The effect of overall weight

[Tony Jacuzzi]

Joe W, John F and all other Mono gurus:

Lets say I have a 21 mono that that weighs 4 pounds fully dressed and an identical one that weighs 3 pounds fully dressed. What do I need to consider regarding CG or whatever on the lighter one. My first inclination is that the boat will be faster, accelerate better, and pull props easier, with a shorter pipe. I think that I will have to re-balance the boat because of the increased speed, but I am guessing that most of the same rules (cg, break point etc.) apply regardless if the boat weighs 3-4 or 5 pounds. What am I missing.. Thanks Tony J

 

[BigChuck]

What are you missing.............? First I would say the weight. It will directly effect how the hull handles.

I have known of a racer who realized after two year that the lighter hulls were NOT the faster hulls!!!

Thus he stop building light weight hulls.

Just my 2 cents...

 

[Tony Jacuzzi]

What are you missing.............? First I would say the weight. It will directly effect how the hull handles.
I have known of a racer who realized after two year that the lighter hulls were NOT the faster hulls!!!

Thus he stop building light weight hulls.

Just my 2 cents...

Chuck appreciate the input on the hull handling but those specifics are what I am looking for. Its been my experience that a well set up .21 3.5 lbs hydro will generally run just as steadily as a well set up 4.5 lb hydro. I am looking to see if there is a way to heat race a really light 21 mono, or what I should look for in the setup. Tony J

 

[Joe_Knesek]

Tony I have to disagree with Chuck. It's simple physics, a light boat will always have more potential than a heavy boat but they do require more detailed setup. My 40 Speedmaster was a good example. It weighed over a pound less than a Seaducer and I had to set the trim tabs & strut much flatter than I expected. I also went to a thinner rudder. The CG was also critical. Moving the motor forward 1/4 inch forward made a huge difference in the boat. All of these changes were needed because the lighter boat reacts to changes more than a heavy one.

 

[BigChuck]

Joe.......Is that not what I said???? All of what you mentioned and more are directly related to the boat handling...............Yes.

It a fine line Tony..................How you work it will have a LOT to do with time to get it RIGHT.

Lake time.

I have one like" Joe mentions" here. But I have put it down for the time. I want to race. I took the Standard hull to the last two race.......................

It will take (some) longer than others. Is it worth it???? TIME................Will be the answer.

Good luck...............Keep us posted on you findings.

 

[Joe Warren]

Joe W, John F and all other Mono gurus:Lets say I have a 21 mono that that weighs 4 pounds fully dressed and an identical one that weighs 3 pounds fully dressed. What do I need to consider regarding CG or whatever on the lighter one. My first inclination is that the boat will be faster, accelerate better, and pull props easier, with a shorter pipe. I think that I will have to re-balance the boat because of the increased speed, but I am guessing that most of the same rules (cg, break point etc.) apply regardless if the boat weighs 3-4 or 5 pounds. What am I missing.. Thanks Tony J

Tony while you did not mention Who`s hull you are running?? I personally build several 3.5 lbs seaducers .21 to heat race. Servos size & placement was always a consirn to keep the boat balanced. I personally liked the fuel tank as close to the engine as possible so the Cg did not change dramatic while burning off fuel in heat racing. With a .21 this wil not be a problem. Also sometime the hull & parts placement was built to spec But may be moved if the hull was not performing as desired. Remember: A very Loose mono will not turn well. If you must raise the strut above mfger specs to get the boat hauling, it will not perform as desired in the corners... Make sure you are on the base line prop with a mfger spec lift? Also I prefer the Novarossi .21 engine. Nothing performs like a Race prepared Nova with the correct pipe & a sharp prop.. Shame when a boater must change the prop due to the Engine mfger being short on power. When you get a nice hull the strut can be set to spec height & the boat will be fast & flat on the water & handle perfect in the corners. Jerry`s .21 has ran in the lower 60 mph with not what I would consider to be the best 21 engine. He has put all of his race knowledge in the building specs. he may rake the prop for lift or tip cup for more Mph But most of the time his boats are tighter on specs @ the strut ride height than most on the water. On a light .21 the strut angle & height would be Most critical. the later .21 Mono`s I liked the pipe & header being bent to the starboard side. less burnt fingers & the weight helps in the corners while in the race chop. A 60mph 20 mono that turns well & stays on top of the water will be hard to beat when you hit the start - Turn & Burn....... I know you pay close attention to detail. So you have this stuff already figured out!!!! Also practice the boat like you race it & come off the water with the extra fuel in the tank for ballast. You can always add weight on bad water days. But hard to remove if built in, jw

 

[John Finch]

If you are not designing a hull and must balance an existing hull..........You will find there is a certain weight that works well for that boat at top speed. If the boat travels faster than that speed the boat will blow off the water. It is better to add weight to the hull at the CG than to push the bow down using trim tabs. You want the balance point to stay the same, because you want the boat to fly level at top speed. Adding weight to the front of the boat will make the boat fall bow first when it becomes airborne. Thus the submarine. Lighter boats always accererate faster than heavy ones, and you can make a lighter hydro go faster because they can run at a negative angle of attack without adding weight. A mono runs at a positive angle of attack, so you have to balance the boat with aerodynamic lift and weight. there is a perfect weight for every mono at the speed it runs. As the boat increases in speed the boat packs more air giving more lift. Lift vs weight!

 

[Rokieboater]

So...are you guys really running a 60mph .21 mono in heat race trim?

How many guys are obtaining this speed in heat race trim?

Is it the correct/right motor that does this. I run a Mac.21 and was wondering if this motor will ever obtain that speed?

As far as a weight is concerned in a .21 mono 4lbs vs. 3lbs I Don't have a clue but I want to run 60 mphs with mine.

Robert

 

[Tony Jacuzzi]

Robert:

My current .21 Speedmaster setup for heat racing is about 48 mph on my GPS. It is very stable and a good heat race boat, and it probably weighs in a tad over 4 pounds. I dont think that I have had the pleasure to see a 60 mph heat racing 21 mono.. Tony J

 

[shoboat]

Boaters,

Kyle Mull's Speedmaster 21 will go 53 MPH in heat race trim and maybe even faster

if they would test more. At our S.A.W. in Flint a few weeks ago we saw David

go 69.2 MPH with his Speedmaster 21. 60 MPH is fast on race water.

Robert,

You need more RPM and better air to accomplish even the 50's.

Have Fun Testing,

Mark Sholund

 

[Rokieboater]

Boaters,
Kyle Mull's Speedmaster 21 will go 53 MPH in heat race trim and maybe even faster

if they would test more. At our S.A.W. in Flint a few weeks ago we saw David

go 69.2 MPH with his Speedmaster 21. 60 MPH is fast on race water.

Robert,

You need more RPM and better air to accomplish even the 50's.

Have Fun Testing,

Mark Sholund

Mark,

Thanks to yout props I can at least reach 30mph Just kidding we can do on honest 45 at these altitudes. Just messing around as I have yet to see a 60-mph heat trimmed .21 mono. NOT THAT THEY DON'T EXIST. I haven't seen one and I race a little in the Southern California area every now and then.

Robert Holland,

P.S. Thanks for all your great props and knowledge that you are always willing to share.

 

[Rokieboater]

Boaters,
Kyle Mull's Speedmaster 21 will go 53 MPH in heat race trim and maybe even faster

if they would test more. At our S.A.W. in Flint a few weeks ago we saw David

go 69.2 MPH with his Speedmaster 21. 60 MPH is fast on race water.

Robert,

You need more RPM and better air to accomplish even the 50's.

Have Fun Testing,

Mark Sholund

Mark,

Thanks to yout props I can at least reach 30mph Just kidding we can do on honest 45 at these altitudes. Just messing around as I have yet to see a 60-mph heat trimmed .21 mono. NOT THAT THEY DON'T EXIST. I haven't seen one and I race a little in the Southern California area every now and then.

Robert Holland,

P.S. Thanks for all your great props and knowledge that you are always willing to share.

 

[Joe Warren]

Robert:My current .21 Speedmaster setup for heat racing is about 48 mph on my GPS. It is very stable and a good heat race boat, and it probably weighs in a tad over 4 pounds. I dont think that I have had the pleasure to see a 60 mph heat racing 21 mono.. Tony J

J crowther & B mcgraw have been able to run 60 mph plus range on a stalker radar gun for 4-5 years in heat trim. I have seen a consistent 57 mph boat that would not run with them.

 

[John Finch]

I cut up a 30 inch Twin Craft about ten years ago and made it smaller and quicker for record trials. It ran 65 mph, but I don't think it would be a good heat racing boat at that speed. I believe most good heat racing 21 boats run about 48 to 50 mph. As you get faster, things happen. Submarines, holes in the water, turtle got me, lochness monster, water too rough, buoy jumped in front of me. That kind of stuff happens. They get "on the edge." We hear about all kinds of fast boats here at the dock, but you have to ask yourself........do they finish races?

 

[Buckshot]

John is right on. Here in D-7 there used to be many 20 monos and it was a fun class. There was one particular boater here that had probably the fastest 20 mono around (at least around here). I loved being in the same heats as him as it was a good gauge of how fast I was for about the first one or two laps then it was usually all over…he was out. The boat would flip, roll, fly, submarine, cartwheel, or some other form of acrobatics not conducive to finishing a heat race. 9 times out of 10 it was not this particular boater who would win a heat let alone the event but he was usually the fastest.

I believe that a mono is designed to run at a certain speed and any more will amplify bad characteristics.

The hulls we where racing at the time were the short SD3 seaducers. We have since went to the 33" versions and lost a little speed but have increased the number of heats finished.

Regards,

-Buck-

p.s. - We run low to mid 50 mph range - Not 60 mph

 

[Joe_Knesek]

All I can say is that my daughter ran a Speedmaster 21 in her first US-1 class at the Internats that may run 50 on a good day and she was competitive and even won a heat. It may have hit 60 MPH on the way home!

 

[Preston_Hall]

Who knows what too heavy, heavy, light and too light are but a lighter boat will probably be slower in race conditions because it will be bouncing around and not staying hooked up. I stopped worrying too much about weight when I saw Crowther at SAW trials hang up his super light F mono and go for the heavy off the shelf model. 88mph ain't bad for a stock hull. But obviously with a 21 things are a little more critical but the same principal.

The best thing you can do for a good handling fast boat is to work with Andy on props. I have seen enormous speed increases by just the change of a prop.