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Does she dive? - Dumas Akula?

R/C Submarine modelers

Postby Brady » Mon Nov 17, 2003 1:49 pm

I've been eying the Dumas Akula kit, but will the stock boat dive? Or is she doomed to the surface unless i tinker with the insides? This would be my first sub project (Experience w/ R/C subs = 0) but I want something that will run underwater. Will I have to modify it? And if so, do these systems cost very much, I'm on a real budget here. Thanks a million for the help.

-Brady

BTW, I've already searched the forum for this particular subject and haven't found anything.
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Postby mike byers » Mon Nov 17, 2003 2:30 pm

Brady
The Akula is also my first R/C boat, and I have every confidence that she will dive (it's the surfacing that I'm worried about). There are many experienced modellers who moniter these forums and whom have given great advice to us Dumas people.

If you can get your hands on a copy of SCR #54? (someone help me here) George Prochenko(sp?) has a great article on building the Dumas Akula. Especially on the hull cut @ the bow, I saw this too late to benefit me.

Good Luck! Let us know how you are progressing.

Regards

Mike Byers
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Postby Bigdave » Mon Nov 17, 2003 4:22 pm

She dives she fly's, not a bad first time kit. For the price it is hard to beat. Give it a try. Dave. :laugh:
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Postby Brady » Mon Nov 17, 2003 7:01 pm

For a sec I didn't know what "she flys" meant, but then I remembered the guy from The Hunt For Red October saying "C'mon Big D! FLY!!!!!!!" and the sub doing an emergency blow :;): As for the incorrect fins, do they still look decent enough with a nice paint job, or should I mess with them? I am an avid 1/48 Aircraft builder, so I am experienced with scrachbuilding and such. Thanks a million for the help.

-Brady :)




Edited By Brady on 1069110315
Brady
 

Postby Crazy Ivan » Tue Nov 18, 2003 1:04 am

Hi Brady,

Since you have done your homework, but did not find what you wanted with a Search :( , let me address all of the questions you have asked in your several posts.

From your first post:
- Does it dive- Yes, dynamically, and very well too as built stock out-of-the-box. I will elaborate later.

- Do you need to add a WTC - No, the kit comes with its own vacuum formed WTC. While perhaps not as robust as the more professional (and more expensive) models available, it is more than adequate for the depths the Dumas is designed for. A word about seals here. The stock Dumas control rod and prop shaft seals are crude and almost guaranteed to bind and / or leak. HOWEVER, if you order the kit from Skip Asay at SubTech, he will include his proven, reliable shaft seals, which are in use by the majority of model submariners that I know. Skip's price on the Akula is competative. Some hobby warehouses may charge a few dollars less, but the SubTech seals make Skip's deal the only way to go.

- Is your four channel radio OK - Yes (if it is a 75mhz surface frequency model), you only need three channels for starters: rudder, dive planes and throttle. You need to add just two servos, and they do not have to be mini. The kit is designed for standard size servos (I use Futaba S3003 equivelents which can be had cheap). You will need an ESC (electronic speed controller), preferrably with reverse, and a motor. I recommend an ESC designed for scale boats, not one for fast racing. I got mine from SubTech. If your ESC does not include a BEC (battery eliminator circuit), you will need to add one to provide a regulated 5 volts to the receiver. There is not a lot of room for a separate receiver battery. You will also need to buy the main battery. I like NiMh cells for their light weight and high capacity. I've run up to 2 hours on a charge. Last, you do not NEED, but WILL WANT an APC (automatic pitch controller). More on this later.


Now:

As to the oversized control surfaces, they really do not look all that great. BUT, they are absolutely necessary (well, maybe not so much the bow planes, but certainly the stern planes and rudder) for decent operation as a dynamic diver. And I do recommend that you start out with this kit as a dynamic diver until you gain some experience with it. My buddy BigDave bought and built his Dumas the same time I did. He decided to install a gas ballast system of his own design right from the start. It took a bit more expense and a lot more time. You have to know what you are doing. However, this allowed him to use nice looking scale size control surfaces. He gets good performance from them because he does not have to "drive" the boat under. You can see a picture of Dave's pretty tail fins (and boat!) in a posting under this R/C Modeler forum by TMSmalley titled "Dumas Akula mods by Dave Welch".

However:

I elected to build my boat stock, and convert it to a ballast system later. I found that the large fins allowed me to ease the boat under with just a moderate amount of throttle. This is because of the way the boat is trimmed. It is ballasted down with lead to just below the scale surfaced waterline. This is the point where the top of the WTC inside the hull is just barely sticking up above the water surface. That means that when you drive the boat under, you do not have to displace very much more water, pretty much just the small amount of volume accounted for by the thin shell of the upper hull. Once under, a small amount of throttle will hold you there. While you cannot exactly sit still and lurk, if you back off of the throttle while several feet under, the boat will rise to the surface very slowly due to the low amount of reserve buoyancy. When I was out to the pond playing with the big boys, where the water was eight or nine feet deep, I sometimes lost tract of my location. I would wonder 'where the h*ll is the boat?' Then I would back off and wait painfully long parts of a minute (seemed like hours ) for the boat to slowly reappear. A danger with this setup is if you go too deep, the WTC can compress, lose buoyancy, and not just float up unless you drive it up. Not a problem in my five foot deep pool, but a scarey prospect out at the pond. It hasn't been a problem just yet.

As to maneuvering, the big stock rudder lets me circle in about half the diameter of my 27 foot pool, surfaced or dived. A word of caution here; you need to dull the edges and corners of the fins and rudder with tape or something. I discovered too late the many slices I put in my vynal liner with this so-called 'pool toy'.

Back at the pond, I could really put on the power. She really flys along with a speed 400 flight motor geared 3:1. But then deph control becomes a problem. I could not hold periscope depth at speed without porposing up and down. Thus the need for the APC. It holds the boat level automatically. I bought SubTech's latest and installed it. Now I can hold periscope depth smoothly with hands off the stick.

I am now converting to a pump balast system and then I will install the scale sized fins. (SubTech is offering these as well as an option.) I will then write another article.


Conclusion:

Order the back issue of the SubCommittee Report #54 for my Akula construction article. :) Join in the SubCommittee if you can to get all the future update articles, and much more. :D Get the Akula kit from SubTech and have fun with it. :laugh: Keep us posted. Any more questions? :cool:




Edited By Crazy Ivan on 1069132587
George "Crazy Ivan" Protchenko
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Postby Brady » Tue Nov 18, 2003 2:38 am

George, you are the best! Thank you very very much!!!! Now I just need to find a CHEAP radio setup ??? . Thanks again.

-Brady :)
Brady
 

Postby TMSmalley » Tue Nov 18, 2003 10:46 am

Shot of Crazy Ivan's Akula at SubRegatta 2003
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In a lost episode of "Voyage's" last season, Big Dave's Akula is
being stalked by a huge prehistoric dogfish.

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Big Dave Welch has come up with an appearance upgrade kit for the Dumas Akula that is going to be (or already is?) for sale by SubTech (www.rcboats.com). He molded up his own scale tail planes and tail cone extention. He also molded in the raised hump on the rear deck.

Dave sent me some more photos that Dave sent me on my website on the "Other Guys' Projects" page.

RC-Submarines.com Other Guy's Projects page
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