Help With Karleson Roundnose Blow-Over Blues

[Tim Strange]

As the title states, I am looking for some help with a blow-over issue with a Karleson Roundnose that obviously likes to blow over. THis particular hull has no air trap other than what is created by the roundnose and the sponsons them selves.

I know that dropping the strut, putting a little down angle in the strut, and adding weight to the front may help with the issue. I have added about 8 ounces of weight to the front, which, during testing seemed to help. During racing situations however, it is obvious that something else needs to be done.

This hull previously (from a previous owner) had a wiper blade installed about six inches from the nose.

1) Are there any performance/handling issues that such an installation may create? Loss of speed...quirkiness in cornering etc.?

2) What is the best way to mount the blade?

3) Are there different ways to position the blade...such as using a "V" shape rather than running it straight across between the sponsons?

4) Any other ideas?

As always, any input will be greatly appreciated. Tim

 

[jeffaustin]

maybe run at half throttle

 

[Duck899]

As the title states, I am looking for some help with a blow-over issue with a Karleson Roundnose that obviously likes to blow over. THis particular hull has no air trap other than what is created by the roundnose and the sponsons them selves.

I know that dropping the strut, putting a little down angle in the strut, and adding weight to the front may help with the issue. I have added about 8 ounces of weight to the front, which, during testing seemed to help. During racing situations however, it is obvious that something else needs to be done.

This hull previously (from a previous owner) had a wiper blade installed about six inches from the nose.

1) Are there any performance/handling issues that such an installation may create? Loss of speed...quirkiness in cornering etc.?

2) What is the best way to mount the blade?

3) Are there different ways to position the blade...such as using a "V" shape rather than running it straight across between the sponsons?

4) Any other ideas?

As always, any input will be greatly appreciated. Tim

What prop are you running? More than likely you will have to use a 1400 series Octura or some kind of lifting prop. You might then be able to run the strut flat or with 1-2 degrees of angle.

 

[Larry K]

Hey Tim!

I think we need more info. Is this 1/8 scale or ? - where is the C.G. - what is the weight (RTR) - what prop - what is the sponson depth from the base line - and, most importantly, what is the shape of the bottom. As far as the wiper blade - put it on your car. All it does for your boat is create another variable by adding unwanted turbulence - IMO

Larry

 

[Dasboatman]

Tim,

What hull is it - from Newton plans, one of Phil's ???

Show some pics of hull on a flat table resting on sponson touch and strut - hang the turn fin and the rudder over the edge of the table so we can see ride angle.

Take some pics of the hull bottom so we can see what is there as far as angles, surface areas are concerned. CHEERS !!! Bob

 

[Al Hobbs]

After racing Steve Muck, MTO, and a wood round nose scale hulls, I'd say that 8 ounces is not enough weight up front.

I would put at least 8 ounces in the front of the left sponson and more than 8 ounces in the nose. The MTO hull needed more than a pound of lead in the nose, plus some in the left sponson.

Also, the boats ran best with 1400 series, 3 bladed props.

At speed there is so much air captured under the hull that just when it looks like it is running great, here comes the spectaculaor blow-off.

Al Hobbs

 

[u60]

Lots of good suggestions already- I have 1/8 scale built from Newton plans and had the same problem. I moved the CG to 3/4" behind the sponsons. Did this by moving radio and fuel tanks around. In oher words without adding weight to the boat. That helped a lot. The final solution was running three blade X series props. I had Andy Brown do a few of them for me. X460 three blade with his tricks and its a real screamer with no tendancy to blow over. X457 3 blade also works well.

 

[Tim Strange]

It happens to be a 1/8 scale Phil Thomas hull...the early version...I think he modified the bottom under nose a bit on the current version. It has a single 20 ounce tank as far forward as it can go in the nose. With the added weight and no fuel the CG is an inch or so aft of the rear of the sponsons. If I remember correctly, it balanced just at the rear of the sponsons with fuel. Strut depth is about 1 1/4 inch with a slight hint of down. The bottom of the hull is pretty flat from the bow all the way to the transom.

Powered by CMB greenie turning a Prather S255 prop. It is pretty quick and handles well in the turns and straight away as is...except for the tendency to blow-over of course.

I really want to avoid adding any more weight if possible. I also don't see adding weight to the Left sponson since the hull shows no sign of torquing in the straights or the corners (with the S255 prop).

I have 1457, x457/3 and another x455 (my other one is at the bottom of the lake) on order.

 

[SayMikey]

It happens to be a 1/8 scale Phil Thomas hull...the early version...I think he modified the bottom under nose a bit on the current version. It has a single 20 ounce tank as far forward as it can go in the nose. With the added weight and no fuel the CG is an inch or so aft of the rear of the sponsons. If I remember correctly, it balanced just at the rear of the sponsons with fuel. Strut depth is about 1 1/4 inch with a slight hint of down. The bottom of the hull is pretty flat from the bow all the way to the transom.

Powered by CMB greenie turning a Prather S255 prop. It is pretty quick and handles well in the turns and straight away as is...except for the tendency to blow-over of course.

I really want to avoid adding any more weight if possible. I also don't see adding weight to the Left sponson since the hull shows no sign of torquing in the straights or the corners (with the S255 prop).

I have 1457, x457/3 and another x455 (my other one is at the bottom of the lake) on order.

8 oz of lead in a round nose is nothing. A few trips to the lake and small strut adjustments work wonders. Round nose boats pack air just like tunnels,your after a controlled air bleed and the wiper blade has worked very well. I tried many 1400 series props before I found a good P255 that settled the boat I have down.......Scribe your strut and document all changes........

 

[glenng]

It happens to be a 1/8 scale Phil Thomas hull...the early version...I think he modified the bottom under nose a bit on the current version. It has a single 20 ounce tank as far forward as it can go in the nose. With the added weight and no fuel the CG is an inch or so aft of the rear of the sponsons. If I remember correctly, it balanced just at the rear of the sponsons with fuel. Strut depth is about 1 1/4 inch with a slight hint of down. The bottom of the hull is pretty flat from the bow all the way to the transom.

Powered by CMB greenie turning a Prather S255 prop. It is pretty quick and handles well in the turns and straight away as is...except for the tendency to blow-over of course.

I really want to avoid adding any more weight if possible. I also don't see adding weight to the Left sponson since the hull shows no sign of torquing in the straights or the corners (with the S255 prop).

I have 1457, x457/3 and another x455 (my other one is at the bottom of the lake) on order.

8 oz of lead in a round nose is nothing. A few trips to the lake and small strut adjustments work wonders. Round nose boats pack air just like tunnels,your after a controlled air bleed and the wiper blade has worked very well. I tried many 1400 series props before I found a good P255 that settled the boat I have down.......Scribe your strut and document all changes........

Interesting topic, I have a MTO 1/8 scale, It's not a light boat but it runs well @ 5200" elevation. Bottom of strut to hull is 1 7/8". Also have a RN Karleson PT spt. 40 hull. One thing I've noticed about both- You have to have the strut lower than pickle fork boats. I have a 5/16" air dam on the MTO and will not remove it- The boat has a tendency to lift the left sponson at the end of the straights. I try to get hydros to balance 1/2"- 3/4" behind the sponsons WITHOUT FUEL. A smallerl prop may serve you better for heat racing. Also got a driving tip- do not chop The throttle suddenly- the round nose boats do not pack as much air under the rear of the hull and if it drops suddenly- blow over . Hope this is some help. Glenn

 

[Tim Strange]

All very good information!

Definitely will scribe a mark in the strut if I dare move it so I can get it back to where it was...since a certain very knowledgeable somebody set the strut where it is now! I may drop the strut just a little to start.

Glenn, I am certain that at least one blow-over occurred from chopping the throttle...so I definitely need to watch out for that!

Also, what are you using for that 5/16" air dam? pics?

 

[glenng]

All very good information!

Definitely will scribe a mark in the strut if I dare move it so I can get it back to where it was...since a certain very knowledgeable somebody set the strut where it is now! I may drop the strut just a little to start.

Glenn, I am certain that at least one blow-over occurred from chopping the throttle...so I definitely need to watch out for that!

Also, what are you using for that 5/16" air dam? pics?

It is a clear plastic angle that the previous owner Installed with supervisor tape (two faced). It was about 3/8-7/16' when I got the boat but cut it I cut it to 5/16". I live at a much higher Alt. than the prev. owner- maybe should not have trimmed it- as it lifts the left sponson at the end of the straights but the fin sucks it back down in the corners(so far). Do not be afraid to add weight or try a 1400 series 3 Blade prop. P.M. your e-mail and I'll send a pic............. Glenn

 

[P THOMAS]

It happens to be a 1/8 scale Phil Thomas hull...the early version...I think he modified the bottom under nose a bit on the current version. It has a single 20 ounce tank as far forward as it can go in the nose. With the added weight and no fuel the CG is an inch or so aft of the rear of the sponsons. If I remember correctly, it balanced just at the rear of the sponsons with fuel. Strut depth is about 1 1/4 inch with a slight hint of down. The bottom of the hull is pretty flat from the bow all the way to the transom.

Powered by CMB greenie turning a Prather S255 prop. It is pretty quick and handles well in the turns and straight away as is...except for the tendency to blow-over of course.

I really want to avoid adding any more weight if possible. I also don't see adding weight to the Left sponson since the hull shows no sign of torquing in the straights or the corners (with the S255 prop).

I have 1457, x457/3 and another x455 (my other one is at the bottom of the lake) on order.

What is the build date on that hull? The new ones have the bottom flat from the transom to about 2 inches ahead of the front sponson pads and the angle of the sponsons is less. The balance point has to be achieved and strut set deep enough. the 1460 is the prop to use, angle the strut but if it hops flatten it out some.

You probally need a deeper strut setting.

This is the info from the setup sheets

Speedmaster SPDS-012-250F Large 3 ¾ deep flat bottom extended strut for cat, for ¼ cable

SETUP

Your boat should balance about 21 to 22 inches from the transom. The 1 5/8 inch strut setting is a good starting

point. Your boat weight, balance point , will determine the final strut depth for your boat.

Weight should be added to the nose of the hull for the perfect ride attitude of your boat.

Lead weights can be secured in the ends of the flotation tubes.

Props that will work on this boat, Octura 1460, x460, x462.

 

[Tim Strange]

Phil, the build date is 7-17-02. It was Kenny Hildreth's boat...perhaps the one you show on the Metime web site? I talked to you about it last year, but couldn't remember what you changed.

The strut is currently 1 3/8 from the bottom of the hull to the bottom of the strut.

 

[Ken Hildreth]

Interesting Topic,

That very boat got my name on the Joe Rood cup. Phil, it is a boat with the deeper sponsons. I would think you couldn't keep it on the water with only 8 ounces of lead in the nose. I had 4 ounces in the left front, and 14 ounces in the nose, I think, it may have been twelve, but regardless, it was much more than you are running now. You have gotten a lot of good advice. I used a 1457 three blade on the boat. But I tend to use 1400 series props alot. A good statement on here was a round nose takes a different style driver, you cannot chop the throttle and expect it to stay down. Ken

 

[Tim Strange]

Ken, thanks for chiming in. I guess I could have asked you about this at the last race...but at the time I thought that I had it sorted out (maybe we did briefly). The one question I have for you now is: Did you run it with the wiper blade?

After 3/4 gallon of fuel, I got a little testing done today. I first ran it "as is" and managed a flip within a couple of laps. Recovered, and ran it out of fuel with no more flips ...Running around 15 second laps on Evansville's 1/3 (?) mile course..this is with a guy and a digital stopwatch. After scribing a mark on the strut, I dropped it about an eight of an inch and ran it with the same P255 prop. It ran stable but developed a bit of "hop" in the corners. This seemed worse the tighter I cut the corners.

I then tried a X457/3...definite loss of speed and more hop in the corners. I then tried a X460/2 which appeared to be as fast as the P255 in the straits and maybe a little less hop. However, it seemed to be bogging a bit in the corners. Not sure if it was a needle/Pipe length/ or fuel issue. It did step up with wiggling the rudder a little bit...not sure what to make of this...

For those interested: Weight is 14 lbs 2 ounces with no fuel, the 8 ounces of weight already added, and foam still soggy from today's run. Balance without fuel is just behind the ends of the sponsons (about 22 inches from the transom). I played with the balance a bit by placing the end of the strut on a scale and adjusting the front of the boat so it was just about the correct ride attitude and pivoting on the back of the sponsons. To get all of the weight off the strut, it required 10 ounces of weight in the nose. To get 1/2 ounce of weight on the strut, it required 7 and 1/2 ounces of weight to the nose. The current set-up show 8 ounces of weight on the strut.

Not sure what my next move will be. For now, I am considering adding 4 more ounces to the nose before I experiment with the air dam. I do know that I will get a 1457/3 and a 1460/3 to round out my prop collection Oh, I have 5 gallons of Elzer 50% ordered also...

THanks all for the input...you have given me a lot to think about.

EDIT: The course is 1/6 mile according to the GPS

 

[Tim Strange]

Some runs from Thursday on Youtube... My link

First runs are with the P255, then after the blown coupler X457/3 and then 1460 at the end.

 

[glenng]

Looking good Tim! May not need a air dam. After all the coments I might add some weight to my left sponson. Hope to be running at sea level soon instead of 5200' here in UTAH............Glenn

 

[Tim Strange]

I'd imagine you could get a bit more power from your motors a little closer to sea level...I think we are just below 400 feet above sea level.

I may experiment with the air dam, after I add more weight. Although the boat seems stable with the strut adjustment, I still feel that it may blow over at any time. The first bit of weight I added helped a lot, and I had no blowovers during testing...however, raceday proved different.

One valuable bit of info I learned by timing my laps is that when hugging the buoys, I am adding a good second or more to my lap times vs.staying 10 feet off of them.

 

[SayMikey]

I'd imagine you could get a bit more power from your motors a little closer to sea level...I think we are just below 400 feet above sea level.

I may experiment with the air dam, after I add more weight. Although the boat seems stable with the strut adjustment, I still feel that it may blow over at any time. The first bit of weight I added helped a lot, and I had no blowovers during testing...however, raceday proved different.

One valuable bit of info I learned by timing my laps is that when hugging the buoys, I am adding a good second or more to my lap times vs.staying 10 feet off of them.

Good Tim save lane 1 for me