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blast tubes

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bob888

Well Known Member
Working on the baffles and I notice a one liner at the end of the section FF2 describing blast tubes to direct cool air to the accessory area, mags in particular. They are apparently to be secured by friction fit in the baffle hole and unclear about the other end. Are these necessary? Any advice on securing them and locating the ends?
 
Possibly not absolutely necessary, but most likely beneficial to magneto life. If you buy the kit, it comes with a few feet of unsplit corrugated tubing. You can drill a 3/4" hole in the baffles and the corrugated tubing fits nicely into that size hole. A little RTV helps to hold it in place. The other end can be secured in place by zip ties or Adel clamps to the engine mount or accessory case.
 
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As Jesse described
 
bob888 said:
Working on the baffles and I notice a one liner at the end of the section FF2 describing blast tubes to direct cool air to the accessory area, mags in particular. They are apparently to be secured by friction fit in the baffle hole and unclear about the other end. Are these necessary? Any advice on securing them and locating the ends?
Click to expand...

I used custom cnc'd flanges made by a fellow RV'er. Apparently you can buy flanges that small. It does make the baffles look better than just using some rtv.
 
I used machined flanges and switched up the tubing to SCAT tubing attached with an Adel clamp.
 
Another baffler

Thanks for the help on the blast tube guys. Here's another one...how important is the airseal fabric around the inlets? It seems I have read somewhere that this can be omitted. I have the air ramp forward edges flush with the aft inlet edge per the instructions. I think it will be awkward and difficult to have the airseal fabric in place when removing the lower cowl, like needing to unscrew it every time.
 
bob888 said:
Thanks for the help on the blast tube guys. Here's another one...how important is the airseal fabric around the inlets? It seems I have read somewhere that this can be omitted. I have the air ramp forward edges flush with the aft inlet edge per the instructions. I think it will be awkward and difficult to have the airseal fabric in place when removing the lower cowl, like needing to unscrew it every time.
Click to expand...

If you use the fabric, you'll need a gap to facilitate getting the bottom cowl installed. The smaller the gap, the harder it is to put the cowl on.

I know of people that don't have fabric installed, but they are in the minority. The deciding factor is what are your temps, which you won't know until you start to fly.
 
bob888 said:
Thanks for the help on the blast tube guys. Here's another one...how important is the airseal fabric around the inlets? It seems I have read somewhere that this can be omitted. I have the air ramp forward edges flush with the aft inlet edge per the instructions. I think it will be awkward and difficult to have the airseal fabric in place when removing the lower cowl, like needing to unscrew it every time.
Click to expand...

To echo Bob, if you go with the fabric you're going to want a gap between the cowl and the ramps or you'll never get the fabric to work. For me I had to keep trimming the fabric back to get it lay flat and I also eliminated the fabric that curls up the sides of the inlet. Once you get it to fit it's not that big a deal to grab it and pull it over the gap - no need to unscrew it which would be impossible unless you installed nutplates. I also had to significantly trim the fabric around the FAB inlet too as that was initially giving me fits--way more then the inlet fabric.
 
bob888 said:
T...how important is the airseal fabric around the inlets? It seems I have read somewhere that this can be omitted. I have the air ramp forward edges flush with the aft inlet edge per the instructions. I think it will be awkward and difficult to have the airseal fabric in place when removing the lower cowl, like needing to unscrew it every time.
Click to expand...

You would be better off with a large gap (1" or more) and good seals which lay properly.
 
Smooth wall tubing available to use for blast tubes?

Is there any Smooth wall tubing available to use for blast tubes?

I'm thinking that Smooth wall tubing would flow more air and be more efficient in the cooling then the corrugated stuff.
 
riobison said:
Is there any Smooth wall tubing available to use for blast tubes?

I'm thinking that Smooth wall tubing would flow more air and be more efficient in the cooling then the corrugated stuff.
Click to expand...

There's a saying we use a lot around the office: "Perfection is the enemy of good enough". More efficient airflow really won't buy you anything in this area IMO, plus as Jesse mentioned, the corrugations make it easy to install on the baffles. Also, IIRC the tubes already come as part of the FWF kit.
 
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I think the KISS principle applies here.

I fitted mine the other day. Two 11/16" (IIRC) holes, pop in the tube, a bead of RTV to secure it and a few zip-ties. Job done in about 10 minutes.....
 
I used the corrugated tubing and just made the hole in the baffling the diameter of the smaller section of the tubing. It takes just a bit to get the tube installed in the hole, but no RTV is needed to secure if the right size hole is in the baffling. I now have 500 hours on mine without RTV and have never had an issue.
 
Yep, that's what I did but the recommendation was to add the RTV to prevent movement and chafing - no big deal.
 
Where to buy flanges?

I’ve seen those really nice aluminum flanges with the radius, and I’m looking for ones that will fit 3/4 tubing.. I know I could just drill a hole and the corrugated tube fits, but I’m looking for a more elegant solution.. anybody have a source for these flanges? ACS only sells 1 inch versions..
 
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