Flat Bottom twin rigger setup

Any one out there know what the setup for the flat bottom rigger is ?? Have always had boats with kick up in the tub.

Boats like Crapshooter ECT. Any input would be helpful.

Ok what particular brand of twin is in question ?? Every boat is different also what power 67,80,90,101rs ? Lenth and Width ?

Tom,

Find the tub height at start of the flat section and set the transom at the same height?

thomaselkins said:

Any one out there know what the setup for the flat bottom rigger is ?? Have always had boats with kick up in the tub.

Boats like Crapshooter ECT. Any input would be helpful.

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Maybe the builder can give you all the infomation that you need.....

Contact to Brett E and Albert A at Florida They will help you set up for Twin rigger Good Luck!

ALLAN YUEN said:

Contact to Brett E and Albert A at Florida They will help you set up for Twin rigger Good Luck!

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Allan he does not have a crapshooter Twin just so you know

There have been several Flat bottom Hydros Crapshooter, Eagle, Roadrunner, UFO,Bullard, However it does take a different set up to properly place the sponsons on the boat.The Boat Tub should be level on most when all of the sponsons are installed at known working angles & all sponsons heels touching the table. Crapshooter runs some of there boats with the transom elevated at the transon 1.5mm from the belly clearence number. I normally flat edge the bottom rear half of all rigger tubs to make sure they are 100% flat. Many of the flat bottom boats you can run the rear of the boat tight but you will have to remain loose on the front end... Or if you run the fronts tight on angle you will have to loosen the rear of the boat up. You will not run both ends of the boat tight. They will just burn up engines with load. This is best explained by telling you that a Flat bottom boat with all 4 sponsons on table at the same time while the tub is level.... DOES NOT Pivot as much front to rear as a Boat with a curve bottom. This is because the curve bottom set up the rears are install 1/8 up on the side of the boat & it can drop the back end in the corners and change the attack angles on the front sponsons and turn fin. Flat bottom boat can & do wet the front sponsons up quicker on Prop lift. I have ran many different types-brands of riggers. These are my observations on setting these boats up. If you have a name brand boat the Boat mfger can best inst you on how to set there boats up... If you are scratch building? what I have told you will help get the boat up and running well. Your known sponson angles do not change because of the tub type changes. But installing the rear sponsons in the proper position is most Critical because it relates to where you will have & will be running the struts in dept.

Mongoose Twins and Original Eagle Twins had flat bottoms. We ran the Transom about 1/16" high as Joe described. The Mongoose ran the rears on the surface. The Eagle ran the rears at the top of the prop hub. Both boats won many major races.

As Joe said. When the boat is set up correctly it will be locked into one attitude. It won't rock up and float the front sponsons like a "Rocker" bottom boat will.

Andy Brown said:

Mongoose Twins and Original Eagle Twins had flat bottoms. We ran the Transom about 1/16" high as Joe described. The Mongoose ran the rears on the surface. The Eagle ran the rears at the top of the prop hub. Both boats won many major races.

As Joe said. When the boat is set up correctly it will be locked into one attitude. It won't rock up and float the front sponsons like a "Rocker" bottom boat will.

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That takes all of the "YEEE HAAA" out of it !!

Thanks guys, very good input. Will for sure get it on the water and work from there

one thing to add although my opinon means little.

Over the yrs i have taken on the idea on boats i build to have the front of the boat NOSE UP .032 - .062 ( 1/32 - 1/16 ) i do that for 2 reasons.

1. if you set you boat up flat or parallel as joe and andy talked about. if you need to tighten the boat up with front sponsons angle. or drop the strut depth. that also changes the TUB HEIGHT. making the front now LEVEL OR DOWN HILL. if you build the boat level to start with and then need additional downforce, now your tub will be down hill after sponsons changes or strut depth.

2. i like to run looser boats. with the tub uphill it tends to loosen the boat up. also makes the boat slightly easier to get up on plane as it don't plow as much.

one thing i will add to these guys statements and all very very knowledgeable and well respected people. TUB HEIGHT in my opinion is the 2nd most important thing to the way a properly tuned boat runs. only thing more important i feel is props.

take that for what you like, just my opinon

hope i helped

chris

Chris,

I run large gas riggers right now and find that I usually have to run a down hill attitude to keep them on the water. They are running 80 mph in heat racing trim and the water gets pretty rough with the larger boats.

I have gone to higher tub heights with good results. What is your opinion on tub height?

John

Hi john

I totally understand the down hill effects.. my THEORY lol if you will is i am trying ( weather or not it works lol ) downforce on the sponsons.. not the tub. again i can't say for sure if that is working or not.. boats don't blow off to speak of so something must be working lol.

as for height.. i am a believer taller the better. again this is just me..

i found taller boats seam to be able to pack more air under the boat. i am guess at best that helps keep the boats on the water. but it also makes them easier to launch. and FREES the boat up so to speak. NOW i will say i did a sport 20 boat a few yrs ago i changed the tub height.. it was a ROCKET. but after 1/2 a tank emptyed it took off like a 747. I think that boat has SO MUCH AREA that it acts like a huge WING. i never got back to messing with it much.

again i don't claim to know much.. i just know what i have mess with myself.. you are much smarter than i

chris

Chris,

I understand. I think we are all experimenting with different things and some of the end results are the same even with different setups. There are so many variables. I think 5/8th of an inch is too low for any boat with one inch about standard and 1.5 to 2 inches works on some of the boats. My view, which may also be wrong, is that the closer to the water the more air pressure is packed under the boat. As we raise the tub air is able to pass more easily. Of course how wide the tub is, afterplane, scale boat or rigger, etc all makes for different variables too.

Hi john

i agree. i had a 20 boat one time that was about 5/8 off the water.. it was like a snow plow. my current boat is 7/8 and have wondered if i could go more. What i don't know is how far is to far. does the size of the boat matter? meaning 21 45 80 ect.

I know from past when i ran eagles.. now take in mind this was ALONG time ago. they were real close to the water. we always had issues with the boat. we had to loosen them up. they they got so loose we couldn't keep them on the water. it was a balance act we always had issue's with. i have no idea what the current boats are like vs the old ones. my guess is the tub height is different maybe andy could chime in?

Do you think the closer to the water the more air pressure. or the taller off the water the faster the air is able to escape from underneath? i could see it being closer the more controlled the air is. which might explain why the closer to the water the TIGHTER the boat is. compressing air but not allowing it to escape fast enough? This is a good topic. i wish i was smarter and new more about dynamics and what not.. i am just a schmuck trying the hard way lol

i would love to be able to build a cheap wind tunnel with some sort of smoke to see the effects of some of the things we talk about.

not to get to out of sorts. What are your thoughts on the down force effects of the OUTSIDES OF THE SPONSONS?? everyone talks about tops and bottoms but i think there is ALOT of effects being good or bad on the outside we are missing.

chris

John Finch said:

Chris,

I run large gas riggers right now and find that I usually have to run a down hill attitude to keep them on the water. They are running 80 mph in heat racing trim and the water gets pretty rough with the larger boats.

I have gone to higher tub heights with good results. What is your opinion on tub height?

John

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The Higher the Better.... But adding tub height while maintaining the sponson angles get to be a challenge then there is engine angle changes for the deeper strut dept. p.s. Some Rigger mfgers have you maintain a added height at the rear of the boat (transom) to allow for a added Air vent. Raising the rear of the tub Does change the angle of the nose of the boat & the bottom of the boat. But at that point in the set up procedure the sponsons have not been put on. So you are positioning the tub for sponsons to be installed.

Joe. I agree. That is how I set up my riggers. First set the angle of the tub, then add sponsons at desired AOA. If I raise the tub I use the Speedmaster Cat strut and cut off the skeg because it will extend deeper and is a bit thicker.

John

John about the only thing you are limited to for Added ride height is Strut dept and keeping the engines & stuffing box tubes somewhat aligned to the struts. Then you need to consider running dept changes of the turn fin and rudder blade. many are making small changes at a time to find the limit of More Performance from the boat itself.

joe

i think when you talk about limiting to strut depth.. i think this is where the WIRE DRIVE is going to come into play. i think there is more options with the set up IF it will hold up to the big motors.

don't know anyone using them on big stuff yet