48" DPI Tunnel

[Foolwitools]

Hi Guys!

I know, I know........... set it up on the shelf and just look at it!!

I just got the boat and don't have any info on balance, ect.

I know the basic 33% balance point and like that......... I'm looking for info from anyone who has been able to make one run .

11cc or 13cc?

Turn fin?

Prop?

Anything will be helpful.

Bob the Fool :blink:

 

[Jerry Dunlap]

Well, since I suggested to DPI that they build a 1/4 Scale Tunnel I suppose I should offer some suggestions:

1. Definitely balance it at 33% - or maybe even 40%. The boat traps a huge amount of air.

2. Power wise, anything from a 7.5cc to a 13cc will move it forward.

3. For an 11/13cc engine, props like the Octura X455, 1455 will work.

4. I suggest running the prop level with the bottom of the sponsons.

I must admit, this wasn't one of my better ideas when it comes to tunnel boats : . I've since done a better job of designing 1/4 scale tunnels, but this is a case where "You dance with the one you brought to the dance." Anyone who can figure out that last statement is welcome to reply.

JD

 

[Foolwitools]

Thanks a bunch Jerry!!!

Bob the Fool :blink:

 

[Jerry Wyss]

Hi Bob, I went through 3 of 'em. The last one I modified the Hull,,I put some

Rocker in the sponsons ,,was kinda fun to do. Also built "anti-dive pads" or

"stumbling blocks", (everybody calls them something different) to "kill" some

of the tunnel,,too much air goes under them boats.

I bought some of the same sheet plastic that they make the boat out of when

I bought the last one. When you have some "rocker" the boat will corner, and they

don't corner worth a dam the way you get 'em,,,they accually corner like the full

size boat the way they come , but we don't race they'er kind of course.

The "pads" kill some of the air under the boat an also help it corner, as well as

putting on some extra speed. But, the faster you go the more your gonna "blow"

the boat off,,,And the faster the landing and they Break some where almost every time. I used a heavily mod 11cc K&B , the extra power of the 13cc was'nt

needed , as the boat is the lightest for its size I've ever ran.

Anything else, Just ask

Jerry

 

[snowdog-2112]

Hey Bob, all,

My brother had one of those some time ago and he had a sweet setup on it. I don't know the details but he was running a stock 13cc with a 7.5 prop, a 447/3 I believe and the engine not only wound up but he was able to turn the boat on dime. Of course, he set the sponsons before entering the turn and never had any trouble. After JD reviewed the videotape I showed him of the boat running, he commented that the performance was the best he'd ever seen of that hull.

Just my $.02

Snowdog

JD, no clue! :blink:

 

[Foolwitools]

I modified the Hull,,I put some

Rocker in the sponsons ]

Jerry..... thanks for your responce!

Not hip to the lingo........." Rocker " in the sponsons.

wat dat meeen? ( Yes, I'm a hull tech dummy.....)

Bob the Fool

 

[Jerry Wyss]

BOB, "Rocker" is a term to describe the running serface of the sponsons,,"Hook"

would be the opposite,,alot of catermarans have hook to keep the bow down in

Big water. Rocker; could be explained or demonstrated by taking your hull and

setting it on a large flat serface and push down on the transom and look from the

side,,you'll see that more than half of the REAR bottom sponson Edge is contacting

the flat table. The boat will look From The SIDE to be Level or slightly NOSE down.

This has to be changed,,cause tunnels don't run this way and get anywhere Fast.

This is why "snowdog 2112" said "boat was able to turn on a dime". Your boat

the way it is will run down the straight with the nose up alright,,but when you go

to turn,, all that sponson will fall down on the water and make you turn Too Much

or Hook in the turn. I went to the rear corners of the sponsons, just below center

of the vertical corner and measured a 1/4in space to start my cuts (mine ended

up being 3/8 in) From the center of that space level across the back of the sponson

to the boat outside edge , marked a line. Same from the inside of the sponson,

from the center of the 1/4 in space, and marked a line toward the front about

18in. . Then from the top and bottom of that 1/4 in space mark to the end points

of the two center lines you just marked. So you end up with two "V" shaped

areas to be cut out. When thats cut out you can push to close the gap and you

now have "Rocker". You have to have some White ABS sheet material to solvent

weld it back together. I used Acetone in a syringe and Watch It any "puddles" inside the sponsons will Soften the plastic, it doesn't take much to weld it back

together. Whew,,that was hard to explain.

 

[Foolwitools]

Thanks Jerry!!

so....the bottom line of the sponson inner rail has a gentle arc..... like the bottom of a rocking chair.

I imagine this lets the sponsons granually settle into the turn instead of digging in all at once.

or am I totally lost?

Bob the Fool :blink:

 

[Foolwitools]

"You dance with the one you brought to the dance." Anyone who can figure out that last statement is welcome to reply.

JD

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in Drag Racing it's " Run what you brung"

Bob the Fool :blink:

 

[Jerry Wyss]

Thanks Jerry!!
so....the bottom line of the sponson inner rail has a gentle arc..... like the bottom of a rocking chair.

I imagine this lets the sponsons granually settle into the turn instead of digging in all at once.

or am I totally lost?

Bob the Fool :blink:

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Thats the general idea Bob. And with some of the sheet ABS you can lay down

a whole new running serface if you melt the old running too much. I did a pretty

good job on the "Welding" and didn't have to lay a new runner,,,Hey, I'm a

Plumber. The "Transom" where the center section meets the the sponson "Booms"

is on it cracks, so laminate some pieces on the transom,(they'll be narrow) but they will help. Also up front and under the "cockpit" looking at the bottom, I cut

a 1inch wide slot from sponson to sponson inside edge and siliconed a hard wood

"beam" across to tie the sponsons, sponson booms and center section together.

And pushed the beam forward so I could clean up the silicone around the slot

and patch the slot.(has to be a good, strong patch). Then built up the anti- dive

pads, and made them quite wide to cut most of the air going under there. Good Luck