30 Spectre tunnel tab ????
 

Gentleman -

I just purchased a 30 Spectre with twin 300 Promax's. It comes with the factory tunnel tab.

This may sound like a stupid question, but how,when, and why do I use this? Is it dangerous if not used properly? I've done a search already but didn't really get the answers I'm looking for.

Thanks,

Mike

Re: 30 Spectre tunnel tab ????
 

Yes it is very dangerous if not used properly. IMO there is no reason to run one on a 30 w/ 300's. I would at the very least put it in the full upright position and pull the fuse if not remove it. Spend some time to learn the boat and then get someone with lots of experience to run the boat with you and show you how to use it.
I run a 30 AMT and run with several other cats (one is a 30 Spectre) and none of that group runs a tunnel tab.
PM me your number and I will be happy to talk to you about it if you wish.

Re: 30 Spectre tunnel tab ????
 

Congratulations :drink:

Not a stupid question at all.
A full tunnel design (30 Spectre) works by compressing air within the tunnel to create lift, this gives you less friction with the water, which makes you fast. The faster you go the greater compression and the more lift you will get.
The way in which your hull is compressing is that its shape bow to stern is like a big wedge. Big/tall opening in the bow, small narrow opening at the transom.
The idea of a tunnel tab is that you can change the size of the opening at the transom, thus increasing compression by lowering the tab.
There are to basic reasons you would want this control.
1) All full tunnel hulls have a certain point at which they will "lope". Loping is similar in sensation as a V bottom proposing. What is happening is that the hull is compressing air to create lift but can not support its own wait and falls back down into the water. This is completely normal for a tunnel hull and the only way to remedy it is to increase compression.
If you have a tunnel tab, you can lower it to increase compression by making the exit smaller.
2) If you are trying to squeeze every last MPH out of the boat. Youve held the throttles down for 5 miles :drink: and you cant get anymore out of her. You can drop the tab, increase compression and get the boat even higher out of the water...looser....faster..

It becomes dangerous when the tab is in the down position. If you stand at the bow of your boat while it is on the trailer and look down the tunnel w/ the tab down...what do you see? The Tab! That is the same thing a wave is going to see at 40, 60, 80 100 mph. Now the important part is AIR compresses....WATER does not.
Compress air? good, nice smooth ride, fast :drink:
Compress water? you cant do that so the boat trips which pulls the bow down. :eek: This is were it can go very wrong..fast. Stuff, hook, buck passengers out...alot of ugly stuff "could" happen. There are alot of people driving cats and never had a problem. There are also some very experienced drivers that forgot to lift their tab and had accidents which did turn out so good.

Again, I would strongly recommend running you boat for a good amount of time to get a good feel for it without the tab. Then work you way into it IF you still think its necessary.

Good luck and I hope this helps.

Re: 30 Spectre tunnel tab ????
 

Tantrum -

Thank you for your reply. That helped, ALOT! Does it help at all with getting the boat on plane? Especially with a load?

Mike

Re: 30 Spectre tunnel tab ????
 

No...if it does its by accident.
Cats are not like V bottoms in that the bow doesnt get very high. My AMT planes nearly flat, the Spectre does get slightly higher but still relatively level.

Re: 30 Spectre tunnel tab ????
 

congrats on the 30' :cool: Awesome boats and a blast to drive. I own a 98 30' with Pro Max's, in the process of selling it as we went up to a 36' earlier in the season.
Anyway we run the tab down with the motors basically trimmed neutral at porpoise speeds (60-80) if cruising in that speed range or on sticky flat water. The tunnel tab makes a massive difference in the porpoise if used correctly, and you will feel very quickly whats right or wrong. With the tab in the full up position, the boat will throttle right through the porpoise window in just a matter of seconds, take a nice set at 80-85 and its on from there, trim up the motors and off ya go :cool:
A few other 30's running around here at Lake Havasu, the consensus from those guys is about the same...to avoid the "dolphin dance" keep the motors trimmed neutral and the tab down until somewhere around 80, then up with the tab, up with the motors, forward with the sticks and bye bye to the DCB, etc next to ya :drink:

Re: 30 Spectre tunnel tab ????
 

I would leave the tab up for getting on plane, put it down when the boat starts to porpoise, on ours that is right about 4,000 RPM and 55-60 MPH.
With the tab down just after the boat rolls onto plane it feels like it wants to stuff the bow, didn't care for that feeling :eek:

Re: 30 Spectre tunnel tab ????
 

Tantrum, that is AWESOME information. Thank you.

Re: 30 Spectre tunnel tab ????
 

Tantrum you are the man. He's the guy that wanted to trade me the viper plus some cash for my boat...Mike as a rookie cat owner, put that tab ALL THE WAY UP AND PULL THE FUSE...TRUST MEi've got almost 200 hrs on mine and have NO DESIRE TO INSTALL A TAB AND IF I DID IT WOULDNT BE A FULL ONE...have seen and heard to many instances where inexperience has won...GOOD LUCK AND BE SAFE

Re: 30 Spectre tunnel tab ????
 

didn't think about a different sized tunnel tab...for reference the tab on ours is approx 10" wide and 14" long

Re: 30 Spectre tunnel tab ????
 

there are a few out there as wide as the entire tunnel...

Re: 30 Spectre tunnel tab ????
 

never seen one that big on a 30'...the tab on the 36' is HUGE

Re: 30 Spectre tunnel tab ????
 

Post some Pictures and have fun with it .I have had 4 of them you will love it.

Dave

Re: 30 Spectre tunnel tab ????
 

I disagree (sorry). I had a 30 with 300's. it would porpoise almost out of control at 75 to 90 MPH. Without a tunnel tab the boat was undrivable. An AMT is a whole different story from what I am told. I sold the boat after 3 months because of this.

Re: 30 Spectre tunnel tab ????
 

i have a 98 30 spectre with 2003 300x's on 8" jackplates, x dimension is 1 5/8's of an inch above the hull spinning 14.5 x 30's and she runs 102mph...with my 15x32's she ran 107+ and have put over 200hrs on this boat...she has a mild porpoise that comes in around 60 mph and goes away at around 80 with little trim. if you trim the motors between 60-80 it will subside by 40%...it has never been an issue with mine. i've run the boat solo, full of fuel, lite on fuel, 5 passengers makes no diff. this boat never gave me an unsettling feeling. the only time it hops is when its to calm...1ft chop or better and there is NO porpoise...perfect cruise speed for mine is 80 on the button...hull goes to work ride smoothes out and its GAME ON.

Re: 30 Spectre tunnel tab ????
 

The tab will help as Tantrum described. I would also advise pulling it up at high speed and not look for that last couple MPH with the tab. Since you boat in Minnesota on lakes I do not think you will have big wave problems to deal with like offshore. I would not even think of calling Mike a rookie cat driver. He has owned a STV and a American Offshore cat. I would say he is a very smart cat driver as he asks for advise on new subjects as I always do too.

Re: 30 Spectre tunnel tab ????
 

No pun intended...just do yourself a favor and if your going to experiment do it wisely. I agree with Brad as far as the leave her up n outta the way, have seen to many instances where ya run it level and they'll trip and hook...practice makes perfect...Mike ya got nothing but time...be safe and enjoy

Re: 30 Spectre tunnel tab ????
 

Dude that is wild. :eek: Mine isn't like that, and I don't have a tab. Something must have been wrong. :cool:

Re: 30 Spectre tunnel tab ????
 

setup hadda be way out somewhere...engine heights, toe, something

Re: 30 Spectre tunnel tab ????
 

Vegas30cat

What kind of top end numbers are you seeing? Props? I think I'm getting 14.5 X 32 Merc Cleavers.

Brad, thanks for the vote of confidence, but I have to admit, this is new territory for me. This has been a VERY helpful thread. It's great to talk with these guys.

Thanks again.

Mike

Re: 30 Spectre tunnel tab ????
 

We run a large tab in our Race AMT. It is nearly never used in race conditions and can make the boat extremely light. I would recommend using it much.

Re: 30 Spectre tunnel tab ????
 

[QUOTE=mikesufka]Vegas30cat

What kind of top end numbers are you seeing? Props? I think I'm getting 14.5 X 32 Merc Cleavers.

15" diameter might work better. Ask the guys who have Spectres.

Re: 30 Spectre tunnel tab ????
 

[QUOTE=Brad Zastrow]Ive had better (WOT) results with larger diameter wheels. I was also told by a couple of set-up guys in the application like yours (ours) to spin the diameter first then the pitch.
With that said I have a pair of 14.5x30 4 blades that work very well (go figure)

My top speed props are 15x32 3 Blades.

Re: 30 Spectre tunnel tab ????
 

I have a 2001 30 with 300x's and absoultly love the boat. I have never been in a nicer cat for this size. The boat does hop in the 50 to 75 mph range. I put my tab down in this range to minimize this. It works fine. I do not use it over 75 because there in no further need for it. One other thing the girls love it for getting in to the boat on the sand bar. Just got a pair of merc 15" x 32's l will let you know what I think.

[IMG]http://i64.photobucket.com/albums/h1...llIMG_8585.jpg[/IMG]

Re: 30 Spectre tunnel tab ????
 

Great shot!

Re: 30 Spectre tunnel tab ????
 

thats what im talkin about...Spectres baby. if they were only a lil better in the ocean i wouldnt be selling mine.

Re: 30 Spectre tunnel tab ????
 

we run 15x32 3-blade cleavers...
in Havasu heat (115 degrees) will run mid to upper 90's, best of 103 in cooler weather.

Re: 30 Spectre tunnel tab ????
 

NO TAB HERE !!