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Sam James cowl

D

donahuedc

Member
I know this subject has been beaten to death. I'm interested in this cowl, but not for the usual reason of increased speed. Sure, I'll take the extra 300 kts., but if I was looking for blazing speed, I'd build one of the other models.
The important things to me are better cooling and better efficiency. Followed by ease of construction, weight and balance considerations, and cost.
It looks like about $1500 for the cowl and plenum. How much discount from Van's to skip his cowl?
If this cowl is 'much' harder to fit and finish than Van's, then it is a non-starter for me. A 'little' harder. OK.
I'm not sure, but if I'm reading right, I have to put the prop further forward. Will this be a problem from a balance perspective? I'm leaning towards the Hartzell. Should I consider a Catto for weight and balance reasons, especially if I use the Sam James cowl?
So many choices. And one can effect another. Thanks for any help and advice.
 
you can get the "short" SJ cowl that doesn't require the 4" spacer.. so you won't need to mess with that at all. In that case, though, you'll need FAB kit from Van's (standard SJ cowl doesn't require it).

If going wiht standard (long) SJ cowl, the cost is a wash.. what you get in credit from Van's plus not having to use their FAB ends up same as SJ cowl. so only difference is plenum (which you may or may not want to use.. your call).

Matthew has a nice writeup w/ photos on SJ cowl installation.. it's very helpful to us who are yet to do this step.
 
Cowl credit

Good timing on this question. I just got my 7A finishing kit paperwork, and I deleted the cowl because I'm getting an Eggenfeller Subaru, which now uses a James cowl.

Anyway, the credit for the cowl worked out to be $850. I had called Vans a few weeks ago to get an idea of how much credit to expect, and whoever I spoke with said about $1200.
When you order a non-standard kit, they note in big bold letters on the form you have to sign and return that components in a kit are discounted, and if you end up buying something you deleted from a kit, it will be the standard price, not the kit price. So I figure the standard price must be $1200 and as part of the finishing kit it is $850.

Dennis Glaeser
 
Yep, and I'm going through this right now in the opposite direction because of the business failures and down right dishonesty of said engine manufacturer. It hurts the pocket book when you get screwed by a... Woah, I'll stop there or I'll get moderated :).
 
Angle Valve Installation

You are correct, this has been beat to death, but we can't be convicted of the same crime twice. The SJ Cowl/Plenum I purchased three years ago was a nightmare to install, the instructions were non existant and we had to cut, reglass and fill every part, multiple times, to get a good fit. I have no problem with experimental, but the stuff I paid a premium price for was prototype at best. Additionally, using a prop extension on a CS prop is not safe, IMHO.

While I have been recently told that the quaility is up and the fit is better, I will use the showplanes.com cowl on my next RV-8. I wish all of you using SJ luck, but I do not have over three months of weekends and nights to spend reengineering the parts to fit. Oh BTW did anybody tell you guys about the $100 FI adapter you need from API to get the intake snoot to fit?

Consider me once bitten twice sly!
 
SJ Cowl & Plenum are good

I have the SJ cowl and plenum. I took the Van's credits. I never looked at it too carefully, but the cost difference was not huge. Will James makes the cowls and although he offers the shorter one, he advises that the longer one is better in a number of ways. I accepted that advice.

I have no standard of comparison, but I think the quality and fit are pretty good. Hard Knox's experience is valid, but perhaps no longer applicable. I'm an inexperienced builder and things look to be going well. I've done all but the final fit of the cowl and have completed fitting the plenum.

I have the RV-7A, Superior IO-360 parallel valve. I used Van's throttle and mix bracket, but had to trade in the mixture cable for a little longer one.

Sam says not to use Van's baffles, but he told me that after I had already begun using them. I still would do it that way, but if you have a band saw and are good at reading Sam's sketches, you can save some $$ and do your own baffles. Also, the plenum means you don't have to mess with all that pop-riveted sealing rubber stuff. It also means you can ignore Van's advice about completing the fit of the lower cowl before doing the baffles; the whole interface between the cowl and the pressurization system is different. A test fit seems good enough to position everything.

There are some issues with fitting the oil cooler, since the plenum is much lower than the normal baffles. Go slowly in that area. Also, it will work easier if you have the battery on the right side so the oil cooler has more room.

I believe (no proof yet) that you would get better and more even cooling with SJ cowl and plenum. Sam tells you to use more metal on baffles under the rear cylinders than does Van's. He says you can get the temps to within 25 degrees. I also believe that the SJ cowl is worth about 0.5 gph in cruise for equal speed (extrapolated from the speed gain).
h
 
Rocket Science

Sam James is making short cowls for standard constant speed props or the standard 2 - 1/4" extension for fixed.

If you want to know why it helps read this:
http://groups.yahoo.com/group/JamesAircraft/message/19

No matter how good you make your stock cowl to baffle seals, there are always leaks, especially where the cowl meets the "soft" baffle seals around the front of the engine. Just a little leak is efficency lost. Unless you can see what is happening at 200 mph with the engine shaking you have no idea how much is lost. This is one of many reasons, including NASA says so.


The bottom line is inlet areas are about 40% smaller and the cooling temps are the same? No rocket science. Less Cooling Drag.


One option, a road less traveled but still traveled is modifying a stock cowl. This includes making your own plenum and fiberglass cowl work. The metal rings can be purchased. The rings have an airfoil shape to promote laminar flow into the cowl. They are not needed (you could mold the inlet with fiberglass, but the rings allow an air tight leak free connection to the plenum.


The gotcha issues Hard Knox had (Robby, sorry correct me if I am wrong) was from the fact he has an Angle Valve engine and FWD FI servo. The longer cowl, one that requires the 4" prop extension or special long hub c/s prop, gives more room for fwd servo. The short cowl makes the FI servo a challenge, catch 22.

It is worth while in my opinon.

George
 
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Will James will freely admits that the original SJ RV-8 cowl had a lot of problems. He is just completing a new mold for the RV-8 cowl and expects to have fixed many of the problems. When I spoke to him a couple of weeks ago, he was close to completing it but was distracted by getting some cowls finished for Eggenfeller. This is still a long cowl requiring the spacer. We'll see how it comes out.

With respect to credit form Van's for deleting items from the kit, there is a better way to do it. Van's kit price is basically equal to the sum of the individual part prices. However if you delete an item, they only credit you with 80% of the price of the deleted item. If you are deleting expensive items, it might be better to order all the parts individually, rather than the kit. This is easy enough to do on the finish kit as it doesn't have that many parts in it.
 
I have the SJ Cowl and Plenum on my RV-9A and there are a couple other RV-9's as well. Here are my comments based on your email:

Extension: Yes, you need a 4" prop extension from Sabre Mfg. ($550) I know there has been some discussion about the Harzell prop on a 4" extension but don't know the results of that discussion.

Cooling - The plenum works great for cooling, no question about it. How much better than the standard baffles, I don't know. The plenum is pretty easy to install. I would consider ordering Van's baffle kit ($200) instead of trying to construct your own using the drawings provided. My cylinders run within 10-15 degrees of each other unless it is cold out in which case the front two run a lot cooler than the back two. So far my cylinders run in the 340's-350's. Climbouts get me to 405.

Ease of Construction - From a strictly process point of view, the SJ cowl is probably just a bit more difficult than Van's cowl. You still use hinges to attach the cowl to the FW and for the top/bottom attachments. You have to do lots of trimming to get a good fit. The aluminum inlet rings aren't that hard to get installed. I think the filtered airbox design is more complicated than Van's setup and requires some work to get made.

There are two issues to be aware of.

1) The kit isn't complete in my opinion. There are lots of small parts and pieces you have to source yourself like the hinge material, filter, hoses, clamps, etc. You basically get the fiberglass parts and aluminum rings and the rest is up to you to source.

2) The instructions are not up to snuff. You'll get about 10-12 pages of text instructions with a few drawings for the airbox setup.

I did a so-so job of documenting the process on my site at www.n523rv.com/cowl but it isn't complete by any means but it might help you make a more informed decision

If you are the type of builder who wants to open a box, find great instructions and put something together without thinking about it... this cowl isn't for you. If you don't mind sourcing a bunch of parts that don't come with the kit and don't mind having to work out issues as they come along and doing some work to get a good installation... then the SJ cowl is a good option. The cowl looks great and the quality of construction is really good.

Cost: It will cost you more! I don't recall exactly but I think I got around an $800 credit from Van's for taking the cowl off the finish kit order.

Cowl: $950
Plenum: $425
Prop Ext: $550
Baffle Kit: $200 (optional, you can make your own)

There is a Yahoo Group that has lots of info and would be a good place to come visit. http://groups.yahoo.com/group/JamesAircraft
 
SJ Cowl prop extension

Just a small note of correction. The Compact hub CS Hartzell does not need a 4" extension. Its actually 2 and 5/8ths inch.

I opted for a 2.25" extension.

Quality of the cowl was very good and I made my own baffles from Sam's limited sketches.

The previous post also ignored the fact that the Van's airbox is not used either.

So I think the cost comparison is more like..

Vans refund 800+200+200 =$1200

plenum 425
cowl 950
extension $360 (2.25")

I go a deal on the cowl ($500) and a second hand plenum($300). So it came out close for me.

More money yes but oh man it looks awesome in its paint!

Frank RV7a finished painting fuse..About to paint wings.
 
What about acrobatics with the prop ext? what is the prop # for the ext hub prop for the longer cowl?
Thanks.
Shine'r
Sunny Pittsburgh, Pa. RV-6 320
 
Aerobatics

Shine'r said:
What about acrobatics with the prop ext? what is the prop # for the ext hub prop for the longer cowl?
Thanks.
Shine'r
Sunny Pittsburgh, Pa. RV-6 320
Click to expand...
The folks at Saber, which is what Sam & Will James recommend for the extension for the FP prop, say that's not a problem. At least one person at Van's disagreed, but was talking about some other extension. Talk to Saber directly for more detail. http://www.geocities.com/sabermfg/
 
The extension!

Simply mimics the installed length of an extended hub Hartzhell prop.

That maybe Van's official line but I have spoken to at least one of their engineers who says ts OK.

A noted engine guy on this forum has also told me he "would do it in a heartbeat" assuming your not entering unlimited aerobatic competitions.

Loops and rolls (about my limit) are apparently all fine as far as my IO360 crank is concerned.

Frank
 
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