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  #1  
Old 02-10-2020, 11:07 PM
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N546RV N546RV is offline
 
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Location: Houston, TX
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Default Whirl Wind HRT + James cowl

It's midnight, which means it's time for my brain to form a burning question that must be submitted to the masses.

I'm planning on a WW 74HRT for my RV-8. I've long intended to just use the Van's cowl, but the post about James Aircraft in the general forum reminded me of just how sexy those cowls look.

WW has a big warning on their site: "Due to the very wide chord of the HRT blade additional clearance considerations must be made when using the Sam James RV cowl as well as Vanís and aftermarket ram air induction systems."

Has anyone worked with this combination, and if so, could you comment on what work needs to be done to accommodate? Thanks.
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  #2  
Old 02-11-2020, 07:32 AM
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N729LS N729LS is offline
 
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Default

FWIW, I have the standard RV-8 cowl with the 74HRT prop. Clearance is minimal, even with the prop flat. I would think that having to chop a 1/2" off the front of the James cowl would reduce the sexiness by a good margin!
Andy
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  #3  
Old 02-11-2020, 08:13 AM
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N546RV N546RV is offline
 
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Quote:
Originally Posted by N729LS View Post
I would think that having to chop a 1/2" off the front of the James cowl would reduce the sexiness by a good margin!
Andy
This is kind of alluding to what I was wondering. I know that the concern is that the wide-chord blades will interfere with the cowl, but I wasn't sure if it was the cooling inlets, the air inlet, or all of the above. And then the question was: what has to be changed to accommodate that?

Seems like either you chop and reform the inlets (which, as you say, seems to obviate a lot of the reasons to being interested in the James cowl), or else move the prop forward somehow, like with a spacer or something - which presents a whole new set of questions and concerns. IIRC the James cowl already requires a spacer, and some people are concerned about gyro effects, so this would be making that even worse.

I think my general conclusion about this combination is "not worth it," but still curious if anyone has tackled it.
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  #4  
Old 02-11-2020, 08:39 AM
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Bob Martin Bob Martin is offline
 
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I have worked with that combo!
I have the James extended cowl for a carb'ed engine with a 2 1/4 inch saber extension. The 74HRT bolted on and when the blade was twisted through it's pitch range it would hit the cowling.
We tried adjusting the travel but lost control of the prop at high speeds.
Bottom line was we were going to have to get a longer extension and do the required fiberglass work to make it look right. The thought of a longer extension and more glass work and then a cowl repaint, was too much and we went back to the Hartzel.
Now if you are starting from scratch, that would be different. Get a 3 inch extension and extend the cowling behind the prop while you are fitting it, easy peezey.

PS..I am glad to hear WW has put a warning on their site about this issue!
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  #5  
Old 02-16-2020, 03:05 PM
tracer tracer is offline
 
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Location: Fond du Lac Wisconsin
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Default WW 74HRT Sam James Cowl

I did this on my RV7. I had to put a .25 stop ring inside the 74HRT to reduce the amount of travel it could have. I now have 3/8 inch clearance between the blades and the induction inlets when feathered. Seems to work fine. I have been running it for 85hrs with no problem. WW provided the .25 inch stop ring and told me how to install it. You test it by using air pressure to the governor to twist the blades.

Last edited by tracer : 02-16-2020 at 03:08 PM. Reason: added more info
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  #6  
Old 02-16-2020, 07:34 PM
sjhurlbut sjhurlbut is offline
 
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Default chop

No need to chop the actual inlets. Just cut the front ring (behind the prop) move cowling aft 1/2 and bond front ring back in place. No one will notice
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  #7  
Old 02-17-2020, 06:40 AM
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Capflyer Capflyer is offline
 
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Quote:
Originally Posted by sjhurlbut View Post
No need to chop the actual inlets. Just cut the front ring (behind the prop) move cowling aft 1/2 and bond front ring back in place. No one will notice
Nice solution. If you or anyone has some pics of this mod I'd love to see them.
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  #8  
Old 02-17-2020, 09:52 AM
climberrn climberrn is offline
 
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I have the 74RV with the stock vans cowl. Put the Ram Air opening too far forward. Close to the face of the front of the cowl. I had an early RV74 so there was nothing in the manual about how far to place the intake back. Was not able manually turn prop fine pitch to test clearance on the ground. Wasnít pretty.

WW was very helpful getting it resolved. A call to WW would be prudent. Could save you some heartache and shipping expense in the future.
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  #9  
Old 02-17-2020, 04:55 PM
sjhurlbut sjhurlbut is offline
 
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Default pics

Quote:
Originally Posted by Capflyer View Post
Nice solution. If you or anyone has some pics of this mod I'd love to see them.
I didn't need this for my last engine/WW setup - I'm just saying what I would do. I would just cut the U shaped ring right behind prop (leave 1/2" or so). Move cowling back and bond ring back in place. Plus gives you opportunity to make perfect fit between prop and cowling
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  #10  
Old 02-20-2020, 07:40 PM
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Sleepy Sleepy is offline
 
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Philip,

I noticed on your builder's blog you are looking at the Titan 370. Great engine and JB is the best.

Before you go too far down the rabbit hole with the 74HRT you should know that as of last October Whirlwind has quietly stopped supporting the 370/375 engines. Check their specifications tab on the all the RV props (i.e. 300 series, 74HRT, etc), it's in red letters.

I called them 3 times back in November to find out what is up. Unfortunately, despite several promises of a call back from the lady who answered the phone, they never returned my call or answered my question as to why the change of heart on the 370/375 engines.

Good Luck
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