Round Nose setup?

Hey i have a sport40 roundnose that was built in MI some time ago i think. It is all epoxy glass. I removed the old solid mount and radio box way in the back to set it up with a rubber mount and better radio box.

Before i start glueing stuff back in, What is the balance point on a round nose supposed to be? The hull is 37 inches long and the afterplane is 20 inches.

Is there a percentage of weight to have on the strut?

Where should the prop be? Drive Dog at the transom or ahead?

Should i install a front tank and a rear radio or a front radio and a tank behind the motor? dont really want to go with two tanks.

I have room for about 14oz fuel in the front.

PHIL

Hi Phil,

Funny thing about shovels is the CG is "usually" way forward of a pickle forks. An example; Testing was done on the Dumas Slo-Mo 1/8th scale boat and at the mid 50mph mark the boat would blow off the water with a CG 1" behind the sponson transom. To get the boat into the 63mph range required a CG a bit over 1" in FRONT of the sponson transom. Keep in mind this was an electric conversion but the boat still weighed 16 pounds RTR.

As a rule I go 15% of the after plane as my starting point for CG on a hydro but like I mentioned maybe 5% would be better on a shovel.

Paul.

PS I sent you an email about the driver figure.

Here is a photo of the boat.

Paul try agian no email here? Phil

Just trying to learn something before I get started on my 1/8 Dumas Miller American later this year. Is the afterplane the flat portion of the bottom aft of the sponson transoms?

As a rule I go 15% of the after plane as my starting point for CG on a hydro but like I mentioned maybe 5% would be better on a shovel.

Click to expand...

Paul, what do you mean "15% of the after plane?" This must be a measurement just aft of the sponson transoms :unsure: ?

I've been running Shovelnoses for a long time and fount that if you can get the boats weight at the strut at 12 oz an a sport and 16 oz on a Scale your go to go..My props have the drive dog end at the transom... My shovel nose was made by Kotch and Hochanberry..It a Thrifway too design and was made in 85....

dannyual767 said:

Just trying to learn something before I get started on my 1/8 Dumas Miller American later this year. Is the afterplane the flat portion of the bottom aft of the sponson transoms?

As a rule I go 15% of the after plane as my starting point for CG on a hydro but like I mentioned maybe 5% would be better on a shovel.

Click to expand...

Paul, what do you mean "15% of the after plane?" This must be a measurement just aft of the sponson transoms :unsure: ?

Click to expand...

dann, yes the afterplane is the length from the transom to the fron sponson back.

I set up the boat with front fuel and center radio box seems to balance ok about 90% of afterplane.

Roy you say 12 oz on sport40 roundnose? Ill check this on mine

PHIL

Yea Phil 12oz ...I set my boats on 3 scales and arange all my equiptment and fuel tanks so that only 12 oz are on the strut RTR...My radio box is in front and my fuel tanks are alongside the engine..

Is that 12 oz. number a set number or is it (boat weight * X% = 12oz.) Does this number change with length of the hull?

Chris I found that 12oz -16 oz remain a constance on every one of my boats no matter the length of the hull,and weight.I have one Shovelnose Scale that 15 lb,and my son's is at 19 lb .Both have only 16oz on the strut,and both handel and run the same. And so do my sport boats too...We been doing this set up since 85 when we got our first Shovelnose sport boats...And not only our shovelnoses but our pickel forks too....

Roy Munoz said:

Chris I found that 12oz -16 oz remain a constance on every one of my boats no matter the length of the hull,and weight.I have one Shovelnose Scale that 15 lb,and my son's is at 19 lb .Both have only 16oz on the strut,and both handel and run the same. And so do my sport boats too...We been doing this set up since 85 when we got our first Shovelnose sport boats...And not only our shovelnoses but our pickel forks too....

Click to expand...

Hello Roy,

Hows about a picture of how you do this and what type of scale?

Thanx

Bob Morton

Hi Bob ....I have 3 small scales that are used to weight small packages up to around 30 lb...I place the trailing edge of the sponsons in the center of the pads of 2 of the scale and the strut on the 3rd one..I place my radio box in front and the fuel tanks along side the engine add all the hard ware and see where I need weight to balance out the hull,and get the strut to 1 lb..As you move things you see the weight at the strut change,and where weight is needed to get what you want.Or where to take off weight...These scales weren't very expencive,but there worth the weight in gold...I built many Scales boats for guys in our area and belive me this sure saves alot of time tweking in the boat. Maybe a strut angle change,and that all...Most of the time we wine up at O deg... I have to learn how to post pictures ..Maybe I can get Rodnney to show me next time he comes over so I can post a picture of my Boat on the scales....

Roy Munoz said:

Hi Bob ....I have 3 small scales that are used to weight small packages up to around 30 lb...I place the trailing edge of the sponsons in the center of the pads of 2 of the scale and the strut on the 3rd one..I place my radio box in front and the fuel tanks along side the engine add all the hard ware and see where I need weight to balance out the hull,and get the strut to 1 lb..As you move things you see the weight at the strut change,and where weight is needed to get what you want.Or where to take off weight...These scales weren't very expencive,but there worth the weight in gold...I built many Scales boats for guys in our area and belive me this sure saves alot of time tweking in the boat. Maybe a strut angle change,and that all...Most of the time we wine up at O deg... I have to learn how to post pictures ..Maybe I can get Rodnney to show me next time he comes over so I can post a picture of my Boat on the scales....

Click to expand...

Thanx Roy,

This is great info for setting up scales, or I will bet it works on ALL hulls

õ¿~ ya later

Bob Morton B) B)

Bob this is the name of the scales we use. Pelouze model Y50 I belive they cost about 25 a piece...

Roy Munoz said:

Bob this is the name of the scales we use. Pelouze model Y50 I belive they cost about 25 a piece...

Click to expand...

Thanx Roy B) :unsure:

Bob Morton

Where can I find a cowl like the one Phil showed, that would fit an 1/8 scale?

I have a U-22 Tosti Asti round nose (wood) and don't have the time to try and fabricate the cowl section in front of the driver, I have the cockpit and tail fin.

By the way, am looking for driver and motor (exhaust pipe) replicas too!

Any help ill be appreciated.

Greg Martin

this is a little cheaper than buying 3 scales.. I use one scale on the strut and have a 1/4 inch plywood board " tapered to a 1/16th inch top edge to provide a good pivot point" , support the boat on the ply board on both sponsons aft edge tips. push the scale to the 1 pound mark and measure from bench to top of scale and this figure will be your plywood board height. that lets you weight the strut with the boat being level. notch out the bottom of the ply board and slide another short also notched piece of ply into it to hold the board up . like a cardboard divider in a "beer" box. my scale strut weight is 11oz. going to add some weight and try it at 16 oz. the boat works ok at 11 but everybody here says 16, might learn somthing with little effort . thanks, gene gager B)

Gene the use of the 3 scales insete on one is to know how much weight is on each sponson too as you add weight..This way you can also balance out the boat at the same time..But you way will work to find how much weight is on the strut..I use to do this first till I added the other scales..Maid my time at the pond more in joyble not haveing to keep adding weight to the left sponson be cause I forgot to compensate for the weight of the turnfin and braket...I know we think it doesn't weight much,but just a few oz at top speed make a big difference....

Roy Munoz said:

Gene the use of the 3 scales insete on one is to know how much weight is on each sponson too as you add weight..This way you can also balance out the boat at the same time..But you way will work to find how much weight is on the strut..I use to do this first till I added the other scales..Maid my time at the pond more in joyble not haveing to keep adding weight to the left sponson be cause I forgot to compensate for the weight of the turnfin and braket...I know we think it doesn't weight much,but just a few oz at top speed make a big difference....

Click to expand...

Hello Roy,

Let me ask this ,should the weight be the same at both sponson tips?

Example five pounds on the left same on the rigth? Or more on the right

than the left.

The NASCAR guys do this with there cars, weigh at each wheel <_<

Thanx

Bob Morton I am going to do this to all my scales when you give me a reply

Bob what I found is that both sponsons should weight the same or as close as possible..My shovel nose (scale ) weight 14 lb ..6 1/2 lb on each sponson and 1 on the strut.. But remember if you change from an Alum, turnfin to S.S..you'll need to add weight on the opposit sponson. I set up a Phil Thomas 82U55 hull and did all the balanceing this way,and them removed every thing out to repaint the boat when the paint wouldn't stick to the primer..When I replaced every thing I placed the wrong weight into the right sponson. Needless to say after the first run I had to remove every thing and put the right weight in the richt sponsons...I was off 1 lb due to the heavy S S turnfin and bracket..I just forgot to re weight the boat to make sure I had placed thing back in the right place... Also another benifitt that I found is you'll not needed alot of lift,so you can use pushing props..Also verry little to no strut angle..So verry little power from your engine is used for lift..I can lunch both my Scales (Shovel nose and my 82U55 hull) by my self by just sitting them in the water..Make for alot of fun when my son and I go to the pond..We can race each other and have bragging rights for the week until the next time..

Greg Martin said:

Where can I find a cowl like the one Phil showed, that would fit an 1/8 scale?I have a U-22 Tosti Asti round nose (wood) and don't have the time to try and fabricate the cowl section in front of the driver, I have the cockpit and tail fin.

By the way, am looking for driver and motor (exhaust pipe) replicas too!

Any help ill be appreciated.

Greg Martin

Click to expand...

I have a cowl like that for the round nose with the long front hood Let me know if you want one. Cant say the hooded part will line up with the cowl you have now.

scale parts

RAINIER UNLIMITED SCALE HYDROS Enumclaw, Wa. Larry Kraemer 360-825-5878

Exhaust stacks, drivers and uniforms, engine parts and complete kits, steering wheels..