Tub with

[dwilfong]

I am building a new 21 rigger and have bin wondering about a few things. One is tub with. Would a narrow tub work better for a heat race boat or a wider tub.

The way I am looking at it is a narrow tub would give you less frontal aria but will it be as stable as a wide tub. Dose the lifting affect of the tub being wider help more than less drag with a narrow tub?

Any thought on this dilemma.

David

 

[Scott Schneider]

In following threads threw the years on said subject my take has been the narrower tubs do better in more adverse racing conditions because they have less aerodynamic lift.

Wider tubs float a bit better riding lighter on the water.

The dynamics of frontal area and the narrower tubs being cleaner is always argued with no clear winner. As they say 101 ways to skin a cat ... pick one and make it work for you :blink:

 

[dwilfong]

In following threads threw the years on said subject my take has been the narrower tubs do better in more adverse racing conditions because they have less aerodynamic lift.

Wider tubs float a bit better riding lighter on the water.

The dynamics of frontal area and the narrower tubs being cleaner is always argued with no clear winner. As they say 101 ways to skin a cat ... pick one and make it work for you :blink:

Scott

Thanks for you insight. So a narrow tub will make the boat heavy on the water putting more weight on the sponsons. Hmmmm.

With a air trap sponson with shingles this should balance things out and make the boat seam wider with the weight on the sponsons. Then the air trap and shingles should make it ride lite on the running surface.

Just thinking out loud.

David

 

[Chris Wood]

i would suggest narrow as you can without making things so tight to work on.. one reason. WEIGHT.

chris

 

[Scott Schneider]

Weight is important too and becomes increasingly so as engine sizes decrease.

As for the tunnel/shingle sponson thing, I too have gone this route on my BIG gas rigger.

It has made boat light on its feet for sure. Likely 1000 combos one could assemble and with some trial and error massaging get good results. That's the "Modeling" aspect of the hobby

Have fun just learning how to make it work for you, want cookie cutter tech ... buy it.

Scott
Thanks for you insight. So a narrow tub will make the boat heavy on the water putting more weight on the sponsons. Hmmmm.

With a air trap sponson with shingles this should balance things out and make the boat seam wider with the weight on the sponsons. Then the air trap and shingles should make it ride lite on the running surface.

Just thinking out loud.

David

 

[Tim_Duggan]

A narrow tub is usually taller than a wider tub, so that sufficient fuel capacity can be carried. When Tom M and I were discussing the FF45, we made the tub a little wider than originally intended, solely to get the fuel capacity to suit the higher revving (and therefore thirstier) engines out there these days.

Tub sides are thicker than top and bottom skins. Roll centre is slightly higher on a narrow / tall tub. So there can be advantages to a wider tub.

 

[Marty Davis]

David:

Design the width of your center section around the fuel tank and the engine mount. If you are using the Speedmaster Mini Mount, you can reverse some of it to narrow it up. If you are building your own, just design it as narrow as you want using the vibration rubbers that fit your application.

Make the tub height as low as possible and the engine mount as narrow as possible while still having as much fuel as you need. I would suggest that you use 8 1/4 oz as your target for fuel capacity. That is enough to start right at port time and complete the race without problem.

 

[dwilfong]

Yes the fuel tank was one of my issues. I am thinking of making the spreed between the tubes longer moving the front one as far forward as possible. Are there any ill affects to doing this?

The amount of fuel needed was what I was wondering. Trying to keep the tub sides short is another. The mounts are no problem make my own already.

Want to try and build some thing with all aspect taken in to consideration.

Was playing with a set up with 4 .12 in it. Two pairs linked with a side jack shaft and driving one drive shaft. Just a rough drawing I did. :blink:

I know I am out of my mind. But think about it running a prop that a .45 runs at 38000RPM. :unsure:

O and the sound can't for get about that.

David

 

[Scott Schneider]

Yes the fuel tank was one of my issues. I am thinking of making the spreed between the tubes longer moving the front one as far forward as possible. Are there any ill affects to doing this?

The amount of fuel needed was what I was wondering. Trying to keep the tub sides short is another. The mounts are no problem make my own already.

Want to try and build some thing with all aspect taken in to consideration.

Was playing with a set up with 4 .12 in it. Two pairs linked with a side jack shaft and driving one drive shaft. Just a rough drawing I did. :blink:

I know I am out of my mind. But think about it running a prop that a .45 runs at 38000RPM. :unsure:

O and the sound can't for get about that.

David

Granted it's been a spell running nitro .21's, but back in the 90's we had K&B .21's, Nova rossi, *Picco P-5's and some other stuff that generally were safe on 8 ounce carried, this allowed starts early in the 2 min clock and hot milling with 6 hot laps and a penalty lap or two :blink:

When the Mac .21's came out 8 ounces was scarry on the not enough side !! had to go to 10 Oz to have the same safety margin. Personally HATED having to start and get launched, get engine hot enough to race going out 30 seconds before the 30 second start buzzer ... too stressful. Mind you riggers get around faster that the other hulls types so that said ... your gamble.

Just thinking out loud ...

 

[Chris Wood]

marty i don't know how you get away with 8 1/4.. i have 10oz and barely any left after going in at 2:15 and running the hole race

chris

 

[gooycheese]

I have always had good luck with 8oz, NR & 3280

 

[Marty Davis]

marty i don't know how you get away with 8 1/4.. i have 10oz and barely any left after going in at 2:15 and running the hole race

chris

No problem at all. I start the instant the clock starts and launch first most of the time. Always have fuel left after the race.

It probably has more to do with our milling styles and racing styles and the amount that we are at Wide Open Throttle.

 

[TUNLBOTR]

marty i don't know how you get away with 8 1/4.. i have 10oz and barely any left after going in at 2:15 and running the hole race

chris

Being here locally where MD and the gang race, I get to see the "Millmaster" work the field for all it's worth. He'll set the pace and then keep lane 1+ and drag the field to the line. Loves to "burp" the throttle to do a P.T. Barnum on them, and SUCKER them over on the clock, or take it to lane 1 and proceed to the next lesson.

I'm sure the FallNats will be another class in session, unless the "Tin Man" shows up to teach his old pal something..

 

[Marty Davis]

marty i don't know how you get away with 8 1/4.. i have 10oz and barely any left after going in at 2:15 and running the hole race

chris

Being here locally where MD and the gang race, I get to see the "Millmaster" work the field for all it's worth. He'll set the pace and then keep lane 1+ and drag the field to the line. Loves to "burp" the throttle to do a P.T. Barnum on them, and SUCKER them over on the clock, or take it to lane 1 and proceed to the next lesson.

I'm sure the FallNats will be another class in session, unless the "Tin Man" shows up to teach his old pal something..

 

[Norm Doerr]

marty i don't know how you get away with 8 1/4.. i have 10oz and barely any left after going in at 2:15 and running the hole race

chris

Being here locally where MD and the gang race, I get to see the "Millmaster" work the field for all it's worth. He'll set the pace and then keep lane 1+ and drag the field to the line. Loves to "burp" the throttle to do a P.T. Barnum on them, and SUCKER them over on the clock, or take it to lane 1 and proceed to the next lesson.

I'm sure the FallNats will be another class in session, unless the "Tin Man" shows up to teach his old pal something..

You noticed that eh? LOL

 

[Wally Marsh]

And thus the phrase "race strategy" was invented

MD and CW, I can't think of two with any more different racing styles, yet both have their share of district wins, US1's, and Green Jackets! So ya gotta pick what works for YOU and stick to it (I'm still trying to figure out my own style

)

 

[Marty Davis]

marty i don't know how you get away with 8 1/4.. i have 10oz and barely any left after going in at 2:15 and running the hole race

chris

Being here locally where MD and the gang race, I get to see the "Millmaster" work the field for all it's worth. He'll set the pace and then keep lane 1+ and drag the field to the line. Loves to "burp" the throttle to do a P.T. Barnum on them, and SUCKER them over on the clock, or take it to lane 1 and proceed to the next lesson.

I'm sure the FallNats will be another class in session, unless the "Tin Man" shows up to teach his old pal something..

Randy:

I have been anxious to see if "Tin Man" is entered this year. I would suspect that the .21 hydro class will be tough this year with all the new JAE's that have been built. I have not seen one run down here yet, so I am looking forward to measuring myself against them.

The Charleston Race is really a neat race to go to, and knowing who the CD is, makes it a certainty that things will run smoothly and fairly.

I think that Chris and I have enough difference in the way we mill and race that fuel capacity requirement is different for each of us.

 

[John Knight]

Marty,

The "Tin Man" is entered in the 20 and 40 hydro classes. We all have our work cut out for us. It will be interesting seeing all of the new hulls in this race. It will be a great test for the JAE's.

John