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Primer, cowl flap, mixture control and gas cap printer friendly version
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Bob Brock
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Posted Friday, August 22, 2014 @ 07:11 PM  

Greetings:

Van of Van's Aircraft told me the last 10% or a rebuild takes 50% of the time.. and I think he was right. Additionally the last 2% never gets done... so it is always an ongoing project. I have been making minor modifications and did some flying so I could provide more information.

1st... Primer... in the past, by the time I got my engine started, I was worn out. Removed the carb, rebuilt it, choke valve, everything... still hard to start. Simply was not getting fuel up the intake to the cylinders. Great Planes has a primer kit for $28 and I got one. The install was not too difficult... a bit of machining and brazing. I have pictures in an album for your review. Took the fuel off the carb intake bolt and the primer input to the intake manifold...really simple! Works like a dream! I only did the primer line to one intake to keep the mod simple. Since I had the panel out I decided to install the cowl flap that came on the aircraft when I purchased it.

2 Cowl flap... again, I did not build this mod, but since I had it I thought I would see if it really worked. I built a bracket for the primer and cowl flap cable next to the hand brake. Nice fit and out of the way. Again, a number of pictures for your review in the album. The Cowl was also modified.. cut back a bit and a piece of aluminum added for strength. If the pictures are not enough I can supply some dimensions.

3 mixture control... on the back side of the intake manifold.. directly behind where the carb attaches was a drilled and taped opening for a fitting... going to a 3/8' aluminum tube, which goes into the cockpit and attaches near the fuel/choke controls. At the end of the tube is a simple valve to open the tube which provides more air to the carb. When opened I can cover the tube opening with my thumb and feel the suction.

4 fuel cap... the plastic original was getting difficult to use... thankfully, Eugenio gave me a brass machined cap knowing that some day I would need it... and that day came. Anyway, I copied Eugenio's design with a larger air intake pointing forward and reused the original float and guide. Works great and looks better than the original.

OK, now for some performance information. As I said, the primer works like a dream and it starts right up. I added pictures of my start up mode. In addition to using the parking brake, I use a wheel chock with a cord and small wt. to allow me to pull it out of the way from a distance from the prop. That way my hat does not blow off. Additionally, I run a rope out of my hanger and tie the trail down. I know that sounds like overkill and perhaps it is, but it only takes a minute. Then I start from behind the prop and my body is always in contact with the leading edge of the wing as I either move away from.. or into the glider. I check the oil pressure right way to confirm everything is working.

I took the 4 up to 12,500' which took something like 25 minutes. On the way up I tested the cowl flap and it did provide more cooling (it never got about 90 C with our without the flap).. about 10 degrees C, but I don't know if the cowl flap is really worth it, except on decent. Then at reduced power, it did keep the oil temp a bit higher if closed. Again, I don't know if it is really worth the modification and I doubt I would have done it had I not had it ready to install. Coming down from 12,500 (that was ground elevation in Tibet in June.. Everest base camp was 17,500) took a long time with power at the bottom of the green.. about 2,200 rpm... and speed of course was in the 120 mph range. I was mindful of carb ice with reduced power setting. Used air-brakes and extended landing wheel to increase drag, but still took a long time to come down. As it was, I circled my home airport from 4,000 AGL just in case the engine decided to run rough. I think the cowl flap does keep the heat in better and perhaps reduced the chances of carb ice. I may install a temp probe in the carb to see what really happens.

(more in next post as I exceed the length limit)

Now about the album... it is at Google plus and to be honest I don't know how the new system works. I marked it for public view... Robert Brock.. so perhaps it is easy to find it. Also I sent it to myself and this is the address:

-39b2853@plus.google.com>

If you can not see the album, please reply and I will find a way to list it again.

Best regards, Bob Brock

Bob Brock
Master Sergeant

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Posted Friday, August 22, 2014 @ 07:14 PM  

cont....

The air mixture control appeared to work. Between 10,000' and 12,500' there was a noticeable increase in power and climb. From what I could tell with both my Garmin and aircraft instruments the added air increased climb by about 150 fpm and increased the RPM by a few hundred revs at the same setting. I don't know the absolute ceiling of the aircraft as I did not bring O2.
going strong above 12,500' with a respectable 300-400 fpm climb as full power. If you are going to fly in the mountains, this might be a worthwhile mod.. simple, cheap and bullet proof.

A couple of things you might notice from the album.. a neat little instrument from Belite... an LED turn coordinator... if is very bright and easy to see... even in bright sunlight. It is on the lower part of the panel below the radio. It is amazing and I love it! I have removed that panel so many times that I built some simple aluminum protectors to keep the panel lower pins from digging into the wood. I wanted to show a picture of the opening window in the snail... it works great for following runway/ taxi way lines and if no one is around, keeping the cockpit clear of empty water bottles. At first I thought it would have to be held closed, but it just stays in the down position.. no air forcing it up.

Still a number of things to finish like the bottom side of the sun shade. I built in LED lights but have to go back to the drawing board. Also, I have a new canopy to mount and perhaps make an open canopy with an extra frame. A new prop is being make by Props Inc. in Newport, Or. I flew down with Jeff's loaner prop and we used Collins prop (currently on my 4)... for the major ideas. Basically we are going to get the new prop an extra inch in diameter to 54" and and extra degree of pitch. I have tried three different props and the one Collin loaned me is the best... but I would like to get my own and return the prop to Collin... hopefully in a week or two.

Donald
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Posted Saturday, August 23, 2014 @ 02:58 AM  

Bob, most interesting and I'd love to see the pictures but cannot.

Your description of the mixture control is not unlike something I've mentally toyed with over the years. Rather than drilling into the manifold I'd speculated on adding a thin fitment between the carb and the manifold, perhaps adapting the air valve from a spray gun to regulate. Unfortunately I have no machining skills or equipment so it remains an intellectual exercise.

Anyway, can you clarify how we see the photos please?

Donald

Bob Brock
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Posted Saturday, August 23, 2014 @ 10:52 AM  

The only "machining" is a drill bit and tap... really simple.. then some compression fittings from any hardware store. The aluminum tube has a simple valve in the cockpit that makes it bullet proof. I sent the album to Collin and hope he can provide a link. If you send me your email, I can sent the album to you. My email address is: Bob.Brock@gmail.com Google has changed the way albums work to fit social media which means I need to ask my teenage daughter how to do it.
Donald
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Posted Saturday, August 23, 2014 @ 12:56 PM  

Bob,

You may or may not get a pm from me, I see the forum pm system thinking about it but it seems to be spinning it's wheels. Anyway, one email address you can use for me is rf3flyer(at)talktalk(dot)net.

The leaning system I had envisaged would involve machining which is why I am most intrigued by yours. Actually, I'm delighted to learn that someone else has even given this any thought whatsoever. The one thing about the RF3, which I own, that disappoints a little is the fuel endurance so any way to enhance that is of interest to me. The RF4 seems better suited to auxiliary tankage but the 3 lacks the capacity for the solution I have seen on several of the German and Italian owned 4s. Heck, I even covet the 38 litre standard tank of the 4. Mine is 30 litres.

So, yes, I'd love to see your photos.

Donald

Bob Brock
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Posted Saturday, August 23, 2014 @ 11:18 PM  

Donald:

Collin really got me into the RF-4d and actually introduced me to the owner of N7725. Frankly, I would never had entered into the project without Collin's support and the knowledge that there were Fournier owners who I could count on for assistance, advice and sourcing. Perhaps the smartest thing I did was spend time in Italy with Eugenio. He was very kind and generous, sharing his extensive knowledge..experience and parts. None of my questions were too ridiculous. Although there might be a number of ways to rebuild, I found that everything Eugenio did was extremely well thought out, based on experience and made sense. I will never have the skills of Eugenio or Collin's engine knowledge. Collin offered to completely rebuild my engine, and of course I agreed. I did not create the modification that were on the aircraft.. I just tried to make them better. I do have an axillary fuel tank and it worked great on a long cross country.. an extra 3 gal. in a portable tank that fits behind the seat and uses a small electric fuel pump to add fuel to the main. Thus far I have not needed it.

Thanks for your email address.. I will send you the album right away.. and hopefully figure out how to post a link that works.

Regards,

Donald
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Posted Monday, August 25, 2014 @ 03:56 AM  

Bob

Got your email with this link https://plus.google.com/u/0/photos/111636319523992347433/albums/6050508924897033009?cfem=1
That seems to work just fine so if you're happy to have it public I'll leave this up. If you're not I'll take it down. Just say.

Donald

[Edit by Donald on Monday, August 25, 2014 @ 03:57 AM]

Bob Grimstead
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Posted Friday, August 29, 2014 @ 06:38 PM  

Hi Guys,

Bob, Thank you very much for the detailed explanation and all the excellent, informative photos.
Donald, Thank you for the link.

With your permission Bob, I'm going to copy that cowl flap on my new Aussie cowlings.

When I first flew my British Fournier with its bigger capacity 1776cc engine, because I was concerned about overheating, I fitted an enlarged fixed cowl flap, and to my surprise it knocked something like 5mph off the top speed.

This suggests that a carefully designed (slightly longer) cowl flap mght actually increase speed and aerobatic performance a little, but keep the engine cooler in the climb on a very hot (30C+) day. As you say, it will also keep the heat in during descent on a moist day.
I've only experiemced carb ice once on my British Fournier during an enforced descent in drizzle going into Paris for René's birthday bash, and I never want to get it again!

Yours, Bob

--------------------

dannparks
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Posted Wednesday, September 10, 2014 @ 06:54 PM  

Glad to see you're cranking away on that last frustrating 10%. Hopefully all the Pacific Northwest Fournier's can meet up somewhere in the near future.

--------------------
Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1

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