1/4 scale power.

[Trickey]

Hi guys i am fairly new to this sport and am currently building up a 1/4 scale tunnel and i have a 13cc k&b to power it,the other day at my LHS i spotted a 16cc k&b and it got me thinking!! Would the 16cc be better or mabey to much power (is that possable???) and i was woundering about the avalibalty of pipes ect for the 16cc .

thanks Trickey.

 

[MarkScott]

Trickey,

First off, welcome to this great hobby!!!! ;D ;D ;D I recently have built up two WOF Solutions. One is powered by a mod 11cc and the other 13cc.. See the Solution Pix thread in Outboards. In my searching for pipes, I've come across those for both the 11cc and 13cc, but have not seen any for the big dog - 16cc... I'd say if you really want one for the 16cc, believe there are those that can create one for you out of a straight pipe. It may cost an arm & leg to have it done.

Mark..

OB Nut Racing: Power, I can never have enough power!!!!

 

[lohring]

Jerry Dunlap ran a K&B .91 powerhead with a pipe on his 1/4 scale tunnel. It was faster than my identical boat with a piped .67. Both used custom built pipes. I have seen standard straight pipes cut and welded to fit outboards. People making carbon fiber pipes should be able to build something as well.

Lohring Miller

 

[MarkScott]

Anyone, help me out... What's a .91???? 11cc = .67, 13cc = .82 16cc = 1.0. I'm looking at the current K&B outboard page and don't see a .91 - for outboard that is.. I do see one for the inboard.

Mark..

OB Nut Racing: Wishing I was at the NATS... 8)

 

[Jerry Dunlap]

Re: K&B 91

I got this powerhead from Skip Wagner at Big Dog Motors. The 91 was originally used as a fan jet motor.

Of all the 1/4 Scale tunnels I've ever seen run, I think my Rinker was the fastest. It also cornered very well.

Here's a photo of the boat. I think the next time I might have an opportunity to race it would be at the 2004 NAMBA Nats at Legg Lake.

JD

 

[MarkScott]

JD... Thanks.. Now I see with eyes wide open ;D Who made the pipe for ya? K&B states to use a P235 for the 11cc.. What do you suggest? Off hand, don't remember what is on my at the moment..

Mark..

 

[snowdog-2112]

Mike,

Think BIG! J.D. leans towards Octura props and I have no idea what size he used on it.

I can say that without pipes, those big engines are NOT RPM monsters but my bro ran a stock 13cc (which I have in my possesion) on the old DPI 1/4 scale and it ran very well. I think he ran 7.5 props as it helped get the R's up and he had very good control over the boat.

Needless to say, The Solution is the succesor and yours should run very well. Big boat...heavy but runs nice! Especcially in rough water.

Oh I can't wait to get back to the race again!

Snowdog

 

[Trickey]

Hay guys thanks for your imput, I belive the 1/4 scale hull that I have is a copy of a DPI its new and fiberglass and not abs, so are they any good?? there is not much choice here. So what should it be?? 13cc or16cc??My other boat is a 1/8 scale not shure what brand ill try and post a picture, its running a k@b 11cc inboad this is my first boat so im still learning alot but am realy enjoying it!!

thanks again Trickey.

 

[Trickey]

sorry no pic ill try again im new to this pc thing aswell!!

Trickey.

View attachment 130

 

[Kris Flynn]

Tricky, that tunnel looks nice!...from what i can see it is not a DPI or a Dumas.

Are you able to get some more pictures of it, closer ones? also what are the dimentions of it?

So it is an inboard tunnel? does the shaft go into the 'trick' outboard so the prop is attached to the prop shaft of the outboard?

Also what outboard are you running?

Kris

 

[Jerry Dunlap]

Re: Tune pipe & prop

The tune pipe is actually a 7.5 Irwin with a metal can muffler on the end of the stinger. I don't think anyone makes a tune pipe for the 11/13/15cc K&B OBs. Hell, for that matter K&B doesn't make the motors anymore, either.

The prop is an Andy Brown reworked 1455. I've run other props on it, but that one works well.

JD

 

[Trickey]

Kris

I think its made by international hobbies?? Its 36" long with a beam of 11"The k@b 11cc is mounted inboard using a Octura strut and rudder assembly and ox455/3 prop seems to work best so far. Sorry I dont have any better pics and dont have a dijital camera(yet) so I can take some better pics but it will take some time!

Trikey.

 

[Finne]

I've seen some tunnels with straight pipes pointing backwards.

wouldn't something like that work?

could proly use an inboard pipe in that case?

 

[MarkScott]

I picked up a so called 11cc J-pipe (Irwin) off E-bay. Since it came with no header, I went searching. Joe Monahan with 707 http://home.earthlink.net/~namba707spec/ sold me one, very nice I might add. With conversations with Joe, he might be able to find a pipe or two for the 11cc / 13cc, but they are hard to come by. The pipe I have matches perfectly with the header from 707..

Tim at PBR might be able to help out also.. At least from a header standpoint.. www.precisionboatsracing.com

I'll have to wait till I get home, but I thought Garcia made OB pipes for the larger motors also.. Trying to find them will be like waiting for hell to freeze over.. And I don't mean Hell, Michigan either!!!

Mark.. err Mike... o what the heck..

OB Nut Racing

 

[[email protected]]

I bought the DPI 1/4 scale tunnel and the K&B 1.0 engine. I used the 13cc pipe and the boat ran very well but always blew over. The other problem w/the DPI is the rear transom MUST, MUST be reinforced or it will break off. The other problem w/such a large O/B is the vibration wore out the bushings in the prop shaft assembly almost immedialtely. I'm glad I sold it. Well mostly because it's so long.

 

[MarkScott]

I've seen some tunnels with straight pipes pointing backwards.

wouldn't something like that work?

could proly use an inboard pipe in that case?

Finne, I'm no expert on this, but I would have to say by using a straight pipe there are two issues to deal with..

1: Pipe will move CG backwards, possibly making one to add weight to the front.

2: Pipe needs to be held upward. As to keep from getting wet and cooling off..

I've run the Black Magic pipes on 3.5's... They do work, but I'd rather use a good J-pipe anyday.

Mark...

OB Nut Racing..

 

[Jerry Dunlap]

If the boat is running an inboard, then I wouldn't call it an Outboard Tunnel. It's an inboard catamaran with a outboard cowling for appearance. The set up would be for an inboard cat, not an outboard tunnel.

Just my opinion, but there's a difference between outboard and inboard powered tunnel hulls.

Jerry D.

 

[Mike Hughes]

If you are going to run the motor stock, I would suggest the smaller of the two. The lower unit is the same as the .67. They have problems breathing. You might even want to cut out between the exhaust holes to open it up.When Jerry came up with this idea 10 or so years ago, the class was stock. No mods. No pipes. We ran the class like that for two years or so. They where not that fast. Most of the time you would see them blow over with a little gust of wind. Everyone had them trapping a lot of air to make some speed. They where only running as fast as a .21 stock tunnel. I use to call it the kite class. Lets go fly a kite. Soon after, they did away with the stock motor because the class was dying. Best thing for the class. The motors where making power. You could pin the hull down and keep the speed up. They were actually fun to watch now. By this time the class was dead. You did not see any 1/4 scale tunnels unless you went over to Uncle Jerry's shop. I can't say I shed a tear that day.

Mike

 

[Jerry Dunlap]

Re: shedding of tears

Mike,

Jeez, you really know how to hurt an old guy.

JD

 

[Trickey]

WEll guys thanks for all your ideas, i think I will stick with the 13cc outboard that I alraedy have for the 1/4 scale and the money I would have spent buying the 16 can go towards a pipe and other go fast bits! But i have alot of work to do first strengthing the hull ect before I get to carried away.Should I fill the sponsons with something ?

I didnt call my other boat a tunnel (but I would have) so from now on I will call it a cat or mabey a cat/tunnel hibrid ;D

Anyway I can see I will be learning alot from this Forum so I hope you guys dont mind to many dumb questions.

Trickey