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wpw4
11-10-2009, 10:36 PM
Can anyone help ? I powered up a Dumas ChrisCraft runabout with a 3p Ammo 36-56 2600kv motor,Castle 120 amp ESC. It draws 50 amps through two 2s2p A123 packs. It is pretty fast (25mph) for the hull and gets on plane very nicely. All data is from an EagleTree data collector. My biggest issue is that it has flipped; well actually slow rolled, and gone turtle twice while powering down into a gentle turn. I can't remember if it flipped in the same rotational direction, it happens too quickly. Is there any experience that would lead one to think a turn fin would solve this problem? ?? Or some other trick?
Pictures of the boat are attached

Rumdog
11-10-2009, 10:40 PM
Prob. because there's no driver.

Jesse J
11-10-2009, 10:50 PM
Come on Rumdog, the guy is being serious - he must have fallen out on the roll!

I wonder if the angle up to the gunwales at the stern might hook you under? I bet that design never had more than 15-20 mph in mind (imagine the real boat in a race with the unlimited hydros and winning?). My personal touch would be some chines; I like the 60deg angle plastic they sell in the architecture dept of the bookstore or at the hobby shop.

Not sure about turn fin, try it?

wpw4
11-10-2009, 10:58 PM
Thanks So as I understand it, your suggesting that it might be sliding in the slow turn and maybe the wake collapse from powering down hooks or pulls one side under.
Would you add one or two chines to each of the planing surfaces ? Can you suggest a picture of a hull I can emulate?
Thanks, It would really make my yachting experience more enjoyable.

sailr
11-11-2009, 12:41 AM
If you could make a video of what it is doing it would be helpful. Is the nose dipping in the turn and then it rolls over? Maybe you need more weight in the stern? Also, keep the weight as low in the hull as possible. Being Top Heavy could also cause it to roll over.

fly2mike
11-11-2009, 03:57 AM
Beautiful job on your Chris!

Jesse J
11-11-2009, 11:45 AM
Here is what I was imagining. You could add this triangle directly to your white water line.

Hope this clarifies. I added an inset of your picture with the green lines where I would add the spray rail. Might help deflect water as well as add lift to the outside on your turns. Just an idea; can't hurt.

Jesse J
11-11-2009, 11:49 AM
sorry pic is now attached

wpw4
11-11-2009, 01:56 PM
Thanks The picture is clear enough. The strip on the waterline would be easy enough to try. I had a nice YouTube video posted but got shut down by the music infringement natzi's. I will just chop it down to a couple min and post it without tunes. You can kind of see the rolling action in the turns. It really handles nicely at 1/2 throttle. The batteries are as low as they can get, and the bow does not dive. when turning. It does push a pretty big bow wake as it comes off plane. I am not looking to race this puppy, but it sure would be nice to make a couple trips to the pond without a small watercraft accident.

Jesse J
11-12-2009, 07:15 PM
let us know when you have vid up, am very interested to see how she rides.

wpw4
11-15-2009, 12:07 AM
I finally got the Chris Craft video up on youtube, You can see a couple spots where it is slowing down into a turn wher it gets pretty far over on it's side. Sorry no video of the actual deed.
See video here
http://www.youtube.com/watch?v=ZzMskuUXiME

sjslhill
11-15-2009, 09:32 AM
Will it do 82 at the time trials?

Excuse me, I really like what your doing and I hope to get it going. Do you like the A123 batteries?

Hats off to you!

Jesse J
11-15-2009, 10:46 AM
Really nice vid, I didn't see the flip though? I do see lots of water riding up along the sides; if it were me, I would run those plastic triangles all the way up to the prow. I designed a flat bottomed boat and it performed similarly until I gave it these spray rails. It keeps the water shooting out and the boat drier.

good luck and great little pond for an excellent build. (you do need a dude and a babe to keep things running good, though)

sailr
11-15-2009, 12:12 PM
The boat looks really good! Runs at a nice attitude. Sorry, I couldn't detect a handling problem on the video. Perhaps you could make another and get it to 'flip' as you call it.

wpw4
11-15-2009, 05:35 PM
That's what is so frustrating is that it runs really well; until it rolls over and turns turtle. I will have to try the strips like Jesse suggests,

With regards to the A123's --- They provide a bunch of power, I get about 17 minutes of goofing around in the pond with my 8 cells. each pack is 2s2p so that's 4500mah @ 6.72v per pack. The packs are a real pain in the neck to make though. The first time I bought a Dewalt power drill pack and took it apart. You have to be pretty careful cause you can weld stuff with those batteries. The second set I bought individual cells from RClipos on line. They were really hard to get the connector bars installed because they didn't have the spot welded tabs to solder to. Anyway performance wise they will let the motor pull 50 plus amps and the pack stays above 11 volts for most of the run. I have attached some plots from my Eagle Tree data collection so you can see the voltage drop as the curent draw spikes at WOT. I like the RPM vs GPS speed, man that prop spins 56K rpm !! As you can see the pond isn't very big so i can only get about 3 seconds of full throttle before the rocks start getting bigger.

Back tothe A123's, I would sure supggest buying them from Max Amps as they are already assembled and in a waterproof case. The big draw for me was that I could bury them in the hull and not worry about them catching fire while charging. I am going to try a couple of my car lipos and see if the weight change affects performance.

Rumdog
11-15-2009, 06:47 PM
A longer rudder would help for sure.

sjslhill
11-15-2009, 09:24 PM
Nice boat....A123's are easy to solder with a 80+W iron.

thanks,
Steve

treystoys
09-21-2014, 08:58 PM
I realize this is ancient, but the issue is the prop, not size, but blade style. I know most people don't think of an x440 prop as a lifting prop, but its not meant to be submerged on an angle and spin that fast.

Trey

dasboata
09-21-2014, 09:50 PM
Nice job on the boat Pretty sure the problem is from the flat bottom. I would defintely install a turn fin. I would start with the scale fins that mount to the keel of the boat so you can keep the boat looks,, scale !

treystoys
09-21-2014, 11:32 PM
Putting skid fins on the keel of an already tipsy boat will likely make it a bit more roll prone. One fin on the preferred turning side of the transom would help, but then for a fun runner that will be turned both directions you'd want one on each side but having a nearly flat bottom transom area will keep both fins in the water turning each way thus killing the usefulness there too. I think a scale like prop with way less rake and probably going from a 3s to a 2s set up would make the boat perform more scale like, but the prop change would keep it from rolling. either way.

Trey

dasboata
09-22-2014, 02:17 PM
Putting skid fins on the keel of an already tipsy boat will likely make it a bit more roll prone. One fin on the preferred turning side of the transom would help, but then for a fun runner that will be turned both directions you'd want one on each side but having a nearly flat bottom transom area will keep both fins in the water turning each way thus killing the usefulness there too. I think a scale like prop with way less rake and probably going from a 3s to a 2s set up would make the boat perform more scale like, but the prop change would keep it from rolling. either way.

Trey
I don't agree I might be wrong or where it is mounted but I see a lot of skiff using them on there bottom ! and I am pretty sure he does not want a turn fin hanging off the side of this boat just saying !!!

treystoys
09-22-2014, 06:29 PM
My statement about the skid fins were of what "would work", not what he wanted. Heck even his trim tabs look out of place on there, and really aren't needed. COG does wonders on a submerged drive set up! Anyhow, keel mounted fins just will not work...look closer at the pictures of the bottom of the boat...see anything that may resemble a keel mounted skid fin? His entire stuffing box is one big skid fin, adding more will make his boat behave worse. A subsurface prop looks nothing like the x440/3 he has on there and would function with way less rake, and take away the paddle wheel effect that a surface drive prop will have on a subsurface drive boat.

I'm gonna let this issue die, lol this fella may never even see this since its a 5 year old article. I happened on it, just lurking. I have a bit of background here as well, I was big into electric boating, mainly the racing variety, back in the day. I got out of the travel racing right around the time lipos were introduced into the sport, but my roots go way way back. Like when a fast electric boat was a scorching 15mph ;) And we were converting MRP sub surface kit hulls into surface drive boats. Fun times...lol

Trey

Stillwet
08-12-2018, 10:02 PM
i realize this is not the same exact CC, mine is the 1941 16' Hydroplane. i'm bringing this back (after another 4 years) because i also knew there might be a problem going from brushed (scale speeds). with all the reading i did i'm surprised i did not come across this thread during my construction. i'm taking heed to what was mentioned here and log into my notes. that said Thanx to all that put your (.98 cents worth in being now 2018). this project has been done for two years and yet hasn't seen water since the final hull test. so much time into such a small boat but they make a wonderful trophy. the only thing left to do is the windshield, the first app was too flimsy, i've been looking for thicker material.