New .12 Rigger Nitro Trident SR

[TomMoorehouse]

Eric.... your rears are non adjustable right???

well try this.... place your boat on a flat table,

set your strut so that it lifts the rears about 3/16" off the table.

now measure your front sponsons AOA by measuring 6" forward from the rear tip of the front sponson. what is that distance to the table top. Hopefully it will be about 3/8 of an inch.

let me know what you get.

 

[MikeP]

Eric,

Someone correct me if I am wrong, I think that your front sponsons are about a 1/2" too wide on each side. Wider sponsons will make your AOA much more sensitive.

-MikeP

 

[TomMoorehouse]

well they are a little wide.... i dont think overly.... my 12 heat racing boat has 1.375" wide while my saw is a touch over 1"

 

[Eric Perez]

Tom, with the rear end lifted 3/16 the AOA is 4.25 Deg. and the distance from the spoon 6" from the rear end of the front spoon is 3/4" (Keep in mind the spoon bottom is curved) See picture

 

[Eric Perez]

Mike, these are the ideas that I had to reduce the "Rigger Dance". I've added a new spin and I'm calling it the BBY Spoon cut. This allows you to go with a wider spoon but the rear is not 90 deg to the inside, instead it angles in -effectively reducing the wetted area and reducing lift.

See attached pic

 

[Propjockey]

Eric -- try an Octura 1938...less lift than than the V937 and a smidge steeper.

 

[TomMoorehouse]

Tom, with the rear end lifted 3/16 the AOA is 4.25 Deg. and the distance from the spoon 6" from the rear end of the front spoon is 3/4" (Keep in mind the spoon bottom is curved) See picture

well Eric.... id try to run it like that.... if it is still squirely make the rears 1/4" off the table.

I think your dancing cause the AOA is too much

 

[Don Templeton]

Eric,

You said you had to use a lot of rudder (I assume left rudder) because of not being able to change your sponson offset. I just thought of something we used to do to help correct that. Bend out the lower rear tip of you turn fin to the right. Maybe about the last 1/2" or so. Trial and error if you know what I mean but it worked pretty well back when we didn't use much offset in our sponsons.

Also, I don't know what kind of starting belt you are using but I bought one from Aeromarine Laminates that is just like the Prathers but only 13" in circumference. It is a very good belt and seems the right size for a .12. Fits right over my engine and pushes against the bulkhead under the stuffing tube. The groove in my flywheel is very thin so I cut it down the center with an exacto knife to fit better.

I also usually put a well under the flywheel just to give clearance for the belt.

I think Tom is right about the AOA. Your sponsons look very short. If they were longer toward the front and had a much more gradual and forward transition from 4 degrees or so combined with less angle on the top "oh never mind, you know what I'm talking about and I just keep rambling on". :

Don

 

[Eric Perez]

Ran the boat this past Sunday at the club race.

Keep in mind this was running against .21 SG's in full oval race trim -Let's say it was a very uneven match for them ;D.

In the morning the water was good, wind was light. The Nitro Trident did the laps with an S220. I had the prop way up and still the rears where not draging. The rigger dance was all but gone. Front was running very light on the water. Turns where good, no handling problems.

I changed the prop to a S215 and lowered the prop a bit, engine RPM was up and it appeared to be running a little better, okay it sounded faster!

About the time of the first heat the wind picked up and the back-straight got rough. my boat started doing some crazy stuff in the back straight. It looked like the boat was bouncing around in the water and the engine bay was getting full of water. The engine quit right in the middle of the straight. Luckly for me the wind quickly moved my boat out of harms way and the other brave souls battled it out till the end.

The next change will be to reduce the width of the ride pad on the current sponson.

Here is a pictue of the new proposed sponson design. It looks a little like the Gillamator .12 SAW design. I expect to have them installed on the boat and tested by the end of the month. As always any comments would be appreciated.

I soaked the new starting belt in glow-fuel for a couple of hours in the coiled position. The belt is showing zero wear even when it is rubbing the flywheel. The belt is more rubbery and slippery than before. New belt is a Prather 15" belt.

The strut has been shimmed to the left with small washers. Still need do more fine tuning as I'm still not running the rudder perfectly in the center.

 

[TomMoorehouse]

i think the new design looks better....

remember you will need some kind of non trip chine if your doing oval.

 

[Eric Perez]

Here are some pics of the modified hammer cut front spoons.

I will test it tomorrow.

 

[Eric Perez]

Since my stuffing tube goes through the radio box and does not come out until 4 inches ahead of the transom my angle on the motor small. I originally used an MACS marine header because of the non-horizontal engine placement. I swapped the header for the straight "air plane" MACS and the pipe stays almost horizontal with the tub. Looks better and will help on those windy days.

I put my Pro-Boat Miss Bud on the scale it was double the weight as my Nitro Trident. The Bud runs wett in calm water -but it runs just right when the water has a little ripple on it.

Since I'm looking for something I can run on the oval with the big boys I think I will take this approach to the design of the new Nitro Trident. I will try to reduce the contact areas of the spoons to make the boat stick to the water.

This reminds me of my little electric cat. On glass water it would not run very free -bring on the waves and the wind and that little boat would run like a champ!

Picture of the Ntro Trident SR12 with MACS airplane manifold

 

[Hammerhead]

How long is your pipe, Eric. Looks a little long. I'm running mine at 7 1/2 inches. I think Tom is running his at 8.

Do you have a video cam? I'm really interested in seeing it run. Even a 10second vid would be cool.

Hammer

 

[E]

Tom the pipe is at 9" +/- 1/2" I run 15% nitro. I still have not done a whole lot of experimenting with pipe length with the Nitro Trident and the new Picco engine. That's next on my to-do, that and getting the new sponsons made.

I'm also contemplating on making a new 24" Aggressor CAT that can hang with the 3.5 tunnels.

I think that Garry Preuss mentioned that a common mod to the MACS pipe is to shorten the stinger. Do you have any mod ideas on the MACS pipe?

I don't have a good way of getting digital video of the boat. I've got a regular VHS-C camera that I can use -I am still debating on the usefullness of a video digitizer for the pc, they are only like $85 but appart from nitro trident footage I can't really think of other uses. The money might be better invested on a new digital camera with video-clip options

So many choices, so little time -and money :

Eric Perez

 

[Hammerhead]

That's the ticket. Those video clips are great. No B.S, right to the point, and don't take an hour to download.

Go with the digital camera.

Hammer

 

[wswatzell]

Eric,

i have a Digital Video Camera. They are the only way to go, & the prices have come way down since I bought mine almost 4 yrs ago. Many more options & less money. ;D I would get one with a "flash card" option for taking still pictures. If you don't, then it uses part of the tape, so the image quality isn't as good.

 

[Eric Perez]

Did a bunch of running on the pond today. The hammer-cut spoons are really making a difference. I spent most of the morning running the boat in the rough spot on the lake.

I was really trying to figre out why the boat had failed me in the back-straight last weekend. It was quite rough that day and my boat was getting out of shape too easily.

From today's testing, the removal of extra contact area on the front spoons has made the boat react much better on the rough spots. The only draw back was that now this put less pressure on the rear and strut height and angle are now more important to help keep the rear end from hopping.

I think alot of the other .12 boat designers are running into the same problems. The boats are so light that the pressure put on the prop is very light.

This is where a higher AOA on the front spoons helps by creating "artificial" force that pushes the prop down on the water.

If the front AOA is small then there is nothing to keep the rear end from hopping like crazy. The other alternative is just to move your CG further back.

The only bad thing of a high AOA is that the running surface must be made just right to keep the front from "launching" off the water when conditions are right.

I will continue to increase the angle of the hammer cut to see how I can optimize rough water running with the current design of the Nitro Trident SR12.

Oh, another thing that I got with the hammer-cut... The boat now turns to the left -when required. I think it's an inherent trait of the built-in anti-trip angle of the hammer-cut. From now on I will incorporate this shape to the bottom of all my sponsons it an all-arround winner!

Picture of the bottom of my modified spoons

 

[Ron Olson]

You've got the Hammer cut pretty close. Actually the cut is further in removing almost half of the rear of your front sponsons.

Boy, I've got to get a digital camera! I'll have to get some shots this week with the old SLR. If you need more weight in the back, maybe go to a larger reciever pack, at least it's useful weight. The Hammerhead .12 has so much room I could probably throw in 1/4 scale servos and a 6-cell pack!

 

[Eric Perez]

Well, came back from the pond

Running the MACS Pipe and Header cut to 7.5". Bumped up the nitro to 40% and lowered the head clearance(Running only the thin washer) with the Picco XP. The plug is still holding up.

I also cut the stinger on the MACS pipe, can't really say if it helped or hurt performance - Can't never find a radar when you need one.

The boat is running better... Past the 40MPH mark not sure exactly where with the calibrated eye-ball method...

I switched out the Prather S215 with an Octura X438 after some strut adjustment speeds seem equivalent to the S215.

I think the Octura X438 has a bit more pitch but is just a tad smaller, the boat seem to like the new prop.

The next change is to do another Hammer cut on the other side of the sponson(inside). On my pond I can go WOT in all areas an never let go. The larger pond has rougher water and that's my design target.