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FAB alternatives...

jferraro17

jferraro17

Opulence, I has it...
Is there an aftermarket FAB or any other options out there for a vertical intake setup?


Thanks-


Joe
 
jferraro16 said:
Is there an aftermarket FAB or any other options out there for a vertical intake setup?


Thanks-


Joe
Click to expand...

I just built a metal box after making 3 cardboard models to get it right and hooked it up with 3.5" scat tube. It is attached to the left intake baffle, same place FAB hooks up for air. I have a problem getting the scat tube to it without touching the cowl...have not decided to continue using it or go off in another direction....don't know of an after market product. I am going to try a product from "intakehoses" to see if it will clear the cowl better than the scat. http://intakehoses.com
 
I don't mean to imply that the standard FAB can't be improved upon or discourage someone from from trying something new but I thought I would relate this story from quite a few years ago.
I was work aircraft parking during the Copperstate Fly-in.
I had just parked two RV-6's that arrived together.
One of the pilots was looking into the exit of his cowling and then began relating the following story.
He had been flying right beside his friend at altitude. All of a sudden his RPM increased (fixed pitch prop) and he began to pull away from the other RV at a pretty substantial pace. He had to throttle back for the rest of the flight for them to stay together.
After landing, what he had found was that his home built airbox had failed and fallen off of the engine and exited the cowl.

Point of post is that their can be a lot more to the design of some of this stuff than might be initially apparent. Over the years I have found that even the smallest little change in something can make a difference that I never would have imagined.
 
I'm just interested in not repairing one every "x" number of hours...I've heard the stories.

I'm also watching a buddy spend a TON of time building his, and thought there might be a better way.


Joe
 
jferraro16 said:
I'm just interested in not repairing one every "x" number of hours...I've heard the stories.

I'm also watching a buddy spend a TON of time building his, and thought there might be a better way.


Joe
Click to expand...

If you think making the standard FAB box takes a ton of time (I didn't think so) please remember that usually any modification will take 3 times as long to design, fabricated and build. Add to that the time wit will take to test to see if it performs as well and don't forget the increased risk involved with the unknown. As an Engineer the only way to know what you get with a new design is to test the baseline and then test the change. If your only concerned about the "time" it is obvious the least time is to go with the known.

As for the "problems" some people have had with with their FAB I have also looked into why. One issue I noted is that on some carbs the mounting plate can not be mounted flat without a spacer due to flashing at the rear edge. Some have notched the plate so much to clear the flashing that it left very little metal near the bolt resulting in a high stress area that resulted in cracks. I filed down the flashing and then used a 3/16" spacer. I believe you will find most RV's have no problem with with the FAB. Also to be considered is the vibration your engine sees. Wood props will produce less vibration and if you use a metal prop having it properly balanced will greatly reduce the unwanted forces on the FAB.

http://picasaweb.google.com/FSmidler/071202N96FSFilteredAirBox#
 
rvbuilder2002 said:
I don't mean to imply that the standard FAB can't be improved upon or discourage someone from from trying something new but I thought I would relate this story from quite a few years ago.
I was work aircraft parking during the Copperstate Fly-in.
I had just parked two RV-6's that arrived together.
One of the pilots was looking into the exit of his cowling and then began relating the following story.
He had been flying right beside his friend at altitude. All of a sudden his RPM increased (fixed pitch prop) and he began to pull away from the other RV at a pretty substantial pace. He had to throttle back for the rest of the flight for them to stay together.
After landing, what he had found was that his home built airbox had failed and fallen off of the engine and exited the cowl.

Point of post is that their can be a lot more to the design of some of this stuff than might be initially apparent. Over the years I have found that even the smallest little change in something can make a difference that I never would have imagined.
Click to expand...

Which says a lot for a by-pass to direct ram air. Filters inhibit air flow, there's no denying it and a filter is not needed in flight.

My filter box will not leave the airplane. It is held together with about 25 rivets and attached to the left intake baffle with 6 #8 screws and plate nuts on a flange. The entire front baffle will leave with it if it does depart. :)

I just noticed this morning that Joe's situation is with a vertical system, a different issue than what I was addressing, which is a horizontal deal with the intake way up front. I agree, building a box at the intake of a carb can be tricky. There are plenty of such devices available. What I was describing is a simple metal box at the baffle intake connected to the induction intake with scat. It's stone simple except for the cowl being in the way.
 
Frank--

Totally understand what you're saying as my build time drags out with the FastBack mod...somethings are just worth it :)

As far as the extensive testing and all, I agree. I personally don't want to take this "experimental" thing to far. The known is good.

Here's the thing, the FAB--at least on my buddy's build--is one of the last things going on. It's at the point that it's just time to be done...know what I mean? He even commented "if somebody sold these pre-made, they would make a bundle".

Now this isn't his first build, and I found this comment interesting, coming from a veteran.

Anywhoo, I thought I'd ask the question after the conversation he and I had, but I'm personally not interested in re-inventing the wheel. It's already time for me to be done! :eek::D

Joe
 
David-aviator said:
Which says a lot for a by-pass to direct ram air. Filters inhibit air flow, there's no denying it and a filter is not needed in flight.

My filter box will not leave the airplane. It is held together with about 25 rivets and attached to the left intake baffle with 6 #8 screws and plate nuts on a flange. The entire front baffle will leave with it if it does depart. :)

I just noticed this morning that Joe's situation is with a vertical system, a different issue than what I was addressing, which is a horizontal deal with the intake way up front. I agree, building a box at the intake of a carb can be tricky. There are plenty of such devices available. What I was describing is a simple metal box at the baffle intake connected to the induction intake with scat. It's stone simple except for the cowl being in the way.
Click to expand...

Maybe you missed my point. The point wasn't that he wasn't able to design well enough that it fell off, it was that it flowed so poorly that he had more power with nothing there at all.
Just because you are working with ram air doesn't mean you will be immune to flow related problems. Building a good flowing system for a horizontal induction engine can be just as tricky as for a carb. Particularly when you are ducting the air from one location to another as you implied with your link to http://intakehoses.com. Consider the snorkel sold by Van's. It is probably not the ultimate in ram air pressure recovery, but it does have some shaping and use of area rules to try and recover pressure. It is far from being just a duct/tube that directs air from one place to another.
 
Frank Smidler said:
As for the "problems" some people have had with with their FAB I have also looked into why. One issue I noted is that on some carbs the mounting plate can not be mounted flat without a spacer due to flashing at the rear edge. Some have notched the plate so much to clear the flashing that it left very little metal near the bolt resulting in a high stress area that resulted in cracks. I filed down the flashing and then used a 3/16" spacer. I believe you will find most RV's have no problem with with the FAB.
Click to expand...

Another approach to this particular problem is to add a doubler to the area that gets notched for the carb. I did this and have had no problems with cracking in ~470 hours.

I'd agree with earlier comments that this is not a place to mess around with unless you know there's a problem. Any modification, even a minor one, adds dramatically to the build time.
 
I also added a doubler or some folks make the mount plate out of a little thicker material. I have about 900 hrs on mine with zero problems.
 
rvbuilder2002 said:
.... Consider the snorkel sold by Van's. It is probably not the ultimate in ram air pressure recovery, but it does have some shaping and use of area rules to try and recover pressure. It is far from being just a duct/tube that directs air from one place to another.
Click to expand...

I have, I borrowed one from a friend's fire wall forward kit just to see how it would fit.

The intake of AFP controller with the Superior cold air sump is considerably forward of the Precision controller intake with the standard Lycoming horizontal sump - for which the FAB was designed. The FAB won't fit unless the 90 degree turn into the controller intake is reduced in volume by about 50%, plus the area around the starter is modified, plus the flange on the FAB does not fit the controller. It is a major job to fix this and the internal movement of air will not be anything like it was originally. Some guy has done this on an 8, I've seen pictures of it and it is very well done but I do not know anything about the air flow situation inside of it.

The straight in ram air device from AFP is working just fine and so does the alternate source of filtered air. Filtered air costs about 1.5" of manifold pressure at this point and maybe that part can be improved with a better filter and/or location and ducting. I know scat ducting is not all that efficient, maybe the rubber elbow would be better, it certainly is smoother and the bend appears to be tighter away from the cowl front than is possible with 3.5" scat. That's what I'm working on.
 
Bill--

Thats a horizontal induction on a carb? I keep seeing "servo", so my little brain is confused. I'm going with an O-360.

GREAT setup, lot's of work, but looks great.


Joe
 
My Custom Carb Intake

Joe,

I've posted pics of the custom air intake on my RV4. Charles Wilhite built it up and it works great. It's all composite with some Carbon Fiber in areas. K&N forward facing filter inside the blue cone....Takes up way less room than the FAB.

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I'm over at Hicks (T67) if you want to see it first hand.

Good Luck!
 
Joe,

My setup is for a horizontally mounted RSA-5 throttle body on the front of an IO360 sump. The top end of this engine is O360, parallel valves. Sorry, its not for a carb. But it might give somebody an idea or two for this type of setup.

BTW, I also started with an O360, but ditched the carb and standard sump when I found out you can mate an "IO" sump onto an "O" top end. All that lacked in getting the parts to work were those intake adapters and a set of IO360-C intake pipes.

The result of this conversion is you get injection, a shallower sump, frontal induction, cleaned up cowl, and another 200 hours added to the project ! :)

Rgds,

Bill W.
 
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Bill F.--

That looks good. How many hours have you flown with it now? Has it been set up like this the entire time or did you start with a "normal" FAB? If so, any changes to power/performance? Any fatigue or cracking issues yet?

I might take you up on a visit...always need to run out to Avery's for something;)

Joe
 
No FAB

I have 20+ hours on the plane to this date.....all with the intake shown...
Incredibly well constructed....no cracks. The way it's made and the way it fits there is little "unsupported" weight. It weighs very little anyway.

The "4" is fast....the performance is as much or more than I expected...my last plane was a 6A with the same engine (0-360) and cs prop (it had a standard Van's FAB, hence the desire for a better mousetrap). It wasn't as fast or nimble, but I expected that.

I think Charles has plans to do a performance test with an 8 on the field (has a std. FAB) and then change out to the composite, horizontal filter version and repeat the test....

Another plus is virtually no construction other than fitting the forward facing K&N filter and the cone. The basic intake body with carb heat is fixed and comes pre made ready to bolt on.

Another thing I did was make the outer cowl intake removable for service ease. This is something I picked up from the RVator some years ago on John Foy's 6. I was going to do it on my 6A, but it just didn't happen. I was determined this time.

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Call me if you want....817-705-6300
 
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