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Cobra plans underway

Old 03-13-2015, 11:23 PM
  #26  
vintageshack
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I finally took some pictures of my progress.. Not a whole lot, but I did get the bottom complete and roughly sanded. I still need to fill in some small cracks and such, then I can seal it.
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Old 03-15-2015, 04:27 AM
  #27  
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Very clean your assembly , it's a pleasure to look.

Don't forget to assembly the "skeg" before seal it.

In my crackerbox my " skeg " fabricated aluminum bracket in L

keep following
Old 03-15-2015, 06:55 PM
  #28  
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Originally Posted by vintageshack View Post
Thanks, that seems like a helpful site! And they ship to Canada too! Well, except for batteries.. Not sure what I'm going to do for a battery yet..
Hobby King. http://www.hobbyking.com/hobbyking/store/index.asp
Old 03-22-2015, 12:19 AM
  #29  
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I decided to try out mixing the 5 minute epoxy I have up here with alcohol one more time just to see if it would work, and it did. I tried it a while ago and the epoxy and alcohol mix wasn't a uniform fluid.. I think last time I was too quick to try to mix them where it is 5 min epoxy and all, and it just turned into a boogery mixture.. This time, I gave the epoxy a minute to settle after mixing before trying to add alcohol, which I added a very small bit at a time. I actually have quite a bit of working time before the mix starts to harden. In the pics you can see the sealed and unsealed parts of the boat. I just need to pick up more 5 min epoxy when I'm home to finish the rest of it. Don't mind the horse pubes, all I had to spread it with was acid brushes.. I'll have to use something else on the outside that wont leave too many hairs in the epoxy.

I also utilized my mad MS paint skills and made a picture of the boat with V12 stacks and a cockpit from a Hellcat.
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Old 05-04-2015, 02:12 AM
  #30  
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Here are a few more update pics. All the panels are glued in place and sealed behind. Still lots of sanding to go! I'm in no rush though.. My test pond is still frozen over! Also, a co-worker has donated a motor, prop, and speed controller to the cause.. Not sure what motor or speed controller, but he is a rc genius so I trust that they will work! Once I get the motor and prop I can start at the fuselage..
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Old 06-15-2015, 12:52 AM
  #31  
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A little more progress.. It`s been going slow, but I`m happy with the results! I did a fir bit of sanding and filling on the main body, and have started on the cowling. The fin you see in the pictures is just a temporary piece used as a spacer for the real fin (once I get some more plywood). I decided to go with the Hellcat cockpit after all and I like the way it looks! I was hoping to have a motor and prop this time I came up to work, but there has been delays... Oh well, at least I can finish up the main body while I`m here..
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Old 06-15-2015, 06:06 AM
  #32  
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So ,Vintageshack,

Following the progress or better the evolution of the project.

I liked the cockpit
Old 07-22-2015, 07:15 AM
  #33  
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News?
Old 07-24-2015, 05:47 PM
  #34  
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Not a whole lot to report on,It has been pretty busy at work lately! I have the hull completely sealed now and I'm hoping to try painting it soon.. I am pretty limited as to what kind of paint to use up here.. I have access to epoxy propeller paint which I think will work well. It goes on pretty smooth (a little sanding will be needed for sure) and it is extremely tough. The only problem is that I am limited to either grey, black or white.
Old 08-11-2015, 11:00 AM
  #35  
rcuk john
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Originally Posted by vintageshack View Post
Any suggestions for a good motor to use with a 10 inch prop?
Late post, I know but have you seen http://www.osengines.com/motors/moto...ifications.pdf ?
OS equate their Brushless range motor to an equivalent Nitro engine.
Must admit this sounds an interesting project .........

Last edited by rcuk john; 08-11-2015 at 11:03 AM. Reason: typo
Old 08-27-2015, 08:35 PM
  #36  
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Late is better than never! That's a handy chart there. From what I've seen on that, the OMA-3810-1050 would work for me, and I could get it for 99 bucks on amazon.
Still not much progress.. I've given the hull a couple coats of paint and done some sanding and it is turning out really smooth!
More to come!
Old 08-31-2015, 05:02 AM
  #37  
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Originally Posted by vintageshack View Post
From what I've seen on that, the OMA-3810-1050 would work for me,
You maybe should see this chart which is the one I MEANT to send http://www.osengines.com/motors/moto...ane-index.html
.... and from that chart maybe see
OSMG9538 OMA-5010-810 (4-stroke .52 size),
or
OSMG9540 OMA-5020-490 (.40 Size)

Last edited by rcuk john; 08-31-2015 at 05:10 AM. Reason: typo
Old 09-01-2015, 03:08 AM
  #38  
vintageshack
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I don't know if they'll be too big? I was looking mostly at the recommended prop sizes.. the biggest prop I can have is a 10 inch one..
Finally, I have a couple more progress pics! I finished up the painting on the hull. I still have to finish the fuselage part. I painted the whole thing with the grey prop enamel, then I taped the bottom off and painted the top with white enamel. I'm definitely going to have to come up with some decals I think.

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Old 09-07-2015, 10:53 PM
  #39  
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A little more progress on the boat.. The forward lower fuselage is almost complete and the rudder is cut out..
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Old 09-12-2015, 05:17 PM
  #40  
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Detail pics of the rudder assembly.

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Old 09-30-2015, 07:47 AM
  #41  
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How critical are the angles - (4º to 5º) for depression and slew to starboard - for the engine on an airboat? I presume that these angles are to counteract lift and engine torque.

Last edited by rcuk john; 09-30-2015 at 07:53 AM.
Old 09-30-2015, 08:13 AM
  #42  
vintageshack
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I'm not exactly sure how critical it is.. The instructions call for a fair bit of accuracy, and the drawings show an exact centre of gravity. Yeah that's what the engine offset is for
Old 10-19-2015, 01:46 AM
  #43  
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The rudder servo and radio are now hooked up. You can also see the cockpit is pretty much done (except the pilot.. captian?). The radio is a FlySky GT2B and I think it'll suffice for what I'm doing. I still need to do some more sanding on the front half.


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Old 10-19-2015, 10:20 PM
  #44  
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Have you used "claw" nuts on the underside to secure the decking plate screws for the engine (ref 37 on plan) and the cockpit (no visible reference number)?
If not, did you add extra material for the screws?
Old 10-19-2015, 11:21 PM
  #45  
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I used nutplates epoxied to the underside. I ran a tap through them first because they would of ripped out of the wood the first time I screwed down the screws..
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Old 10-26-2015, 01:14 AM
  #46  
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another attempt to post – slow broadband timing out!


Another version of Cobra but this one is in PLY and not balsa (my personal choice here).
The main laterals (Ref 21) are 6mm ply, the frames are 3mm and the majority of the skin will be 1.5mm.
Some differences in construction such as making butt joints of the stringers into the nose piece (Ref 20) rebated joints for strength.
Balsa will be used for Refs 25 and 27 but the nose (Ref 20) is pine.
I prefer to use a staple gun to secure parts while the glue dries. My glue of choice is a D4 type adhesive. I don't know about the rest ofthe world but in the UK we have four grade of “waterproof” glues graded from D1 to D4. D4 is totally waterproof after drying. The most popular type of GP wood glue in the DIY stores over here is only a D3 grade.
A couple of pictures showing the joint changes and the staples included in the post …..
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Old 10-26-2015, 01:29 AM
  #47  
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Looking good! It should be plenty strong made mostly out of plywood. I used the 100% waterproof gorilla glue so I'm hoping it is true to its word!
Old 10-27-2015, 01:51 AM
  #48  
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Have you thought about a method of securing the canopy above the fuel tank/battery box compartment yet? Whatever the fuel source access will be needed.
Just started working on the "boxes" for the power source and cockpit ....... and thinking there may be a problem here.
Old 10-27-2015, 02:33 AM
  #49  
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I'm not too sure yet.. Maybe something similar to what is used to secure rc truck bodies..
Old 11-24-2015, 06:16 AM
  #50  
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As far as I have got and at a stand still now until some time next year ....
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