sonerai, and that should not protrude. I would be interested to hear what others have done so that their cowl hinge wires do not require extreme force to insert.

Tom

[schrome]

Hi Tom,

I had - and still have - the same problem, although it diminishes somewhat over time as the hinges wear in. The main problem is that the top and bottom halves of the cowling don't quite match each other, something I might have tried to fix while building had I realized how aggravating it would be. It's a three handed job - two to hold the cowling together and the third one to muscle the pin into the hinge. Some things that have helped...

-make sure the leading ends of the pins are rounded like bullets;
-use a little wax lubricant on them;
-leave all the screws loose until the pins are installed, then tighten them.

Another tempting reason to split the cowling at the firewall.

Ed

[peterzabriskie]

Guess I just got lucky here, the first builder did a great job on this and my pins slide in and out easily. I use a little oil on them, the tips are rounded like Ed said, I did use a pliers to hold the wire and twist and shout them in the first few times but it still was *gently* force, nothing hard.
-Pete
Looking thru my photos, I have some good ones of the inside of my cowl, I will PM you with them they may help. I think he(1st guy) may have every so slightly bent the hinge over the length to a curve. All those short straight sections become dead ends for the tip each time they encounter, the only point to turn is the small space between each straight hinge unit.

[n3480h]

Thanks Ed. I did bullet-nose the wires, and I'll try the lube. I think I'll try some heating and cooling cycles while its together, to see if I can't get the two halves to conform a bit better. You are right, the top and bottom don't match very well. I seriously thought about going to Dzus fasteners. And I thought about splitting at the firewall. At this point, 48 screws would be a lot easier than those two wires. I talked to an RV-8 builder who produced a very nicely done cowl installation - he had the same problems. He did say the wires go in easier now that they've worn in a bit.

I also noticed that the bottom lip of the smiley inlet does not line up well with the intended direction of airflow to the sump, so that will get modified to correct the bottom lip. Also found several voids under the gel coat around the sharper angles in the front of the smiley inlet, so those have been filled. I think I will also follow Gaston's lead and install a bottom panel to allow easier access to the sump, so that the bottom cowl will not have to be removed for oil changes. With all the corrections I've had to do to this cowl, I may have been time and money ahead to lay up my own.

Tom

[wafer]

Tom-

I usually refrain from making comments as I do not have much Sonerai usage to back my experience. I too have problems with my cowl pins. I will say after 15 hours of engine time, it will be easier to put the pins in as the cowl does some conforming with the engine heat. In my experience, putting in the pins are currently not perfect but manageable as I still need to finess the cowl. Ed has great suggestions above.

I write this to encourage you to hang in there. I would not want to deal with ~48 screws everytime I wanted to open my cowl....and making a cowl from scratch is a major undertaking!

Mike

[n3480h]

Thanks Mike. I am hanging in. Spent the day matching the rear of the cowl to the front of the FGlass skirt. Lots of sanding, but I finally got the lines right. There is now a uniform 1/32" gap where they overlap, and I can live with that. The cowl pins are still in and the cowl is centered on the engine centerline. Lots of putzing required to get it right, but it looks good. Also got the lines laid out on more carbon fiber for the rear baggage deck. Next is to install quick mounts for fishing rod holders. When this Sonerai is done it is going fishing up in MN for pike and walleye, and west to Custer state park in SD, for trout. (I keep telling myself this so I can keep the goals in mind, lol).

Tom

[shawnson]

one thing that made life much easier for us on the lancair was to put the cowl pins in an electric drill and spin them in at high speed while gently or not so gently banging on the side. this made the cowl pins go from massive PITA to about a 3 min job. i think it also helps to speed up the wear in process of the pins.
one thing i heard noted above, your hinge pieces are not one piece? the way we did ours the entire hinge curves with the cowl front to back, is that not how it is on the sonerai?

[pttim]

I have 10 screws holding the cowl together total.

Ed dont split the cowl at the firewall, you might regret it as I did.
The two piece cowl did not retain its original shape.

Tim

[oahupilot]

A little valve lapping compound may help fix your pins. Put some valve compound on the pin then work it in or out or use drill as suggested earlier.

Another thing to consider is how much are you constricting the cowl to reach a certain shape around the fire wall. The extra tension normally makes it much harder to install the pins.

I eventually just split my cowling at the firewall and ended up building a composite joggle to hold it all together and keep it properly shaped and spaced. It was some work to split it but I am very happy with the results. Splitting the cowl has some advantages, like keeping the alignment between the canopy skirt and cowl accurate. I still use the pins along the horizontal split with screws around the joggle to hold it all together.

[n3480h]

I don't have the firewall fabricated yet. I wanted to get the cowl mounted and secured first so I can make a template to fabricate the firewall to match the cowl - allowing for the seal that I will add when its done.

Is that an outlet heat shield I see in the first picture?

shawnson, yes the hinge on the Sonerai cowl is a continuous run of extruded aluminum hinge, 3 feet long. It follows the inside curvature of the cowl. Part of the problem is that I (correctly) mounted mine "blind", so none of it shows externally. That makes visual alignment pretty much impossible. I finally achieved some measure of success by removing the top half hinge and sandwiching in a .050 thick strip of aluminum to offset the top half of the hinge in the direction it needed to go. Next step is to put some heat in the cowl to "stress relieve" the fiberglass. Hopefully that will help the hinges align better.

Tom

[oahupilot]

Tom,

Not so sure what you mean by "heat shield outlet" . All the wires run through canon plugs, oil and fuel lines have bulkhead fittings at the firewall, control wires also go through cable safe bulkhead fittings.

[n3480h]

I was asking about the lighter gray rectangular piece at the bottom center of the first picture. It appears there are, or were four straight stack cutouts in the lower cowl cheeks, so I was curious as to what the light gray piece is.

Tom

[oahupilot]

Tom

its just some aluminum to prevent the exhaust from chafing the cowl and burning through it.