Challenger 43

[fred 75]

Rough water last Sunday afternoon (better conditions in the morning...Less Wind)... Maximum Runtime: 35 minutes. Top speed: 66 km/h (41 mph).

https://www.flickr.com/photos/laurent_lamacz/sets/72157706030919511

https://youtu.be/t1qVFVnV-zA

IMG-20190318-WA0004.jpgIMG-20190318-WA0002.jpg

[tebby2]

Very nice run. How did you do against the gas boats?

[fred 75]

First place. It was a 2 hours race.

[tebby2]

Awesome job Fred, keep up the good work! I would have kinks in my neck for a week following the event. Standing, holding your transmitter and racing for 2 hours is hard work. Personally I like sitting if I have open water and a run time of 20 or more minutes. Don't think you can sit and race with the competition is right on top of your boat. March is a little too cold in New England - USA. It will be another month before all the ice has melted from the outdoor ponds. Looks like it was chilly where you were holding the race. There appeared to be quite a few winter coats among the participants in the YouTube video.

Charlie

[Peter A]

Excellent job Fred. Love that rough water, it slows the gassers down, and turns them upside down!

[Peter A]

Fred, I have a question. How are you getting a top speed of 70+ kph with an X457? The speed calc, which I have found pretty close, gives a speed of 60kph. 65-66 is what I get with a Prather 245, and what the speed calc says it should do. What am I missing? I know you are a bit lighter with the 16AH batts, but the weight does not make a great deal of difference IME. What am I not getting right here? The Prather has a bit more pitch but similar diameter to the 457, therefore gives higher speeds.

[Brushman]

Hello,

this is also very surprising for me to have this 70Kph speed with this prop. some people are very good for speed/runtime optimization. the secret is a combination of distance at the transom and height of the prop, work on the prop, some work at the rear of the hull... Some french racers are really talented to extract 5-10% more speed, and also 10% in run time...
This challenger hull is also exceptionnal for its low drag...

[fred 75]

Hi Charlie and Peter,

First of all, there is a misunderstanding: I am not alone during the race. It’s a teamwork: 1 or 2 friends are with me for 2x1 hour race or 2x2 hours race. That’s the spirit of that kind of race for me (and In France, generally speaking...a kind of tradition...)... «*!**pilot*!**», «*!** co-pilot*!**», and someone for mechanical things and packs changes. And we switch. It’s a kind of training for the main event: 24 H race (Viry). It’s a very nice feeling to see your friends race with your boat. They can give you good advices and their perception.

For the speed, all is about tuning, time, work...and Luck sometimes ...Speed calculator is just a good starting point. Many ways to impove slippage.

Brushman is right ...about the hull particularly...

[Peter A]

Hmmm would have been good to get a Challenger hull, but difficult to get one here, certainly costly, but I may save my pennies and see. And I understand Aeromarine can be hard to communicate with.
My boat is running clean and free. I put on some trim tabs and that has improved the ride and turning, especially left turns. I can turn hard rudder at full throttle and the boat does not 'misbehave'. I might look at making some spring steel turn fins that are a bit thinner, but I don't know where I can make a lot of gains. I think a bit of prop work is in order, de-tongueing a bit should unload it and improve current draw, perhaps gain a little speed.

Any hints on improving that 'slippage'?

[fred 75]

In my opinion:
1. No trimtabs.
2. Detongued prop could be a good option.
3. As Brushman said : height of the prop, lenght from the transom, angle, could make a Big difference.
4. Weight is not neutral...

I would like to see your boat...and drink a beer with you...

[Peter A]

Trim tabs are close in by the stinger, the hull handles better with them so far. More testing when I get the new motor.
Will detongue the prop. I want to get a hold of an X457, shouldn't be too hard as that was a nitro prop and not many nitros running these days.
Drive line centre height is around 1/2" from bottom of V.
I have a servo adjustable stinger and bringing the angle up while running brings an audible difference in rpm. I am going to play around with end points on this to find the optimum range. My initial settings are reasonably good.

Come down under! Bring your boat with you. I don't drink anymore but...already consumed more than my share. Lol.

[tebby2]

Hello Fred,

Just one more question about your Challenger 43 set up. I finished my boat last week and have had it in the lake four times since the weekend. I'm running the same set up as your boat with the COG at 33% from the stern. I was wondering about the trim angle of your stinger. On my boat the stinger is set parallel with the keel. At high speeds the boat wants to become airborne and jumps off any waves into the air and likes to do 180's if it doesn't come doesn't come down straight and level. I'm very pleased with the 2X6S 16,000mAh setup that includes the TP 4070 440KV motor and an Octura 457X/3 prop. The boat tops out at around 50 -51 mph (on calm seas) according to the Taranis GPS telemetry - plenty fast enough for my needs. However I would like to keep the boat in the water at high end speeds not having it airborne at any bounce off the water.

Charlie

[Peter A]

Hi Charlie

You just cannot run high speeds in rough water, the faster you go, the less control you have. I would suggest that you prop down and use throttle. You need to keep in mind that the scaled speeds are way past that which full size boats do, and even they cannot run flat out in rough water. It is all about running to the conditions. Propping down will give you longer run times also, I would suggest an X457 two blade or Prather 245. Also move your cg back to 32% or so that when the boat jumps it stays level and lands flat.

Peter.