Lower Cowling Doesn't go Back On Easily

[Subsonic]

I've been unable to get both sides of my lower cowling front top-most bolts in the bowl at the same time since I bought my Tri-Pacer a year ago. I'm always half-a-hole diameter short on one side or the other, from being able to squarely drive the last screw in. And I've tried about every sequence on starting bolts, slackening them, pulling, pushing, etc., to no avail. My nose bowl has several repairs from being pushed and squished and vibrated. Lower cowling isn't much better. I've been replacing nut plates or anchor nuts now that I have rivet squeezers and replacing broken out pieces of the flange on my nose bowl where previous bolt hole alignment wrestling matches have been muscled into submission. If I'm looking at the right part numbers at 'spruce a nose bowl is $1,603.00 and bottom cowl is $2,910.00. I imagine some fitting is required, painting, etc. Figure about $5,500.00 installed, as a ballpark estimate, right? So, for those prices I'm incentivized to try and fix mine. Does anyone know the correct dimensional width of the nose bowl at the cheeks? I recognize the cantilevered engine cowl is a 'soft-box' monocoque design, (without the rigidity of a true 6 sided box) due to the top cowl flaps that roll over the sides and held down by the cowl latches. The result is that the loads aren't equally distributed at all points, leading to degradation of the structure at these overloaded points. If you look at a few of these lower cowlings on different Tri-Pacers, you'll see the same kind of failures - cracks, bending, stripped attachment lugs. I think one of the most observable weaknesses in the design is due to top cowling tensile loads and lower cowling compression loads are reacted through the nose bowl, which bows outward at the cheeks. The soft box really is in need of a space-frame truss to accurately establish nose-bowl position and shape. And, perhaps just shape. So, why am I writing this analysis summary down? To see if any of you have already walked this path and found a relatively stable solution. Thanks.

[rocket]

I almost always pull the nose bowl and bottom cawl off together... its a function of the curve. the screws holes don't line up until all the screws are tight :/

start at the middle and work your way outboard... and cus or talk dirty to her.


Rocket

[Subsonic]

Rocket, she's heard plenty of dirty talk, and sweet talk too. Do you have a split nose bowl? You're not pulling the prop off to do that are you? Thanks.

[smcnutt]

I almost always pull the nose bowl and bottom cawl off together... its a function of the curve. the screws holes don't line up until all the screws are tight :/

start at the middle and work your way outboard... and cus or talk dirty to her.

Rocket

That and I leave all of the screws loose until they are all started and then I pull the upper cowl latches shut before i tighten the screws. Then I pop the latches and tighten the last ones that were covered where the two cowls meet. Our nose bowl stays on as it's not the split type.

[rocket]

No split cowl but I go from floats to skis and the prop gets swapped. I unscrew the top aft screws and lower trailing edge screws and just pull the whole assembly off.

I did fit a new nose bowl and the oil cooler is now square in its hole and the flywheel as well. it took some fiddling but in the end it fit well. I havnt had it off yet though...

Is cawl spelled with an" O" ? who would have known...


Rocket

[PA-16]

Mine is a PA-16, not exactly the same, but close. It lines up fairly well, it helps to have two people when putting it on. I put the rear top screws in on each side first, than the rear bottom inside screws and than move to the nose cowl screws and than start filling in the rest. They all line up good.

Maybe yours is not original? Is there a way to tell if it is original? You could have someone help you get it on and hold it up and drill new holes that are in the correct position.

[wyandot jim]

Well,
This is the way you do it if you are cheap and want to get rid of the Ugly Piper nose bowl.
New PMA nose bowl from Wag Aero, make new top piece between the reused doors (.032 6061 T-6 with reinforcing angles), and make a new bottom cowl (.032 6061 T-6) $80 for a 4x12 sheet . Since the nose bowl was given to me buy a forum member I probably don't have $50 worth of material in the whole thing. There were a whole bunch of bad words while making the stuff. Wags nose bowl is around $200. All the screws line up and it is easy to install.. I install a strip of .032 on the inside of the bowl to attach the nut plates to. That is the way I did the one on my Starduster 45 years ago and no problems of loose plates. I also use more plates than original and NO COUNTER SUNK Washers.
Anyway just a way to save money and have a nice cowl that fits and looks good IMHO.






The top piece.

[Subsonic]

I finally got all the screws in, and I didn't even have to convert my Tri-Pacer to a tail dragger to do it! And, Jim - I like my nose-gear and big ole' large-mouth-bass air scoop just fine, thanks. Background: I had replaced the top-forward (bottom cowl) nut plates and found they really needed a 10-32 tap run through them to get the aluminum skin hole trued up to the nut plate holes. Now the nice flat head screws with stainless countersunk (and aerodynamic!) washers are all seated nicely. All is snug and rattle free. Now to get a passenger door catch installed, and finish the right wing flap inspection port fabric patch doping, paint my struts, wing cuff fairings, install the wheel pants, headliner, etc..

[JohnD]

A little off topic; where do I find the part no for the cowling screws (or just the correct size) ?

[Steve Pierce]

If someone hasn't modified anything they are 10-32x 5/8" truss head machine screws. Drawing 11966 calls them out.