garrett ,
. jerome here .. i have an old AC magnum 67 mono .. this model is used with a .67 nitro engine but i run it with a zenopah engine .. doesnt matter what engine extualy , its the principle. .
ok answer nr 1 with a mono you want to run the props pretty far from the transom .. why ? becouse the shape of the mono hull will tear a hole in the water right where ur transom ends . if u put the prop there it has much less effect .
my hull is 43 inch i have a 6 inch drive .. my prop starts at 5 inch .
answer 2 . running a mono in turns can make the hull shake and lift the transom if u have a bad setup and mount the rudder close to the transom . ., in oval racing you want to steer the hull with full power in a turn .. if you mount the rudder away from the transom the reaction from the hull will be more easy on you . in other words . you have full control . its a game of torque VS arm .. if you know what i mean .. the prop play's a key role here too .
answer 3 make sure you have the rudder parralel ore behind the prop , again in front of it will steer real nervous , i run my rudder parralel with the prop .. this setup works for me .. the most guys run it behind the prop becouse it can make steering more easy .. think of this .. steer a bit to the right . .place the rudder in front of the prop and u need lots of power to turn . (the prop pushes the hull straight) no same story .. but with the rudder behind the prop ..(now the rudder control's the prop) and smooth steering will be the result .
answer 4 .. see 3
tip .. mr John Finch wrote a setup about mono.s its called mono mania . study that and learn .. its problably 5 years old. . i read it , learned it and right now i am pushing this mono with 58 mph in a full turn without any problems at all .
[SIZE=14pt]this is what i found for u about mono.s from John Finch !.[/SIZE]
As Mono Director, it is my job to foster the growth of the class. To accomplish this goal, I will be clarifying design criteria and even letting out some of the secrets that put the top drivers in the winner's circle. I can't do it all in one article, so stay tuned throughout the year in this section of the newsletter.
As you know, if you have been reading your newsletters, the Rule Book section on Mono hull classifications has been cleaned up a bit in an attempt to better define a Mono hull. By definition, a Mono hull is a boat that has a continuous wetted surface while operating at racing speed. This means that it cannot have steps, sponsons, or any other appendage that keeps the model from having one continuous wetted surface. This includes the bottom profile when the boat banks to negotiate a turn. I know that the real boats have steps and wings, but IMPBA does not recognize these as legal features in the Mono class. There are modellers that feel threatened by these advancements, so these changes have yet to take place in IMPBA.
To be successful in the Mono class it helps to have an understanding of Mono hull design in it's purest state. By that I mean the understanding of weight, balance, aerodynamic and hydrodynamic drag, lifting area, planing area, and power to weight ratios. You see, a pure Mono is far more difficult to tune for all out potential than a three point Hydro. The key word is potential! When it comes to a beginner or intermediate level model the Mono is by far the easier to handle and trim than the Hydro. But again, that is because we have accepted the Mono as a heavy sluggish vehicle with no hope of going extremely fast.
On the other hand, as a modeller who has two Mono hulls that consistently run over 70 MPH, I know that we can do better. The problem with a 70 MPH Mono is that it wont finish a single heat in a race with five other models cranking up the wakes. So, it is a compromise of stability and speed that we must make as we put together a Mono hull that goes fast but still finishes races.
In today’s heat racing scene, a 50 MPH Mono is capable of winning races in all four engine classes. The fact is that most Mono hulls clocked at big events are only running 45 to 48 MPH. They look like they are going faster, but that is only because they are not trimmed properly. The boats that look slower, because they are trimmed properly, are the ones that are going faster and winning the races. So, the first subject to be covered in this series will be that of running hardware on the boat and how it affects the trimming of the model.
HARDWARE SETUP
Deep Vee models are the best type of Mono for heat racing. They handle traffic and rough water conditions very well. Vee angles ranging from 19 degrees to 23 degrees seem to work best for heat racing. Shallow vee boats are faster on calm water and deeper vee boats work best in rough water.
If a model is designed well, it will work with almost any hardware set up. If a model is lacking in some areas, you can sometimes help the handling of the model by changing the hardware set up. Today I will cover trim tabs
TRIM TABS
Trim tabs are those plates at the transom that are used to adjust the ride angle of the model. Usually, they are mounted on the transom about an inch up from the keel to as far out as to the chine line of the model. The chine line is the corner where the bottom of the hull meets the side of the hull. The chine line extends from the transom (back of boat) to the bow (front of boat). The tabs are usually split into two adjustable plates on each side of the hull which makes two separate adjustable tabs on each side of the model.
INSIDE TABS
The innermost tabs are adjusted up and down to direct the bow of the boat either up or down. Adjusting the tabs downward will push the bow of the boat down as water leaving the trailing edge of the tabs causes lift at the transom, thus pushing down the bow. Raising the trailing edge of the tabs will reduce the lift at the transom and allow the bow to run lighter on the water. If the boat leans to the right because of engine torque, which it most probably will, the right or starboard tab is adjusted downward at the inside trailing edge, (edge closest to the prop), to shoot water downward off the right hand tab, which in turn will lifts the right side of the model. Keep in mind that lowering the right tab will not only lift the right side of the model, but also cause the bow to be pushed down as well. If the boat is leaning to the right and also running very wet, it would be better to raise the left inside tab (tab closest to the prop on the left side of the boat).
So, you are adjusting two things when you adjust the inside tabs: the hull attitude bow to stern and the ride left to right. Most hulls that are set up properly for heat racing are adjusted with the left tab slightly down and the right tab about 1/16 of an inch deeper than the left tab.
OUTSIDE TABS
The outer tabs, close to the chine line, are used primarily for adjusting the ride thru the comers. The right outermost tab adjusts the ride for right hand turns and the left outermost tab adjusts left hand turns. If they are flat with the hull, the boat will turn a predetermined radius. If they are pushed downward, the model will turn a tighter corner 'because the water shooting off the tab lifts that corner of the hull at the transom, which in turn causes the keel at the bow to be forced into the water with more authority. You see, a Mono slides as it turns, and if the bow digs in, the boat turns sharper.
If you raise the outside tab, the boat will become less sensitive in the corners as the bow rides lighter on the water and slides through the turn.
Most models I have worked with are too sensitive in the corners, so the outside tabs have to be raised considerably to get good linear turns out of the model. Some boats work better without an outside tab, and some models, like the Seaducer, don't use tabs at all. The Seaducer type hull does not bank hard to negotiate a turn, so the tab scenario described does not apply to it or any other Mono that stands up in the corners. Now you have the knowledge it takes to trim tabs to your advantage. There are other things that can be done to trim your Mono too, so stay tuned for the next issue of MONO MANIA.
Because there's no such thing as a boat that's TOO fast!
and some more
We talked about trim tabs in the last issue of the newsletter and how they affected the ride of a monohull. In this issue of MONO MANIA, I will elaborate on the strut and how it affects the ride of the boat. We already learned that we could compensate for torque roll by bending the right inside trim tab downward to shoot water off the bottom of the right side of the model. The downward stream of high speed water lifts the right side of the boat and fights the natural need for the model to roll to the right as viewed from the transom. Torque roll can also be adjusted out of a model by positioning the strut off center or by raising the strut.
TORQUE ROLL
Monohulls tend to roll over to their right in a clockwise direction as viewed from the rear of the model. This is because the prop grabs water in a counter clockwise direction and the resulting action is that the engine, which is attached to the hull, is forced to rotate clockwise as the prop encounters the resistive force of the water.
To help fight torque, you can position the strut to the right of the keel. With the strut just a bit to the right of the keel, one eighth of an inch or so for example, the lifting action of the prop is distributed more to the right side of the model. The added lifting force on the right side of the model helps to deter the engines rotational force and reduces the amount of down trim tab adjustment that is needed on the fight inside tab for keeping the boat from leaning on it's side. That was a secret, so don't tell anyone!
The angle of the strut up and down will determine if the bow rides light or wet. Negative angle, which angles the prop thrust cone downward, will cause the transom to be lifted and the bow to be forced downward. Kicking the strut back, so that prop blast is pointed up will cause the bow to ride light on the water. I recommend that the strut angle always be perfectly parallel with the keel or within two degrees of parallel. The reason is this: When the boat leaves the water during a race, the tabs will have no affect on keeping the boat from blowing off the water. If the angle of the strut is positive, the prop may push the boat into blowing off the water. If strut angle is negative, the bow will be pushed into the water and the boat may submarine. If the strut is parallel with the keel, the prop will push the boat straight and level until it settles back into the water. Of course this is assuming that the model is balanced aerodynamically with the proper center of gravity.
Another variable is strut depth. The deeper the strut is in the water, the more the boat is lifted out of the water. As the strut is made more shallow, the boat is allowed to settle into the water. Surface drive struts are popular because they allow the model to settle into the water. This helps to get the trim tabs into the water to stop chine walk.
Now you know how to fight the chine walk problem. We will talk about prop walk in the next issue, so stay tuned and read the Roostertail from front to back. An informed model boater is a better model boater.
ok copy .. print , learn and get that mono running . .
jerome
