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Cobra plans underway

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Old 12-30-2015, 05:30 PM
  #51
rcuk john
 
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Seen on UK eBay for 135 ..........
http://www.ebay.co.uk/itm/Olympic-CO...0AAOSwJcZWfXHM
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Old 01-02-2016, 01:27 AM
  #52
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That's pretty neat! I didn't realize it was an actual kit!
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Old 01-11-2016, 04:36 PM
  #53
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vintageshack, the boat coming along nicely, the cockpit looks similar to a second world war fighter plane, looks great!
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Old 01-11-2016, 05:52 PM
  #54
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Thanks arcdude! The cockpit is from a 1/16 scale F6F-3 Hellcat model I had when I was a kid.. I never finished it because my cat decided to jump on my desk (which the fuselage was pinned to) in the middle of the night.. Oh well, at least I finally found a use for the beat up plane! Anyways, Christmas was pretty expensive, so I will have to wait a little while before I can finish it. All I need to finish is a motor, esc and battery.. In the meantime, I am starting a new boat for my son.


Its a Miss Take that has been scaled down to suit a .049 cox engine. I am planning on ordering the throttle conversion kit for it as well. I haven't given up on the cobra though!
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Old 02-07-2016, 07:42 AM
  #55
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These are some really great examples of Cobras, Vintageshack's version with the cockpit and paintjob really capture the spirit of the world-war-fighterplane-crossed-boat that caught my imagination when I first saw the plans!

I didn't realise that there were so many (or any) people building these things when I built mine.
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Old 02-08-2016, 10:48 AM
  #56
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Thanks for the compliment! When I was researching it there wasn't anyone actively building one that I could find.. All I did find (besides the plans) were a couple grainy YouTube videos!
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Old 02-08-2016, 10:49 AM
  #57
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Do you have any pics or videos of your build?
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Old 02-08-2016, 11:06 AM
  #58
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I thought I had searched quite extensively before I started, but somehow I completely missed this thread. I actually posted my whole build on Instructables dxf files and all, didn't wanna go cross-posting here since I am a newbie on the forum and had already posted this in the other thread here about Cobras (seriously, how bad was my pre-build googling?).

Oh, and I have contributed to the low-quality videos of cobras on youtube ;-)

https://www.youtube.com/watch?v=-BIGV8Xkay0
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Old 02-12-2016, 09:20 AM
  #59
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Hay guys I redid the Miss Take plans for a airboat guy some time back now. He was having problems with parts not lining up so I drew some plans based on the ones posted above to help him out.
link of his build with plans in PDF format....note we may have resized I cant remember...anyway every little bit helps right
http://www.rcgroups.com/forums/showthread.php?t=596900
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Miss Take dwg file.zip (34.2 KB, 30 views)

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Old 02-17-2016, 11:03 PM
  #60
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Hey ossum! I read through your build on instructibles, very impressive! Looks much easier piecing everything together with the cad drawings! pinky_d_brain, I am having a bit of problems fitting a couple things together, but I'm just kind of figuring it out as I go! I don't have auto cad, so sadly I can't open the file you posted... Thanks for the link though!
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Old 02-18-2016, 12:38 AM
  #61
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Thanks. It really did go together like a jigsaw puzzle, I was pleasantly surprised myself ;-)


If you are looking for DWG viewers, there are some free options http://www.autodesk.com/products/dwg/viewers


On a related note, if you are looking into CAD, I have started using Autodesk's Fusion 360 now, which is free for hobbyists, and am loving it. It is comparable to SolidWorks as far as I am concerned (which I used at work, but could never afford for personal use).
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Old 02-22-2016, 12:13 PM
  #62
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If you fallow the link there are pdf drawings of the CAD drawings. sorry I should have added them to the Zip file
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Old 03-11-2016, 07:11 AM
  #63
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Well, some more progress .... 2 coats of sealer, 2 coats of primer and the first top coat.
Still one more top coat to put on and then a coat of polyurethane to proof the paint against the glow fuel.
Then it is onto connect up the Rx and servos, fit the fuel tank, the windscreen and test out.
The round hole in the side of the cockpit is for the Rx run/battery charge selector switch and not visible on the other side is a square hole for the charger plug adaptor.
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Old 05-23-2016, 07:22 AM
  #64
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Well, "dry" run to check floatation revealed that a 10" prop on the 7.5cc engine is TOO big - needs to be no more than 9" diameter.
Anyone know the formula on how to convert a two bladed prop size to a 3 bladed prop? Maybe reduce O/D by 1" and ADD 1" to pitch???.
Hopefully may get to run it next week - early weed season permitting.
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Old 05-23-2016, 01:48 PM
  #65
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Looks good. DOWN 1" in size and UP one in pitch.
ie. 10-6 two blade to 9-7 three blade.
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Old 05-25-2016, 11:24 AM
  #66
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My airboat is promising…..
The first run went well until I tried the first RH turn at which point the boat flipped over to the right during the righthand turn and capsized. None of us at the club can put reason on that but all was well and after drying out everything worked fine despite the RX being aircraft style (bare in the hull).

Second run gave are several laps without further problem. It sure starts to really “go” on the straights lifting and almost taking off. I need MORE right rudder for the turns. I am considering changing the rudder from plywood to aluminium as well.
The prop really should be no larger than 8" in diameter but I can live with the cut-down-to-9" one for now.
I may have to consider ballasting. At present it is set to be just a little stern heavy to allow for the nitro fuel.
I may also have to consider some sort go guard around the prop .......
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Old 06-09-2016, 01:21 AM
  #67
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After testing the way forward my craft will involve some changes ...

1.) The prop was originally 10" x 6" but was reduced to 9" diameter after flotation testing. However it is STILL catches the water surface before coming on to the plane, so that will be changed to an 8" x 7" three bladed prop. I have the prop ready and have a spinner on order.

2.) The rudder will have to be changed to a DOUBLE servo cable. Basically I am loosing RIGHT turn at speed due to the water pressure on the rudder bending the snake from the servo. I may take the opportunity to also change the rudder to 3mm Aluminium sheet at the same time.

The potential of this craft leaves me wondering if our club's water will be large enough for its maximum speed - only time will tell.
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Old 06-09-2016, 04:44 PM
  #68
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Quote:
Originally Posted by rcuk john View Post
After testing the way forward my craft will involve some changes ...

1.) The prop was originally 10" x 6" but was reduced to 9" diameter after flotation testing. However it is STILL catches the water surface before coming on to the plane, so that will be changed to an 8" x 7" three bladed prop. I have the prop ready and have a spinner on order.

2.) The rudder will have to be changed to a DOUBLE servo cable. Basically I am loosing RIGHT turn at speed due to the water pressure on the rudder bending the snake from the servo. I may take the opportunity to also change the rudder to 3mm Aluminium sheet at the same time.

The potential of this craft leaves me wondering if our club's water will be large enough for its maximum speed - only time will tell.
Just a thought. If you want to keep the weight down, an aluminum plate rudder might get too heavy. You might consider a frame and skin rudder with some sort of internal aluminum stiffeners or a .5mm aluminum skin laminated to the outside. You might also consider a hard straight pushrod for your rudder. Flexible rudder linkages rarely are successful on boats due to, as you have found, water pressure on the rudder at speed. While a dual cable may sound good, unless the cables are parallel and evenly tensioned, they can be a serious headache as well
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Old 06-12-2016, 07:52 AM
  #69
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Good to see your boat is complete! I, unfortunately, have run into some delays with mine.. I ended up with a collapsed lung at work (Iqaluit) and was hospitalized up there for 7 days.. Then, to make matters worse, I couldn't fly out for almost a month because my lung was still partially deflated, and that's the only way to get out of there! I ended up on disability for a couple months, and finally, I took a job closer to home (significant pay cut though) so I wouldn't have to do the rotational schedule anymore and to be closer to my family. So, needless to say, my boat has been put on the backburner until I can get all situated with my new job! At least I managed to get the boat home from Iqaluit..
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Old 06-12-2016, 10:57 AM
  #70
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ouch . . a pneumothorax they definitely are on the high pain list did you end up with a pipe sticking out of your chest or did they manage to sort it out with a big needle through the top of your shoulder
make sure you take it easy for a good while or you could get another spontaneously
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Old 06-14-2016, 06:18 AM
  #71
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Oh, I ended up with two holes in my side! They put the first one in, my lung inflated too quick and started to fill with fluid, so they had to put me under again and install a larger tube that went in 16 inches! It was a little unnerving looking at the xrays and seeing this giant tube just above my lung! I'm not sure they knew exactly what they were doing there.. Ya don't want to hear from a doctor that you were a resume builder for them!
I've been off work since March taking it easy and trying not to pop my lung again, and just recently started a job working on water bombers.. No fires nearby so its been pretty slow! I'll probably get a chance to do some work on the boat soon.. If I can find some extra money, or someone really nice who wants to donate parts to me!! Also, I may even change my plans about having an electric boat, since it is no longer in Iqaluit (hard to get nitro fuel there)
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Old 06-14-2016, 07:18 AM
  #72
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you were put under. . . . arnt you the lucky one all of mine they did on the ward and ended up pushing me half way around the ward trying to get the dam tube through my rib cage
gald you are on the mend
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Old 06-17-2016, 11:25 AM
  #73
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This will be my final post on this thread ....
Attached picture shows the three bladed prop and the extra control link to the starboard side of the rudder.

VintageShack - I will PM you over the weekend.
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Old 09-23-2016, 09:55 AM
  #74
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Well, the boat is still on hold! The funds weren't there for me to finish it this summer, and I may of gotten a little distracted with another project...
http://motorbicycling.com/showthread.php?t=61861

I haven't given up on it, but I don't know when I will get a chance to finish it! One day maybe..
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Old 09-23-2016, 01:57 PM
  #75
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nice little project (the bike)
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