Boot Cowl/firewall reinforcement

[svyolo]

I am doing final assembly now, and have been thinking about this for a while. I look at the whole Boot cowl/cowl, and I wonder if it is supported enough vertically. The lower cowl seems pretty well supported, the upper does not. The upper seems supported mostly by the lower. Bob's manual and plans don't specify anything that I found.

Does the upper cowl need support to the frame?

[gregc]

While not exactly clear on what you are thinking, I can say that the entire assembly is really quite robust once it is all together. I wouldn't worry about it.

[svyolo]

The lower engine cowl is very stiff and properly supported around its perimeter thru the boot cowl to the next station. The upper cowl isn't supported by anything that I can tell. Vertically, yes by the firewall, but fore and aft - nada. Does it need it? Is the lower cowl support enough? Bobs manual on the cowling doesn't mention any reinforcement that I can tell.

[gregc]

One thing I didn't think about - I have the Companion which has the engine 6" closer to the firewall and therefore a shorter cowl overall than the 4 place. Also I used some extruded hinge I already had and a somewhat heaver side channel (mostly to give me a wider target for the fasteners but it it is a bit stronger than the kit supplied channel). No fasteners from the cowl door to the firewall flange. I agree with Jared on not running the engine with only half the cowl.

[jaredyates]

The upper cowl is supported fore and aft by the screws that hold it to the firewall flange and forward boot cowl. For the piece to move fore or aft all of those screws would have to shear. It is supported up and down by the lower cowl primarily, and by the nose bowl and channels secondarily. Once everything is complete, the top of the cowl will also have some support from the baffles
I would recommend having at least one or maybe two quarter turn fasteners in the cowl doors through the firewall flange and nose bowl flange also. Because these doors are curved, they will provide support when they are latched closed, which is any time it matters.
Also, personally I don't consider it an option to run the engine with only half of the cowling on. I have seen folks do this with other types occasionally.

[Mark Goldberg]

The channels that reinforce the cowl door hinge line provide support. And the attachment screws to the firewall and nose bowl as well. Mark

[Battson]

svyolo last weekend - I was trying to bend the front of the cowl just a fraction of an inch (say 1/8th) - so I could reach my arm in and adjust the idle stop screw without de-cowling. I could hardly even move it that much.

Not sure if I correctly interpreted the question, but that cowling design of Bob's is STRONG

[svyolo]

Thanks to all.