Cobra Tunnel build

[normlee]

Hi,

This is my first post , thanks for all the info here this forum is great!

Just received a cobra tunnel hull from Dan, this is my first tunnel build and will be fitting a k&b 3.5 ss.

Can anyone give me some tips on mounting the engine please? I am not sure if I need to drill and tap or through bolt the prather mount. Any info will be much appreciated, I am guessing that getting this right is very important for setup.

Thank you,

Norm,

Brisbane Australia

 

[Dan Hutchinson]

There is a 1/8 aluminum plate in the transom and will require drilling and taping

 

[Dan Hutchinson]

If you need anything else Please feel free to contact me via here

 

[normlee]

Awesome, thanks Dan

 

[Tim leyde]

Dan is a great guy with plenty of knowledge. Enjoyed my Cobra!

 

[normlee]

Yep, Dan is good to deal with, that's for sure.

What engine height should I bolt the engine on please? I read somewhere to set the shaft inline with the lowest point of the hulls with 40% travel down and 60% up. Is this what you fellow Cobra Tunnel owners think?

Regards, Norm

 

[Dan Hutchinson]

Norm. Put the center of the prop shaft even with the bottom of the sponsors. are you using a motor mount ? You will need one! Prather makes one fully adjustable. And one other thing it needs to be balanced at 7 1/2 to 7 3/4 from the back

 

[normlee]

Hi,

Can anyone please post a pic of their steering linkage setup please for a Cobra tunnel, much appreciated.

Cheers, Norm

 

[Dan Pralle]

 

[chuck st romain]

It's a vision but they are all similar. I put a 1/2 inch "z bend" to clear the tanks

 

[chuck st romain]

 

[James montgomery]

enjoy your cobra, dan is a good guy ....heres a few pics of mine too.

 

[normlee]

Thanks guys, much appreciated. Just about finished the new build now, looking forward to see what this hull will do. Any suggestions for a prop and speed with a k&b 3.5 SS? Also should I set up the CG of the boat with or without a full tank of fuel?

Thanks, Norm

 

[moparbarn]

Set the cg rtr, minus fuel. I run a lynx cut x440/2 on mine with a k&b. Mark Sholund/Props4u knows what to do on the prop (-; Speed? Fast enough to be impba d-12 2014 champion in both b sport & mod, 7th (I think) overall & top finishing k&b at the Herb Stewart race in fla. last fall. Speed is nice, but finishing all your heats is better!!

 

[chuck st romain]

Mark sholund is the go to man for props.

 

[normlee]

Thanks guys, how do I get in contact with Mark Sholund?

 

[moparbarn]

Mark goes by shoboat here on iw.

 

[normlee]

So I finally have the Cobra together, with no fuel in it, everything on board including a 1600mah life receiver pack in the nose it balanced out just under 8" from the end of the sponson. Do you think I should add weight aft or run it as is?

Cheers, Norm

 

[moparbarn]

Move the RX to the front of the radio box & the battery back as far towards the servo tray as you can, that's the way mine balanced out. Battery all the way up front was too nose heavy, boat would hook in the turns.

 

[normlee]

Ran my new Cobra today, awesome fun, never run tunnel boat before, only mono and hydroplanes. There is nothing like fine tuning the perfect trim angle and engine height to get them riding on air!

Thanks Dan, looking forward to dialling in this hull, already thinking I need a more powerful mill to take advantage of it