Porposing Badly on a Blackjack 29

[Monger]

I'm fairly new at RC boats so a little help would be greatly appreciated. Recently bought a BJ 29, and have been running it on 6S ( very carefully) I cannot get it to run over half throttle without it Porpesing. I've adjusted the strut with a slight neg. pitch/ lowered strut/raised strut, and repositioned battery locations endlessly to correct COG. I have been running CNC 445/642 props also.Pond conditions are usually smooth.

Help!
Monger

[kfxguy]

I'm fairly new at RC boats so a little help would be greatly appreciated. Recently bought a BJ 29, and have been running it on 6S ( very carefully) I cannot get it to run over half throttle without it Porpesing. I've adjusted the strut with a slight neg. pitch/ lowered strut/raised strut, and repositioned battery locations endlessly to correct COG. I have been running CNC 445/642 props also.Pond conditions are usually smooth.

Help!
Monger

Welcome to the bj 29/geico 29/mystic 29 world! That's a common issue. There's a few fife re t way to fix it but the most common is to blueprint the bottom of the sponsons. Yes, sand your brand new boat on the bottom side till the pads are flat. You may need to add resin or epoxy. Then repaint it. If you have a geico....your sol because it's impossible to find matching paint. I put trim tabs on mine and it stopped it. You can add weight to the front and that helps. Strut angle helps too. There are a few threads on it that are either reading. Good luck to you as this boat is a labor of love to get right. I threw the towel in early myself.....but I might would have another one.

[Chrissharp]

Try this
http://forums.offshoreelectrics.com/...inting+sponson
BHchieftain has some nice tutorials on blueprinting the geico/blackjack boat.
Put your boat on a table with the rudder off and make sure the strut is following the table. This boat likes to lift at the transom creating bounce. Most of the bounce can be removed from playing with strut angle but on my boat I feel that the rudder is causing lift because it is not square with ride pads. I left my boats at the lake and will not be able to test this theory for a couple weeks. It is a fun boat but I would recommend extra epoxy over the wood areas as they will start breaking loose. If you run any props over the stock one just watch the temps. With a little patience it can be dialed in.

[champion221elite]

The "dialed-in strut mod" is another good place to start. Basically, you remove the strut from the boat and use a Dremel tool to make an oblong cut in the bolt hole that secures the strut to the transom hardware. This mod allows the strut to have additional down angle to help reduce if not eliminate the hull bounce.

Here's a link so you know what I'm talking about.

http://forums.offshoreelectrics.com/...t-modification

My BJ29 bounced really bad until I did this mod. It runs great now, and I never had to mess with blueprinting the sponsons. Your sponsons might still benefit from a blueprint job, but the strut mod is a fast and free place to start.

[BHChieftain]

Hi,
I made a 3 part video on how to tune the Miss Geico/Blackjack to deal with the porpoising.

http://www.rcchiefhobbies.com/Tutorials.html

As Champion said, you can do the strut mod instead of blueprinting which I'd say removes about 80% of the issue, but blueprinting sure does make the boat handle like a dream. It is easier than it looks. Note, even without any mods, if you set up the strut and COG correctly the bouncing usually is only an issue on smooth water-- once the water chops up a bit it breaks the surface tension on the sponsons and the boat runs better.

If you'd like a copy of the setup guide for this boat (which also covers the strut mod) email me at [email protected]

Chief

[Monger]

Chief,
Is the 2 oz. portion enough to do the 2 sponsons?

Monger

[BHChieftain]

Hi,
Yes, the small tube is enough,
Chief

[Monger]

No Matter Where You Go-There You Are! Thanks Chief

Hi,
Yes, the small tube is enough,
Chief

[Monger]

Chief,
On the sponsons, is the angle still maintained on the sponsons ( Inside edge to Outside edge ) after using the Epoxy? I am about to blueprint the sponsons on my BJ 29.

Monger

[BHChieftain]

Chief,
On the sponsons, is the angle still maintained on the sponsons ( Inside edge to Outside edge ) after using the Epoxy? I am about to blueprint the sponsons on my BJ 29.

Monger

Hi,
Yes, keep the stock angle. All you are doing on the blueprint is to get the sponson flat (take out any concave spots), and also get a sharp 90degree angle off the rear sponson. You do want to get the sponsons even with each other so that if you place the boat on a flat surface there is no rocking, but the sponsons themselves won't be perfectly flat on the table (there is a little "camber" in them).

Chief

[Monger]

Blueprinting Sponsons

Hi,
Yes, keep the stock angle. All you are doing on the blueprint is to get the sponson flat (take out any concave spots), and also get a sharp 90degree angle off the rear sponson. You do want to get the sponsons even with each other so that if you place the boat on a flat surface there is no rocking, but the sponsons themselves won't be perfectly flat on the table (there is a little "camber" in them).

Chief

Thanks Chief!


Monger

[Monger]

Chief,
Thanks for the info. I just finished Blueprinting the sponson's on my BJ 29. Ran it this morning, and I can honestly say a 90% improvement. Will tweak COG of batteries/ Strut position to fine tune this weekend.
Thanks again for all your help. It does really work!
P.S. If I wanted to paint the sponsons, what prep, and paint could I use?

Monger

[Minimac27]

Hi guys I'm also fairly new to the boat hobby and I just wanted to say thanks Chief. I think I learned more in those vids than I would have anywhere else. I did the strut mod and a noticeable difference was seen and now I just need to blueprint the sponsons.

[tool131]

I too am new to rc boats and my BJ 29 was bouncing all over the place and tough to control at higher speeds (anything above 60% thottle) thought It was something I would have to get used to, after making the adjustments Chief showed us the boat calmed down and handles perfect at 100% can't thank you enough. NOW, had can I get my wife to calm down about me getting into rc boating???

[BHChieftain]

I'm glad the tips are working for you!
Chief