Cobra 2 build & setup tips!!!

[Hayden Bright]

Anyone running the cobra 2 hull, I will be running stock OS xm so any setup info, please share.....Thanks in advance

Hayden

 

[Kevin Krogness]

Talk to Dan Hutchinson.

 

[Hayden Bright]

Yeah have talked with dan, wanted to here from everyone else who runs this hull with OS engine.

 

[Kevin Krogness]

Ahh I see!!

 

[Hayden Bright]

Was hoping for some positive feedback from this hull.

Was just trying to start a place to talk cobra 2 really & get some ideas from the guys who have run these hulls, what worked - what didn't work & so on. B)

 

[Tim_Duggan]

Mine is still in the cupboard waiting to be built - too many other things on the go.

 

[DeanJohnson]

Hayden,

Not that many running the new gen 2 hull quiet yet. They're out there, but not as many as the gen 1. I've got a gen 1 that runs pretty well; if you're interested in what my current set up is to use as a starting point, let me know.

Dean

 

[Hayden Bright]

Dean,

That would be great when you get a chance, post it up thats why I started the thread.....Need input johnny five need input.

 

[DeanJohnson]

Alright Johnny Five, here's my set up:

Cobra Gen 1

Motor - OS (head shim removed)

Weight - 4lb 10oz

CG - 8 3/4" from the rear sponsons

Engine Angle - 0 deg

Engine Height - Since I don't have a set up board, I measure from the sponson bottoms to the bottom of the cavitation plate, and mine measures 1 1/2"

Prop - 40x53 that's been worked by Mark Sholund

Bottom of the hull has been blue printed and skuffed with 800 grit sand paper. The skeg has been sharpened. Weight distribution and how you set your CG seems to be important for cornering. I added a very small amount of lead to the nose, but mostly added weight throughout the mid section, mainly under the front half of the radio box. This helped me be able to run full out into a modest wind without jeopardizing straight line speed, but also sit nicely entering the corner.

I'm sure others will have different set ups, but this one suits my driving style nicely. Now, go burn some nitro!

Dean

 

[Robert Elder]

Thanks for posting your setup details. I have a gen 1 Cobra with an Irwin piped K&B that flies on the straight aways but won't turn unless I really slow down and, even then, has a tendency to hook. My CG was around 8" but now I have added some weight just in front of the radio box to bring it to 8 3/4". I am anxious to try this out and see if the turning is improved and what effect it has on the straight line speed.

 

[DeanJohnson]

Hi Robert,

I would reconsider adding weight in front of the radio box. Try adding it under the radio box about an inch behind the front of the box. Cut your weight to the width of the recessed area and the radio box will sit nicely on top of the weight. Also, if your hooking or spinning out in the turns, check your prop height. It it's too high, this could be a possilbe culprit.

Dean

 

[Robert Elder]

I built the boat using a pull/pull cable setup like the VS1 so I needed to mount the radio box securely to the hull. I tried the elastic band thing but the radio box still moved too much. As a result, I can't easily place weight under the radio box.

I have some fishing weights in a balloon secured in front of the radio box now. The plan is to test that and adjust the weight/CG to get the handling where I want it and then maybe I will use stick on lead on the top of the radio box or split the weight requirement between just in front of/ just behind the radio box.

Thanks for the suggestions. I will also see about the prop height. At the moment I am 0 degrees and the bottom of the bullet is about 3/16" above the setup board.

Oh ya, the motor is mounted on a HiJack so it is a bit farther back from the transom than an OS or most other setups.

 

[DeanJohnson]

Definitely don't put weight on top of the radio box. You want the weight as low as possible; if you add weight to the top of the radio box, you're making the boat top heavy and that would be counterproductive to your goal in the turns.

Dean

 

[Hayden Bright]

So getting this bad boy to turn without hooking seems to be the tricky part in setting up the cobra.

The cobra does seem to ride very light on it's heals , so adding weight in the right place to help it bite enough to turn and then dial out steering until it won't hook.

Sure it won't be that easy :blink:

Should keep me interested for awhile then, if it worked perfect the first time out i'd get bored of it very quick :lol:

Thanks for the input so far guys, keep any developments you have posted to share.

 

[Robert Elder]

HyperHydro, I ran today and the boat handles better with the CG forward without loosing any speed. The hull was porposing a bit so I brought the prop down a little bit at a time and it started porposing more. In fact, on the last run it bounced so bad it blew over at full speed and ended up separating part of the hull along a seam. I thought porposing meant the prop was too high. Did I get that wrong?

I think I am getting close now. I have repaired the hull and will remove the ballon with lead (maybe it was bouncing?) and install some stick on lead as low as I can and rebalance the hull to get the 8 3/4" CG. The prop is now set 1/16" above the setup board.

Anything else to change?

 

[Hayden Bright]

Well I hope to have mine on the water in a few weeks, so i'll get some video of my maiden voyage to post up.....Fingers crossed all goes well

 

[DeanJohnson]

Hayden,

Do you run with the CR boys by chance?

Dean

 

[moparbarn]

robert, sometimes porposing can be caused by too much weight too far foward. the prop/engine tries to lift it, but can't hold it up. more weight farther back......hope to test my cobra 2 this sunday. so far, it seems to want to balance farther back than most, likes the engine kinda high, & MUCH less prop than i'm used to. larger props seems to want to roll the hull. i'm running a k&b with an old 707 mount, not a lot of setback. seems better than with the hijacker, so far.

 

[Hayden Bright]

Hayden,

Do you run with the CR boys by chance?

Dean

Dean

I'm in australia my friend

Moparbarn

Thanks for your input and good luck with your sunday test session Keep us posted on how it goes.

Small prop as in like 38mm?

 

[Hayden Bright]

Well had the maiden voyage today & all went well with the boat, my set up was way off though with the os really struggling to make any rpm at all.

I had the os cav plate about 1 1/2 above setup board, but the prop was just way to high and pulling the hull down so bad it was making a wake and the os couldn't turn up at all....

She turns nice though & i'm looking forward to the next testing session, i'll post some video up next week hopefully.