New Builder Several Questions

[Mark Moyle]

Before I fly my almost finished Pacer.... will be installing clear teflon tape to the fabric surfaces and painted steel/aluminum surfaces.....maybe 1/8" beyond the door skins. I'm also going to install between the lower boot and cowl... across the top of the boot cowl....butted against the antichafe tape. Might turn a little yellow over time? I'm also installing the same automotive film used to prevent rock chips on lower fender panels.... that film will be applied to the front sides of the Maule oleo gear struts and PA18 gear legs.... thicker black rubber stuff to the leading edge of the horizontal stabilizers. I used urethane tape...the stuff used to seal steel siding/roofing panel where the boot cowl trailing edge attaches....then carefully removed the excess that squeezed out... hopefully will prevent the edge from working into the paint/fabric.
Mark M.

[Sebastian]

Thanks Mark

[JimParker256]

Hmm. Looks like you could rivet (or glue) a small strip of aluminum, bent into an "L-shape", right where the baggage door rubs against the fabric, with the "L" to the inside of the door opening. Not sure that's the "best" answer, though. Other thoughts?

[Sebastian]

Ok Guys I have run into a bit of a problem. I have put my exhaust on the engine (Veterman brand) and even with all the flex joints that were put in the pipes it still hits the cowl. I have turned it every way I can think of and no luck. I am attaching some pics. The only solution I have come up with is to put a bubble / blister (I don't know the proper term) on the side of my cowl. (NOT HAPPY)

Has anyone else had this problem and what was your fix? I know the brain trust on this forum has ideas. IMG_1744.JPGIMG_1745.JPG

[jaredyates]

Talk to Clint B an see if he can help you out. In my experience he is really helpful.

[Ed.Meyer]

Agree. Clint was very responsive for us as well fixing a small problem promptly.

[Clint B]

I haven't trolled through the bearhawk forums in the last 10 days or so, so I've missed this.
Sebastian called this morning and we discussed different ways to resolve this.
For the rest of you that are building a bearhawk 4 place, here are a few things about the exhaust:
its jig built on a lycoming engine, and using the prototype bearhawk exhaust that we built about 10-12 years ago, we take 1 pipe out, and replace it, take another pipe out, replace it ect. This method ensures that there is very little variation from 1 exhaust to another.
It seems from plane to plane, the bottom cowls seem to be the wild card. Some people build their cowlings tighter than others is my basic conclusion.
In this case, I will likely swap Sebastian his exhaust, and build him one that fits more tightly to the engine. Otherwise he will have to change his bottom cowl.
for the rest of you still building, it's best and easiest to install the exhaust before you build the bottom cowl, as 1/2" makes a huge difference in clearance.
Hope this helps! Clint Busenitz /Vetterman Exhaust

[Bcone1381]

Clint;

It will be quite some time before I have my engine and start building my cowling. My visual perception is that the bottom cowl runs straight back from the nose bowl (provided by Bearhawk Aircraft in my kit) to the firewall. How does one adjust the bottom cowl downward to add a bit of space for the exhaust?

I can see using some blisters, or a different cowling as an option to create some extra space. Are there any tricks of the trade that I am not thinking of before one starts using an english wheel to form a convex compound curb on the bottom cowl?

Brooks
Patrol Quick Build

[whee]

Brooks, I bet the variation is placement of the firewall and nose bowl. Like you said, the bottom cowl runs straight between the two.

[Bcone1381]

Whee, Thanks for responding....school me....

Can I adjust the placement of the firewall? I had not thought about that. Maybe I can bias it downward a little bit if needed...never thought about it. I never thought about installing the engine and exhaust before I installed the firewall. Sometimes I wonder what else I am missing.

Help me understand how I can adjust the placement of the nose bowl, because I envision the nose bowl gets matched up the the position of the spinner.
(And the Spinner position determined by crankshaft, which is determined by engine mount with is directly bolted to my fixed Fuselage attach points)

[whee]

Brooks, I'm not capable of schooling anyone on anything and I don't think you are missing anything. The variation I was referring to is builder placement of parts. While we try our best the firewall may not be placed exactly where Bob depicts in the plans, the nose bowl my not be exactly centered on the crankshaft, etc.

In no way am I saying Sebastian did anything wrong but perhaps his firewall was place a smidgen higher than the plane that was used to build the original Vetternam exhaust. Or perhaps the builder of that plane lowered the nose bowl a bit to allow for engine mount sag that happens over time. There is small variations in all of these planes, that's just the nature of homebuilt airplanes.

I'd build is as close to plans as possible and test fit everything. But don't listen to me, I'm going to build my exhaust to fit my cowl for my one-off engine installation.

[Mark Goldberg]

There is some builder variation on how tight builders wrap the cowling sides around the lower longerons. Mark

[Clint B]

Hi Brooks, I don't have experience building the bearhawk cowl, but as Mark said, there seems to be some variation. Why, I don't know.
i see you are building a patrol. They have a roomier cowl so you shouldn't have any issues. Clint

[jaredyates]

Speaking as someone who has built two cowls for the same airplane, I'll say that one source of variation is in how low the exit air opening protrudes. If the cowl were wrapped all the way around the firewall without any exit opening, then the space in the cowl would be less variable, but as you mock up the lower cowl sides with side clamp clecos, you can produce some variation there.

[Bdflies]

Haven't done a 4 place, but I agree with Clint about the Patrol. My Vetterman system tucks very nicely under the Patrol cowl. Absolutely no concern.

I would strongly suggest having the exhaust system in place, when designing/installing stuff like engine controls and sensor wiring. I built the most elegant mixture control bracket. It worked smooth and sure. Admiring my work, it occurred to me that there could be interference with the exhaust. Since there was no way to route the cable through the muffler, my nice bracket went into the trash. Think about the stuff that's 'variable'. Things like wire, hose and cable routing. Then consider stuff that's 'fixed', like carburetor, exhaust and prop governor. Put all the 'fixed' stuff in place before working on the 'variable' stuff. I don't know that I consider the cowl construction to be 'variable', but it sure couldn't hurt to have the exhaust in place, before finalizing that structure.

To Jared's point, if I ever build another cowl, I won't keep the lower cowl so tight under the engine. I'll let it droop a bit. Not only would this allow just a smidge more room, for hoses and control cables, but I think the droopy, lower exit area might help cooling. It's my impression that the tightly contoured lower cowl leaves the air exit area at a slightly higher pressure state. A very slight 'cut throat chin' might produce a lower pressure exit. I'll consider building another, to test that.... But not anytime soon!

Bill

[Bcone1381]

I am sure am glad I asked my questions....You all gave me ideas that will make things a whole lot easier.

A little side note: A process I developed for my build is as follows. I developed a flow chart of tasks which begins at receiving the kit with numerous steps to the test flight. Then I made up my own set of instructions for each task, (which includes an attempt to make an exhaustive list of hardware and tools for each task.) I brought together the all the hardware lists for all the tasks, then sent in one order for all my hardware to Spruce. I knew my goal of a single hardware order was ridiculous to achieve, but I have found great deal of accuracy. I would be embarrassed to count how many hours I put into determining bolt lengths off the plans. But now I can just go to my instruction sheet, pick out my parts, and go accomplish the task.

Whats that got to do with all of your inputs? Well, I am going to take all these things you guys have brought up, and add them to the instructions that I have for making the engine cowl, and for the Firewall Forward. A year or two or three when I come to it, I will have have the information and this thread referenced.

Bill, Jared, Clint, Mark, Whee, I owe you guys a beer.

[Bcone1381]

Jared, can you share what factors went in to your decision to build two cowling?