21 Wild Thing Cooling

[BobBonahoom]

My 21 Wild Thing is my first mono and I am struggling with it. I can't seem to get enough cooling water to the engine. The line is clear, so I am wondering if my rudder set up is the problem. Can anyone tell from this picture? Does the inlet need to be on the other side of the rudder for a mono?

Thanks

 

[Terry Keeley]

I've found that cutting the water back and richening up the needle cools the best.

Looks like a lot of prop, what is it?

 

[brad nichols]

Do you have it trimed to the right as this would take water away from the inlet in the rudder? If not flush from head out through the rudder as it may be clogged in the blade. Or do richen and prop down.

Brad

 

[BobBonahoom]

Terry, the prop is a 1614/3 that Sholund did. 42 mm dia, 2.8" COB pitch and 3.1" TE pitch. I have an X-440/3 and an M440/2, but neither seem to be as fast as the 1614. What do you use?

Brad, not sure about the trim, but that makes sense. Usually boats want to turn right so you put in left trim, which should push more water through. I will check it.

Maybe I am too lean? Not used to listening to a mono. I need to spend a whole day with this boat to "get to know it"

 

[John Finch]

Bob,

First off your rudder is way to long. That will push the bow down and cause lots of drag. The rudder pickup on either side is fine but the hole really should be openned up a bit on that particular rudder. I always drill a second hole on the other side of the rudder so water enters on both sides. Terry is right on with the prop size. If the prop is too large for the boat/engine combo that will heat the motor big time. Also, you need to run the tuned pipe longer on a mono than on a hydro. Just some thoughts to consider.

 

[brad nichols]

Listen to John as it is his boat design and he will get you going in the right direction.

Brad

 

[BobBonahoom]

I was hoping John would chime in. Thanks all of you!

 

[Terry Keeley]

Sorry, forgot about this.

I've got a gear setup so my props are bigger than normal, but when I ran a Seaducer sub surface the best prop was the 440/3.

I bet you're over-propped and possibly lean. I've found my mono has to have a coupla "burps" down the saw to be right, if it screams the whole time it's over center.

What motor/pipe/fuel/plug you running? How long is the pipe? (engine C/L to middle of band if any)

 

[BobBonahoom]

Sorry, forgot about this.

I've got a gear setup so my props are bigger than normal, but when I ran a Seaducer sub surface the best prop was the 440/3.

I bet you're over-propped and possibly lean. I've found my mono has to have a coupla "burps" down the saw to be right, if it screams the whole time it's over center.

What motor/pipe/fuel/plug you running? How long is the pipe? (engine C/L to middle of band if any)

Terry, I am running a Nova 21-T 7 Port with an OPS 3280 pipe and a standard medium heat plug on 60% Punch fuel with 12% oil. I can run my hyros at 8" to 8-1/4" with that set up, so that is what I was doing with the mono. But like John said, the pipe is probably too short. I just milled an additional slot on the right side of my rudder for water and made both holes bigger. I cut the rudder off about 1/4" below the water slot. I am working on the pipe right now. I am thinking of going all the way to 9", but that seems really long.

What do you guys have your pipes at?

 

[BobBonahoom]

What a difference! Cutting off the rudder, doubling the water flow and lenghtening the pipe to 8-1/2" made a big difference in performance. The boat is looking competitive now.

 

[brad nichols]

Way to go!!

Brad

 

[Terry Keeley]

What a difference! Cutting off the rudder, doubling the water flow and lenghtening the pipe to 8-1/2" made a big difference in performance. The boat is looking competitive now.

Good stuff! You will prolly get to 8" or so with the 3280 and an X440/3. The Speedmaster mini rudder will help too, it's thinner and helps a bunch.

What plug? 21's like fairly hot plugs in my experience. Still running the 1614/3?

 

[BobBonahoom]

What a difference! Cutting off the rudder, doubling the water flow and lenghtening the pipe to 8-1/2" made a big difference in performance. The boat is looking competitive now.

Good stuff! You will prolly get to 8" or so with the 3280 and an X440/3. The Speedmaster mini rudder will help too, it's thinner and helps a bunch.

What plug? 21's like fairly hot plugs in my experience. Still running the 1614/3?

I tried the X-440/3 and it was slower than the 1614/3. It seems to really like the 1614 and does not seem to be overloaded by it. I was running a cold pug (99) before because anything hotter would vaporize. Today I moved down to a medium (97) and no problems. I did not see any change when I put in the hotter plug. (I have some work to do to get the needle right yet). I don't have a 3rd channel needle in this boat, so it is trial and error.

I will check that rudder out.

I run 8" pipe on my hyrdos. John said you can't go as short on a mono, so I went out to 8-1/2". Maybe thats good with the 1614.

 

[Terry Keeley]

What a difference! Cutting off the rudder, doubling the water flow and lenghtening the pipe to 8-1/2" made a big difference in performance. The boat is looking competitive now.

Good stuff! You will prolly get to 8" or so with the 3280 and an X440/3. The Speedmaster mini rudder will help too, it's thinner and helps a bunch.

What plug? 21's like fairly hot plugs in my experience. Still running the 1614/3?

I tried the X-440/3 and it was slower than the 1614/3. It seems to really like the 1614 and does not seem to be overloaded by it. I was running a cold pug (99) before because anything hotter would vaporize. Today I moved down to a medium (97) and no problems. I did not see any change when I put in the hotter plug. (I have some work to do to get the needle right yet). I don't have a 3rd channel needle in this boat, so it is trial and error.

I will check that rudder out.

I run 8" pipe on my hyrdos. John said you can't go as short on a mono, so I went out to 8-1/2". Maybe thats good with the 1614.

Yup, sounds like you're finding out what it wants.

Any speeds yet? BTW, don't believe all the "keyboard" speeds out there, my 2x champ runs 47-48 in race trim, seen 56 once on the gun but could never race it like that.

 

[BobBonahoom]

Mine was doing about 42 on our pocket radar before these changes. It is handling much better now, which makes it seem a lot faster. My guess is, that it may be getting near 45. Thursday, when my son is with me, we will check the speed.

 

[BobBonahoom]

Terry, how deep is your mini-rudder below the bottom of your hull?

 

[shoboat]

Bob,

You may have to reduce the diameter of the 1614/3 Chopper just a little for better RPM.

We have been working on the next step up the 1615/3 Chopper with 20 degrees of Rake

and if you have a great motor set up what a difference this propeller can make. We have

Found 40 mm is the way to go so far in testing. I have cut down some other 1614/3 Choppers

and they run Very Well also.

We are always looking for a little more in our set ups.

Thanks,

Mark Sholund

 

[BobBonahoom]

Bob,

You may have to reduce the diameter of the 1614/3 Chopper just a little for better RPM.

We have been working on the next step up the 1615/3 Chopper with 20 degrees of Rake

and if you have a great motor set up what a difference this propeller can make. We have

Found 40 mm is the way to go so far in testing. I have cut down some other 1614/3 Choppers

and they run Very Well also.

We are always looking for a little more in our set ups.

Thanks,

Mark Sholund

Hey Mark,

I have two of the 1614/3 props. The second one has too much diamter even though it has slightly less pitch. It loads down the engine and does not run well. I am thinking I will take the diameter down to 41 mm? That should allow more RPM to develop, shorten the pipe a little, etc. What do you think?

[SIZE=small]As Shown[/SIZE] [SIZE=small]Meas 1[/SIZE] [SIZE=small]Meas 2[/SIZE] [SIZE=small]Average[/SIZE] [SIZE=small]Prop[/SIZE] [SIZE=small]Pitch COB[/SIZE] [SIZE=small]T.E. Cup[/SIZE] [SIZE=small]Pitch COB[/SIZE] [SIZE=small]T.E. Cup[/SIZE] [SIZE=small]Dia mm[/SIZE] [SIZE=small]Pitch COB[/SIZE] [SIZE=small]T.E. Cup[/SIZE] [SIZE=small]Notes[/SIZE] [SIZE=small]ABC[/SIZE] [SIZE=small]1614/3 Chopper[/SIZE] [SIZE=medium]41.6[/SIZE] [SIZE=medium]2.9[/SIZE] [SIZE=medium]3.2[/SIZE] [SIZE=small]Sholund more pitch, less dia[/SIZE] [SIZE=small]ABC[/SIZE] [SIZE=small]1614/3 Chopper[/SIZE] [SIZE=medium]42.0[/SIZE] [SIZE=medium]2.8[/SIZE] [SIZE=medium]3.1[/SIZE] [SIZE=small]Sholund more dia, less pitch[/SIZE]

 

[Terry Keeley]

Terry, how deep is your mini-rudder below the bottom of your hull?

About 1.5":

I noticed you don't have any tabs on it, here's what I ended up with to handle the "marbles".

BTW, had it out today, the track was hot and sticky, best I saw was 46.6...

 

[BobBonahoom]

Terry, I have my Speedmaster 21 standard mono rudder at 1-1/4" and it turns great. I do have trim tabs on it, but only two, see pic. I put fins on mine, but I see you don't have them, instead you have two sets of tabs. Did you find that to work better?