Gas Scale setup

[harvknox]

I got my Gas Scale in the water this Sunday.A little background on the boat then my main problem ,I think.

Bud T-6

Wood hull

CAD program by ML boat

Lazer cutting by Kevin Visconti

Framing mods by me

Epoxy cowl and rear wing by Jeff Snell

RCMKRZ modified by GIsmo

2"flat band aluminum pipe from Gismo.Set at 12" from engine flange to center of flat band.

Radio box in bow,hard plastic 16oz. fuel tank behind engine.

Rear of drive dog at rear of transom

Dry weight 21#.I coated the wood parts inside and out with 2 coats of West Systems epoxy slightly diluted with alcohol then scraped down with a credit card.I scaped the exterior with a razor blade after building.This is how I am now running the boat until I hope to get it dialed in,then paint.

Props tested:

6717/3, 3.95 pitch.Motor won't pull load at 1 1/2" strut depth.At 1 1/8" strut depth boat will not get on plane.

6518/3,5.0 pitch.Trouble getting on plane,drags tail.Speed slightly slower than 1/8 scale

6518/3,4.2 pitch.gets on plane easier and about same speed as the 5.0 pitch,tail drags

CG is about 2" rear of the front sponsons.No extra weights

After the first runs the strut was raised between 1 1/4" and 1"

I think my main problem is the extra drag from the rear.Of course the high weight does not help either,but I can not change that.

The rear ride pads and the rear of the canoes are very close to scale.I knew the boat would have a rear weight problem, and I made the bottom of the ride pads 3/32" below the bottom of the afterplane.At this time I have not included the mini steps on the ride pad bottoms.

The consenses of our local guys is not to add weight to the nose of an already heavy boat,but to possibly increase the depth of the ride pads and work on the prop and strut.

Do any of you out there have experience with mini steps or have suggestions on props,cg,strut ,and any other ideas?

Remember this is Gas Scale.Boat is 54 1/4" long and 28" wide.

Harvey Liberman

Knoxville, Tn.

 

[P THOMAS]

I bet the guys from the NW club can tell you how close you are on your setup, weight, prop, and motor. There are several turbine style boats racing this season.

I dont think the 20 lb weight is too much, but using a modded motor that may have lost some torque to be able to pull a bigger prop with that heavier boat may be a problem.

What is the front sponson pad angle 3 degree? you may have to use 4-5 if the boat rides heavy. I would install stepped pads on the front and rear.

What is 3/32 below afterplane?? the rear shoes?

 

[harvknox]

Phil,yes,the bottom of the rear ride pad is 3/32 " below the afterframe.The moded RCMKRZ was new for this boat.It's never been run before.

I'll check the sponson angle.Have you had a boat where you added stepped pads and have seen a change in performance?

 

[P THOMAS]

Phil,yes,the bottom of the rear ride pad is 3/32 " below the afterframe.The moded RCMKRZ was new for this boat.It's never been run before.

I'll check the sponson angle.Have you had a boat where you added stepped pads and have seen a change in performance?

Well You can set the strut depth about the same as sponson depth to start. the bottom of the afterplane line should be level. I always seem to have to set it deeper than that to keep the boat on the water.

ON my Zipp T boat the stepped pads added speed for sure. They will help get the boat up and running too.

Sounds like the rear shoes are too shallow too, with the strut set as above you could have the bottom of the pads about 1/4 higher and it should work.

 

[u60]

21lbs is not that heavy for a gas scale. Most of the gas scales out west are in the 19 to 22 lb range and with a good set up will run an honest 65 plus MPH. Are you running a 26CC Mod motor or the 29.5CC mod? Do you know where the CG is? A good starting point would be a few inches behind the sponson backs. You might try a 270 2 blade Prop to start with. You might also try pulling the pipe back about 1/4". A little movement on these pipes makes a big difference. Don't be afraid to move the pipe. And make sure you don't have to much of the header extending in the pipe. Hope this helps. One more thing, these gas motors need a lot of air. So make sure that you are getting plenty of air to the carb. Look on youtube on channel Hydroguy637. This is my brothers channel and look at the U95 and the US. THE U95 is his, weighs about 20lbs race ready with a 26cc mod zenoah. The US is mine and is 21lbs with 29.5CC MOD motor. The videos are of the first run of my US. Needs a little fine tuning but both boats run very well and weigh about the same as yours. Fred

 

[jwo]

I Would ask do you have a tach? I do not run one yet. But how does the engine sound? Is it bogging or sound as if it is not getting on the pipe? A 6518 should let it spool up. As U60 said try a 270. If not lengthen the pipe a little. Those hulls do tend to run uphill so to speak. If you have a video post it so we can see how it is running. John

 

[harvknox]

Phil,so far the highest that the strut was set was 1" below bottom which is 1/4"below bottom of ride pads,with shaft parallel to bottom.John's comment about this style hull tending to run up hill is certainly true here.There is only the slightest contact with the water at the back of front sponsons.The boat seems to travel on ride pads and bottom.

Phil,I measured the sponson angle at 3 degrees.I determined this by placing a straight edge from the ride pad bottom to the rear edge of the front sponson and measuring the angle at the front sponson.Interestingly I checked Roger Newton's drawing and the angle measured 7degrees.My 3/32"ride pad would decrease Roger's angle only about 1 degree.Curious the difference?

Phil,since the front sponsons hardly touch the water,would the angle be much of a factor?It may be a factor in getting on plane.

John,the 6717 pulls the engine way down.The 6518 allows the engine to rev.I don't have a tach,and can only listen to the engine.

Fred, the engine is a 26cc RCMKRZ,modded.The header has not been cut off yet.I have always waited until I get the tuning close so I don't cut off too much.The York 1 ran a bit like my boat,but faster.It also seemed light on the front sponsons,but lighter than mine on the rear.

Most of us are going to the Atlanta Spring Nats this week end,which leaves one week to test before going to Evansville.Most of the boats there will be different flavors of the 8255 hull,with some 30cc engines in the mix.

I'll try all the ideas I get.I'm going to try more strut heights,add mini steps to pads and round up more props to test including a 270.

Harvey

 

[P THOMAS]

Try some of the 2 blade gas sport props too. Im sure the hull is ok just need some time on the setup. I have not heard who all is going to appear at Evansville with gas scale. I have alot of work to do on mine.

 

[jwo]

I Marty chimes in he can better tell you about the engine. The header can not go into the pipe at all on these things. It may take a couple of them if you happen to cut it to short. 3* is a good angle. Mine are 2.7*. You can back cut the 6717 to releave it. That engine should turn 1 with know problem. Try running it with out the rear wing and see if that helps get the rear out of the water. If it does add or move some weight forward to compensate.

 

[Piston1]

I bet the guys from the NW club can tell you how close you are on your setup, weight, prop, and motor. There are several turbine style boats racing this season.

I dont think the 20 lb weight is too much, but using a modded motor that may have lost some torque to be able to pull a bigger prop with that heavier boat may be a problem.

What is the front sponson pad angle 3 degree? you may have to use 4-5 if the boat rides heavy. I would install stepped pads on the front and rear.

What is 3/32 below afterplane?? the rear shoes

Phil, if I can chime in on what I saw Sunday. The boat looks good on the water like a scale boat should. I recommended Harvey to increase the ride high of the boat by adding the same amount on all four corners. The front angle of attack looked good but I do not think Harvey knows how much it is. The boat looks real good on the water and it was driving real good. It was holding the water good on a windy day and it really looks like the real thing riding on the water. Watch out for Harvey he might be coming to get you all. I was impressed but I did not tell him. I am telling him now.

 

[kcvnd]

When I saw it the ride looked great! I think adding to the rear shoes would be a great idea.

 

[P THOMAS]

I bet the guys from the NW club can tell you how close you are on your setup, weight, prop, and motor. There are several turbine style boats racing this season.

I dont think the 20 lb weight is too much, but using a modded motor that may have lost some torque to be able to pull a bigger prop with that heavier boat may be a problem.

What is the front sponson pad angle 3 degree? you may have to use 4-5 if the boat rides heavy. I would install stepped pads on the front and rear.

What is 3/32 below afterplane?? the rear shoes

Phil, if I can chime in on what I saw Sunday. The boat looks good on the water like a scale boat should. I recommended Harvey to increase the ride high of the boat by adding the same amount on all four corners. The front angle of attack looked good but I do not think Harvey knows how much it is. The boat looks real good on the water and it was driving real good. It was holding the water good on a windy day and it really looks like the real thing riding on the water. Watch out for Harvey he might be coming to get you all. I was impressed but I did not tell him. I am telling him now.

That sounds good, If it is staying on the water in the wind, adding some depth andsome steps/ shingled pads will help loosen it up. Plus you have the areodynamic advantage of front and rear wing adjustments. Setting the rear wing down in the back will get the rear up too.

 

[Jeff Schindler]

Try some of the 2 blade gas sport props too. Im sure the hull is ok just need some time on the setup. I have not heard who all is going to appear at Evansville with gas scale. I have alot of work to do on mine.

Update on Evansville Gas Scale:

We have Trophies.

I have Harvey & Phil entered. Carl might be close to ready, but I haven't seen his boat or his race entry. Mikey's boat is not ready.

 

[chris thornton]

Mine is not even close to being ready.

 

[P THOMAS]

Try some of the 2 blade gas sport props too. Im sure the hull is ok just need some time on the setup. I have not heard who all is going to appear at Evansville with gas scale. I have alot of work to do on mine.

Update on Evansville Gas Scale:

We have Trophies.

I have Harvey & Phil entered. Carl might be close to ready, but I haven't seen his boat or his race entry. Mikey's boat is not ready.

Mine is not too close either If I can get a coat of paint on it I can bring it. Planning on Mt vernon race for sure, get those boat s done.

We could get Mike Board racing, he bought my last year boat, all it needs is the motor installed. How bout it Mike you wanna race??

 

[harvknox]

Phil,don't worry about the paint.My boat will not be painted for the Evansville race either.The wood hull is scraped down over the epoxy coating.The glass parts are bare glass.The boat is complete except for the driver and rear view mirrors.This weekend we'll be doing more testing if my back holds out.One of the guys throws the boat in,but I end up getting it out of the water.You know how it is with scales. I've added additional height to the rear ride pads and added two mini steps to each pad hoping to raise the rear of the boat and reduce surface tension to increase speed,also going to a smaller prop for more rpm and lengthing the pipe 1/4" for more torque.No weight added to bow yet.

If anyone has more ideas,feel free to share.

 

[P THOMAS]

Yea cool bring it over to the race it can be tested there too. I realy will try to get mine ready to test

 

[Joal Garner]

run a ride plate on your shaft , it works wounders

 

[BobGutsell]

They're not allowed Paul.

 

[Dasboatman]

"They're not allowed Paul."

Hey Bob G.,

Where do you read that they are not allowed?

IMPBA:

Engine and Boat Specificatiomns 7. The drive dog must not extend beyond the transom unless the prototype's strut and/ordrive dog did so. Photo documentation may be requested for proof by rcae CD or district scale director.

NAMBA:

Hull Specifications 9. The propeller drive dog may extend one drive dog length beyond the transom.

CHEERS !!! Bob Johnson.