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Show me your horizontal induction snorkel fit!

Draker

Well Known Member
Are there any good build logs that depict the steps needed to get this snorkel done? Vans' plans, well, they leave a lot to the imagination. I have an E-mail chain going with the mothership, but I thought I'd request any pics VAF builders might have, too. When properly attached to the injector servo and rotated so the inlet faces up, I'm observing the following problems:

1. The snorkel inlet is not centered horizontally behind the cowl inlet--it is pretty far outboard. No amount of rotation seems to improve this.

2. The snorkel inlet is too far forward, you can see in the below picture it actually contacts the cowl inlet.

3. The snorkel inlet is too high. My guess is it needs to get cut before aligning with the metal inlet ramp.

4. Assuming I need to cut the top of the snorkel, I will need to both match the angle of the inlet ramp AND possibly the horizontal tilt of the cowl inlet. Will the air filter still fit in the resulting oblique shape?





Is this an acceptable position for this thing, or do I need to think about chopping it up?

I've read the various "Frankensnorkel" threads [1] [2] where builders have chopped theirs all apart and/or re-made them. Trying to avoid having to do this if possible. But if I gotta do it, I'll do it.

Anyone have good step-by-step pictures of this sub-assembly? It would help me figure out if I'm on track or not. The more stock, the better!

EDIT: Oh, and since it's probably important: IO-360-M1B
 
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Start at post 534 here. I had to go a bit off script unless I wanted to modified it around the starter. It is working just dandy right now! And yes, the filter will fit in the weird shape that you have to trim it to. It is rather flexible.
 
My snorkel and I are not speaking right now

Let me say that the baffle / snorkel project was one of the most off script so far.

My build is a -7 with an AeroSport IO-360, Precision servo and Skytek NL-149 starter. The snorkel shipped by Vans was unlabeled before the troubles began, so no help with a part number there... ( I almost feel like the one I got was for a -14 ?) The only thing I can say about that part was that it cleared the starter just fine (after removing the two unused lugs on the starter).

The rest of the construction was a show... and not the good kind.

I'll admit that the only real way I could have wrapped my head around all this was to see a plane in person where measurements could be made.

In the end I cut the snorkel in two in order to shorten it about 1 1/2", and rotated it slightly for alignment. The filter mount ended up being nothing like the plans that came with the parts (actually, I did use the S shaped pieces to hold the filter) but the rest was my own design.

If I did this all again, I would mount the snorkel to the servo (temporarily) before doing any of the cowl fab on the left front corner. See how the intake end of the snorkel lays out and then build your cowl and filter box to fit the intake. I had to go back and rebuild part of the baffles there to get everything to line up. You might also consider doing something like is done on the -14 with a flange that mounts to the cowl and screws into the snorkel. Mine is one piece.

So, I will include a couple of photos. It did work, but not without a lot of creativity.

Good Luck!
 

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I did not follow the instruction order on my -M1B snorkel install.

I decided where I wanted the filter to be, fabricated the filter cage and ramp area and then cut the snorkel apart, fitted both ends to injector and filter cage and glassed it back together.

My notes say the filter centerline was 3/16 outboard of the center screw in the angled baffle piece on the front of the cylinder. Filter is aft as possible. Flush with edge of baffle angle piece.

Like the instructions do say, this ramp needs to be twisted to match the engine baffle and cowl inlet lines. The filter fits fine. The twist is not noticeable after construction.

Afterwards, the snorkel inlet needed to move 3/8" aft and 3/4" towards craft centerline.

Study where to cut. Choose and do it.


***Edited*** I got home and had access to my log pictures that follow:
 

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Looks good - I'd say you are very close. Just need to trim as needed. If it touches something, cut it and put a patch on it. There are parts that you can't easily change, like the angle of the ramp and the size of the filter and the servo inlet - use these as constraints, and cut everything else. If you go to far on the snorkel, it's easy to re-do it since it's fiberglass. You can also trim the intake on the cowl - it does not need to be as deep as stock, since you will have some rubber/silicone baffle material.
 
Final Fit

When u get the snorkel figured out, 3 suggestions that have worked well for me, 600+hours.
1 - install nutplates to attach the air dams in front of the cylinders. May or may not need to change their size.
2 - put a 90deg bend into the front of that top plate to give it some strength, rigidity.
3 - I put the label on the alternate air door to advise me at annual that I didn’t lose a washer and nut into the engine.

 
Are there any good build logs that depict the steps needed to get this snorkel done? Vans' plans, well, they leave a lot to the imagination.

I have the same airplane and engine as you. Here's a series of entries from my build log that show how I did mine:

http://www.rv7blog.com/2011/01/02/baffles-air-duct-filter/
http://www.rv7blog.com/2011/01/16/air-filter-brackets/
http://www.rv7blog.com/2011/01/23/air-filter-retaining-ring/
http://www.rv7blog.com/2011/01/30/left-baffles/

I did have to alter the shape of my duct in one place to allow it to clear the alternator. I also had to figure out a lot of the filter mounting bracket stuff on my own - hope some of these pictures help. There's a lot of this kind of thing involved:

Houston-we-have-a-problem-teaching-activity.jpg


1 - install nutplates to attach the air dams in front of the cylinders. May or may not need to change their size.
2 - put a 90deg bend into the front of that top plate to give it some strength, rigidity.

These are both good ideas - I did the same on my installation.
 
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Alignment

Getting the right snorkel (VA-132-1,2,etc.) to fit the IO-360-M1B or IO-360-A1B6 with the Avstar/Precision/Bendix FI servo was a challenge.

I made a tool to facilitate this alignment, allows for a soft-fit so you can reliably reposition/rotate the VA-132-2 to the correct angle, etc.

2" SCH 40 PVC with a slight bevel cut into the end that mates to the FI servo. Hold in place with masking tape. Fit the VA-132 over and rotate into position.

Attached for your enjoyment:
 

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Ryan, You didn't show any pics of the lower area. From looking at some of the other posts it seems there is normally an interference with the starter that needs to be cleared. If you haven't done that yet maybe that is resulting in the intake being rotated outboard. If you were to make those clearance cuts would that allow the intake to rotate inboard and essentially move the top inboard? At least from your pics that seems to be your biggest problem. The top will need to be trimmed at some point too I assume.
 
Start at post 534 here. I had to go a bit off script unless I wanted to modified it around the starter. It is working just dandy right now! And yes, the filter will fit in the weird shape that you have to trim it to. It is rather flexible.

Thanks, Jereme, how did you decide the angle of the #2 side baffle? Was it arbitrary, or were you aiming for a certain amount of metal outboard of the filter hole? I see you put the screws and angle bracket on the outside. I may have to do that too.


Seems a lot of people do end up cutting the snorkel in half and glassing it back together. I'm hoping to not do that, but I suppose it's not the end of the world.

When u get the snorkel figured out, 3 suggestions that have worked well for me, 600+hours.
1 - install nutplates to attach the air dams in front of the cylinders. May or may not need to change their size.
2 - put a 90deg bend into the front of that top plate to give it some strength, rigidity.
3 - I put the label on the alternate air door to advise me at annual that I didn’t lose a washer and nut into the engine.

Already did #1. #2 and #3 are great ideas. Thanks!


Exactly what I was looking for! Nice step-by-step. Thank you very much!

Getting the right snorkel (VA-132-1,2,etc.) to fit the IO-360-M1B or IO-360-A1B6 with the Avstar/Precision/Bendix FI servo was a challenge.

This is another great topic: How to ensure good alignment of the snorkel with the FI servo. I'm a little worried that my "wood cylinder" is moving around quite a bit as I rotate the snorkel, I can't seem to tape it on very securely. I was thinking about instead making a wooden cube "Fake servo" that bolts into the engine case and has the cylinder rigidly attached where the real servo inlet would be. No tape needed.

Ryan, You didn't show any pics of the lower area. From looking at some of the other posts it seems there is normally an interference with the starter that needs to be cleared.

Hey, Ray. That's one thing I did not encounter that a lot of builders do: I'm seeing no clearance problem with the starter. There is something that stops the snorkel from rotating any farther counter clockwise, and I'm going to have to figure out what that is so the snorkel doesn't rub on it, but whatever the obstacle is, it's not the starter.
 
Well it sounds like this is another "fun" part to look forward to. I have the IO-370 so I hope that doesn't make it more complicated.
 
Subscribed!

I am subscribing to this thread because I am at the stage to fit the cowling on my RV8.
 
Thanks, Jereme, how did you decide the angle of the #2 side baffle? Was it arbitrary, or were you aiming for a certain amount of metal outboard of the filter hole? I see you put the screws and angle bracket on the outside. I may have to do that too.

No problem Ryan. I was not aiming for a certain amount, just trying to get it to meet up with the inlet. The side piece that comes off number 2 just needs to angle to the point where it meets the baffle rubber that will be on the cowl inlet if that makes sense.

I will say that mine looked almost identical to yours at your stage in the pictures. The snorkel is just a little too "wide" as it comes from Van's.

With my setup as you mentioned I had to do the screws/nutplates a little different and make a custom filter retainer piece. No big deal at all.

P.S. Make sure you do the baffle mod on #3 and #2! I did it to number 3 and it is my coolest cylinder. I forgot it on number 2 and it runs about 20-25 degrees hotter than the rest. I'll be adding it possibly this week to address it.
 
Baffle mod

No problem Ryan. I was not aiming for a certain amount, just trying to get it to meet up with the inlet. The side piece that comes off number 2 just needs to angle to the point where it meets the baffle rubber that will be on the cowl inlet if that makes sense.

I will say that mine looked almost identical to yours at your stage in the pictures. The snorkel is just a little too "wide" as it comes from Van's.

With my setup as you mentioned I had to do the screws/nutplates a little different and make a custom filter retainer piece. No big deal at all.

P.S. Make sure you do the baffle mod on #3 and #2! I did it to number 3 and it is my coolest cylinder. I forgot it on number 2 and it runs about 20-25 degrees hotter than the rest. I'll be adding it possibly this week to address it.

I'm subscribing as well. So what is this "mod" of which you speak?
 
Ryan, your snorkel looks to have ended up in about the same position as mine. Yes as others have said trim the fibreglass parts as necessary including the cowl inlet.

Bear in mind that you do not necessarily need to leave enough space outboard for a conical bend. The RV-14 plans show a method of using flox to basically reshape that outer cowl inlet so that the baffle seal will fit to it at a 90 degree angle and seal without the conical bend. I didn't get any good pictures but the -14 plans show this well.
 
Thanks everyone for the pictures, it really helps to see how this thing is supposed to look at the various stages of the build. I decided to go ahead and be a builder rather than a parts assembler, so after locating the areas that inhibited the snorkel from rotating and cutting them away, I've got the inlet in a much better position.





Next task is to sand the inlet down to 3/8" below the ramp. I predict lots of smelly, dusty fiberglass work tomorrow...




I'm subscribing as well. So what is this "mod" of which you speak?

I think the mod he's talking about is the one described by DanH in this thread. The way I understand, because the "fin depth" around cylinders 2 and 3 is very small, there may be an airflow problem. Air has trouble getting to the bottom of those cylinders in the problematic areas. There are a number of different methods to correct this described in threads, but the basic idea is to re-shape the baffle around these areas to improve airflow.

I was considering doing it, but it seemed pretty complex to get right. Not sure if I'll bother, but the theory makes sense to me.
 
I think the mod he's talking about is the one described by DanH in this thread. The way I understand, because the "fin depth" around cylinders 2 and 3 is very small, there may be an airflow problem. Air has trouble getting to the bottom of those cylinders in the problematic areas. There are a number of different methods to correct this described in threads, but the basic idea is to re-shape the baffle around these areas to improve airflow.

I was considering doing it, but it seemed pretty complex to get right. Not sure if I'll bother, but the theory makes sense to me.

Yep that's the one. Trust me, especially if you are going with electronic ignition you do not want to skip this one. Dan does a great job of addressing this but the much easier "washer trick" works as well despite some peoples hate in it. Yes adding a spacer opens up a little gap towards the top of the head where cooling air isn't utilized, a very small one that can be sealed with RTV.

Someone(s) will most likely be along shortly to tell you that the washer method is inferior despite a very large number of people already employing it with success... :)

Can you tell I have researched this one a lot before? haha
 
Looking ahead, it looks like I am almost certainly going to have that (common?) problem, described in this thread, where the #2 cylinder oil return tube interferes with the alternate air door's rotation. Another future puzzle to tackle later.

 
I think the mod he's talking about is the one described by DanH in this thread. The way I understand, because the "fin depth" around cylinders 2 and 3 is very small, there may be an airflow problem. Air has trouble getting to the bottom of those cylinders in the problematic areas. There are a number of different methods to correct this described in threads, but the basic idea is to re-shape the baffle around these areas to improve airflow.

I was considering doing it, but it seemed pretty complex to get right. Not sure if I'll bother, but the theory makes sense to me.

When I received my M1B engine, I found that the troublesome fin casting area has probably been cured by Lycoming. This is the front face of my No2 cylinder, facing the left air intake. The fins have plenty of air flow. I used the jeweler file to clean up the valley section of the minor sand casting artifact (showed up as silver blotches in the picture). It seem production quality has improved and the work on the premium Thunderbolt engine probably demand more quality.
 

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Looking ahead, it looks like I am almost certainly going to have that (common?) problem, described in this thread, where the #2 cylinder oil return tube interferes with the alternate air door's rotation. Another future puzzle to tackle later.

In case anyone is wondering/curious, here is how I decided to avoid the alternate air door's contact with the oil return tube: I built up the fiberglass towards the aft of the snorkel so that the flat exterior of the snorkel angled outboard a little bit. Only a small amount of fiberglass was needed to angle the door away from the tube. Let it cure, sanded it super flat and drilled it perpendicular to the surface.



 
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Frankensnorkel

They picked the perfect name. I revived the thread because I'm fighting the square peg in a round hole.
First problem is the snorkel is outboard of where it should be licated by about 1/2". I'm thinking the easiest answer it to cut the snorkel and work each end separately then glass it back together.
Second problem is it contacts the cowl at the forward/outboard corner just below the rectangular corner. That one looks like some sanding and glass work will fix the problem.
No runs on the starter. Maybe I got lucky?
Gotta love the instructions. Pencil drawings? Really?

Then after all this is done, I need to figure out how to plumb the plenum to the inlets. Feels like I have two 1000 piece puzzles with no image and someone modified the pieces the threw them up in the air!
 
I cut 2” out of the middle of the snorkle and fitted each end. Then fill the center gap with foam, sand outside to shape, cover with glass, dissolve the foam. Did not really take much time.
 
They picked the perfect name. I revived the thread because I'm fighting the square peg in a round hole.
First problem is the snorkel is outboard of where it should be licated by about 1/2". I'm thinking the easiest answer it to cut the snorkel and work each end separately then glass it back together.
Second problem is it contacts the cowl at the forward/outboard corner just below the rectangular corner. That one looks like some sanding and glass work will fix the problem.
No runs on the starter. Maybe I got lucky?
Gotta love the instructions. Pencil drawings? Really?

Then after all this is done, I need to figure out how to plumb the plenum to the inlets. Feels like I have two 1000 piece puzzles with no image and someone modified the pieces the threw them up in the air!

I don't know if this picture will help you. I had to trim at the red line and bend the tab inward for more clearances. The view from the bottom shows how the tripple bend tab fits inside the intake. The outter corner is close to the cowl but there was no interference. The air filter slot is make so it can slide in from the front and the forward ramp will keep it in place, in addition to the filter rubber design.

This part took a huge amount of time for me to build. I suspect it was the same for everybody. While fitting the plenum, I had removed most of the crank gear and all the equipment in front of the fuel servo.
 

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When I received my M1B engine, I found that the troublesome fin casting area has probably been cured by Lycoming. This is the front face of my No2 cylinder, facing the left air intake. The fins have plenty of air flow. I used the jeweler file to clean up the valley section of the minor sand casting artifact (showed up as silver blotches in the picture). It seem production quality has improved and the work on the premium Thunderbolt engine probably demand more quality.

Hey Phat
I found the same thing on my IO-360 M1B from last year. All my CHTs are running within a few degrees of each other in climb with standard baffling.
Mike
 
Frankensnorkel beaten

I beat it. One end anyway. This thing is like herding cats while wearing a blindfold and riding a wild stallion. Pencil drawings. Really?
Solution was to cut it in half.
I had to fabricate a replacement bracket. Actually five of them. I finally got it right on the sixth.
Now I can fit the servo end and glass the two back together. Finally, some progress.
20220408_154334.jpg
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Frankensnorkel

It's back to one piece and actually fits. Now I can cut the servo flange and fit the alternate air door. What a chore. This thing was at least 1/2" too long.
20220419_143905.jpg
 
It's back to one piece and actually fits. Now I can cut the servo flange and fit the alternate air door. What a chore. This thing was at least 1/2" too long.
View attachment 24834

Can I make a recommendation? Redo your air dams to be removable now, while you are still putting things on and off bafflewise. A piece of angle aluminum and some nutplates under the baffle ramp.

You'll end up cutting them down several times (mine ended up being about 3/4" high to get CHTs within 2-4 degrees front to back and side-to-side), as they are WAY too big to begin with, and most of the ones I've seen cut down in place look...like they were cut in place. That is, not very neat.

Anyway, nice job on the snorkel! It's a pain in the you know where :).
 
I'll second Joe's comment about making the dams removable... I've build two sets now working on fine tuning the CHT's. 5 minute job to swap out
 
Air dams

Thanks. Ill take care of that next time they come off. I was wondering why they were so big.
 
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