Now the trouble starts

[snowdog-2112]

Hey all,

Here's a strange problem that I hope was just an anomalie. :blink: In an attempt to clear a porpoising problem, I lowered the engine on one of my boats and ran it yesterday. After doing so, the engine was very difficult to needle and the revs would not pick up. Also, the short session was made even shorter by the flex shaft breaking. I can see the shaft breaking if the prop was to high but with it "more in the water" and less porpoising why would it break? As I mentioned earlier, I hope it was just an anomolie.

Anyway, I was running a remote needled CMB .21 with a (redhead water jacket)??? on a K&B lower unit and a P215 propeller. Not that those are important but thoght I'd throw them in there for S'sss & G'sss. :lol:

Thanks for the help.

Snowdog

 

[Jerry Dunlap]

Brian,

A 215 is a lot of prop for that motor - at least it is in my opinion. I run either a stock X440 or a X640 trimmed down to 37mm diameter.

JD

 

[GTR]

Hi SD

Your demonstrating classic too big prop, too deep in the water syndrome. Your shaft snapped from too much load probably and your needle is difficult to set because the motor's is overloaded. A P215 is about equal to an X541.

For the hopping you could have tried a touch of down trim on the ob or a little weight on the tips.

Keep trying

 

[Bart Drieghe]

Like i said lol , u should have been busy with someone and not with your boats lol :lol:

just kidding ,

Bart

 

[Chris Wittrig]

Another thing to try. Somtimes the boat will show a porpoising charcteristic if there is too much negative trim. It really depends on the boat type as well. One of the first things we will do is trim it out and lower it down (just to get the height back to where it was before you trimmed it out). What could be happening is it is driving down the nose and bouncing back up.

Absolutely true about too much load causing the cable break. With as large of a prop as you are using you would want it a touch higher than if you were using say an X440 or cut down 640 as Jerry suggests.

We manufacture an engine mount both for the .21 and .45 that allows very fine height and trim adjustments. You will find that once you are in the ballpark very minor changes make a big difference.

Good luck.

 

[Grimracer]

Right on Chris..

Snow. Try this when you get a chance.

Go to the LHS and pick up some evergreen plastic angle strips..12" long is good. 1/8”X1/8” is all that is needed.

Ca the strips to the bottom of the sponsons. Look at the letter V and this is how you will glue the strips to the bottoms. The V is pointing down. Place this towards the outer edge of the bottoms. Near the nontrip..

It need not be pointed in front and it should be glued from the back of the sponsons forward. In other words the strip will end 12" from the back of the sponsons.

Make sure you set the motor back as it was.

If this does not help...Humm...tell me what kind of prep work you do to the bottom of the sponsons...if any....

Grim

 

[snowdog-2112]

All,

I'll try to answer these one at a time and in order.

JD, love ya and all you do for us but my question about the 215 is; wasn't it made for the 3.5 engine?

GTR, trim is zero right now with quite a bit of weight up front...about 7 ounces. I'd hate to add more.

Bart, she was with me! B)

Chris, maybe your suggestion would be the easiest and the first to try. Maybe I'll get to try it on Sunday.

Grim, I hear you pal and I'm gonna show my ignorance here but what is the purpose of putting the strips on in relation to the porpoising?

And FYI, the boat sticks to the water like glue in the turns so no problems there!

Thanks all again,

Snowdog

 

[Grimracer]

Snow

Lift and surface tension is the reason.. A lot like Chris said… the water is sticking to the bottoms and climbing up and down, up and down the length and width of the sponsons. The strips will make the boat run a tad higher out of the water helping eliminate the problem. They will also shear away the water before it as time to lock on to the nontrip.

If the boat sticks like glue in the corners or anywhere for that mater we have a problem.. The boat should fly at all points of operation.

It can hunker down if you need to lift going in to the corner but past that point the boat should be in full flight even if you are not squeezing full power.

Grim

 

[snowdog-2112]

Grimmy,

So, if I hear you correctly, you're saying that the boat "turning on a dime" while wide open is the sign of a problem? I'm guessing that a bit of positive trim from this point will provide many answers? What shall I look for? I have the height right now at a point where the boat bounces just very slightly. Do you suppose that 1 degree of positive is going to be enough? What other suggestions do you have?

Snowdog

 

[Jerry Dunlap]

re: wasn't it made for a 3.5 engine?

There's lots of props that could be classified "made for a 3.5 engine." It has been my experience that some work better than others. I haven't had much success running the 215. Doesn't mean it's not a good prop, just that I've found better choices.

JD

 

[Grimracer]

Grimmy,
So, if I hear you correctly, you're saying that the boat "turning on a dime" while wide open is the sign of a problem? I'm guessing that a bit of positive trim from this point will provide many answers? What shall I look for? I have the height right now at a point where the boat bounces just very slightly. Do you suppose that 1 degree of positive is going to be enough? What other suggestions do you have?

Snowdog

Snow

Not realy...just if you are a racer..

The boat (mine always run on a cource) turning like this could be a problem if its winning racers you are after...sorry but as a racer i guess that im always thinking racing and others might not... Shame on me...

When it comes to racing and winning races..i have always said..

Dont just drive you boat around..drive your boat around something..

What kind of prep work do you do to the sponsons after you have built the boat?

Lemeknow

Grim

 

[Chris Wittrig]

Wow...7oz up front (depending on what front is) is a lot. That too may be the problem. With the engine parallel it could be trying to fly/hang the nose, but the weight is causing it to fall over. Again, depending on the boat, I would hesitate to trim it out much past parallel. .5 to absolutely no more than 1 degree but, again, depends on the boat. Did you ever tell us what it is?

Take some of that weight out 1 oz at a time and make one and done laps. It is entirely possible as well that you were real sensitive to height and were blowing the tail at the top end and nosing the boat over. Like I said before, that ballpark is a small one. A cleaver prop like the 215 should be fairly neutral, but trying an X series prop and bending on it accordingly to help the back squat down a little may be helpful.

So many things that could be causing the problem.

 

[snowdog-2112]

What kind of prep work do you do to the sponsons after you have built the boat?

Grimmy,

This boat was built by Topfuel443 so I can't answer anything about prep work. He said the boat ran well when he had it so I don't want to point at it. I think it's just that I'm having trouble finding the sweet-spot.

Snowdog

 

[snowdog-2112]

Wow...7oz up front (depending on what front is) is a lot. That too may be the problem. With the engine parallel it could be trying to fly/hang the nose, but the weight is causing it to fall over. Again, depending on the boat, I would hesitate to trim it out much past parallel. .5 to absolutely no more than 1 degree but, again, depends on the boat. Did you ever tell us what it is?
Take some of that weight out 1 oz at a time and make one and done laps. It is entirely possible as well that you were real sensitive to height and were blowing the tail at the top end and nosing the boat over. Like I said before, that ballpark is a small one. A cleaver prop like the 215 should be fairly neutral, but trying an X series prop and bending on it accordingly to help the back squat down a little may be helpful.

So many things that could be causing the problem.

Chris,

The C/G is set at 33% with that amount of weight and besides the hopping, the boat runs and turns very well as I described above. But as Grimmy mentioned, it might be to good as the boat sticks to the water like glue in the turns. I haven't had a chance to run the boat with positive trim yet as we went to Paris yesterday and today was WAY to windy.

Hopefully, I can get a report to you Monday.

Thanks again,

Snowdog

 

[MarkScott]

Wow, I'm running a S215 on the motor to the left and it flies.. Maybe I should go back to a 440... Then again, there's a x1440 coming to my door soon..

Mark..

 

[snowdog-2112]

15 Mar 04

I ran the boat again today after putting in a slight bit of positive trim and changing the prop to a 1440. I wasn't able to determine if the porpoising quit due to rough water as it was quite a bit "lumpy". The positive trim seemed to be a bit to much as the boat blew over on the second pass. Right in front of me!

After several retrievals due to blowovers or dumpings, I almost gave up as the boat was not handling the "lumps" very well. Then I considered a prop change. I removed the 1440 and put an x440 on and the engine not only ran better but the boat seemed to handle the water better except for an occassional "squat" in the turns. After two passes and a bit of extra speed in the left turn, it seemed that the boat wasn't going to make it so I slowed the throttle to make the turn. This was not a good thing as the boat died in turn two and with the wind blowing from behind me, it was too far to reach with the tennis ball and that is where I end my update for today. :angry:

If there are any particular questions you might have, let me know.

Thanks,

Snowdog

 

[XtremeRcBoats]

Hi Bryan,

i hope you got your boat back. We once before tried my 1440 on your tunnel and back then it didn't ran very wel either. I now also have a x440, nice little prop. The 1440 cavitates a lot at first but when it pick up it goes veryt well. Still my no. 1 prop. Bought it a couple years back from Jeremy Lee.

 

[Grimracer]

Snow

What hull is this?

Xtreme

What mods were done to the 1440 prop..

ROCK ON

Grim

 

[Slideblues]

Hinge pin slop might be whats causing the weirdness.

Hold the boat in one hand and try to move the skeg fore and aft with the other, new bushings and a new hinge pin might take up the slop if any,

Just a guess,

Gene

 

[snowdog-2112]

Gene,

You are dead-on the money! I had known the hinge pin was loose but didn't consider it an issue. I WILL correct it Post-haste! :lol: Man, you learn something everyday! Thanks!

Grim,

It's a TopFuel443 special. It's the predocessor (sp)? to Slideblue's SAW boat he and Topefuel were working on.

Snowdog