# Shadowcast Vented "pocket Tunnel"



## blondmonkey777 (Oct 18, 2012)

Anyone ever have any experience with venting a tunnel because I know this boat should be able to run mid 30's with a 25 hp. If you ever drive one you can feel how much suction the tunnel pulls down the back of the boat and makes it stern squat. Maybe a vent somewhere in the tunnel would help or cure the problem.


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## AfterHours2 (Aug 2, 2010)

Is this happening with a jack plate, cav plate and tabs installed? I thought performance wise, a tunnel should be atleast accompanied by a jack plate and others mentioned in order to be functional...


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## Dillusion (May 21, 2012)

A shadowcast is NOT going to run mid 30's with a 25hp, sorry dude.

Extensive testing has been done with a 25hp and the max was 32.7mph I believe, but the average mph being ~28.


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## blondmonkey777 (Oct 18, 2012)

The only reason that the boat isn't running faster is the tunnel is holding it back. The shadowcast is one of the lightest 16 ft boats around, next time you drive your boat look behind you and the water exiting from the hull the boat is not even close to riding across the top of the water. Im sure creek runner will chime in because we he was driving my boat he was saying the same thing that it almost seems that boat isnt getting on a full plane in the back because of the suction of the tunnel.


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## Brett (Jul 16, 2008)

When testing the tunnel on the Grass Slipper,
venting the tunnel increased speed by about 10%.
Venting can be accomplished by adding tubes from the top
or vent shells along the top inside edges of the tunnel.

my experience...

https://picasaweb.google.com/bdefalco/PocketTunnel


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## paint it black (Nov 3, 2007)

That's really cool, Brett! A friend of mine had a very popular skiff company vent the tunnel on his HPX T, they drilled a hole through the top of the tunnel, ran a hose up to the cockpit and put a knob so he can open and close the vent. It did absolutely nothing as far as performance, and then ended up getting a lot of water in the boat somehow. Oh yeah, they also charged him $450 to do it. lol


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## Guest (Jan 18, 2013)

> The only reason that the boat isn't running faster is the tunnel is holding it back. The shadowcast is one of the lightest 16 ft boats around, next time you drive your boat look behind you and the water exiting from the hull the boat is not even close to riding across the top of the water. Im sure creek runner will chime in because we he was driving my boat he was saying the same thing that it almost seems that boat isnt getting on a full plane in the back because of the suction of the tunnel.


Exactly why it should be offered without a tunnel. Is there anyone who has increased their performance with this small pocket tunnel because I have yet to here one. 

*Decreased running performance in both speed and shallow running

*Noticable squat while Poling

*Removing grass off their prop and lower unit as the tunnel pulls it straight to the motor like a Mini Black Hole. Wonder if the grass can be sucked against the water induction vents or running over a plastic bag not seen.

Talked with Mel a while ago pricing out the 18' Shadow Cast as I'm also starting a New Panga build. The 18' is close to a perfect Micro Skiff except 2 things. The tunnel would be filled in and the outside Gel Coat sanded off and sprayed depending on the weight savings. Momentum Boatworks did this years ago and Chittum Skiffs as well to shave off 80lbs. or so vs. Gel Coat.

IMO, No Manufacture gets them all right. Ankona hits with the SUV 17, Copperhead and Shadow Cast, but misses with the SC tunnel which decreases all around performance and misses Big Time with the Cayenne as it's too similar to the Copperhead which says 95% of customers testing both Skiffs even if it does perform great.

Out to pasture........


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## Guest (Jan 18, 2013)

> That's really cool, Brett! A friend of mine had a very popular skiff company vent the tunnel on his HPX T, they drilled a hole through the top of the tunnel, ran a hose up to the cockpit and put a knob so he can open and close the vent. It did absolutely nothing as far as performance, and then ended up getting a lot of water in the boat somehow. Oh yeah, they also charged him $450 to do it. lol


Well we a know those Maverick's Pole like Crap anyway! :


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## paint it black (Nov 3, 2007)

> > That's really cool, Brett! A friend of mine had a very popular skiff company vent the tunnel on his HPX T, they drilled a hole through the top of the tunnel, ran a hose up to the cockpit and put a knob so he can open and close the vent. It did absolutely nothing as far as performance, and then ended up getting a lot of water in the boat somehow. Oh yeah, they also charged him $450 to do it. lol
> 
> 
> Well we a know those Maverick's Pole like Crap anyway!  :



;D


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## blondmonkey777 (Oct 18, 2012)

Ya I have gone back and forth about filling it in, I know that would help out the boat a lot.


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## Dillusion (May 21, 2012)

> > That's really cool, Brett! A friend of mine had a very popular skiff company vent the tunnel on his HPX T, they drilled a hole through the top of the tunnel, ran a hose up to the cockpit and put a knob so he can open and close the vent. It did absolutely nothing as far as performance, and then ended up getting a lot of water in the boat somehow. Oh yeah, they also charged him $450 to do it. lol
> 
> 
> Well we a know those Maverick's Pole like Crap anyway!  :


They do. Smart asses. :-*


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## Creek Runner (Sep 1, 2011)

Venting the tunnel would help but minimal. But I wouldn't waste the money chasing the small increase I would fish it like it is and then upgrade into a nicer boat when the time comes.

Also you will have to run the engine lower because you will lose some of the water in the tunnel. 

Shadowcast777 just got to find some fishing holes closer to the boat ramp.


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## el9surf (Dec 23, 2008)

Of all the downfalls listed I have yet to notice any issues with mine. Maybe it's because mine has tabs and I can adjust the attitude of the bow while on plane. It floats in spit, doesn't squat, poles well and has a great ride for a small skiff. With the 25 it starts to chine walk at wot. Not sure how much faster you need to go?


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## Brett (Jul 16, 2008)

> Also you will have to run the engine lower because you will lose some of the water in the tunnel.


Gonna disagree with that comment, CR.
Pocket tunnels don't create a hump like a compression tunnel.
They act as a cookie cutter, leaving a slot of water that's basically
at the same level as the surrounding natural water level.
Running angle is the why, length of the pocket tunnel is the how.
Diagrams included in my build link provide a visual of how it functions.
Venting breaks the vacuum created by the forward motion of the hull.
Hard part to get right is the amount of vent area needed to provide
adequate air flow and the vent location to facilitate flow
and to prevent a geyser into the hull.


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## Creek Runner (Sep 1, 2011)

> > Also you will have to run the engine lower because you will lose some of the water in the tunnel.
> 
> 
> Gonna disagree with that comment, CR.
> ...


We will just agree to disagree my friend!  

We use a baffle to keep water geyser from happening


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## Megalops (Oct 23, 2011)

> Exactly why it should be offered without a tunnel. Is there anyone who has increased their performance with this small pocket tunnel because I have yet to here one.
> 
> *Decreased running performance in both speed and shallow running
> 
> ...


Do the fellas at Panga Marine know what they're getting into?  ;D


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## el9surf (Dec 23, 2008)

Just wanted to clarify that the tunnel on the sc doesn't cause a buildup of grass on the motor as suggested. I ran mine in the lagoon during the fall when there was a ton of floating grass and didn't have a single issue. All skiffs have areas where there can be improvement and the sc is no exception however the issues previously mentioned are not accurate.


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## paint it black (Nov 3, 2007)

Any skiff with sponsons attracts grass to the propeller, as does any tunnel hull. It's when you put both together that it can be unbearable (HPX Tunnel with a 70 yamaha is unbearable on those flamingo days with the floating grass).

Shadowcast doesn't have sponsons, so I assume it's not as bad as others. But to say that it doesn't attract any grass at all should not be accurate.


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## Sheremeta (Nov 29, 2010)

> Anyone ever have any experience with venting a tunnel because I know this boat should be able to run mid 30's with a 25 hp. If you ever drive one you can feel how much suction the tunnel pulls down the back of the boat and makes it stern squat. Maybe a vent somewhere in the tunnel would help or cure the problem.


The right prop makes a big difference too. I have two props that I switch back and forth. Both are similar pitch however one has much longer blades. With the longer blades I can raise my engine up much higher and increase RPMs without loosing contact with the wash from the pocket tunnel. With the shorter blade prop I cannot take full advantage of the pocket tunnel.


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## blondmonkey777 (Oct 18, 2012)

Right now I have a power tech sra 3 which is 10 inches around. It hooks pretty good which one do you have?


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## Sheremeta (Nov 29, 2010)

I'm using a 13p 8" diameter mercury vengeance with a yamaha hub and a 17p 9 inch diameter power tech prop. I know I can do better and im looking for another prop. If I can't find it I'm calling ken at prop gods.


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## Guest (Jan 21, 2013)

> Just wanted to clarify that the tunnel on the sc doesn't cause a buildup of grass on the motor as suggested. I ran mine in the lagoon during the fall when there was a ton of floating grass and didn't have a single issue. All skiffs have areas where there can be improvement and the sc is no exception however the issues previously mentioned are not accurate.


What's not accurate? All skiffs have issues with floating grass and ANY Skiff with a tunnel will make the problem worse per how a tunnel works. That being said, ShadowCast owners have mentioned the "grass issue" to me as we'll as posting this info. IMO, the ShadowCast would perform much better without a tunnel and being that I have yet to hear/read ANY advantage to the tunnel from Owners or Ankona confirms that. If the said statements are untrue I'm sure many would like to know including the OP. Why not just take the same route as other Manufactures and offer a Tuunel and Non-Tunnel version of both the 16' and 18'?


Imagine the Squat when there are actually people Poling.




















Gheenoe LT25 without tunnel and and almost identical Specs. 6 gallon fuel tank in rear as opposed to the above SC Skiffs with built-in bow aluminum tanks.


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## CurtisWright (May 9, 2012)

> Anyone ever have any experience with venting a tunnel because I know this boat should be able to run mid 30's with a 25 hp. If you ever drive one you can feel how much suction the tunnel pulls down the back of the boat and makes it stern squat. Maybe a vent somewhere in the tunnel would help or cure the problem.


Yea, It will make it as fast as a non tunnel boat, but you lose on plane draft. A jack plate is required because the faster you go the lower the water pocket drops and you have to be able to lower your motor to keep up with it.

A non tunnel never loses suction so the water column generated by the tunnel never falls. Thus no jack plate is required.


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## CurtisWright (May 9, 2012)

> What's not accurate? All skiffs have issues with floating grass and ANY Skiff with a tunnel will make the problem worse per how a tunnel works. That being said, ShadowCast owners have mentioned the "grass issue" to me as we'll as posting this info. IMO, the ShadowCast would perform much better without a tunnel and being that I have yet to hear/read ANY advantage to the tunnel from Owners or Ankona confirms that. If the said statements are untrue I'm sure many would like to know including the OP. Why not just take the same route as other Manufactures and offer a Tuunel and Non-Tunnel version of both the 16' and 18'?


Tunnel is superior on Soft Bottom. (AL, MS, LA, and Tx) I love my tunnel and will never own a boat without one. The tunnel seems to be a FL only issue.

From my calculations the SC tunnel is ~12in x 36in x 3in that is 0.75 Cubic FT. Water weighs 62.4lb /Ft^3 so you only gain about 46lb of boyancy without the tunnel. You could get youe 46Lbs back by ditching the Center Console.


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## el9surf (Dec 23, 2008)

> > Just wanted to clarify that the tunnel on the sc doesn't cause a buildup of grass on the motor as suggested. I ran mine in the lagoon during the fall when there was a ton of floating grass and didn't have a single issue. All skiffs have areas where there can be improvement and the sc is no exception however the issues previously mentioned are not accurate.
> 
> 
> What's not accurate? All skiffs have issues with floating grass and ANY Skiff with a tunnel will make the problem worse per how a tunnel works. That being said, ShadowCast owners have mentioned the "grass issue" to me as we'll as posting this info. IMO, the ShadowCast would perform much better without a tunnel and being that I have yet to hear/read ANY advantage to the tunnel from Owners or Ankona confirms that. If the said statements are untrue I'm sure many would like to know including the OP. Why not just take the same route as other Manufactures and offer a Tuunel and Non-Tunnel version of both the 16' and 18'?
> ...


The stern squat you see in the demo boat pictured is due to a lack of weight in the bow combined with a heavy 4 stroke 20 hanging off the transom. The boat pictured had a 3 gallon plastic tank under the bow which was probably half full. I have a 12 gallon aluminum tank and the boat sits dead even. I still haven't seen the grass buildup issue mentioned. Been running the lagoon a lot without any issues.


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## blondmonkey777 (Oct 18, 2012)

While poling the boat with one at the bow and one on the platform the boat is dead even. I pole over oyster mounds in jacksonville all the time and honestly have been a few inches above them and never scraped any part of the boat. But after trying to get stuck in around 3 inches of water I feel like the tunnel does help because it doesn't suction the mud like a flat bottom would.


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## copperhead (May 30, 2008)

Like to clarify some points.....

Question (or speculation) on stern squat with with 2 people poling loaded for actually fishing. It doesn't, period. I don't care what it 'looks like' floating around with nobody on it. I care what it does in the real world, with people really fishing and the SC 16 is a sub 5" draft boat.

Tunnels / Non-tunnels....

If anyone really wants a SC16 or the SC18 without a tunnel, that can be done (at a different price and not cheaper).

Most people have fallen for the premise that you can make a non-tunnel skiff and then just drop in some "magical mold insert" to make it a tunnel. If you have a skiff that runs and poles perfectly, why would anyone think you can just drop in a tunnel and it will still be perfect?? Common sense should tell you if you change one thing, something else is going to be affected. Marketing departments usually avoid this issue however.

The tunnel should be an integral part of the design process from day 1 and that's how the SC's have been done. 

Venting......

I suppose, go have some fun with it. On venting, if you get it in the right place, you won't have a geyser issue. Call me I'll fill in the how's. BUT, the design intent of the SC 16 was to run with 9.9-20 hp range. What makes it work with a 9.9 is the ultimate reason why its not going to be really fast with a 25 anyway. The 25 really overdrives the hull design. The SC 18 is for the 20-30 hp range.

We will soon have an Ankona forum to make it easier to get some of this type of information out and a place where Ankona owners can more easily exchange information.

Thanks!

M


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## paint it black (Nov 3, 2007)

Another thing, I believe there's less freeboard on the back of the Shadowcast than there is on the front. Making it appear as if it's squatting more than it really is. I have poled one of these in spit and was amazed by how easily it poled in front winds, and how shallow it got.


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## luckybone1 (Oct 22, 2012)

Amen Copperhead !!!


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## Dillusion (May 21, 2012)

I thought the shadowcast had a 8 gallon bow tank, not a 12?


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## Guest (Jan 22, 2013)

> Like to clarify some points.....
> 
> Question (or speculation) on stern squat with with 2 people poling loaded for actually fishing.   It doesn't, period.  I don't care what it 'looks like' floating around with nobody on it.  I care what it does in the real world, with people really fishing and the SC 16 is a sub 5" draft boat.
> 
> ...


Mel,

We have talked a lot over the years and you better then anyone know my Posting Style is "Outspoken", but Un-baiased based on what I hear, see and know. This is a "Disscusion Forum" where we all will agree or disagree from time to time, but no one should be "Coy" and afraid to speak their opinion. 

I will retract my statement on the ShadowCast "squat".

I never implied that your tunnel design was "just dropped in" without thought. I stated the tunnel did not work because I have yet to see a single Skiff set-up to utilize the tunnel unless clamping a 9.9 motor with stock prop does. 

* Jack Plate with or without set-back to optimize motor height 
* Cupped Prop
* Compression Plate to draw more water to the prop
* Trim Tabs

Here are some General Accepted Facts on the Pro vs. Con of a tunnel debate.

Pro: 

*Able to run very shallow when on plane
*Ability to raise the motor high
*Excellent Hole Shot in shallow water

Cons:

*Drafts up to 2" more
*20% loss in top speed
*More likely for surface weeds to foul prop/water intakes
*Loss of sharp turns with increased prop blow-out
*20% worse in chop due to lose of (surface, running pad) in order to make the tunnel


I found this information on MicroSkiff (ECC Caimen review) and ECC.


To the OP. If interested in Venting your Tunnel maybe give Kevin a call at ECC.


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## blondmonkey777 (Oct 18, 2012)

Hell I think I'm just going to take creekrunners advice and fish the hell out of it, I don't think its really going to make that much of a difference and these redfish and schooled up to nice up here in north Florida to have my boat away from me lol.


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