Finicky pipe

[Don Ferrette]

Don, did you remove any material off the trailing edge of the blade other than the notch at the base?

Just do the notch, start small & work your way up as needed.

 

[John Knight]

For those that are confused exactly what and how to drill out the pipe, the following is provided for you:

1. Look at the pipe through the stinger end. You will see the internal baffle a few inches inside the pipe.

2. Take a drill bit slightly SMALLER than the ID of the stinger. DO NOT use a drill bit that is the same size as the stinger. Must go smaller!

3. Drill straight through and open up the baffle. Again, DO NOT drill any of the stinger out.

4. Flush, flush and flush all metal filings out.

What this will accomplish is to open up the baffle some to release the gases and backpressure. Better pipe flow means more potential rpm.. The internal baffle is tapered towards the stinger so looking at it from both ends will not look the same. Just the way they are designed.

If you are reluctant to drill them out that much at first, then start with a smaller bit and test it. Move up to a larger one as you become more bold. I can simply tell you, if you follow # 1-4 above, it should work with no problems. I didn't even detect any needle changes being required. Maybe I was just lucky but it worked.

BTW, these pipes are made in Russia. This guide is only for the AB parabolic pipes. I have not even looked at the black 67 quiet pipe that CMD makes so I cannot comment on them.

John

 

[Heartbeat]

Will this mod work on a 3.5 OPS quiet pipe?

I can't get seem to get the pipe to work.

Thanks

Mike

 

[John Knight]

The only brand that I have experimented on was the CMD's. I would suspect that the principle would logically be the same but cannot say for certain. If you want to take the plunge, maybe in steps, progressively larger, may be worth the while. Sometimes taking the gamble is worth the result. If not, then it will be for the junk box.

Anyone out there bold enough to have tried it before so we can advise our buddy here as to what to do?

 

[tracerbob]

I will be in Atlanta so look me up and I can show you what I have.

John,

How will I find you at the Spring Nats. It might be easier to find me. If Glover Jeffcoat can get away that weekend, We'll be using his trailer. Just look for the one with "Panama City Model Boaters" on it.

 

[John Knight]

Bob,

I know Glover, Chris (& Lisa) and a Keith Timmons, all from the PC area. Would that be you or a brother? My canopy was near them last year.

I have a spare 67 parabolic (my other extra one is at the bottom of the lake in Atlanta) that I could loan to you for testing before you drill on yours. Mine has been drilled. I also have a 84 pipe drilled out. If they don't work, I have some MAC and OPS nitro pipes. I have some T Mod mufflers to quiet them down. If that fails, then Jerry Crowther (Seaducer) and John and/or Andy Brown normally come as well.

The best suggestion that I can give is to bring some smaller props to try. You may be overloading the engine. I have found that the water in Atlanta is harder and sometimes I have to drop a size or reduce pitch in my prop.

I plan on getting there on Friday morning.

John

 

[Eric Canto]

You COULD go through all of that meticulous effort........or..........you could just do what I did at a record trial when I was running out of day light. Just grab a Makita drill, put on a bit that is the same ID as the Muffler stinger and drill the #@$% out of the pipes without even taking them off the motors, do not clean a single scrap out the pipes, then throw the boat in the water and make the first ever official IMPBA passes with a twin over 100MPH............106.8 to be exact......

 

[tracerbob]

Hey John,

I'm Keiths older brother. Got out of boating for a few years, then, Jumped back into it last year. I've known Glover for a long time.

Already drilled out the pipe. Ran it last weekend with a marked improvment in performance. Now I'm just trying to fix a problem with it sagging coming out of a turn. Happens half way through the turn and doesn't clear up until it's 10 feet or so past the exit buoy. I think I'm going to try Don Ferrettes suggestion of back cutting the prop (X457/3) a little and see if it helps unload the prop a little bit. Pipe originally set to 11 inches, moved it out to 11-1/4. Hope it don't rain Sunday!

We'll probably show up at the Atlanta pond about mid-afternoon. Chris should be there too.

 

[John Knight]

Bob,

Good to have you back into the fold. My guess is the prop is loading it in the corners. I know Don well and I strongly suspect he is dead right. Have to unload the prop. Going smaller or reducing the size would be the first step. Keep me posted on the test.

I cannot take credit for the idea. Came from the Crapshooter guys, mostly Tony and his son Brian Jacuzzi. They were among the smokers - creaming most everyone else. Didn't take long to start asking questions!

John

 

[tracerbob]

John, I'm going to try an X455/3 Sunday and see if it unloads in the corners before I back cut my good prop.

 

[Don Ferrette]

John, I'm going to try an X455/3 Sunday and see if it unloads in the corners before I back cut my good prop.

You are going to give up a good bit of top end going to the 455/3 unless you pitch it up significantly. The mod I said to do can be done a little at a time with a round file at the pond, I've done this many times & you won't lose any top speed.

 

[tracerbob]

Hey Don,

I trimmed up the prop a little bit. I think this is a good starting point. Didn't take any material off the trailing edge though, just squared it up.

 

[tracerbob]

Another shot. Comments welcome.

 

[Don Ferrette]

Hey Don,I trimmed up the prop a little bit. I think this is a good starting point. Didn't take any material off the trailing edge though, just squared it up.

Very good. See how it does & if it's not enough don't be afaid to go further with it. just go a little at a time until you get it pulling strong thru the corners. B)

 

[tracerbob]

If it's not enough, Do I widen the cut section out towards the blade tip by increasing the diameter of the cutout without making it any deeper, or...do I trim the entire trailing edge starting at the blade tip, increasing the angle or "rake" towards the root. If this works, look out! I'll take this to the pond tomorrow and try it out. Thanks for all the help Don.

 

[Don Ferrette]

You can go wider & a little deeper on the relief, just a little at a time & run until you get rid of the corner sag. I wouldn't do anything to the trailing edge. B)

 

[tracerbob]

Well, got a run to run a couple of tanks through before the rain set in. There was an improvement, but not out of the woods yet. So, I'll trim a little more and try it next weekend.

 

[Don Ferrette]

Take a small round file with you to the lake next time, file it & run until you hit the sweet spot. Then you can do your final re-balance & finish at home. Been there, done it that way many times.

 

[tracerbob]

Next installment..With the Atlanta race coming up, I pulled the parabolic pipe off and went back to my original setup (Mac pipe/stinger muff set at 11.5). The boats back to haul a$$ trim again. One minor thing though, speed is good in the straights, but it really picks up speed in the corners but with a slight loss of acceleration out of the exit buoy. Any suggestions? One more thing. I was using a X457/3 from Andy Brown.

 

[Don Ferrette]

Next installment..With the Atlanta race coming up, I pulled the parabolic pipe off and went back to my original setup (Mac pipe/stinger muff set at 11.5). The boats back to haul a$$ trim again. One minor thing though, speed is good in the straights, but it really picks up speed in the corners but with a slight loss of acceleration out of the exit buoy. Any suggestions? One more thing. I was using a X457/3 from Andy Brown.

When you say slight loss in acceleration, is it sagging a little? :blink: