Jump to content
Sign in to follow this  
Techno

Setback

Setback  

7 members have voted

  1. 1. Setback

    • Euro zero
      2
    • Euro 5"
      7
    • Euro 10"
      3
    • Euro 18"
      0
    • ProComp zero
      7
    • ProComp 5"
      5
    • ProComp 10"
      1
    • ProComp 18"
      0


Recommended Posts

I remember from the readers rides the fairly extreme setbacks some were using.

Have you run without this setback?  How does the boat perform in the 70-90 area, does it do anything to the porposing?

Is this something the euro gets a bigger advantage from than the ProComp? I realize you need to subract a little to place them even but even with that there is a still a large setback

Consider the poll just between Euro and non-Euro

Share this post


Link to post
Share on other sites

TECH,

I use 5.5" of SB on my PCS. Mostly cause it is a full interior and floor boat, and I do have it loaded up with the full family at times.

The SB helps to lever the bow a little more to get over the hump!

Also, the jack allows me to dial in engine ht. too

Share this post


Link to post
Share on other sites

Ok and here is my view. I disagree with Anthony ( I think this is the only thing that we don't see eye to eye on).

I see only two advantages to the jackplate, 1- it alllows the motor to be trimed higher with out hitting the race cowl, and 2- Like Anthony said it is easier to adjust.

Now my points.

The Pro Comp was designed when a 240hp 2.4 was the power of choice (the river rocket had some aerodynamic changes to compensate for the 260+hp engines of it's day)Roark built that boat to run with NO setback. It is my favorite of all the STV's to drive. Speed of 110mph are easy to obtain, and the correct set up is also easy, Roark drilled the holes in the transom 2 3/8 inches down so that with the motor mounted in the center hole with a CLE the motor height was perfect. Add a 14.5X 28-32 cleaver and you are set. (some like the 15" props too) If you run the Pro Comp in this configuration it will be over 5mph faster (in 2.5 configuration a little less with a 2.4), will not have the "mid range hop", and will carry weight better.

The STV is not an air packing hull like a Mirage, it operates a lot like an airplane wing, if you run the angle of attack to high it stalls or creates drag, but flat it has a lot of lift and little drag. The setback off sets the balance, and will not allow the boat to fatten out as it is designed. If you can watch old Mod-vp tapes (Rusty Campbell, and Ted Greguc) they are always out front, and they run very flat, another person to look at is David Carver in the ODBA, watch him run he never runs the boat bow high, yes I realize he has a lot more power, but what we do happens a little slower, but in the same steps.

Now another point I feel I need to make is that, you need to keep in mind that setback is supposed to help you with bowlift, but this is a boat that doesn't like it, and the fact that you make matters worse by adding a setback, what you have done now is add bowlift that the boat doesn't want, and moves 370lbs 5 inches behind the boat compounding the problem. The STV requires neutral lift.

To add credential to what I have said, the River Rocket also runns best with no setback, but like I noted above it had the 2.5 in mind when it was built. As with the motor on the transom it too had to much lift, as such you will find the driver 12" ahead, this is because with the added power to keep the boat in balance at speed less lift is required.

Now I have/get many e-mails asking for set up opinion, and those that have followed my advise have written back pleasant suprises.

I hope that helps.

RT

Oh I might add, that the boat will go faster with some weight in the front (right up at the bow)------I gotta keep these #### secrets quiet....the boys are gonna kill me.

Share this post


Link to post
Share on other sites

GREAT Post ROB,

YES I ceratinly forgot the point about the tilting and the rear cowl. That is one I just take for granted.

Someday when I have more resources I will certainly try removing the setback. It's just too hard to justify as I have no complaints with the ride...and you know me...100mph is fast enuff!

I don't disaggree with you on this...cause I know you have experience with both setups. Me...I only know it with setback!

Actually when I was putting the rig together, Roark advised that it would make the boat slower and Thought it would be OK when I only had 150 hp on the back!

Share this post


Link to post
Share on other sites

Rob;  I have a manual jackplate with 4" of set back and a drag SS with an additional 2" built in.....for a total of 6" on my River Rocket center steer.  I run 3/4 to 7/8" above the pad and never had to trim the motor beyond the point where it is exactly parallel to the boat bottom.  As a matter of fact, I find that when launching, the boat does not have to be trimed in at all.  It launches best when the prop shaft is parallel to the bottom.  I hear about so many STV owners complaining about the midrange porposing.  I have never experienced this problem with my setup.   Driver weight probably has more to do with setup problems than anything else. I weigh 165 lbs.

Share this post


Link to post
Share on other sites

WAY2,

You 2 make some valid points. I would agree that with your weight and the power that you have from drag motor, you would blow rite thru the porpoise zone.

Even with my little 240 hp, with incresesd seat time, point her into the wind and I can blow rite thru the bounce!

Add some passengers, then the bounce is harder to coax outta'er without adding some additional trim.

Yes I too Generally come out of the hole neutral or even slightly positive, for best results. Remember getting that surface prop close to the air gets her wound up and running faster!

What Prop do you use??

Share this post


Link to post
Share on other sites

Ok...I don't own an STV..... but it's not out of desire. I have a 18' eagle warrior (Seebold) with a 2.4 EFI Mod-VP. I'm not getting the top end I should. One change I made after putting it up for the winter was to go from 5" to 8" of set back. The seebolds said to use 4" but it doesn't seem to work. The tunnels are very deep, seating is quite a bit forward, and I'm no lightweight. In the pictures of STV's I've seen, there seems to be a lot of built in setback with transom notches and molded in set back. What is the "real / effective" setback on the pro-comp and Euro? Say, from front of lower unit to the pad running surface at the notch.

Thanks

Share this post


Link to post
Share on other sites

Anthony SS

    I have a bunch of different props. Depending on conditions and what I'm after, my favorite is a 22 ET.   For a day of cruising I use a 28 ET.   My Yamaha drag props 22 and 24, don't seem as efficient as the ET's.   I have a 14.5 32 Lab Cleaver that is a good prop if you want to take the chance of killing yourself going for the really high numbers.  The 28 lab cleaver is also a decent all around prop.   My fingers are getting numb typing this....its 59 degrees in my house and  I REFUSE to put on the heat because after all, this is FLORIDA !!!

            Richard

Share this post


Link to post
Share on other sites

Dave R;   The measurement you ask for would be impossible to give because it would depend on what trim position the motor is in.  It would cause the front of the lower unit to be at different distances from the rear of the pad.  My River Rocket has a built in setback of 12 inches, from edge of inset pad bottom to rear of setback.  Richard

Share this post


Link to post
Share on other sites

On my 98 Euro with 99-280 the first summer I went without setback and didn't like how the boat handled. And it didn't help being the first year owning a STV and a hiperformance boat(period)! Second season the CMC 5.5 was added and solved most of the porpoise in mid range(70-80) with the Merc ET28. Merc lab cleaver has none! Weight has an enormous effect on the way the STV handles. I weight 240, hopfully less this  summer, but I did find out when using a cleaver the boat airs out very easily with almost no porpoise. My guess is the cleaver lifting the rear helps keep the attack angle better and permits the hull to lift equally front and rear. I think maybe adding 2 more inches would help but I don't want the engine sticking back anymore, and if I want to go fast I do it alone-safety tip!

Share this post


Link to post
Share on other sites

The board is cookin' now. Great posts. BTW Euroski, what pitch cleaver are you running? Last time out I ran a 29 pitch RE-3 Mazco with 5.0 inch manual L&S plate with prop shaft at 1/2" above pad. With Balzy weighing around 175? and me about 90 lbs more, and 3/4 tank of fuel, we ran 102 GPS. I have the ski bottom and the boat is not a light lay-up version. I think there was more to go but if Way2 thinks its cold typing at 59 degrees, try flying down a river at 100+ in the low 40's! :0 We decided to do our tweaking on a bar stool.

Share this post


Link to post
Share on other sites

Way2fast - thanks for the reply. I was assuming prop shaft parallel to boat bottom, but you are right...the measurement from transom notch to transom engine mount is better. No wonder so many STV owners run "no set-back". A built in 12" is quite a set-back already. I might have to be prepared to go more than my 8". I have a long wait to see if the added 3" has any effect. And of course I'm doing other things at the same time so I may never know how the added set-back helped.

Thanks again.

Share this post


Link to post
Share on other sites

YES we is COOKIN!,,

THANKS for the Responces WAY2 and all. As usuual a great variety of setups and preferences and in the nd the sum is usually a fast boat.

HEY DAVE R....even tho you don't got NOSTV...You are always welcome here! Let us know how we can help you out!

Share this post


Link to post
Share on other sites

Now I may stick'in my noze up in wher I ain't poze ta be, I no ya'll jus left out tha LTV by accident, right!!! I mean hey, LTV wuz yher first, and they are still a few that haven't fliped and tore up!!! I had a lenghty conversation wit Mr Summerford when building my LTV(which I have passed on to Raptor)...He recomended no more than 6" setback(the LTV haz 8" built in to hull)...I also dun sum pad mods that he recomended...I did a lot of testing with the boat(with small HP, 2.0)...The boat worked it's best with 3" setback...It left harder and didn't feel flighty over 90, az it did with 6" setback....till I got the LTV, I thought the more setback the better, cuz I run 20" on my Laser 380 Vee bottom...I think on the Tunnells(On which I'm no expert,an don't claim to be) the setback iz determined souly by the weight and air packing capabilities at the speed U plan on running....jus my opinion, REX ;)

Share this post


Link to post
Share on other sites

Techno - thanks. It seems all the STV's have much more set-back than I currently have ( and more than Seebold recommended for my boat). All tunnel boats are different of course, but it gives me something to think about.

Dave

Share this post


Link to post
Share on other sites

:D I maybe buying a Euro Ski. How much set back would be needed with a 200 merc? This will be the first boat I owned  with a name other than Hydrostream.

Mike

Share this post


Link to post
Share on other sites

HEY HYDRO,

Thanks for supporting our brd. I hope the aquistion of the EURO pans out for you. Streams are GREAT Boats...but the Euro will reinvent Performance boating for you.

Generally 5-6" is the rule of thumb for Euros. You can't go wrong with that amout. Some may consider more, depending on your indiviudaul wt..

Your 200 would be a great start on the Euro. If it is a stocker speeds could be right in the 90 mph mark! To do that you'll have to swing a 30" wheel at about 6400. So hopefully you have a 200 that makes decent power to 6400 RPM. It may need some mild intake and exhaust work to get there!

Hope this helps some. Let us know if we can help you find that Euro

Share this post


Link to post
Share on other sites

Ok, to answer some questions in the above posts. First all STV's have the same setback, Pro Comp (SKI), Rocket, and Euro.

Way 2, They River rocket needs the setback for slower speeds due to the driver being so far forward, but the boat would be faster on the transom. (not that you need to go faster).

Euro Ski (administrator), you notice how with the cleaver you said that their is no porpose------VICTORY, you have got it right. I have stated before, that a properly set up STV does not have this porpose that a lot talk about. I have also stated that the setup window is small, but it is easy if you follow what the boat is telling you.

Now I also remember having the bounce, and it sucked. #### when I first got my first STV I could not get it over 92mph, then it would blowout. circa 1990.

Rex, has it Listen to Roark, he knows.

RT

Share this post


Link to post
Share on other sites

I forgot to mention that, this past summer I had a 1996 Euro (the very last Roark built ) with a 2.4 200 Carb, that motor was a bucket of bolts with drilled exhaust and a land and sea nose cone. It had 5" of set back, ran a 14 X 30 stock merc chopper ( we tried everthing on it and that was best )(also commonly refured to as the small balde chopper ) and it this boat would run 88 on GPS at 6600 rpm.  I had a Euro before that that I sold and the new owner put a 1995 2.5 XRi 200 with a land and sea cone (I would use a bobs) and it ran 92 on GPS with a large blade 30 chopper on the 6700 rpm limiter and this motor was 100% stock.

I hope that helps

RT

Share this post


Link to post
Share on other sites

I would like to show you all two pictures on how a great running STV shold look.

http://www.hydrostream.org/Racing/RacingPage.htm

At the top and bottom right their is a picture of Mad Max and David Bush. These are perfect attitudes.

Also remember that these are in the quarter mile and the bow will come down even more with greater speed.

I have thought that the andle of attack causes the bounce. Think of it this way, Like I mentioned the boat operates like a wing, if you get it to high it stalls, combine this with excessive gearcase drag and you have bounce. Now if you add set back you can force the hull to pack air. Like forcing a sqare peg into a round hole, with force it will work, but it is a patch, as opposed to looking for the round peg and doing it the right way.

Thoughs on this.

RT

Share this post


Link to post
Share on other sites

HUM..ROB,

THAT STV looks like it lost the outer sponsons and is about to BLO-Over....

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×