Installing & Removing B-Model Cowl With Prop Installed

[Spaceman]

Have you B-Model guys run into issues with getting the cowl on and off once the prop is installed? I have found it really difficult to wedge the lower cowl in behind the prop without running the front of the cowl into the back of the prop and scratching it.

So far I can't get the upper cowl on at all! Since the aft edge has to go under the windshield skirt, I can't seem to figure out a way to install the aft edge and then rotate the front down into place with the prop there.

I know the front of the cowl is in the correct place relative to the prop flange once it's installed, but in order to get the cowl on I need to somehow squeeze it behind the prop.... Is there a trick I'm missing?

[pappas]

The lower cowl can be put in place by pushing aftward on the 2 spots that contact the rear of the prop. The fiberglass will bend enough to get the lower cowl up. The order is to insert the lower aft pin first, raise the cowl until it is in place, then secure the side pins.

I was never able to get it to clear 100%, but it was enough that it did not do any damage to the cowl. I have not seen one that did not have at least a few light scratches in the rear of the prop hub's clear coat. But nothing deep.

The top cowl was a different story. I could not get the top cowl under the firewall upper lip and in place at the nose without badly scratching the upper rear of the top cowl. So, I decided to change it up. I looked at the way my RV-8 upper cowl was built. My B-model top cowl doesn't go under the forward upper fuselage lip. I made and riveted a scalloped strip of aluminum to the bottom of the upper fuselage lip, creating a 1-inch "ledge" (?) for the top cowl to rest on. I made the rear of the upper cowl a little shorter and secured it to the lip it rests on using 1/4 turn fasteners. That solved my problem.

I know that description is a little difficult to imagine, but look at how Vans does the cowl on an RV-8. I also used Vans method for attaching the sides of the lower cowl to the forward fuselage. I was able to eliminate the 2 piano wire pins that Sonex has sticking out of the side of the cowl. (hose are fiddly to install and remove). I didn't like that on my first Waiex and didn't want to deal with them on this one. Even after my forced landing, it looks better than Sonex's design.

[Spaceman]

Hey Lou,

Thanks for the info. Yeah that's about where I'm at with the lower cowl... I get the bottom edge around the gear legs and pushed all the way back, then I can push on the front hard enough to flex it into place behind the prop, then I do the bottom hinge pin followed by the two sides.

I think I can picture what you're talking about with the upper cowl. It would be so much easier if the cowl went on top of the windshield skirt! Then you could just drop it straight down.

Something like this?



Now that I'm thinking about it, I can probably still do what you're talking about without too much trouble. I could trace where the windshield skirt ends onto the cowl, cut the aft ~3/4" off of the cowl along that line, then rivet a strip along the bottom of the skirt, and then the cowl should sit on top of that.

I just already have all my Skybolt fasteners already set up, so I will have to try and drill out and reuse all the receptacles that I have on the aft edge of the cowl and move them to the new strip. I hope I can reuse them because I don't feel like waiting for more parts!!!

[Scott Todd]

You should spend whatever time it takes NOW to make the cowl easily removable. I see too many homebuilts where the cowl is a major pain to remove. That just discourages inspection and regular maintenance. My new Onex has about 25 hours now and I take it off almost every flight and at least every few hours. I can take the top off as fast as I can remove 16 cam fasteners and the bottom I pull 4 hinge pins. It takes about 5 minutes to put them both back on by myself. I use a little height adjustable rolling stool to support the lower cowl. Insert the two bottom pins and then rotate it up about the 20 degrees or so and insert the two side ones.

People at the airport are always surprised how easy it comes off and on. I always say "why wouldn't it be" ?

[T41pilot]

Chris

I've got my top cowl under the lip but it was a pain. I had to trim some fiberglass back at an angle on the nose area of the cowl to clear the prop during installation. I didn't trim off much but it's certainly a tight squeeze and I have some light scrathes on the back side of my prop as well. I also had to leave the retainers off the aft skybolt fasteners and keep them pulled up when sliding the cowl under the lip during install. So the process is install the lower cowl first. Then slide the aft side of top cowl under the lip while squeezing the sides at the same time to force the aft edge to better form to the shape of the lip. Press the front down into place when aft edge is in place. Secure the first skybolt fasteners on either side in the front while holding the cowl down. Once it stays in place on its own then push down the aft fasteners into their recepticals and lock them in place. Definately a job to get my cowl in place but it works for now. If I can see an example of what Lou is describing and can live with the finished look of it, I may change in the future.

Got a date with the FAA on December 3rd for my Airworthiness. Wish me luck.

[pappas]

Chris,
That picture is exactly what I am talking about. It was easy to do and I didn't scratch any paint during install or removal. I used hinge pins on the sides and bottom of the Waiex, but on the RV-8 I did it exactly like your photo shows. Really easy and fast. You will be glad you did it that way.

[Spaceman]

OK, that's what I'm going to do! I'll report back with results. Hopefully I can get this done tomorrow; this is one of the very last things I think I need before airworthiness inspection!

Yeah I definitely want to make sure it's easy to get off and on. I am lazy and I don't want to be tempted to skimp on inspections and maintenance later because I don't feel like taking cowls off.

[Spaceman]

Lou I did what you recommended! It took a few days of messing around but now I can get the upper cowl on and off pretty easily without mangling the prop.









My only issue now is these little gaps in the corners. Now that I've moved the aft edge of the cowl a little bit there seems to be no way to make it follow the contour of the windshield skirt all the way to each end... All I can think to do is add some fiberglass or filler to the top of the cowl to just blend it into the skirt a little better. But the gaps aren't that big; I will deal with it later!

[Spaceman]

Got a date with the FAA on December 3rd for my Airworthiness. Wish me luck.

Also, good luck with your inspection Gregg! I think I will get mine done in the next few weeks, hopefully. I just submitted all my stuff on AWC today.

[T41pilot]

Thanks Chris

It took a couple weeks for my application to hit my local FSDO. They decided to use my plane to train a new hire so I'm getting double teamed. I had to wait for 2 guys to be available instead of one so I've waited a couple months in all to get here. You may have better luck than that.

I like your solution to make separate pieces instead of one long strip. I will probably be going the same route at some point.

I still have a nasty oil leak on my engine that I will have to address further next spring. I suspect a leak around a case saver but have to get some adjustable pushrod tubes so I can get the super tin out of the way to see what's going on while the engine is running. I'm tired of pulling the head off every time I thought I had it fixed and didn't. I need to get some time in another Sonex before I fly anyway so having to fix a couple of things in the meantime isn't a big deal. Good luck with your inspection and let me know if you get your instructor cert. I'm still on board to be your first customer if you have it by next May. I have a LODA to handle my side.