Zenith Aircraft Builders and Flyers
Online Community of Zenith Builders and Flyers
Engine Cowl and Mold construction
Hello all,
I started looking for an engine cowl for my setup over a year ago and couldn't come up with a solution, so I am now in the process of designing and building my own engine cowl. (Zenith 701/ULPower 350iS) I know this is a bit of an odd combination, but it should make for a Hot Rod Sky Jeep... :)
I almost have the male plug ready for the next step (see attached picture), but I am a newbie and I have questions:
*Is it worth the time and effort to build a female mold from this male plug?
*Vacuum bagging a good option?
*Should I just do a one-up production and layup the cowl material on the male plug?
*If I use the male plug for the final product, how do I clean up the layer overlaps and smooth the surface for paint?
*Fiberglass or Carbon Fiber?
*How many layers, what type, and what weight of fabric?
*Do you all think there would be any interest for building a few of these to sell?
This is just my concept and style. I'm sure it will take some fine tuning to get everything right, especially with the rear-mount oil cooler.
I have taken the EAA Composites class, but this is still a big project for a first timer. I made a post in the 701 specific discussion back before I started. There was some great information and I hope those guys will continue to share their knowledge here for everyone to see.
Also, here is a short video link to the spray foam process I used for the plug:
Thanks for looking and I really appreciate any and all feedback, suggestions, criticisms, or any other input you are willing to share!
-Jon
- Attachments:
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IMG_1450.JPG, 1.1 MB
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Replies to This Discussion
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Permalink Reply by Jon Humberd on
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I am just outside of Chattanooga, TN. If you were closer, I might try to hire you to come help me with this composite project.
Someday, I intend to fly to Big Bear Lake. Maybe we can at least meet up so you can inspect my cowl.
I'd like to lay-up this whole thing in one sitting. Is this realistic?
Aircraft Spruce will roll or fold the fabric. I assume it should to be rolled?
I also found few pinholes that didn't completely fill-in with the paint. Will wax take care of those, or do I need to take another step?
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Permalink Reply by Bob Hartunian on
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Should be able to layup plies within ~1 hr if plies are precut. As you begin to apply plies, it will go faster.
Does not make any difference if glass is rolled or folded. Neither will break fibers.
If pin holes are small, wax should cover them.
Might be helpful to have a second pair of hands to move and position plies.
If you want to talk on phone, my cell number is 909-486-0038 and email is; bobh5@earthlink.net
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Update:
I finished laying up the first attempt last night and it went pretty well. I am hoping I can remove it without destroying the male plug. If so, I plan on laying up a second/better cowl and keep the first for a spare. I tried to incorporate some foam core in the construction and being the first time for me, it took quite a while to get everything laid out, ready, and then it was also very time consuming to get everything complete with the layup. We spent several hours and probably were pushing the working time of the slow-cure epoxy. I learned a lot from this first big job.
One thing I experimented with that really seemed to work well was, once complete, I wrapped the whole cowl layup tightly with pallet wrap (basically saran wrap). We didn't see any sagging underneath, but didn't want to take a chance. The pallet wrap held everything tightly in place and it peeled off very easily this morning. It also left a smooth finish on the top layer that should be relatively easy to sand and finish.
More to come later and I will add pictures soon.
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A lot more time invested and mold design changes/refining, but Cowl mold version 2.0 is almost ready for a layup! I hope to give it a try tomorrow evening. Wish me luck!
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Hopefully the final lay-up will happen tonight. Moving forward, when is the best time to finish the surface for primer? Should it be done before the cowl is freed/released from the mold, or would it be better to remove the cowl from the mold and have it attached to the airplane before it is sanded and smoothed?
I plan to use epoxy and micro balloons to make a filler/paste for the final smoothing before primer.
I also plan to fly for a while with only primer on the cowl, at least until I am sure the cooling and ductwork functions properly.
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I'd remove from mold and have easier access to all surfaces for priming. Then attach to plane for flight testing. And finally smooth and fill on plane for final coating. You might also paint inside surfaces with reflective finish to cool from engine heat.
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