AB Marine Intimidator Endurance Boat

[DanInWV]

I have found from experience so far that 32% is the 'magic' number for CG.

How is this measured? Length of hull, 30-35% total length from the stern?

[srislash]

How is this measured? Length of hull, 30-35% total length from the stern?

Yes the measured length of the running surface. Some hulls have a big overhang at transom but that is not included in the measure. EG: if hull is 41” and has a 4” overhang then it is 30-35% of 37”

[Peter A]

Ok, so after a few weeks of this boat sitting I have decided to get it ready for racing. It will be an oval racer for now, but it may be possible to use it for the original purpose later, we'll see.
So a bit of placing and balancing and what was clear was that it would not work out the way it is to get CG right.
So....
Saturdays mission, tear it out and redo.

Before.
20190112_114609.jpg

Gutted.
20190511_133511.jpg

End of the day.
20190511_154609.jpg

Now a few bits to do. I will make a tray for the rx and battery that will be removable but cover the stuffing tube, and I am waiting on some battery trays which I ordered on Friday and should see later this week.

[Peter A]

Done, ready for a run on Saturday and see how she goes.

20190522_171151.jpg

[srislash]

Woot, woot

[Peter A]

Got it on the water Saturday, no issues with speed, temps and runtime for ovals, it corners well too. Just has a problem with getting really loose at speed, I think the drive line needs to come up a bit to settle the hull in the water. I will fit a flood tube and strut, but I will live with it for club day this coming Sunday.

Screenshot_20190527-073222_RCM Telemetry.jpg

[Peter A]

Well the boat had it's first racing yesterday. Straight out and won the first two heats, second in the third and slammed upside down in the fourth for a DNF. That is against bigger gassers.
That ticked me off as one boat tried to squeeze inside me when I was in lane one for the start, then cut across me for turn one and then his son cut me in turn 1 and I was out. Nothing like the same old people not holding lanes (basically cheating) to get in front! Fortunately no damage and the hatch seal works great.
Rant over, I was pretty happy with the way it ran. I had changed the turn fins and readjusted the stinger and trim tabs. It only used 2400 mah for a race on an X452/3. Next is change out the stinger for a flood tube and strut so the hull will settle better at speed and I can run bigger props. There is more in this boat yet.

[RayR]

Are you using a shaft oiler for these extended runtimes?

[Peter A]

Are you using a shaft oiler for these extended runtimes?

The original setup was grease, then changed to an oil cup with teflon liner due to heat in the stuffing tube. Heat=friction=power losses. The oiling system worked fine and was sufficient for 20 min runs. Now that the boat has been reset up for ovals I have gone back to grease.
In my Osprey which I am using again for endurance racing, I use grease and have a spring loaded pressure pot I made which continually pushes grease into the stuffing tube as it runs. This works well.

[Peter A]

Update. I have fitted a flood tube and am awaiting parts from OSE (hopefully see them today or tomorrow) so that I can finish the strut conversion and hopefully test this coming Saturday.
Will do some pics then.

[Peter A]

Ok so having changed to a strut/floodtube setup here is where I am at. If I set the strut down the boat chine walks at speed. When I lift the strut up the chine walk goes away but I get porpoising. Not short sharp porpoises but long bouncy ones.
I have tried adjustments to the strut height and angle, I find that a bit of negative is helping. I have adjusted the CG as far as 35% but that hasn't fixed it.
If I lift the strut too high the prop loses a fair bit of bite. I have tried different props and am running on a X455/3 atm. I have tried a ABC 2414/4 as the original owner reckoned a four blader used to settle it down.
It is only when at full throttle I get the porpoising. I could just prop down more and lose the top speed but I want to win! LOl. Actually I am winning and the top speed is better than the gassers, just want to get rid of the instability if I can.

Any thoughts anyone?

BTW I changed out the motor for a TP56110 650 kv and have gone back to 10s. I am running it so far on 1P for a heat race, but can go 2P for longer running or extra weight.

[srislash]

Geez this sounds like my DF 35”, man I fought with it just as you are. And pretty much same results. The only thing in the end was installing trim tabs. I did not want to run them but... and now it’s solid as can be. Took very little trim.
Another thought, a longer strut? Like get the prop further back from the transom. This thought since you mentioned the negative helping. Or how about a ABC prop with 15 or 17* rake?

[Brushman]

hello,

more weight can help to reduce porpoising, with the 2P setup?

[Peter A]

The boat has trim tabs, I hve tried with and without, the boat corners better with them but otherwise they don't have any real effect on the porpoising issue. The 2414 prop is 15* rake, the problem occurs when the speed gets up, I will have to throw the telemetry in and pinpoint where it occurs. I am using a long strut also. More weight is definitely the next thing to try, so I will run 2P next chance I get on the water. Just a matter of playing around untill I find the 'sweet spot'.