20 boat prop weight

[shoboat]

Ron,

I have three new 21 Hydros to weigh for you in the morning.

I can tell you that our 21 S.A.W. boat only has 8 ounces of

strut weight on it. Good topic!

Mark Sholund

 

[Charles Perdue]

I will throw myself out there and expose my inexperience.
Isn't the strut weight a direct relationship to the COG front to back on the boat? As your COG moves forward your Strut weight will lessen, and adversely as you move the COG towards the rear of the boat.

The strut weight should be taken from the very rear of the sponson ride surface and level with the strut.

It is also possible to get the strut weight too light.

One other thing to throw into the mix is the thrust line( an imaginary line that is the same as the strut angle extended forward to the front of the boat). When setting up an airplane, this makes a lot of difference, especially with a pusher set up and our boat system is a pusher. What effect, if any, does it have on a boat? Something to think about.

Charles

Charles:

I agree with you about the thrust line. That is in effect the angle of the strut. The less strut weight, the less angle that you need on the strut. The prop will become super efficient at lifting the rear of the boat the less strut weight you have and thus the less angle required. On my current boat I have to run .8 degree of strut angle. IF I had more or less strut weight that would change.

I had a roundnose 1/8 scale that was a good boat. It had almost zero strut weight. I couldn't run a 1400 series prop because the prop would blow the back end up and out of the water and cavitate. But, it sure would work well with a de-tounged X series prop. I didn't have to run ANY strut angle. So , I am really not sure that you can get too little strut weight. Maybe???

The recent trend to the sponson-forward rigger design tends to add a larger portion of the overall boat weight on the strut. Hmmmmmmmmm?

Charles

Ron

The strut weight on a VERY SUCESSFUL BOSS 21 heat racing boat design was 14 oz after the battery pack was moved to the rear of the boat.

 

[Ron Zaker Jr]

I will throw myself out there and expose my inexperience.
Isn't the strut weight a direct relationship to the COG front to back on the boat? As your COG moves forward your Strut weight will lessen, and adversely as you move the COG towards the rear of the boat.

The strut weight should be taken from the very rear of the sponson ride surface and level with the strut.

It is also possible to get the strut weight too light.

One other thing to throw into the mix is the thrust line( an imaginary line that is the same as the strut angle extended forward to the front of the boat). When setting up an airplane, this makes a lot of difference, especially with a pusher set up and our boat system is a pusher. What effect, if any, does it have on a boat? Something to think about.

Charles

Charles:

I agree with you about the thrust line. That is in effect the angle of the strut. The less strut weight, the less angle that you need on the strut. The prop will become super efficient at lifting the rear of the boat the less strut weight you have and thus the less angle required. On my current boat I have to run .8 degree of strut angle. IF I had more or less strut weight that would change.

I had a roundnose 1/8 scale that was a good boat. It had almost zero strut weight. I couldn't run a 1400 series prop because the prop would blow the back end up and out of the water and cavitate. But, it sure would work well with a de-tounged X series prop. I didn't have to run ANY strut angle. So , I am really not sure that you can get too little strut weight. Maybe???

The recent trend to the sponson-forward rigger design tends to add a larger portion of the overall boat weight on the strut. Hmmmmmmmmm?

Charles

Ron

The strut weight on a VERY SUCESSFUL BOSS 21 heat racing boat design was 14 oz after the battery pack was moved to the rear of the boat.

Thanks

 

[Ron Zaker Jr]

thanks for the numbers so far,keep them coming, checked my Ninja last night 10.4. Any SG'S or RR outhere?

Ron Jr

 

[rctinman]

Hi Ron..

No RR or SG, but my Jaugar III, 12.25 oz. I think my Hawk will be close to your Ninja, but haven't checked it yet.

Have a good one!

Steve Ball

thanks for the numbers so far,keep them coming, checked my Ninja last night 10.4. Any SG'S or RR outhere?
Ron Jr

 

[longballlumber]

Hi Ron..
No RR or SG, but my Jaugar III, 12.25 oz. I think my Hawk will be close to your Ninja, but haven't checked it yet.

Have a good one!

Steve Ball

What's up Pop's? I am really interested in this topic. Looks like a training sessions is in order for me. I will try and call in the next couple of days.

Mike

 

[Zach Davis]

thanks for the numbers so far,keep them coming, checked my Ninja last night 10.4. Any SG'S or RR outhere?
Ron Jr

What are the total weights of the boats? Just curious if there is a ratio that works well?

Thanks,

Zach

 

[Tony Jacuzzi]

Ron heres our BlackJack, not sure if the measurement position on the strut is the same as everyone elses .. Tony J

 

[Tom Foley]

Ron heres our BlackJack, not sure if the measurement position on the strut is the same as everyone elses .. Tony J

Tony , just a thought after looking at that huge strut on the boat with the big rear sponsons ..you coud probably take that strut to the belt sander and reduce a bunch of unnecessary weight .with those big sponsons I doubt that big flatbottom strut is needed ..could be wrong .

 

[Brad Christy]

Tom,

That "big" strut is all of 3/8" wide and 2" long with a 1/8" thick tapered blade. There isn't much weight that can be removed from the strut without losing physical integrity. And it's flat on the bottom for a reason.

Also, the sponsons are only about .700" wide on the bottom.

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

 

[K-ZAM]

Ron heres our BlackJack, not sure if the measurement position on the strut is the same as everyone elses .. Tony J

Tony that is kinda lite, you may want to add some weight to the stern. I think 14-16 oz tail weight is perfect for heat racing. I have done a great deal of testing and those numbers seem to work well.

Good Luck.

KP

 

[Tom Foley]

Tom,
That "big" strut is all of 3/8" wide and 2" long with a 1/8" thick tapered blade. There isn't much weight that can be removed from the strut without losing physical integrity. And it's flat on the bottom for a reason.

Also, the sponsons are only about .700" wide on the bottom.

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

Photo makes it look so much larger ! :lol:

 

[jason jury]

What kind of prop weight numbers are out there on your 20 boats, just curious. Please list hull brand,thanks

Ron Jr

hi ron 1st boat taipan 21 , prop weight is 0265 grams.. 2 nd boat f,f 21 prop weight is 0.270 grams.

i put 2 blocks under the rear edge of the 2 sponsons and only put the prop on the scale , not the strut this is what i determin as prop weight.. hope this helps mate.. i had to move the battery pack to the rear of the f,f21 to give it more prop weight .. the rigger had the hops, this cured the issue.. jason

 

[Niklas Edlund]

Kep's 09 - total weight RTR (no fuel no prop); 1750 g / 3.86 lb / 61.73 oz.

Prop weight (messured with rudder blade on scale): 449 g / 15.84 oz.

Afterplane from back face of drive dog: 575 mm / 22.63".

/Niklas

 

[diamondback21]

thanks for the numbers so far,keep them coming, checked my Ninja last night 10.4. Any SG'S or RR outhere?
Ron Jr

What are the total weights of the boats? Just curious if there is a ratio that works well?

Thanks,

Zach

I weigh the boat and multiply the weight times 15%. ex. a 63 ounce boat would be 9.45oz on the prop.

 

[Zach Davis]

thanks for the numbers so far,keep them coming, checked my Ninja last night 10.4. Any SG'S or RR outhere?
Ron Jr

What are the total weights of the boats? Just curious if there is a ratio that works well?

Thanks,

Zach

I weigh the boat and multiply the weight times 15%. ex. a 63 ounce boat would be 9.45oz on the prop.

Cool,

Thanks,

Zach

 

[dwb2620]

20 Eagle SG = 1.2 lbs

 

[John Knight]

thanks for the numbers so far,keep them coming, checked my Ninja last night 10.4. Any SG'S or RR outhere?
Ron Jr

What are the total weights of the boats? Just curious if there is a ratio that works well?

Thanks,

Zach

I weigh the boat and multiply the weight times 15%. ex. a 63 ounce boat would be 9.45oz on the prop.

Ron,

With that formula, my 20 RR Extreme is 7.49 oz. on the prop. I have no scales available to verify it however. It is 3#, 12 oz. without fuel. It is quick but not as quick as Kentley's or Preston's.

John

 

[Ron Zaker Jr]

thanks for the numbers so far,keep them coming, checked my Ninja last night 10.4. Any SG'S or RR outhere?
Ron Jr

What are the total weights of the boats? Just curious if there is a ratio that works well?

Thanks,

Zach

I weigh the boat and multiply the weight times 15%. ex. a 63 ounce boat would be 9.45oz on the prop.

Ron,

With that formula, my 20 RR Extreme is 7.49 oz. on the prop. I have no scales available to verify it however. It is 3#, 12 oz. without fuel. It is quick but not as quick as Kentley's or Preston's.

John

Thanks to everyone for getting these numbers posted. I am trying to correlate what they really mean to performance.

 

[Tim_Duggan]

Anyone willing to share their numbers for 45 riggers?