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Thread: Flying without spinner

  1. #1

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    Flying without spinner

    I Think I remember reading here somewhere someone talking about saving 2 pounds of weight on a nose heavy airplane by flying without a spinner.

    What's the down side to flying without a spinner? How much speed loss, cooling considerations?

  2. #2
    G44's Avatar
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    Higher CHT (possibly).
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  3. #3
    Cub Special Ed's Avatar
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    Some engine/prop/aircraft combinations require spinners for engine cooling purposes.
    "There are 3 kinds of men. The one that learns by reading. The few who learn by observation. The rest of them have to pee on the electric fence for themselves." Will Rogers
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  4. #4
    Steve Pierce's Avatar
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    I removed the spinner on my 150 hp Super Cub and saved 2.7 lbs. I haven't noticed any difference in cooling but don't have CHT/EGT instrumentation eaither. I know the engine will overheat on a Cessna 182 but have seen no issues with Super Cubs. I don't see the spinner on a required equipment list.
    Steve Pierce

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  5. #5

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    I could detect no real difference in speed loss or temps after removing the spinner. I was flying behind a cgr-30.....When your airspeed is measured in days instead of Mach #s, I don’t think deleting the spinner matters. Maybe you could detect a slight speed loss if you had a slicked up cub with a cruise prop and little tires?
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  6. #6
    jnorris's Avatar
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    I was flying without a spinner on my Pacer back in the day, and an FAA guy came up and said "Wasn't that airplane certificated with a spinner?" That's all he said, and he walked away, but I got the point. Check to make sure it's not required equipment per the TCDS if it's a standard category airplane.
    Joe

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  7. #7
    cgoldy's Avatar
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    I have had my spinner on an off a couple of times on an O.375 where I watch the temps carefully. Haven't noticed anything yet.
    Javron O-375 wide body extended wing cub
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  8. #8
    Binty's Avatar
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    No difference what-so-ever.
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  9. #9
    Kodiakmack's Avatar
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    I'd like to resurrect this thread. Steve, you mentioned you can't find anywhere on the Type Certificate that lists a spinner as required. I agree. However, was the airplane originally certificated with one, as the Fed mentioned to another poster here? I'm asking around the A&P's I work with, and they are all leery to go down the "show me where it says I can't" hole. I know half the fleet in AK run without spinners. I guess I'm looking for a definitive place that points towards it being OK.

    On a side note, is there anything one would want to do for a spacer to make up for the small amount of space you're deleting by taking away the spinner back plate, or would you just mount straight to the bird and go fly?

    Here's what was under the spinner when I took delivery of the bird..... VS What it looks like at the moment.....I think I prefer the current setup, but want to make sure I don't get in an unwanted conversation with our conservative FSDO here in Utah. Click image for larger version. 

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  10. #10
    courierguy's Avatar
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    I've been flying with a 6" skullcap on my RANS 7 for the last 2700 hrs, and have just fitted a 12" , what the plane and most importantly the cowl was designed to use. The exit area of the cowl was set up for X amount of ram air, I've been cramming in XX. I will be gaining 2.3 pounds, which I hate. Only doing this for possible drag reduction, not cosmetics ( same reason my gear is covered and faired)
    cooling changes if any will be interesting. I know my plane well enough to pick up on any minor difference, and have decent instrumentation to quantify it. I hope for a noticble speed increase, 2 or 3 mph, that would be a big increase on a 80-85 mph plane, Percentage wise. IF NOT, it's all coming off and the 6" back on, but at least I will have satisfied my courisity.
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  11. #11
    Kodiakmack's Avatar
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    I’m interested to hear what you see as a difference.

    im still curious.....will the feds slap my peepee if I fly without a spinner on my 1946 pa-12?
    HAVE FUN. DON'T DIE.

  12. #12
    courierguy's Avatar
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    Due to the big gap in the RANS cowl, not using a 12" spinner as intended may be more draggy then the tighter cowl I see the Cubs use? And also let more air in then the outlet may be able to let out? That lower cowl outlet, knowing the RANS guys, wasn't just guessed at but sized for the 12 " spinner install, we'll see.

    It may be a while before I can report back on the spinner issue, I may have an issue with compression on one cylinder. I thought it was pretty doggy the last few takeoffs, but was thinking it was just the snow, was HOPING it was just the snow.

    That's a sliding cockpit controlled lexan shutter over my oil cooler BTW, with some summertime lightening holes taped over for the winter.
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  13. #13
    RaisedByWolves's Avatar
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    I saw no change when my spinner cracked and I took it and the backing plates off and got a skull cap. Been running it for 1000 hrs or so


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  14. #14
    Cubus Maximus's Avatar
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    Piper used to advertise them without spinners. So I assume it was an option, just like the right hand fuel tank and electrical system.









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  15. #15

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    I’ll take that 845lb one
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  16. #16
    Kodiakmack's Avatar
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    Now one mechanic is just being picky. He said “well that’s for a super cub not a super cruiser”. I think I’ve seen what I need to feel warm and fuzzy. We’ll see what the IA says Thursday on inspection day.
    HAVE FUN. DON'T DIE.

  17. #17
    skywagon8a's Avatar
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    Look at Item 5 on the equipment list. Of the 7 different propellers which are approved on the PA-12 Type Certificate, the Beech controllable propeller is the only one which specifically states a spinner must be installed. This is telling me that the spinner is optional on all of the other propellers.
    https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/45b0fe3b1c17780186256a61006c7931/$FILE/a-780.pdf
    N1PA
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  18. #18
    courierguy's Avatar
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    I got my 12" spinner on the RANS, and it has a SLIGHT wobble. Whether or not there is a allowable minor wobble tolerance, or if all other spinners are absolutely true I don't know. I do know I will give up after this one as I can't think how to do it any better. Flight test soon, and if there isn't a bit of speed gain it will come back off pronto and go back up on the Wall of Shame, right back where it was for the last 12 years, and I'll console myself with dropping the 2+ pounds it added, and will at least have satisfied my curiosity over if they are just for looks or cut drag and maybe help cooling. Before anyone chimes in, yes I do know they can be a major hazard if they come loose in flight, and while the final decision is mine alone, I'd appreciate any opinions IF you can tell by looking at this 27 second video. And just imagine it's a Lycoming not a Rotax. https://www.youtube.com/watch?v=V93rPdk32M0
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  19. #19
    BC12D-4-85's Avatar
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    Prop balancers put a marker (soft chalk or felt ink sharpie) on a stick and briefly touch the spinner while running. Tells them where the offset part is so they can adjust by loosening the screws and adjusting the spinner. I did have one come off a C-185 in flight....all I saw was a blur. Didn't notice much change in performance. We were IFR over the Brooks Range on floats so didn't linger about to figure out what happened. Side ears of backing plate separated.

    Gary
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  20. #20
    courierguy's Avatar
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    That never occured to me, and I can see how that could work. Right now my holes are tight/perfect all around, so no adjustment is possible. Determining which way to nudge it a bit would be easy enough, and then with just a very minor ovallating (spelchek is fine with that....) of the 3/16" machine screw holes on one side, and enlarging them away from the edge, not towards it, and then when snugging up the screws a little pressure to hold it there until the clamping force locks every thing down, worth a shot. An hour or so of careful work with a small rat tail file would do it, it's not like its out of whack that far.

    The horror stories I've heard involving spinner failures were trashed cowls, broken props, and motors torn from mounts, but they were maybe old pilot stories, nonetheless, I'll proceed cautiously.

  21. #21

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    Years ago I lost my skull-cap spinner somewhere between Uranium City, Saskatchewan and Yellowknife. Must have come off in flight. Never noticed.

  22. #22
    BC12D-4-85's Avatar
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    If I can find them I try to use those softer plastic, rubber, or fiber washers under the spinner screw heads. Helps reduce metal wear and over tightening which can eventually deform the spinner. I think some Cubs came with them. Not sure.

    Gary

  23. #23

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    No spinner, no skull cap for over 100 hours now.

    I saved 19 pounds, gained 11KTs airspeed, and can land 50 feet shorter now.

    (if you believe any of that last sentence, I have one I will sell you)


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    I actually noticed no change whatsoever at my slow speeds vs a skull cap. No cooling changes worth noting.
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  24. #24

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    What do you call that? Hub condom. I like it. What’s it made of? Latex or lamb skin

  25. #25
    courierguy's Avatar
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    Quote Originally Posted by motosix View Post
    No spinner, no skull cap for over 100 hours now.

    I saved 19 pounds, gained 11KTs airspeed, and can land 50 feet shorter now.

    (if you believe any of that last sentence, I have one I will sell you)


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    I actually noticed no change whatsoever at my slow speeds vs a skull cap. No cooling changes worth noting.

    JUST a crush plate, but a fancy anodized and engraved one, first time I've seen that! That laser, water jet, or CNC 'd?
    Half the reason I'm continuing with this is I want to prove to myself I can install a spinner wobble free, and it's not costing me anything. And the WX is no fly and I have the time....my next move is to cogitate up a soapstone holder on my tractor bucket, so when positioned in front of the tied down and running plane, I can then slowly bring the soapstone closer and closer to the spinner to make a mark on just the "high" side to indicate how shifting it a hair may eliminate any wobble whatsoever. For the final and very controlled movement of of the soapstone, I'm thinking some threaded rod on a bracket, C clamped to the tractor bucket, something I can micro control. If I end up with a mark clear around the spinner it won't be much help. I will attempt to keep the tractor blade and the soapstone holding device out of the spinning prop while doing all this. Just holding a stick out to make a mark would require a steadier hand then mine I think. Actually, if the WX improves I'll fly it as is first, and if no difference in performance is noted I won't bother with any of that but will yank it off posthaste. I half hope that's the case.

  26. #26
    skukum12's Avatar
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    Quote Originally Posted by motosix View Post
    No spinner, no skull cap for over 100 hours now.

    I saved 19 pounds, gained 11KTs airspeed, and can land 50 feet shorter now.

    (if you believe any of that last sentence, I have one I will sell you)


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    I actually noticed no change whatsoever at my slow speeds vs a skull cap. No cooling changes worth noting.
    Ok motosix, i believe every word. Now sell me a crushplate like that in black or greeen. Seriously, i need one now. Did you make that? Or where can i get one?

    Hate to put ugly safety wire over it though...
    Last edited by skukum12; 02-16-2021 at 10:18 AM. Reason: Additional
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  27. #27
    BC12D-4-85's Avatar
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    The prop folks I've seen do it look for wobble. If noted they take a wood stick with a marker and quickly touch the spinner. Just a brief tap. Felt tip magic marker on the last job. Low engine speed but fast enough to not be shaking much. Then they go about their measuring of imbalance, calculations of weight at station, and add them. If the spinner gets removed they recheck the wobble.

    Gary
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  28. #28
    Kodiakmack's Avatar
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    Any suggestions on how to balance with no spinner and no holes on the ring gear/back plate for weights?
    Last edited by Kodiakmack; 02-16-2021 at 11:06 AM.
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  29. #29
    skywagon8a's Avatar
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    Quote Originally Posted by Kodiakmack View Post
    Any suggestions on how to balance with most spinner and no holes on the ring gear/back plate for weights?
    One method which, a longer screw is used with washers added at the appropriate location.

    What did you decide on whether you were required to use a spinner or not?
    N1PA

  30. #30
    Kodiakmack's Avatar
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    Sorry I had a typo on the last post. So no spinner to add washers to.

    As for basis of not using a spinner, I’m going with what someone pointed out, that there are propeller options in the TC that specifically require a spinner, implying that for others it is an option. Also, there is no part number for my engine/prop setup, so I’d either have to fall into owner manufactured or custom to really put one on anyways. I think I could pass a red face test and honestly believe it’s the safer better option.
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  31. #31
    skywagon8a's Avatar
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    Be careful on your "owner manufactured" statement. You would still be required to make that particular part in accordance with the appropriate approved part data. Owner manufactured only means you don't have to buy a PMA'd or otherwise approved method of manufacturing a part by someone else.

    Without any holes in your starter ring gear you could add washers for balance to your prop bolts, assuming they are long enough.
    N1PA

  32. #32

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    Quote Originally Posted by skukum12 View Post
    Ok motosix, i believe every word. Now sell me a crushplate like that in black or greeen. Seriously, i need one now. Did you make that? Or where can i get one?
    The one pictured is the only one in existence and is for a Lycoming O-235 motor which is useless to 99% of Cubs. It is CNC'd, then EDMd for the logo, then anodized.

    I draw up designs for people and work with local & online CNC places to help the parts get cut. One-off parts are not cheap, however designs get magnitudes cheaper as count goes up. Most online CNC places allow a huge range of anodizing colors, so black or green would be easy enough. As soon as I get my new prop in (with a crush plate to measure), I am going to get one for an Titan 340 designed and cut which might work for you if you have a Lyc 320? Which motor are you running?

    Email me at dave AT ColoradoCub.com if that is easier so we don't drown this thread. You can see some of the other Cub parts in the works for my airplane at that web address as well.

    edit: I should point out that everything stated above is for EXPERIMENTAL Cubs. Sorry, you certified guys have different hoops to jump through.

    (the attachment is the real unsung hero on the nose of my Cub. It saved ~15 lbs all the way out at the prop!)
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  33. #33
    BC12D-4-85's Avatar
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    Here's one method I've seen for balancing. Normal prop bolt length limits washer numbers to achieve balance under head while maintaining thread penetration in the crankshaft flange. They are typically long enough to extend behind flange...or can be replaced with longer the meet specs. Being so close to the crank C/L meant more weight was needed than if the weight had been added further away from center...like under the bolt's head or on a spinner or ring gear. A skull cap goes over the assembly. Does it work? Yes. Lots of repair station equipment involved and log entry. Needs to be checked periodically for integrity and balance.

    Gary
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  34. #34
    courierguy's Avatar
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    That above picture tells me, if that was my cowl, that a big spinner would be perhaps counter productive, that cowl was made for a skull cap or even no spinner. As opposed to the cowl gap I have (huge), obviously meant for a 12" dome, which led me down the path of a possible drag reduction or slight increase in speed.

    Here's a good shot of the mini I've been using. I need a crush plate anyway for the Prince prop (unlike the ground adjustable types) so the only extra weight is the stem, an allen screw, and the dome, maybe 4 ozs. If I do end up putting it back on, I will, for the first time polish it, seems the least I can do. It's an idiot proof deal, and I really like the way it pops on or off with just the one allen head screw.
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  35. #35
    courierguy's Avatar
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    That above picture (T-Craft, pert sure) ) tells me, if that was my cowl, that a big spinner would be perhaps counter productive, that cowl was made for a skull cap or even no spinner. As opposed to the cowl gap I have (huge), obviously meant for a 12" dome, which led me down the path of a possible drag reduction or slight increase in speed.

    Here's a good shot of the mini I've been using. I need a crush plate anyway for the Prince prop (unlike the ground adjustable types) so the only extra weight is the stem, an allen screw, and the dome, maybe 4 ozs. If I do end up putting it back on, I will, for the first time polish it, seems the least I can do. It's an idiot proof deal, and I like the way it pops on or off with just the one allen head screw.

    Here's the new one. We all know Forest Green compliments Kubota Orange perfectly, right??? But since I had the paint already and also have a lot of other stuff the same color, I thought why not? I can't tell what color it is from the cockpit anyway.
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  36. #36
    BC12D-4-85's Avatar
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    Orange is easy to find if it decides to depart. The shape does fit the cowl's form nicely. I suppose in lieu of running and marking any spinner or backing plate offset just pulling some plugs and rotating the prop against a fixed reference would work.

    How do you get to your home? Is there a road nearby?

    Gary

  37. #37
    courierguy's Avatar
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    A county gravel road, 1.5 miles to a paved 2 lane rd., then down the mountain and 3 minutes later I can get on I-15, and another 10 miles it joins with I-86. Point being, a great mix of boonie living combined with pretty easy access to the real world. I have a brother who lives on McGrath Rd BTW, he was good friends with the late Cliff Everts.

    I did that when I set it up, had a clamped stick 1/8" away, plugs out, clamped tight, nothing moved when I drilled it, I was pretty surprised (teed off) to see it wasn't perfect. Not horrible by any means, but not perfect. I'll sneak up on the fine tuning next, the looks are actually starting to grow on me a bit.

    When I carry my fat ebike on the rear rack of my Prius, the mileage hit from the drag is evident, with the real time fuel/mileage gauge I have. When I carry it on the same rack but now plugged into the hitch of the Silverado one ton flatbed, I can't tell any difference. That may be a simile for my lesser powered and lighter plane perhaps benefiting a bit from this spinner, whereas a 180 hp SC may just not notice as much, and even 2 mph gain is a pretty big gain when you're cruising in the 80's, I'll take it if I can get it.

  38. #38
    BC12D-4-85's Avatar
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    Yes it's a small world isn't it? Lots of well seasoned folks live here, especially for the summers. All well armed BTW. How much do you think cooling drag detracts from your speed? Or other stuff like that exposed exhaust? Ever consider just a straight pipe to the tail and fly away from the noise?

    Gary

  39. #39
    courierguy's Avatar
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    Cooling drag, turbulence around the cowl with that big gap, who knows, I will find out, probably not a huge amount but just a little less can't hurt. The Swiss Muffler (goggle it) is an additional muffler to the stock under the cowl one, it and the Prince p tip prop make my plane one of the quietest in the air. It doesn't seem to hurt engine performance either, I've done static checks. Drag....yeah probably but I do it to keep my rural strip as stealthy as possible. I've run into newer neighbors at the mailbox, people that live down the road a mile, where I have flown over while climbing out, and they've said they never even knew I flew out of my place, much less been annoyed by the noise, that's why I do it, I call it the SBMS, sneaky bastard muffler system. It's the "if a tree falls in the forest...." thing, it didn't happen if no one heard you.
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  40. #40
    courierguy's Avatar
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    It was a cheap enough experiment, (forget the hours of labor, fitting etc.) but yielded absolutely no speed increase, so back on the wall it goes. Besides adding a bit over 2 pounds, it also made the top cowl removal just a bit more hassle. I did make a slight adjustment after making a mark on it while running, and was happy enough with the trueness of it. So at least for my bird it's usefulness is right up there with a hood ornament, KISS. I'm not disappointed at all, I just lost over 2 pounds!
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    Thanks BC12D-4-85, marcusofcotton thanked for this post
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