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Looking for pics or build logs with removable scoop

IowaRV9Dreamer

Well Known Member
I’m going to have to install the 360 scoop on my 320 pink cowl. I’ve searched but have been unable to find any pictures of the process or finished result. If anyone has any, can they post them here?

I’m trying to decide between mounting the new scoop on the outside of the lower cowl, or making it flush with a flange.

Thanks for any help,

Dave
 
Hey Dave, Rod Bower has some videos of one way to do this on his website. ramairforhomebuilts
basically you are drilling through the flange of your scoop to the cowl. you could then remove the scoop, packing tape and mold release the flange and reattach. Then use epoxy micro or other fairing compound and a spreader to apply on the cowl bottom and flange to make a gradual transition. Use a hotel key card or .032 Al scrap to trace the flange line through the epoxy and you have your rough parting line. Let dry, sand, rinse and repeat until smooth finish. Add you screws or quarter turns after. One way to do it.
 
Converting a 320 cowl for a 360, How I did it, this is a cut & splice saga... sorry no pics...
I found I had to increase the cowl depth by 1", & widen it to accommodate the larger FAB360 air box. Along the way I drilled temporary holes in the lower cowl for screws or clecos as needed, easily filled in later.

- cut a plywood panel to the shape of the lower firewall - so it fits inside the lower cowl & preserves the side to side & vertical dimensions of the existing lower cowl.
- use a dremel tool to grind the inside fiberglass layer and honeycomb back where needed. Caution, don't grind into or disturb the outside layer. You can than use a micro slurry to re-seal the honey comb edge and create a sloped transition from inside & outside fiberglass surfaces. Follow up with a couple layers of glass over that and strengthen the outside layer.
- screw your plywood form to the lower cowl to stabilize it.
- use an oscillating cutting tool or similar to cut the side wall of the scoop/exit port off the bottom of the cowl.
- use a series of aluminum strips to space the scoop away from the lower cowl (in my case, 1") & attach with a couple clecos per strip.
- once you have the required vertical height you want, tape some light poly plastic sheeting to the inside of the cowl, forming a pocket along the gap you created.
- prop up the cowl on it's side.
- mix up some 2 part urethane foam and pore it along the gap, just enough so it expands thru the gap & you can sand it down to the required shape. Repeat foaming & shaping on the other side.
- lay up 2 layers of glass over the gap joining the scoop back to the lower cowl. All around.
- next day, remove the plastic, chip out the urethane foam, & remove the aluminum strips & clecos.
- lay 2 additional glass layers to the inside surface of the cowling for more strength.
- you've basically done the scoop depth modification, now to widen the scoop for the FAB360 housing.
- cut the whole scoop off the lower cowl, about 1" outboard of the scoop all the way around.
- split the scoop in half front to back.
- using more aluminum strips, cleco the two halves back together to the required width using more aluminum strips.
- again tape a plastic pouch inside of scoop, again follow the foam, sanding, glassing as above to join the two halves of the scoop.
- use scoop to trace new cut out on lower cowl.
- repeat again the clecoing, glassing steps to make the cowling one piece again.
Sounds like a drawn out process but realistically can be done in 2 days with cure times. Smoothing out and getting ready for paint afterwords is just another joy working with fiberglass...

If you are just mounting a new scoop to the lower cowling, I vote for mounting it to the outside (this prevents internal flange areas that might later infringe on exhaust/alternator/or other interferences), glue it in place with a epoxy/flox mixture, after it is cured, grind the square edge off from around the scoop & feather it smooth with micro/epoxy slurry layers.
Inside the cowl, seal any exposed honeycomb with a micro slurry, followed up with a couple layers of light glass.

or

You can follow some steps of the cut & splice process above for flush.
 
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Or... are you asking about a Removable Snorkel Inlet? (Like discussed on some threads recently?)

Simple task-
Draw cut line defining removable inlet, generously paint mould release on inside of snorkel, lay up about 4 layers of glass on inside of snorkel, let cure, drill cleco positioning holes thru snorkel and glass flange aft of the cut line, drill screw pilot holes forward of cut line, pop fiberglassed flange out of snorkel, trim flange to width you want, install nutplates for screws, cut removable inlet portion off snorkel, clean mould release off glue surfaces, Glue flange in with flox slurry & cleco flange in place, attach your preferred flexable duct arrangement to the removable inlet, done... till paint
 
Talk a little about what you are trying to do.

You can check DanH posts, he did the inlet and the exit chute aft. I made a couple of new exit chutes for my James cowl. No flange. It was a lot more work than I expected to yield a really smooth contour. I ended up with yet another mold for a glass part.

All this depends on what you want to do. Buying a spare cowl (from another builder) could be the best option unless you want to make an experimental performance project out of this.
 
I have pictures of how I made the ram air inlet on my cowl removeable.
I did it on my RV3 but the process would be the same.
Email me if you would like the pictures.
Sf3543 at sbcglobal dot net
 
a bit more explanation

Thanks for the helpful replies, especially Ralph's detailed tome which I will study.

My situation is RV-9A, with an O-320 engine (vertical induction) and O-320 cowl. I decided to go to a RSA-type fuel injection servo which requires an O-360 FAB and O-360 cowl. Unfortunately I have already fitted my cowl to the airplane with quarter turn fasteners and don't want to re-do it.

I temporarily mounted the oil pan, servo, and FAB top plate to see how bad the situation is. You can see the results in the photos. The scoop / cowl junction bumps up against the mixture side of the servo (and yes I think it will be worse when the mixture arm is correct). In addition, the top plate of the FAB is nearly at the bottom of the air inlet scoop.

I spoke to Vans and they offered a new cowl (no thanks) or the $200 FAB-6-SCOOP-360-1. It is my hope that the 360 scoop will be both wider at the top (to clear the servo body) and lower. I'm hoping to get some examples of how to attach it, ideally in a removable manner.
 

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Keep the cowl as is except for minor mods, like to clear the mixture arm. Instead, design and build a new airbox. There's nothing sacred about the stock Vans box.

Nice example here, from Chris Zavatson: http://n91cz.com/airbox/airbox.htm
 
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Keep the cowl as is except for minor mods, like to clear the mixture arm. Instead, design and build a new airbox. There's nothing sacred about the stock Vans box.

Nice example here, from Chris Zavatson: http://n91cz.com/airbox/airbox.htm
Thanks Dan - I thought about changing up the FAB, but I was worried about the "wet dog shake" causing the side of the servo to hit the side of the cowl as shown in my picture. Its almost zero clearance now. I am going to go look to see what can be done.
 
I’m with Dan. Put a bump on the cowl to clear the linkage and fab an new FAB.

Should work fine.

Peter
 
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