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Collin
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Posted Monday, March 8, 2010 @ 04:14 PM  

Looks Fun!
Bob Grimstead
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Posted Monday, March 15, 2010 @ 08:49 AM  

Oh, it so was fun!

Clip coming on YouTube as soon as I can sort it out, but here are some photos to give you the flavour.

Yours, Bob

Bob Grimstead
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Posted Monday, March 15, 2010 @ 08:57 AM  

As you can see, you don't need a helmet or goggles, and you probably don't even need sunglasses. It's just that it was hot and bright. Of course, you do need an electric hat if you want to talk on the radio.

The slipstream/propwash just ruffles my silver tresses, but doesn't touch my forehead, which is perfect. When wearing a helmet, you don't feel it at all.

Yours, Bob

Bob Grimstead
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Posted Monday, March 15, 2010 @ 08:33 PM  

Okay Guys,

The clip is now up & running at: http://www.youtube.com/watch?v=FQCFn6swXsQ

It was taken by young Maree Vervoort from David Brown's Christen Eagle.

An RF4 in formation with a 'Muscle Biplane'? -- It's possible!

Inevitably, there's a bit of aerobatics in it too. A Fournier mirror again after twenty years.

Yours, Bob

Bob Grimstead
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Posted Saturday, March 20, 2010 @ 08:20 PM  

Hi Guys,

I have now flown a low-level aerobatics practice in the rain, and established that I do not get wet, even when taxying. It's only after I park that the rain gets in!

If I were doing this again (and I just might, in Britain) I would make the middle hoop out of aluminimum, so that it distorts when my face hits it in an accident, rather than my face distorting on impact.

Yours, Bob

joethepro
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Posted Tuesday, April 5, 2011 @ 04:36 AM  

Has anyone tried vhb tape to fasten windscreen to frame? The tape is expensive but they use it to hold the sides of trailers on and metal panels on the sides of skyscrapers. It is a scotch product and has the advantage of allowing flex with great holding strength. In theory you could attach wing skins with it with no rivets. John monett tried that with glue on the origin moni. Results, one wing sleeve floating down after the plane landed in a vertical pile. Thus putting the x in experimental!
JamesB
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Posted Tuesday, April 5, 2011 @ 10:15 AM  

Slowly making progress on my open cockpit mod. I had originally wanted to make mine like the German example with a turtle deck & wind deflectors. But, the way my compass is attached to the instrument panel & some other details on my 5B meant that the "torpedo" style on the first page of this thread simply was more practical. It may not matter much, but when I contact the local FSDO, I can show that the mod uses the same materials as the factory canopies (although their questions may be more about turbulence on control/lift surfaces). Will cover it in Lexan. Should give a nice, open feeling.

It won't have the aesthetics of the turtle deck, but it will cost less to make, will be flying sooner and each time I replace the canopies with the open cockpit, it will take a lot less time. So....expediency/convenience wins.

jb92563
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Posted Tuesday, April 5, 2011 @ 03:21 PM  

I have 3 60yd rolls of the 3M VHB tape that was in fact used to secure a Tedlar (Similar to Mylar) wing skin on an aluminum frame on the Lazair I used to own.

I would not use the VHB tape for that application as the middle layer material can degrade over time and will allow flexing, which will lead to vibration, harmonics and boom, windshield in your face.

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

JamesB
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Posted Sunday, April 17, 2011 @ 11:18 AM  

So, the frames are essentially done. 4130 tubing on factory canopy frames. The tall hoops are the top of the two windscreens. The double hoops on the rear allow the fastening of the turtle deck section and the rear windscreen. The twin hoops behind the front cockpit are on separate frames -- so front and rear can be opened separately. By doing it this way, it will only take a few minutes to change from canopies to open cockpit. Another way I saw this done looked good, but would require removing part of the instrument panel every time and posed other issues. So, for me, practicality & functionality won over looks. (Not that I think this will look bad.)

I tried to render what it might look like if (instead of all clear covering), I made the covering a white opaque, except for the windscreens. In this example, I experimented with the idea of applying some material to the first few inches of the windscreens on either side to create a continuous patch of white, front to rear--making the windscreens look a little more integrated. Will need to decide just what I'm going to do. It may be that I'll first try Lexan all around -- which allows color to be applied to the inside. Don't know yet.

JamesB
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Posted Wednesday, August 3, 2011 @ 10:01 AM  

I've got some time between projects at the office, so am working to replace my canopies with the ones I got two years ago from Thermotec in CA.

I'm also making some progress on the open cockpit mod.

I thought I'd be able to cover the frames with a 1/8" thick, bendable plywood called LitePly. Although it bends, it fractures and crushes too easily for my comfort. So, I'm going to continue covering it in LitePly, then use those pieces as templates to cut Lexan. I plan to screw it all on so that I can change the covering material later. But a simple covering in Lexan should be straightforward enough to get me in the air while the weather is still warm (if I can keep up this pace). Still quite a ways to go. Will post more photos as more covering is accomplished.

jb92563
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Posted Wednesday, August 3, 2011 @ 11:45 AM  

Looks great!

Maybe you should cover the litePly with PolyFiber?

I made an interesting observation.

I have a sheet of 1/16" Lexan I bought from Home Depot 4 years ago and when I finally tried to bend it a bit it developed cracks and soon thereafter broke. I was rather surprised that it broke so easily as I was trying to get it to match the curve on the "Snail" on the RF4D.

I used some heat instead and got a good contour match for the "Gear Window" on the RF4D.

Does Lexan become brittle over time or has Home Depot been selling substandard Lexan?

When I first bought it I had bent it much more than that as I was going to use it to replace a straight flat wrap section of canopy on my HP-11 glider.

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

JamesB
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Posted Friday, August 5, 2011 @ 00:44 AM  

Don't know if it becomes brittle over time. That might be influenced by environmental conditions around it. If that's so, probably good for it to be bent to shape while it's fresh, so it will tend to hold that shape over time.

Finished the plywood templates. Have now removed the rear windscreen and used it as a template to transfer that shape to the polycarbonate sheet. Just an electric, hand jigsaw with a fine blade did a good job cutting the polycarbonate. I bent it to the shape of the rear windshield, and it seemed to bend without problems. It's stiffer than the plywood; will get some additional clamps to help hold it. Permagrit tools that I got for composite materials seem to do a nice job of smoothing and shaping rough edges. Will also take a belt sander to the hangar tomorrow as an additional way to shape and smooth rough edges.

Will try drilling it and attaching it to the frame tomorrow. Then continue onward with the other pieces. My focus will be to get the basic structure done and test fly it to make sure I actually like it before I spend a lot of time detailing its appearance.


JamesB
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Posted Sunday, August 7, 2011 @ 10:32 AM  

End of Saturday, despite two pieces that had to be recut and reinstalled due to my "superior" skills -- got the rear cockpit done except for the front bulkhead.

One screw up was at the end of Friday; was tired; just wanted to install that one last piece....when I should have left it for when I was fresh the next day. Mis-drilled it. The other may not have been avoidable....a very difficult piece due to the way it bent. Had problems with both the shape and placement of fastener holes. So, took the time to install it anyway just to confirm where the holes should be and what its form would look like once attached.

Note to self -- just because your templates are 1/8" thick doesn't mean that 1/8" polycarbonate will be the same shape. Because it is stiffer, it may not bend in quite the same ways as the LitePly. (never would have expected that -- but, that's why I bought an extra sheet of plastic stock if I need it)

As much as possible, left the protective wrap on the plastic sheets until the installation is done. Will start on the bulkhead today and continue to the front cockpit.

Over all, it's going well. Cosmic duh.....I found that if I clamp my cut pieces to the workbench -- the shaping/trimming can go a lot faster. (really basic woodworking concept--safer too) Not only can use more pressure with hand tools, but this lets me add the use of a belt sander...picking up speed. In general, worked on a lot of things to make the installation of each piece more efficient.

Once the pieces are on, will be time to install a rubber seal around the base.....then on to flight testing.

I think that this will be one of those interesting things where a clear plastic covering will be better for passengers (as you can see out more; get more light). Using an opaque covering (obviously, except for the windshield) would look better from the outside. I may get some thin, white plastic sheeting to install behind the clear sometime to see what it looks like (part of the advantage of using screws instead of rivets).

Ruined a lot of screws during installation. The stainless screws are a lot softer than the tubing. Can't tap the tubing for a sheet metal screw (that I know of....too late now, anyway). So I got some stronger screws that I run through the holes first (using them like a tap), then use the stainless screw. The tough screws only last a few times before their threads are flattened. On some places (near a weld or through flat metal stock), I went through 5 of the tough fasteners before I was able to get enough of a thread cut that the stainless would work.

Will see how much I can get accomplished today.

Jorgen
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Posted Sunday, August 7, 2011 @ 03:43 PM  

Thanks for sharing James,
you've got a very interesting project and congratulations to your progress. I bet it will feel exhilirating when you get in the air with your open-cockpit RF 5b!

May the 4's be with you/ Jörgen

JamesB
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Posted Tuesday, August 9, 2011 @ 10:05 AM  

One more piece to shape & fasten to the framework. Add weather stripping to the bottom of the frame where it meets the fuselage. Then test flights -- hopefully later today.

Collin
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Posted Tuesday, August 9, 2011 @ 03:54 PM  

Hi James,

Looks great and will be fun. I am flying the C170 to California next week. When I get back lets meet somewhere for lunch.

Collin

JamesB
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Posted Wednesday, August 10, 2011 @ 11:15 AM  

Flying it yesterday seemed to indicate that I get very similar cruise numbers for the same RPM as I get with canopies. I think it does sink faster, engine at idle in the landing pattern. Will try to get some sink numbers soon. Did power on and off stalls, slow flight, steep turns--and couldn't find anything of concern.

During the flights yesterday, flew into the yellow--just a bit above 100mph and looked for any signs of depressions or evidence that the 1/8" polycarbonate was having problems -- nothing was detected.

The engine did run hotter than normal. After experimenting, it seemed as if the airplane wants more nose down trim than it does with canopies. With more nose-down trim, the engine cooled down to normal temps.

Will post more when I learn more.

But so far, I'm pleased with the result.

Bob Grimstead
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Posted Thursday, August 11, 2011 @ 01:44 PM  

Hi James,

That looks excellent.

Now I wish I had used transparent sheeting for my canopy decking.

I might try experimenting when I get back to somewhere that the sun occasionally shines.

My only question -- are you experiencing a draught (draft?) on the back of your neck?

Yours, Bob

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

JamesB
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Posted Thursday, August 11, 2011 @ 05:01 PM  

Hi Bob.

I was up on a cool day in a light jacket. Although I felt moving air, I didn't notice a strong draft on the back of my neck. Will check over the next few flights. My guess is that a more upright windscreen protects the top of your head, but creates a stronger backdraft. Mine are fairly sloped...keeping the original angle of the canopies. Will see how that balance of over-the-head airflow versus backdraft seem to go over time.

Jorgen
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Posted Thursday, August 11, 2011 @ 05:32 PM  

Hi James,
congratulations and thanks for sharing that moment! I think your open cockpits look outstanding and I bet it feels very different flying cabriolet. I take it you are not entirely without experience driving a cabriolet, hmmm? Another hommage to Hr Ferdinand Porsche, I gather. I wish you many happy cabriolet hours both on and above planet Earth!

May the 4's be with you/ Jörgen

JamesB
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Posted Friday, August 12, 2011 @ 12:47 PM  

Jörgen -- I've been accused of merely adding another cabriolet to the garage...also German construction wtih a horiz. opposed German engine....hm-m-m. Having owned Porsches & VW's on and off since '68, there were those who thought the RF5B was just another German mechanical device for me.

Bob -- Went flying yesterday. Started to relax some now that I was assured that there were no monsters hiding in the handling, parts of the new structure that were going to rip off in the wind, etc., etc. A really great flight. A warmer jacket helped. Biggest issues are wind noise at my ears & wind noise in the mic.

About the wind: I do get some air on the back of my neck, not much. The strongest airflow is just above my head. Yet, I am getting quite a bit of airflow from the sides--making fairly loud wind noise at my ears. My in-ear headset (Clarity Aloft) seems to do slightly better than an almost new Lightspeed Zulu (which transmits a lot of the wind noise that hits the hard surface of the ear enclosures). Similarly, the headset mics pick up quite a bit of wind noise.

I've ordered a larger foam muff for the mic. Will also try making a hard "cup" or shield for the windward side of the mic.

Need to experiment a bit with the ear noise. My leather flying helmet has zip enclosures over each ear, so I've suffed some cotton in those pockets. Some of the wind noise comes from the front, under the flying helmet. If I can seal the gap around my ears (maybe with the foam/gel cushions for a headset), I can cut off that source of noise.

Quite possible that the wind from the sides is what's reducing what would have been wind rolling over the top of the windscreen down the neck.

One of the new Mercedes has a quiet mode for its cabriolet where a spoiler extends at the top of the windshield, smoothing & shaping air flow to significantly reduce air turbulence for passengers. I've never seen anyone do that for an airplane....but it's a possibility depending on the structure.

Did a couple of landings yesterday. On final flair just at full stall at the runway, I feel I have the stick further back than I did with canopies. So, there may be some turbulence or blanketing of the elevator that reduces its efficiency at that extreme end of the handling envelope. That said, I have not run out of stick travel, it's just closer to full travel than before. Will poke around more with aborted landings, etc.

Cloud layers have been low enough that I haven't had a chance to see how my engine off sink rate compares to what I would expect with the canopies. We should have clearer skies this weekend. Will try to get more info.

I hope to have the new canopies on in the next couple of weeks. At that point, I'll be able to do some back-to-back canopy/open-cockpit flights which might be more illuminating.

Not that it will add much, I do have HD footage from the GoPro of the test flights. Will add more from nicer weather and will get something up on YouTube before long.

Donald
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Posted Friday, August 12, 2011 @ 12:54 PM  

Looks like that would be good fun on a nice sunny day. I'm going to keep my lid on, though.
JamesB
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Posted Saturday, August 13, 2011 @ 11:36 AM  

Early evening yesterday, flew up to about 4,500', shut off engine, feathered the prop. Slight areas of lift & sink. Much of the descent was in the 100-200 fpm, with a moderate amount in the 200-300' fpm (indicated). Under similar conditions with canopies, I'd expect to see most of the descent in the 100-200+ fpm. At times, it increased to 300-400 fpm, but seemed like these were areas of sink, then leveled out again.

I think that the sink is in the general range of what I'd see with the canopies, but at the bottom end of the performance range of what I'd see. I don't think the open cockpit is as good -- then again, never expected them to be. That they're even vaguely close is excellent (as far as I'm concerned). Certainly not the 4:1 of a biplane.

Overall, the glider isn't as slippery as it is with canopies. With canopies, I often have to watch my forward speed during a descent as it can quickly slide into the yellow -- not so much with the open cockpit. I think in the landing pattern at engine idle, I see about the same sink with gear down/spoilers closed as I see with canopies/gear down/and about an inch or so of spoilers.

Under power, I'm seeing about the same cruise speeds.

Once I have the new canopies on, I'll try to offer more info.

Yesterday, used a plastic shield on the mic to reduce wind noise -- worked very well. Tried some initial soft sponge seals around my ears -- also worked very well so that the wind noise was at a very reasonable level. This improved the quality of radio transmissions & how well I could hear other aircraft. Also used some black electrical tape across the top of my goggles to provide better sun shade -- also worked well. So, am dialing in a lot of the details. Over all, working out well.

[Edit by JamesB on Saturday, August 13, 2011 @ 11:48 AM]

Jorgen
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Posted Saturday, August 13, 2011 @ 04:54 PM  

Thanks for sharing that, James. Good tip on the mike and headphones too. As a hangglider pilot I think you will enjoy open cockpit soaring. The increased wind noise can actually be another helpful input that makes you a litttle less dependent of the vario.

May the 4's be with you/ Jörgen

JamesB
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Posted Sunday, August 14, 2011 @ 04:46 PM  

An HD video:

http://www.youtube.com/watch?v=DJvsc4UKigg

Bob Grimstead
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Posted Tuesday, August 16, 2011 @ 05:33 AM  

Great Stuff James,

Many thanks for such detailed information.

I believe you can get a little leather cap for your mic to suppress the wind noise (maybe from Aircraft Spruce?)

When I had my Fly Baby, I used a tennis ball with a slot cut in it, plus ANR modifications to my Peltor headset.
That combination greatly reduced perceived wind noise, although the tennis ball was a bit big and ugly.

Your performance and handling are exactly what I would expect, both very slightly degraded if you look carefully.

Slight modifications to the rims of your windshields might reap big dividends, (but of course they might also make things worse).

A small, curved Pleixglas shield on the side of my old Caterham Seven's windshield stopped the displaced wind from going straight into my ear and greatly reduced in-cockpit buffeting and noise, so the same sort of thing along the tops of your screens might make a big difference.
Maybe a one-inch strip of soft, thin aluminum folded with a twenty- or thirty-degree angle and then curved and taped along the upper edges of your windshields would smoooth out the airflow and reduce both drag and in-cockpit turbulence/noise?

Or not?

Experimentation is the name of the game.

Very good luck, and enjoy those summer breezes, as I do.

Yours, Bob

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

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Posted Tuesday, August 16, 2011 @ 07:41 AM    YIM

These work very well indeed in an open cockpit.

http://www.aircraftspruce.com/catalog/avpages/micmuf.php

JamesB
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Posted Tuesday, August 16, 2011 @ 10:40 AM  

Yesterday was the first soaring weather here since the test flights. A few observations:

- The RF5B soared well with the open canopies. (Probably not a big surprise given the other information.)
- If I had thought temps got cool near cloudbase with canopies -- whoa baby -- it's gets downright cold near cloudbase in an open cockpit.
- Thermals are somewhat abstract when you try to feel them as they push the glider and activate the variometer. It's another to have a bolt of upward moving air sort of slap you in the face -- faster than any reading from the variometer. Very interesting.

On a slightly different note, since the new mods perform almost identically to the original canopies, for a variety of reasons, I'm going to treat them as a second set of modified canopies where the windows that were in the originals have been expanded in size. Since they are on the same frames, essentially use the same materials, employ the same angles as the originals and don't affect the strength or structure of the aircraft and -- this is a reasonable approximation of what's been done. Other RF owners have changed the shape of their canopies to allow more headroom. I've made a set with larger windows.

Jorgen
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Posted Tuesday, August 16, 2011 @ 04:36 PM  

Excellent film James,
theme from Star Trek? Open cockpit thermalling is as you note different and the vario suddenly becomes more of an "average-lift" indicator, airmovement on your face is much more direct and you can learn to read them just like a gauge, only faster and they often "slaps you in the face"- or butt! I remember one discussion among hangglider pilots were most of us expressed disatisfaction about not beeing able to "see" thermals. One bloke remarked dryly: "-You should be glad you can't- if you really could see how a thermal looks, rotors, turbulence, horns, fangs and all nobody in their right mind would voluntarily fly into them!"

May the 4's be with you/ Jörgen

Antti
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Gender: Male
Location: Finland
Registered: Sep 2009
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Posts: 26

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Posted Saturday, August 19, 2017 @ 08:53 AM  

This is - and has been - an interesting thread. However, most of the pics seem not to be online anymore. I've been planning to do an open cockpit conversion at some point and the point might be now. I've transported my canopy into so called "my shop" and got Markku's old cracked one for test purposes.

So, would some of the designs still be available for examing them and what is the situation with the "torpedo" one on the first page? Is it considered as legal factory option? If so, how about the paperwork?

Cheers,

Antti

--------------------
***** RF4D OH-370 - RF4D OH-371 - RF5 0H-386 *****

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