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Old Jan 31, 2011, 10:04 PM
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1/4 scale Cobra

I'm attemping to post pictures
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Old Feb 01, 2011, 07:18 PM
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1/4 scale Cobra

Hopefully here are pictures. All hardware is scratch made. Air scoops and bow light were from solid pieces of brass cut out and hand filed,shaped polished and chrome plated. Steering wheel turned on lathe from a 4" bar stock aluminum, polished and painted. Chris Craft logo cut out on scroll saw from brass sheet then chrome plated. Turtle deck was formed with styrofoam
then covered with three layers of epoxy reson and 4 oz. cloth. Wind shield was formed from plastic storm door material heated to 200 degrees for 5 minutes and placed in male /female wood form. Door edge guard was used for frame. Boat is 54" long and
expected to weigh 27 to 30 lbs.
Gauges are currently resized Dumas decal. Would like to get pictures of the real ones so I can make them look better. Also
need idea on size and profile of gauge trim rings. The last thing is to get pictures of Crusader Marine logo to go on dummy
engine valve covers. I hope you guys like what Iv'e done so far . Thank you ,Gary
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Old Feb 01, 2011, 07:29 PM
Veni, Vidi, Feci
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Perfect! Thanks for posting... it will be great to see more pics, of her maiden voyage.
Can you tell us about all the metal work? It looks great.
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Old Feb 01, 2011, 08:01 PM
Grumpa Tom
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Wow! That's fantastic work you have done!
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Old Feb 01, 2011, 08:03 PM
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1/4 scale Cobra

Her are pic of progression of air scoops and step pads.
Step pads : Trim cut out of brass sheet
I made mold and cast silicon rubber pads
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Old Feb 01, 2011, 08:13 PM
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1/4 scale Cobra

I still have a little tweeking to do on the hatch cover and seats.I also have some one working on the flag for the front flag staff. When I get it , I have an idea how to make the miniature grommets for the flag from 3/32 brass tubing. I will post it when I find out how it works out. See you later , Gary
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Old Feb 01, 2011, 08:22 PM
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Sharp boat!, I bet that thing will make some serious waves at the local pond
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Old Feb 02, 2011, 01:25 AM
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Nice metal work.
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Old Feb 02, 2011, 09:14 AM
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Beautiful work Gary. You did a fine job on the model and the finish. I like the scoops that you made and the steering wheel is super. Hope you'll take some video when you get her in the water and post it here. Pete
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Old Feb 02, 2011, 02:39 PM
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Very impressive, very impressive indeed! Thanks for sharing as there are a lot of great features on your model and ideas.
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Old Feb 02, 2011, 08:50 PM
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Great model and fine metal work. I do have a question about the exhaust for the gas version. Does it run to the transome?
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Old Feb 02, 2011, 09:49 PM
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This thread added to WOODIES: Wooden Pleasure Craft Build Logs listing.

Path: RCGroups -> Boats -> Scale Boats ->"WOODIES..."

Looking real sweet...
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Old Feb 03, 2011, 04:03 PM
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Reply for cuzzo20, Since I am so ignorant about how the forum works I was unable to send picture through the private message system, so I will do it this way. It may not be of use to you but it is the only reference I have. Than you,
Gary
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Old Feb 03, 2011, 04:14 PM
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1/4 Scale Cobra

Grayman, The gas engine has a tuned quiet pipe which extends all the way to the transom where it exits through the exhaust port. I will also need to do the plumbing for the water pump for cooling. I made the rudder shaft from tubing
for the pickup. The motor has an electric starter and clutch so will draw water when idling. Thank you, Gary
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Old Feb 09, 2011, 02:56 AM
Spreckels Lake, GGP, SF, CA
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New thread started over here ?????
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Old Feb 09, 2011, 05:50 PM
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Nice boat... I can see you have put alot of work into it... Now where do the animals sleep?.....
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Old Feb 28, 2011, 05:46 PM
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Question

Does anyone have any information about boat trailers used for the Chrsi Craft Cobra? I would to build one for my boat but need pictures or drawings to do so.
Thank you , Gary
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Old Feb 28, 2011, 06:32 PM
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Was there any such thing as a Chris Craft trailer? I've seen old pix, CC's on the back of trucks, in simple cradles, etc... but no modern trailers like we use today.

Unless there was such a thing, you won't go wrong just building a trailer along the lines of any modern unit. And in 1/4 scale, you could probably use real mini-trailer tires, or wheels from a lawn-garden cart!
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Old Mar 01, 2011, 11:11 PM
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Chris craft Trailers

Patmat. I have a 1953 Ad for Chris Craft trailers. It shows four models. The
largest one had a capacity for 2300#. It has a rectangeler frame with 6 cross
bars and tandom wheels. It is hard to determine the size of the trailer and if
it was used for the Cobra, the end of it would have to be short of the transom
to clear the prop shaft. It also does not show any rollers or pads for the boat
to rest on. They may have been options based on the hull being used.
It also says that the trailers were blue and had yellow fenders Trailers also had shocks. Since this ad is from 1953, it may not show the one for the Cobra.
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Old Mar 01, 2011, 11:36 PM
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Chri Craft Trailer

Picture of Ad.
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Old Mar 01, 2011, 11:43 PM
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http://www.chris-craft.org/discussio...pic.php?t=3226

Scroll down.
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Old Mar 02, 2011, 12:18 AM
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Milford Mi.
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Chris Craft trailer

Millertime. Thanks for the reply. It appears that the boats were hauled in
their cradles on the trailers. I think I can bulid a mockup of one first before
making the real one. The suspension was unique for the time. Independent
and with shocks. It looks like they may have been swing arms with coil springs and shocks. it looks like it will be an interesting project. Thank you. Gary
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Old Mar 02, 2011, 06:31 AM
Veni, Vidi, Feci
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Hey, here's a picture that looks just like yours-- only upside down!

That's some neat history. CC also offered small boat kits, and some of those trailers look like they would have supported that market.
So when did the modern boat trailer become the norm?
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Old Mar 02, 2011, 10:49 AM
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Beautiful boat and excellent metal work.

Ed
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Old Mar 02, 2011, 12:33 PM
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1/4 Cobra

I,m currently having the seats redone. I had to make some changes to the seat back so the old one didn't fit right. While I was at the upholerers a customer came and mentioned that I might consider them to make a cover for the boat. I
decided to do that as well. It will be a week or so before I 'll pick it up. Will post more when ready. Thank you, Gary
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Old Mar 03, 2011, 12:42 AM
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Here is a trailer that I made for a 29" boat.
No, I do not sale trailers.
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Old Mar 24, 2011, 11:55 PM
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Chris Craft Trailer

This is what I have so far.
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Old Mar 25, 2011, 12:22 AM
Taking care of the pond.
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Looks nice.
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Old Mar 25, 2011, 05:23 PM
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1/4 scale Cobra Trailer

Millertime, I used the Ad that you sent me to build it. I know I don't have the right suspension system but hope to change it later.
It appears tht some of the early trailers used a cradle on the bigger boats.
I'm trying to find a good picture of the fender so I can see what the logo is. I can tell that the large letters are Chris Craft but can't tell what the small ones are. By looking at the rest of the ad, it could be Chris-Craft Corporation, Algonac. Mich. or Chris-Craft Trailer Division. I don't know for sure. I will try to go to the Chris- Craft Club sight to find out. I'll post when I find out Thank you , Gary
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Old Mar 26, 2011, 02:35 AM
Taking care of the pond.
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Your Welcome Gary, I will have to see if I have some pictures of my 1960
Chris-Craft trailer. I think that it was a original trailer.

Don
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Old Apr 04, 2011, 01:43 PM
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Toledo Expo

Sorry guys, I had thought about having my Chris-Craft Cobra at the Toledo Expo but, the two parts that I outsorced did not get done.
I had been working on the trailer while the boat was at the upholstery
shop. Two days before the show they had not started on my job. Since I didn't
give a hard deadline , I guess it was my error also. I also am having someone working on the burgee which as well isn't done. I guess I will have to wait til next year for Toledo.
Currently I am not informed of any other shows within reansonable driving distance for this year. I'll keep you posted. Thank you ,Gary
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Old Apr 05, 2011, 08:55 AM
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When do we get to see this monster in the water and running? She sure is beautiful. Pete
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Old Apr 05, 2011, 01:36 PM
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Cobra

Norgale, The ice is almost gone around here. I hope to launch when I get it from the upholstery shop. I have a few minor things to fix before its ready.
I'll keep you posted. Thank you , Gary
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Old Apr 06, 2011, 08:58 AM
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Lookin' forward to that. I forgot about the ice situation so it's understandable why the boat isn't in the water yet. Pete
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Old Apr 08, 2011, 09:59 PM
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Cobra Burgee

Hi guys , I would like to thank Frank G from MACK Products. He gave me
a web address for ModelFlags.com from the UK.
They had Cris Craft flags and burgees for my Cobra. They come in several
sizes so I ordered a 125 MM and a 150 MM. approx. (5'' and 6'' )in length. HopefullyIi will have them in a couple of weeks. Thank you Gary
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Old Apr 08, 2011, 10:44 PM
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Power sorce for 1/4 scale Cobra

Hi guys, While attending the Toledo Expo I was able to talk to a couple. of fellow boaters. I was showing them pictures of my Cobra discussed what power I had planned to use. Currently I have a 700 HO motor with a Traxxis esc. on two 7.4 v. 5000 mah nimh batteries. I was told that this system will not be large enough to power my Cobra. The boat will weigh about 28 to 30 lbs. running. I might burn out the esc. or motor under such load. I would like to get as much information as I can before making a change. The system I have may be better suited to convert my 40" Dumas hull to electric. Any feedback will be appreciated.
Thank you ,Gary
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Old Apr 09, 2011, 07:19 AM
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From what I can see with my HO trains these motors turn too slow for a boat.
I thought the electric motor in the Cobra was just for emergencies. Go back to MACK to get the right sized motor for this boat but tell them the motor is just for emergency retrieval and not for full performance.. Pete
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Old Apr 22, 2011, 09:57 PM
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1/4 scale Cobra

Here are pics. of the new seats. I still haven't got the boat home yet
because they are still working on a form fitted cover. Thank you , Gary
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Old Apr 23, 2011, 12:40 AM
Taking care of the pond.
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Nice...
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Old May 01, 2011, 09:37 PM
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Cover for Cobra

Here are some pictures of the Cobra cover. I finally got it back, so now need to do some miner fixes and adjustments. Hope to hit the water this next week end.
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Old May 01, 2011, 09:47 PM
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glgirvin, that is one awesome looking boat... It will look so good in the water, thanks for sharing
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Old May 02, 2011, 01:21 AM
Taking care of the pond.
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Very nice...
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Old May 02, 2011, 09:50 AM
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Bring it to the pool in West Bloomfield, May 14, two weekends from now:
http://www.rcgroups.com/forums/showt...0#post17999121
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Old May 03, 2011, 01:47 AM
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pool run

Patmat, I won't be able to make it on May 14. I only get one weekend per month
off. It happens to be this week in which Sunday happens to be my mothers
95th birthday, her 72nd anniversery and Mother's day. So I think this takes priority. Thank you, Gary
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Old May 09, 2011, 07:56 PM
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Cobra got wet

Hi guys, I was able to launch the Cobra, but had less than steller performance.
The boat made one circle and stopped. When I got to it smoke was coming out of area where the motor is . I assume the motor burned out. I didn't get more than 30 seconds of run time. The rudder was still working so I believe the esc
is all right. The batteries, ecs and motor did not feel hot. I tried to get motor to
turn with wires connected directly to the battery but nothing happened.so I believe the motor is the problem. I didn't have my spare motor with me ,so could
not make the switch.
All I was able to accomlish was some still pictures. Thank you, Gary
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Old May 10, 2011, 12:05 AM
Taking care of the pond.
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She looks beautiful on the water.
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Old May 10, 2011, 05:33 AM
NeverAgainVolunteerYourse lf
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Did you use the motor in your picture titled electric option, wow, thats way too small. did you put on the same prop as the gas option.

Are you hoping interghange between style's of power ?

Cheers
Nick
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Old May 10, 2011, 11:20 AM
GILL
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Absolutely beautiful, fantastic job. This size boat needs some horse power. I would use 2 speed 900's geared together, running on 12 volts, direct drive. That would give you almost 1/4 hp at 13,000 rpm.
In the picture the 900s are the power ones 3,000 rpm@ 12 volts they are pushing 55mm 5 blade 1 inch pitch props.
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Old May 10, 2011, 11:39 PM
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1/4 scale Cobra power

Hi guys, The power I have is a 700HO motor , a t-max esc and two 7 cell nimh
batteries running on 16.8 volts. The prop is a 6717/ 3 . It is the size that I run
on my gas race boats.
I put spare motor in and everything checks out ok. Maybe I at least should go
to smaller prop. I have also been advised to go to 900 size motor.
The final running weight is 33 lbs. Since electric power is new to me , I appreciate any imput. Thank you, Gary
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Old May 11, 2011, 11:03 AM
GILL
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Her's a picture of the 900 motor with the 750 (800), 550, and 540 size.
987 motor:
7 pole
6mm (1/4 in) shaft.
51.9mm dia.
69mm length

the 700 is about 1/2 the horse power of the 900.
at 35 lb you need more horse power.
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Old May 11, 2011, 01:52 PM
1/2 a bubble off
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Where would I go to buy one of those 900 motors?
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Old May 11, 2011, 11:51 PM
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Power for Cobra

FrankG from MACK mentioned the use of a 900 motor but, I don't see it on his web sight unless one of his motors listed as another number. He said I should use a 900 motor 780 kv to spin the prop I had about 9000 rpms to get approx. scale speed.What I don't know is will I have to use a totally different complete
system, ( batteries,esc etc.) I will try to call him to find out. Thank you, Gary
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Old May 12, 2011, 01:17 AM
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M.A.C.K. Products Marine Motor Model #7720, is a 920 size case motor.

http://www.mackproductsrc.com/mack_power.htm
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Old May 12, 2011, 03:44 AM
NeverAgainVolunteerYourse lf
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The electric will only be for pottering around if you use the can motors, and the prop is way too big unless you either gear down or find a low rpm motor.

The gas motor is equivelant to about 4HP, 250 watts is around 1/3 of a HP.

Getting this to move on electric is going to be expensive.

Nick
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Old May 12, 2011, 10:12 AM
GILL
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Polks Hobby has them for$ 35.00 ea.
www.polkshobby.com
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Old May 22, 2011, 10:09 PM
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1/4 scale Cobra

Nick 75AU, I built the boat intending to power it with a gas engine. After
talking to a friend, he mentioned using an electric motor because it would be cleaner, quieter, no gas odors and I could have a reverse. So that is why I put an electric motor in it.
I also didn't fuse the system so the motor bacame the fuse. I have changed a few things and am waiting for the next run Thank you ,Gary
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Old May 24, 2011, 05:29 PM
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Hi,

Gary, fantastic looking boat you have made!
Well, like Nick mentioned, you would need quite a different set-up to get it truly
moving. To get it planing properly, I guess you would need at least 2,5-3KW
power for it minimum. I played with quite similar sized project myself some years back, 67" length Riva. I used 2 pces 10-pole watercooled outrunner Flyware T-REX 700kv motors, 2 x 10series LiPo batteries 6000mAh.
Each was end of the day pushed 100amps at apprx 34 volts, 3.4KW,(total apprx 6.8KW/9,3hp) water rpm apprx 16.700rpm with 55mm prop. Ok, for scale like moving that was
a bit overkill, but anyway gives an idea where the window is moving.

Best regards,
Hannu
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Old Jul 22, 2011, 08:09 PM
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1/4 scale Cobra

Hi guys, I finally got my boat back in the water but was not very impressed. I tried by using a 900 motor and x455/3 prop. I did not burn out anything but it went about as fast as a rubber duck in a wind storm.
I will just have to try plan A whitch is the Zenoah. I have been working on it to get the electric starter to work properly. I built a test stand to try it out. At first it seemed to work great but the gear flywheel spun off stripping the threads on the hub. After fixing with parts from the other unit.
I tried to start engine again and the motor did not have enough power to turn engine over. I put second assembly on and it worked ok until after about 5 minutes running the engine, I shut it down to restart. The whole end cap of the electric motor had come off. After putting it back on, this motor didn't have the power to turn over engine.I tried about 4 times for 3 to 4 seconds to start engine and the wires to the electric motor came off by melting the solder. Also the oneway bearing failed. The new version of E starter does not use the the oneway bearing and has a bigger motor ( 580). I put it on the engine and when I
tried to start it , the adaptor broke. I emailed manufacturer and reply was that a billot adaptor is available that would correct that problem. I am waiting for parts
before I can resume testing. I'll let you know what happens. Gary
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Old Aug 11, 2011, 01:46 PM
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1/4 scale Cobra photos

Here are some of the pictures. I hope to get action shots when the gas engine is installed. Thank you ,Gary
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Old Aug 11, 2011, 01:54 PM
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Great pictures, although, Barbie should have ponied up for two extra pilings on her dock.
She does add a nice scale to the pictures, even if she is a bit small for scale.

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Old Aug 11, 2011, 04:00 PM
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That looks so good that I think you should now make a real one full size. Pete
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Old Aug 12, 2011, 02:17 AM
Taking care of the pond.
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I like it.
I can't find the like button.
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Old Nov 28, 2011, 10:59 PM
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Cobra in water

I tried running the Cobra last week. Not ideal conditions . 40 degrees and 6"
waves . Still not very fast. Used twin 900 motors and 58 MM 4 bladed prop.
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Old Dec 01, 2011, 04:38 PM
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Milford Mi.
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1/4 scale Cobra

Hi guys, I would like to show you what I am working on. A 1/4 scale 1955 Chevy to pull the the Cobra. I traded a boat for a 1/4 scale Nascar chassis and have
obtained a 1/4 1955 Chevy fiberglass body. I bought a set of wheels and
tires and put whitewalls on them. I'm still setting up the body mounts in order to attach it to the chassis. I obtained a razer scooter that I think I can use the motor and battery pack for power. what do you think ? Thank you ,Gary
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Old Dec 01, 2011, 05:57 PM
Veni, Vidi, Feci
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I think you're having too much fun!
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Old Dec 02, 2011, 01:18 AM
Taking care of the pond.
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Joined Apr 2004
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Nice car.
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Old Dec 02, 2011, 01:28 AM
Grumpa Tom
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Wow!
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Old Dec 02, 2011, 02:44 AM
WooHoo!
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Kewl!
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Old Dec 23, 2011, 11:45 AM
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Milford Mi.
Joined Jan 2011
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ESC for 24 v motot

Hi guys, I posted this question on th car forum, haven't got answer yet. Band1 replied about the chassis, but not the esc. I am
looking for an ESC that will work with the 24 v. motor I am putting in my 1/4
55 Chevy. Most of the ones I have found that they are either too low voltage or the high voltage ones are for brushless motors. The only place that looks promasing is a company that supplies components for robots. Any assitence would be appreciated. Thank you, Gary
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Old Dec 23, 2011, 03:07 PM
Veni, Vidi, Feci
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The robot boys do a lot of higher voltage stuff, may have something.

Did you try it on 12v? Maybe that's enough!
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Old Dec 23, 2011, 03:32 PM
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United States, PA, Slatington
Joined Feb 2007
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I second. Look at the robot market. I have ordered from the Robot Market place and would recommend them. I currently run a robot ESC in my tug and will be purchasing from them again.

http://www.robotmarketplace.com/prod...lers_main.html
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Old Dec 23, 2011, 09:17 PM
NeverAgainVolunteerYourse lf
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I also have used Robot Market place, Ive got the IFI Speed controllers at 120 amp. They can drive 4 700 motors in parallel. You could get away with a much smaller 60 amp 883 unit from them. You do need the PWM cable, and don't run more than 6 volts, 4.8 ideal into the receiver (the PWM cable will fail at anything over)

Nick
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Old Dec 24, 2011, 12:08 PM
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Milford Mi.
Joined Jan 2011
186 Posts
esc for 55 Chevy

patmat I was able to get the motor to work using a traxxas EVX 2 esc and 16.8 v nimh batteries but, I was told it could harm the motor running on low voltage. The motor and battery pack came from a Razor scooter. The speed control for it was broken at the handle. I noticed that two wires coming out of the speed control. One went ot the handle control and the other goes to the brake lever. My guess is that the wire going to the brake lever is simply an on /off switch
so you can't have power to the motor when the brake is on. I am assuming that if I jumper that wire, I may be able to hook up the other one with an esc.
In the pictures these wires plug into the white recepticles. Since the wires are small, I think the current to handle control is reduced and may allow me to use a lesser voltage esc. I appreciate any help any one give . Thank you ,Gary
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Old Dec 24, 2011, 12:17 PM
Veni, Vidi, Feci
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No worry, you won't hurt the motor...that was told to you by someone who doesn't understand dc motors.
Only if you have a situation which forces a given load , and near the motor's limit, will reducing volts (and increasing current) cause harm.
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Old Dec 24, 2011, 02:02 PM
WooHoo!
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Did you look into



Vantec RDFR Series Controllers - An Overview
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Old Dec 24, 2011, 03:14 PM
NeverAgainVolunteerYourse lf
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Australia, QLD, Regents Park
Joined Mar 2007
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Trash all of that original control, it has no speed regulation at all.
As patmat wrote low voltage wont harm the motor, it just runs slower, if you halve the voltage you only get 1/4 the power, as you probably wont go racing with the trailer on the back the motor will most likely have enough grunt to power the car. My only concern with the the traxxas ESC is that they are not designed for a large multi pole motor like the scooter motor.

Cheers
Nick
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Old Dec 25, 2011, 07:19 PM
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Australia, QLD, Ashgrove
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nice looking boat did you make it

alex
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Old Dec 26, 2011, 10:17 AM
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Milford Mi.
Joined Jan 2011
186 Posts
1/4 scale Cobra

Hi Alex111. The Cobra is entirely scratch built. Look at the previous pages of this thread to see other pictures. Thank you, Gary
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Old Dec 28, 2011, 08:21 PM
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hey its ok gary nice job on it
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Old Jan 01, 2012, 12:41 PM
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Milford Mi.
Joined Jan 2011
186 Posts
ESC for 24 v. motor

Nick AU75, Thanks for the advice. I finally was able to contact Dan from Robot Marketplace. He siad the Victor 883 ESC should work with my setup along with a driver cord from the receiver to the esc. I ordered it and am waiting for it to get here. Will let you know how it works out. Thank you, Gary
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Old Apr 05, 2012, 04:27 PM
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Hardware

Quote:
Originally Posted by glgirvin View Post
Her are pic of progression of air scoops and step pads.
Step pads : Trim cut out of brass sheet
I made mold and cast silicon rubber pads
Hi I am building a Century Sea Maid 54" 1/4 scale I see you made all your hardware would you be interested in making somemore or do you know where I can buy some? I got ahold of Dumas but they said the didnt have any for a 1/4 scale, thanks Chuck
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Old Apr 05, 2012, 04:53 PM
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Wet Goose http://www.wetgoose.com/index.html
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Old Apr 05, 2012, 10:46 PM
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Quote:
Originally Posted by glgirvin View Post
Nick AU75, Thanks for the advice. I finally was able to contact Dan from Robot Marketplace. He siad the Victor 883 ESC should work with my setup along with a driver cord from the receiver to the esc. I ordered it and am waiting for it to get here. Will let you know how it works out. Thank you, Gary
Hi Gary, i wasen't sure what to tell you about the esc but
let us know if it did work out .
I built a tractor for truck pulling and i will contact the company to see
what they think if it doesn't work out for you. I need a 12v motor and esc too.
Great job on the boat ! Paul.
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Old Apr 06, 2012, 09:35 AM
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Quote:
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Thanks gravman! much appreciated
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Old Jun 16, 2012, 09:13 PM
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Milford Mi.
Joined Jan 2011
186 Posts
Question. Swordfisk ESC.

Hi Guys, I tried the Cobra on a new setup. Its a Castle 2028 motor and a
Swordfish 240 Amp ESC and 8s lipo batteries. When I tried it, it would run about 3 seconds and shut down . I pulled the throttle to 0 and it would go again for about the same time and shut down again. It did it everytime I tried regardless of throttle of setting. There was no heating of wires , control or motor. Does anyone have any experience with this ESC? Thanks, Gary
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Old Jun 16, 2012, 09:30 PM
NeverAgainVolunteerYourse lf
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Australia, QLD, Regents Park
Joined Mar 2007
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I think the ESC is shutting down on high current, my honest opinion is you are running the motor on too many cells.

The motor is 780 Kv (correct me if I'm wrong) 8 cell is 30 volt nominal so the motor is trying to spin the prop at 23 500 RPM, this is much higher than even gas boats with surface drive props and a sub surface prop puts a higher load on the system

I can't recall if you mentioned the prop size, but guessing a 70 mm prop, for sub surface less than 10 000 rpm is going to be much closer to the mark.

I tried my Riva Corsero on 6 cell 500 Kv motor with a 48mm prop and it was way overpowered to the point I could not get it over 1/2 throttle.

Cheers
Nick
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Old Jun 16, 2012, 10:00 PM
Veni, Vidi, Feci
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G- you were also shutting down on part throttle... Did you see my note about the possible radio problem?
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Old Jun 16, 2012, 11:17 PM
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Milford Mi.
Joined Jan 2011
186 Posts
Swordfish ESC

Nick 75 AU The prop is a 955/3 . the motor did the same thing on the stand
with no load. I was told from Castle when I bought the motor that if I tried to run it on low voltage that it would pull high amps. I originally was going to run it on 4s
batteries. I think I think the problem has to do with the programing of the ESC. The only things I changed was the cutoff point from 12 to 24 v. and the type of start from standard to soft start.Everything else is at default settings, So I don't
know what to do until I can talk to someone who uses them or knows more about it. Thany you, Gary
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Old Jun 16, 2012, 11:30 PM
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Milford Mi.
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Swordfish ESC

PatMat, I just read your Email about the auto shut off .I'll try other radio before changing the ESC. Thank you Gary
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Old Jun 17, 2012, 12:16 AM
NeverAgainVolunteerYourse lf
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Australia, QLD, Regents Park
Joined Mar 2007
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55 mm prop,

Power(watts) = Voltage X Amps

The amount of amps a motor will draw depends on the load, running a motor on lower voltage lowers the RPM and with the same load will reduce amps.

If you want to extract the same power out of a motor at lower voltage the amps have to increase to give an equivalent power and this is where Castle are coming from. In this case you would then have to fit a larger prop to increase the load.

I am 100 % positive the load, RPM is too high and the motor will pull silly amps and the boat will be too fast with the current 8 cell set-up.

Obviously its hard from the other-side of the world to diagnose a set-up problem with a radio or ESC, one issue could be the timing set into the ESC, the only advice I have is to set it to Castles specs for the motor.

Cheers
Nick
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Old Jun 17, 2012, 08:22 AM
Veni, Vidi, Feci
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I mentioned to Gary that it might be something with the radio. From a Swordfish description:

"Auto shut down when signal is lost or radio interference becomes severe for more than 3 seconds .After radio connection has been reestablished, moving the throttle to the lowest position can restart the motor."

This is exactly the behavior we saw yesterday.

Gary- Could also be something glitchy in the ESC's opinion of signal quality. The ESC knows nothing about the radio, it just looks to see if it's getting a believable PWM command stream from the Rx (which should be a non-stop string of pulses, one pulse every 20 ms, each pulse between about 1 and 2 ms long).
Another way to test would be with a simple "servo tester":
http://www3.towerhobbies.com/cgi-bin...ster&search=Go

...which merely puts out a user-adjustable PWM stream.

Also make sure the lead from Rx to ESC isn't running next to any "noisy" wires.

The pic below shows the Cobra getting up on plane for about 1 second, before the shutoff!
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Old Aug 23, 2012, 10:07 PM
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Milford Mi.
Joined Jan 2011
186 Posts
Cobra launch

Hi guys. I haven't kept up with what I am doing with the Cobra. I now have my fourth attemp twith the drive train. I now have a 2028 Castle motor with a 240 amp
Swordfish ESC. and two 4s lipo batteries. My first attempt was at Heritage Park,
Canton ,Mi. The boat would start and stop about every 3 seconds. It would start after returning to off and up again.
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Old Aug 23, 2012, 10:26 PM
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Milford Mi.
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Cobra launch

Hi guys. I haven't kept up with what I am doing with the Cobra. I now have my fourth attempt with the drive train. I now have a 2028 Castle motor with a 240 amp Swordfish ESC. and two 4s lipo batteries with a 955/ 3 prop. My first attempt was at Heritage Park,Canton ,Mi. The boat would start and stop about every 3 seconds. It would start after returning to off and up again.
Patmat sent me info on the ESC. If it does not get a good signal, it will shut down and can be restarted in 3 seconds. I rerouted the wire fron the ESC away from the battery cables and everything seem to be allright.
I tried again at Heritage Park,Taylor,Mi. and things worked OK until the drive
shaft broke. It was a 1/4 " cable like I use for my gas race boats. It twisted off about 2" inside the stuffing tube.
You can see and hear what happened on youtube by going to "MSMBC Running at Heritage Park, Taylor Mi." Everything happens in the first minute
or so on the video. The main focus was not on my boat , but you can see it in the background and hear it on the second pass in the top of the screen.
I 'm not sure of the condition of the cable because it may have used in my race boat prior and may have been weakened. I will try again with the new cable.
I also was having handling problems at top speed and wonder if it the same as what the real Cobra had.I think I was going faster than scale speed. I let you know how things work on next run. Thank you, Gary
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Last edited by glgirvin; Aug 23, 2012 at 10:29 PM. Reason: spelling
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Old Aug 23, 2012, 10:37 PM
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Milford Mi.
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New setup for Cobra

Hi guys , I forgot to post pictures. Gary
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Old Aug 24, 2012, 12:16 AM
oldtribefan
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United States, GA, Kennesaw
Joined May 2007
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Your Cobra looks great on the water! Good luck getting her all sorted out.
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Old Oct 19, 2012, 09:36 PM
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Milford Mi.
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1/4 scale Cobra running

Hi guys, I am trying to post video of my Cobra running. I seem to be having trouble doing so. Let me know if it comes through. It may have come through in the video gallery area. Thank you, Gary
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Old Oct 19, 2012, 10:25 PM
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Milford Mi.
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1/4 scale Cobra

Hi guys, I am not able to get my video into this forum. I don't know the procedure. It went to the video gallery. Any help would be appreciated. Thank yoy, Gary
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Old Oct 19, 2012, 10:30 PM
NeverAgainVolunteerYourse lf
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Australia, QLD, Regents Park
Joined Mar 2007
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Try this

http://www.rcgroups.com/forums/showthread.php?t=1755077

1/4 scale Cobra
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Old Oct 19, 2012, 10:35 PM
NeverAgainVolunteerYourse lf
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That is running really well, congratulations , bit of porpoising but I think the hull form has something to do with that.



Cheers
Nick
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Old Oct 19, 2012, 10:58 PM
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Milford Mi.
Joined Jan 2011
186 Posts
To Nick 75AU. Thanks for reply. At least I know its on the forum, just not where I thought it would be. It doesn't look too bad for a 33 lb. boat Thank you, Gary
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