wandersen
Well-Known Member
- Joined
- Jul 31, 2007
- Messages
- 519
- Reaction score
- 140
I've been puzzling out the fit of the Firebolt nose bowl. I thought I would post some pictures and solicit comments.
The nose bowl is clamped up with a 3/8" plate over the ring gear, then the MDF 14" diameter board to clamp it in place. In other words, the cowl is 3/8" forward of the front ring gear flange. Up until I build it out, I can always move it forward and backwards.
Engine is pretty much 0/0 degrees. Two 1/8" AN970-7 washers on both lower Barry mounts, and another pair of washers on the top and bottom left side engine mount to firewall bolted connection made this straight. Note to self, next time building an engine mount, jig it up to account for a bit of sag from the compression of the engine mounts.
I'm going initially with a Catto prop. I do want to have the option to swap out eventually to a constant speed prop. I've looked at the MT (MTV-9) and the Whirlwind 400C. Pros and cons for both, but I believe with my math below, I can swap out to a whirlwind without and change to the cowl spacing. An MT would require a move of about an inch with their stock spinner spacing. I will call Flight Resources to see what the MT spacing options might be.
I would like to get a 14" spinner to match up with the Firebolt nose bowl. Nichole from Catto believes she may have a line on a 14" spinner. The default from Catto is the 13" Vans spinner. While a 13" would work, a 14" would fit exactly around the Firebolt nose bowl ring. I will also give York a call tomorrow as they have a 14.5" option (thanks Chris for that find.) Anyone else know of a composite 14" spinner with some length (~20-22 inches)?
For the Catto prop, I'm planning (at least this particular hour) on a 1.25" spacer on the crank flange. You can get these from Saber Manufacturing. The flange on the Vans spinner is 0.6" back to front and made out of 0.060" aluminum. This gives a backplate to spinner rear distance of ~0.54". (I think the York is similar - Smizo??) With a 3/8" spacing plus 1/4" spinner to cowl gap, plus 0.54" gives 1.129". If I don't trim the spinner as tight, a 1.25" spacer should do me nicely.
I had a very informative conversation this morning with NDTOO on his firebolt nose bowl mounting. This was very informative and helped answer a bunch of my questions. - thanks!
For the whirlwind 400C, the spinner to mounting flange distance is 0.662" Spacing would be 0.662" - .375" = 0.287" which is close to my 1/4" gap goal.
I will mount the nose bowl assuming the engine will settle 1/4" (IO-540).
The possible chafe point is the starter. I worked a bit on the casting with a grinder. There is a lot of beef there that could be removed. I've also seen other starter drives that would not be any problem with clearance. It's now currently a 1/4", and not enough.
I believe I will need to do some fiberglass work on the inlets to angle the air direction upwards, not just straight back. This should improve the flow dynamics. You can also see there is not enough clearance for the prop governor.
NDTOO gave me great advice for clocking the cowl to the engine. Align up the air intake at the bottom with the RSA5 fuel servo. I'm using the 90 degree intake fitting from AirFlow Performance.
I need to split the cowl. No way to get to the top #1 plug without this.
Had to reduce the height of the firewall by 3/8". I believe the engine centerline is 6" below the top longeron centerline, vs the intended 5-1/2". This is an error on my part building the engine mount. Not shown, but the cowl to firewall to front instrument panel line is straight within a 1/16" or so. You can see some of the fishing line I'm using for alignment. Thanks Dave Baxter for that hint on a previous post (palm slapping forehead).
Here are some pictures to considers. I'm looking for anything I might be forgetting.
Ward
The nose bowl is clamped up with a 3/8" plate over the ring gear, then the MDF 14" diameter board to clamp it in place. In other words, the cowl is 3/8" forward of the front ring gear flange. Up until I build it out, I can always move it forward and backwards.
Engine is pretty much 0/0 degrees. Two 1/8" AN970-7 washers on both lower Barry mounts, and another pair of washers on the top and bottom left side engine mount to firewall bolted connection made this straight. Note to self, next time building an engine mount, jig it up to account for a bit of sag from the compression of the engine mounts. I'm going initially with a Catto prop. I do want to have the option to swap out eventually to a constant speed prop. I've looked at the MT (MTV-9) and the Whirlwind 400C. Pros and cons for both, but I believe with my math below, I can swap out to a whirlwind without and change to the cowl spacing. An MT would require a move of about an inch with their stock spinner spacing. I will call Flight Resources to see what the MT spacing options might be.
I would like to get a 14" spinner to match up with the Firebolt nose bowl. Nichole from Catto believes she may have a line on a 14" spinner. The default from Catto is the 13" Vans spinner. While a 13" would work, a 14" would fit exactly around the Firebolt nose bowl ring. I will also give York a call tomorrow as they have a 14.5" option (thanks Chris for that find.) Anyone else know of a composite 14" spinner with some length (~20-22 inches)?
For the Catto prop, I'm planning (at least this particular hour) on a 1.25" spacer on the crank flange. You can get these from Saber Manufacturing. The flange on the Vans spinner is 0.6" back to front and made out of 0.060" aluminum. This gives a backplate to spinner rear distance of ~0.54". (I think the York is similar - Smizo??) With a 3/8" spacing plus 1/4" spinner to cowl gap, plus 0.54" gives 1.129". If I don't trim the spinner as tight, a 1.25" spacer should do me nicely.
I had a very informative conversation this morning with NDTOO on his firebolt nose bowl mounting. This was very informative and helped answer a bunch of my questions. - thanks!
For the whirlwind 400C, the spinner to mounting flange distance is 0.662" Spacing would be 0.662" - .375" = 0.287" which is close to my 1/4" gap goal.
I will mount the nose bowl assuming the engine will settle 1/4" (IO-540).
The possible chafe point is the starter. I worked a bit on the casting with a grinder. There is a lot of beef there that could be removed. I've also seen other starter drives that would not be any problem with clearance. It's now currently a 1/4", and not enough.
I believe I will need to do some fiberglass work on the inlets to angle the air direction upwards, not just straight back. This should improve the flow dynamics. You can also see there is not enough clearance for the prop governor.
NDTOO gave me great advice for clocking the cowl to the engine. Align up the air intake at the bottom with the RSA5 fuel servo. I'm using the 90 degree intake fitting from AirFlow Performance.
I need to split the cowl. No way to get to the top #1 plug without this.
Had to reduce the height of the firewall by 3/8". I believe the engine centerline is 6" below the top longeron centerline, vs the intended 5-1/2". This is an error on my part building the engine mount. Not shown, but the cowl to firewall to front instrument panel line is straight within a 1/16" or so. You can see some of the fishing line I'm using for alignment. Thanks Dave Baxter for that hint on a previous post (palm slapping forehead).
Here are some pictures to considers. I'm looking for anything I might be forgetting.
Ward
Last edited:
