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Oil cooler position on CB-705A

chris mitchell

Well Known Member
What a frustrating evening! I've spent the last three hours trying to understand the instructions on OP40-3 and OP27 about the position of the oil cooler and the associated FF-709 on CB-705A. I'm afraid to follow this query you will need at least the drawings, if not the parts as well!

The CB-705 A has no predrilled holes hole for the ignition lead or for the oil cooler. OP27 calls for the cooler to be as high as possible to improve cooling, but gives no vertical measurement for the lower edge of FF709. Offering the CB705A up to the number four cylinder confirms that the top edge, together with the top edges of CB-705B, is going to need trimming to fit under the cowl. If I mount the cooler too high it won't fit under the cowl.

It looks like another one of those situations where its difficult to start because you don't know where you are going to end up when you finish, if you see what I mean, unless I am missing or misunderstanding something. The critical bit of missing information seems to be that OP27 has absolutely nothing about the position of the oil cooler brace CB-705B although OP40-3 specifically says "position the oil cooler brace CB-705B on the CB-705A cylinder 4 aft baffle as per plans OP 27A. See figure 2". I don't have OP27A, only OP27.

If I cleco the CB-705B to the top two holes on the flange of the CB-705A, it looks as though the FF709 (oil cooler doubler) will just fit into the lower area of the CB-705A, but the set up then looks nothing like the OP40-3 drawing. Another way would be to align the top inner corner of teh brace withe top corner of the flange of CB-705A, which would give a final result pretty much like the OP40-3 drawings.

What am I missing or am I just going to have to guesstimate the vertical position of the cooler?

Thanks

Chris
 
Chris,
Since no one is answering I'll take a try. On my RV-7 I trimmed the aft baffles between 3/8 and 1/2". When I was satisfied I clamped the cooler on the aft baffle for a trial fit and determined its best location. I drilled the doubler and made the cutout for the cooler. I played with the reinforcement piece last. You can see by moving the cooler as high as possible there isn't much left of the one side of the #4 baffle reinforcement. I used a newer baffle kit from Vans which has significantly better drawings, but still leave a lot to the imagination. Hope this helps a little.




 
Thanks - that's pretty much what I'd concluded I would have to do when I finally gave up at midnight last night, so I'm glad to hear I wasn't so far short of he mark.

Funny that the instructions give this step as the first one. I'll do the rest of the (aptly-named) baffling and then have a big trimming session.

Will it ever end? 90% done and it feels like at least 99% to go.

Chris
 
I agree with Rick completely that the 7 and 8 firewalls are significantly different. I trial fit the cooler on the aft baffle with the upper cowling in place to allow the highest position while providing ample clearance around any motor mount/cowling issues. I also attached an 063 angle and a curved piece of aluminum to the brace and the aft baffle to augment air flow through the cooler. I placed the ignition lead pass through slightly inboard. I didn't want to weaken the #4 baffle anymore than necessary. The baffles are a slow process, possibly the worst part of the build. Just one day at a time.
 
Oil cooler position on aft baffle - can it go somewhere else??

Rick, thanks - I looked at the potential positioning last night and can see immediately that large proportion of the cooler will be immediately behind the cylinder - seemed to me it wasn't a great place for cooling!!!

I see from Kevin Horton's site that he made some extensions to get it a bit further away for the cylinder. Of course in England we think anything over about 70degF is major heat wave, but it might be less of an issue here than it would be in warmer places although we do have the odd hot day.

So - other RV-8 builders - what have you all done about mounting this cooler? I've seen at least one suggestion to put it on the firewall?!

Thanks

Chris
 
Firewall

Hi Chris
I mounted mine on the firewall with the RV10 firewall mount kit roughly in place of the forward battery location so far seems OK (almost done):rolleyes:
 
Wait!

Just build the baffles, cut, trim, get them to fit first. After you have the baffles installed, then proceed to the oil cooler. If you mount the cooler before you get the baffles fitted it will hit the cowl.

If you build according to the plans and put the oil cooler doubler where the drawing depicts it to be the cooler will be to high. Probably works great in a -7 but you will be cutting away MUCH more than a fraction of an inch above cylinder 4 on an -8.

It looks fairly straight forward on the drawing but.... Before you cut the hole in the baffle, cleco (as best you can) the doubler and tape the cooler in place. Put the cowl on and look in from the back to ensure you have clearance. Of course, if you haven't got the cowling mounted by this stage don't even attempt the baffleing.

Take a long look at the pics Rick linked to, if you can, find an -8 to go look at. Take your time. It's really easy to ruin the number 4 baffle while trying to mount the cooler.
 
I feel your pain

Chris,
I have a RV6 and the CB-705B was just not going to work. If I used the CB-705B the oil cooler would be to low. I guess with the 6 the baffling has to be cut down lower than the 7. I went with the .063 angle method. The bottom of the FF-709 is 1.5 inches above the bottom edge of the CB-705A
005pp2.jpg

006iq8.jpg

Aaron
 
RV8 Oil Cooler Position

For my $.02 worth, I mounted the oil cooler on the firewall in the FWF battery location (I never plan to relocate my battery). I did this for several reasons, first I felt the baffle location would cause heat radiation problems and increase my oil temps, second I did not feel the baffle material was strong enough to support the oil cooler and deal with engine vibrations (causing cracks, etc.) and lastly I wanted the flow of hot air from the oil cooler routed down the exhaust area and out of the cowling/assessary area. The final thing I did was use a larger scat tube to route air to the cooler. It turned out great and my oil temps are almost always in the low to mid green.

Jim
 
Size Scat?

Hey Jim,

I was thinking of that same position for the oil cooler. What size Scat did you use? I have read reports that 3" is insufficient and 4" works much better.

Regards,

Michael Wynn
RV 8 FWF
San Ramon, CA
 
per plans

I mounted mine per plans, as high as it would go. Ended up grinding a lot of material off support structure in order to get the needed curvature for cowl. temps have been at the high end of the green this summer, esp. when heavy &/or long climbs (as when flying chase for a certain RV10!).
 
I agree with Rick completely that the 7 and 8 firewalls are significantly different. I trial fit the cooler on the aft baffle with the upper cowling in place to allow the highest position while providing ample clearance around any motor mount/cowling issues. I also attached an 063 angle and a curved piece of aluminum to the brace and the aft baffle to augment air flow through the cooler. I placed the ignition lead pass through slightly inboard. I didn't want to weaken the #4 baffle anymore than necessary. The baffles are a slow process, possibly the worst part of the build. Just one day at a time.

Rocky - can you post a couple of pictures of the 063 angle and curved piece of aluminum? My oil temps are ok but I'd like them lower so am looking at other people's -8 installations.
Thanks.
 
what they said

Chris,
I agree with those that said to trim baffles and then mount the oil cooler as high as possible. You'll still have to whack a lot off the corner. I also used some 1/8" material as doublers to stiffen up the assembly and work as spacers. The SW cooler is slightly different than the Van's cooler.
If you use a SW cooler you won't have any cooling issues. We just flew my friends 8 to OSH. He has his SW cooler mounted on the baffle per plans. Daytime highs in the upper 90s. Oil temps well within the green.
FWIW,
JB
 
It's the 8406J
Bought from Pacific Oil Cooler Services (800) 866-7335
Talk to Mark. They often have re-conditioned ones. 6 mo. warranty. That's what I bought.
New ones have two year warranties. They start counting when the engine runs not when you buy.
 
Firewall mount Photos

I'd about decided to to the normal RV8 baffle mount of my oil cooler, and thought I'd ask if there is enough experience to suggest mounting on the FW is a better solution.

Photos please of FW installations.
 
Old reply from an old RV8er

I've been flying my RV8 with FW mounted oil cooler since 2002. It is a great alternative location if you don't want the baffle mount. Engine temps are in the low green. FYI, I installed the kit per the plans, with 3 inch scat.
 
Back of the baffle for me

I also reinforced the baffle with thicker aluminum around the cooler to try and prevent any future cracking. In addition, I used 1 inch aluminum channel to position the cooler further aft and away from the cylinder. The cooler is as high as it can possibly go, almost too much:eek: I am running a stock cooler, during hot days, 100 degrees, I can see the oil temp go up to 200 but not much further, my baffles also have more leaks than a dry wooden boat.

Randy
8A
 
Van's EA2006 Oil cooler

Thanks for all the recommendations, I waited to try cutting the #4 baffle for the oil cooler until I had the baffling cut to fit the upper cowl. When I trial fit to visualize where the cooler will mount, I discovered that the wider (7" vs 4.5") EA2006 cooler could easily run into the engine mount, even with the flange cut off.

I'll also have to make a new FF-709 to accommodate the larger width.

Considering the firewall method again. Just re-read Capt. Kirk's email and photo, is it the VA186 and VA187 that allow a 4" scat? Do you move the heater air intake to the #4 side where the oil cooler would of been mounted?
 
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