Thorp Air Command - T18.net

Having become adept at baffling myself and those who I encounter, I have decided to baffle my rather new engine as it is running a tad warm while still in rather cool ambient temps. Upon close inspection, the current baffling is in need of help and has now been removed. I have a nibbler, brake, dykes, a large sheet of 032 6061 T6 and the requisite full fridge of beer.
I could use the current baffling as a template and planned as such for the most part, but after even more close inspection, the current baffling is incomplete. I looked through the drawings and could find no drawing of any baffling. I reckon I could hit the volumes of newsletters, yet have conducted a search of the forum and come up flummoxed, (lest you think I had halved the barley pop inventory and neglected all due diligence)
Any baffle templates out there, kits, tricks or tips?

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Fraser MacPhee
N926WM
Serial #279-1
Angel Fire, NM (KAXX)

For what it's worth I really liked the baffling on 633PM. Besides being a bit worn, patched and 30+years old it is pretty much exactly what Bob,Bill,Wendell and David Read have on their airplanes with exception of the lack of front baffle which prevents air from spilling out over the flywheel and down (don't forgetbthat piece on the new set).

If it were me I use the existing set as a template (first choice) or order a set from Van's and adapt it (talk to GG).

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

FYI you will not find drawings for baffling in the plans or in the NL. If memory serves me John Evens walked away from his project for several years at the baffle phase, that's just how big of a pain they are!

Also, if your starting from scratch again go buy ALOT of poster board, you do not want to cut into that .032 until you have a set made from "paper".

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Roger that Lee - part of the issue with cooling I think is the 3.25 unfiltered induction air scat tube and the 1.5 inch heat muff tube coming off the rear baffles - that induction is taking a lot of pressure off the top - Am installing a filter on the induction air, mounting a new oil cooler on the firewall, and a remote oil filter as well - I am going to put that front baffle plate on as well as I will still be drawing air off the top with the induction air.
Great tip about the poster board. I may be going overboard with new baffling, but in a couple of years, you won't recognize this plane, and that will be a good thing.

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Fraser MacPhee
N926WM
Serial #279-1
Angel Fire, NM (KAXX)

Yeah, that scat is on tha big side to say the least. I think you could get away with a 2.5 or 3 inch. As far as the aft baffle induction air pick up remember that the only pressure you are loosing is what the engine is "sucking", much like a ram air induction, it's pressurized in flight. There are several production aircraft (including the T-17) as well as many thorps flying with the same setup. It sounds like you are giving the engine compartment the "going over" it needs so ... Rock-on, take pics and in a few months you can tell us the entire story in the NL!

Can't wait to see that little thorp when you're done with her Frase!

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Fras - Vans sells baffle plans for $7.00! (I assume they are full size drawings, but it would be worth a call to find out.) Sounds like a great investment if you are going to go from scratch.

They also sell actual baffle kits for $240, but that's a lot of coin for a Scotsman and a Dutchman.

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In theory, theory and practice are the same. In practice, they are not.

There you go Frase $7 ... Can't beat that! You're probably better off with that instead of the pre made set anyhow as Gary had to modify his for cooling and the thorp cowl anyhow. I recently had to modify a set of vans baffles for a friend of mine, they do not have enough space between the baffles and the fins causing high CHTs. I added about 1/8 inch around all 4 and the CHTs all dropped 25-75 deg.

BTW ... I cannot take credit for discovering that, go back a few NLs Gary did a good writeup on the vans baffles a while back.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

They will, I have and it does work. About a year ago I posted a message and pics concerning my purchasing the Vans baffles plans for my 0-360. Best $7.00 you will spend. They are VERY accurate and will save you HOURS of needless work making your own templates. Full size, just cut and trace. Bend lines, hole locations and the cut outs around the valve covers are VERY accurate. Some mods will be necessary to fit the Thorp cowl (top cutting), but well worth it. Couldn't find my pic of the individual pieces, but here is the finished product. If you are not making the enclosed plenum you should make the "standard" baffling in less time. If you are really CHEAP, you can sell the "used plans" to a friend for $3.50. I also recommend you check out the Vans site for other aircraft items, ie; hardware, etc. as these can be as much as 1/3 less than Spruce.

As with any Thorp procedure, consult with your Doctor as serious side effects may occur. [:0]

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Thanks all for the responses - oh and Lee - I like the induction the way it is (except I want to filter the air)- but without the front dam and the rest being a little loose, it is not going to do the job for my designated mission - high level cruise would be fine I think, but a lot of my flying is low level futzing and de-stressing that require constant temp watching in summer . I'm harder on a starter than anything else.

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Fraser MacPhee
N926WM
Serial #279-1
Angel Fire, NM (KAXX)

Roger that cuz, I hear you. I was just trying to put your mind at ease a bit on the aft baffle intake not taking as much air away as one might think.

Btw unless you changed the cht probe you're picking up off the spark plug, you may want to switch to a bayonet, or you may be chasing gremlins as mentioned in the other baffle thread going on.

Also I have a banjo style fliter box laying around you can have if you like.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Thanks anyway Lee - I like the current setup - it just needs a little tweeking.

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Fraser MacPhee
N926WM
Serial #279-1
Angel Fire, NM (KAXX)

Ok Frase .. Just to clarify, I Was not talking about the Thorp per-plans banjo box, I was talking about the filter box that goes behind the baffles inline before the carb box.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Update - basic baffling is complete, mounted, braced and looking good - next phase is the induction - after over reading, over thinking, mentally and physically calculating, losing sleep and taking a month off my life at each little step, it occurs to me that I need about 7.2 square inches of opening area (0-320)optimally for all phases of flight. Seems about right per my previous plane's induction opening. My hangar neighbor talked me into buying the K&N filter used on the RV-8 - it is approx (it's not in front of me as I type)6.5 inches by 5 inches - obviously I have to take into account dirt and other foreign clogs, but that's a lot more surface area than I calc'd per Garrison's wisdom. As I am inducting air off the rear port (driver's side) baffle, and as this filter and the resulting box will protrude down into (behind) the lower #4 cylinder fins, it occurs to me I may be robbing some cooling air from that cylinder, sooooo.....as my cross section of air need not be as large as said filter (and I do wish a quality filter and a smaller one I cannot seem to find), do I make the induction "inlet" smaller and use partial surface area of the filter, or keep the opening the same size as the filter without worry of robbing cylinder #4 of cooling air.

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Fraser MacPhee
N926WM
Serial #279-1
Angel Fire, NM (KAXX)

Frase,

If your system is tight, you will only take as much air off the cylinder as the engine needs. Square inches of filter opening(unless unreasonably small) have no effect on the amount of air going into the engine. That is the job of the throttle. Moreover, the plenim effect of the cold side of the baffles serves to level out the air flow through all of the cylinders since the incoming air flow is broadly distributed to the tops of the cylinders. I take my carb air off the right side and my oil cooler air off the left. My cylinders run in the 350-360 degree range at cruise.

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Bob Highley
N711SH
SN 835
KLAL

With all those caculations, sounds like you are building a Time Machine rather than a baffle ! [:0]

RB