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Jun 20, 2016, 03:47 PM
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Questions about rebuiling a Dumas Coast Guard 44 MLB.


I have a Dumas CG 44 lifeboat that I built about 35+ years ago. I'm going to sand down every thing and patch a couple spots in the hull, and finish all the details that I don't on finish before.

So here is what I'm working with . . . . .

The hull I covered with 2 or 3 coats of epoxy resin and then used K & B two part epoxy paints

The superstructure I painted with K & B two part epoxy paint.


After several hours of sanding and filler and more sanding I have this . . . . .
Last edited by Rudy Ackerman; Jun 20, 2016 at 04:03 PM.
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Jun 20, 2016, 04:02 PM
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Ok now for the next steps . . . . .

I guess I need to add a couple more coats of epoxy resin to the hull. I see several different brands at home depot.

Should I put something on the superstructure, maybe a dupe or something else.


In another thread I saw where they then primed that whole boat.

Do you have any suggestions on types of paint? I would prefer rattle can that and not repeating the whole 2 part maxing mess.

Will I need to clear coat over the paint/decals to protect them?

Thanks
Jun 20, 2016, 07:14 PM
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Guard-Officer's Avatar

I'm no help for your paint questions, but will follow your progress!
Cheers
G-O
Jun 20, 2016, 07:22 PM
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Upgrading the running gear.


For propulsion I will keep using the two Dumas 6 volt motor's

Any suggestions for a couple of ESC's for "brushed" motors. It would appear that they only draw a few amps each so a couple 10 amps ESC's should do fine.

The running hardware kit came with 1/8" propeller shafts, however I see all the 3 blade propellers require a 3/16 shaft

So has anyone used either of the 1/8 to 3/16 shaft adapters from http://www.shipsnthings.com or http://www.offshoreelectrics.com?

On top of that I will change the motor mounts so that all the dog bones/gears/shafts line up better.


Here are the 3 blade propellers options I have found
Dumas 3 blade brass 1 3/4" Dia with a 2" pitch.

www.shipsnthings.com
Brass Propeller 3 Blade 1.80 Dia with a 1.5" pitch
Brass Propeller 3 Blade 1.80 Dia with a 1.75" pitch

http://www.harbormodels.com
Brass Propeller 3 Blade 1.70 Dia with a 1.9" pitch
Jun 20, 2016, 08:10 PM
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prepare for painting


Hi Rudy, First determine for sure whether you used epoxy resin or polyester resin. If it was epoxy, you will need to stay with epoxy. I f it was polyester, you can cover with either one. From what I see in your pictures, at this point I would cover with one layer of 2 oz. clothe and which ever resin is appropriate. It usually takes me one coat resin with the clothe, one coat to fill in the weave and one or 2 coats to finish. after sanding smooth, continue with primer and paint. I prefer to use Klass-Kote epoxy paints, which very much like the old K&B epoxy paints because it is so much tougher than rattle can paints. On natural wood or stained surfaces, I will Klas-Kote epoxy urethane clear as top coat and also seal in any decals or vinyl graphics. For the small jobs ,I use the Preval aerosol canisters instead compressor and spray gun . I have gotten good results this way. Normally I mix one part A, one part B and one reducer. I may have to add more reducer to get the spray to come out right. I hope this helps. Thank you,Gary
Jun 21, 2016, 12:24 PM
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Looking good.
Jun 22, 2016, 03:46 PM
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Ok I have to ask . . . . .

Why the layer of 2oz cloth, The craft done not need the added strength that it will add, and it would appear to add more texture that will then need to be smooth out
Jun 22, 2016, 04:20 PM
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RUDY-Just some food for thought. If it were me and you are running 1 3/4 diameter three blade props, I would go direct drive with the two Dumas motors and get rid of the gear train.

The motors you have are rated at 5000rpm and have pretty good torque, so I would drive the props direct.
Jul 12, 2016, 01:38 PM
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OK at this point I have patched the hull, and re glassed the whole boat with Bob Smith industries FINISH-CURE 20 minute epoxy.

Heading to home depot for some rattle can primers and paint.
Jul 12, 2016, 03:31 PM
boat butcher
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.

Mark
Jul 12, 2016, 03:32 PM
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What ESC will you use?
Jul 12, 2016, 04:58 PM
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Rudy Prop Shop UK makes a 1.7dia 1.5 pitch 3blade, 4 blade, 5 blade and you can specify shaft diameter, thread needed [no 5-40 as he does not have the tap], setscrew attach. Not cheap but work VERY Nice. Use your motors direct drive, lose the gearboxes. when you do that will need to replace shafts for longer ones so order threaded one end. Recommend the MTroniks Viper 25 or 15. Use a 25 single and 7.2 volt 6 cell. Should be reliable as a rock.
Jul 12, 2016, 05:39 PM
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Quote:
Originally Posted by CaptLee
Recommend the MTroniks Viper 25 or 15. Use a 25 single and 7.2 volt 6 cell. Should be reliable as a rock.
I will be ditching all the gearing and running a twin throttle setup with two ESC's. I have also seen that the dumus 6 volt motors only pull about 3 amps under load. So two of the Mtroniks tio Marine15's would appear to be more then enough.

For battery power I have a couple of 2S 5000 mah hard cased LiPo packs from a RC car that I will be using.

Correct me if I'm missing something.
Jul 17, 2016, 02:10 PM
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Unsupported prop shaft?


Ok I working on mounting the motors back in the boat.

Looking at going direct drive and removing all the gearing that came with the dumas running gear setup.

As the stuffing tubes are already installed and I have no plans to replace them. The prop shaft will have to be longer and the ends/u joint will be unsupported.

If I keep the motors where they are, the unsupported part would be about 4 inches long

I can move the motors towards the back some and the unsupported shaft would be about 2 3/4 inches.

To move the motors back more would require major cutting to the frame right there.

So is 4 inches of unsupported prop shaft to long, or should I move the motors back shorten to 2 3/4 inches?
Jul 17, 2016, 03:40 PM
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You will have to obtain two different size bass tubing from you hobby shop. One will have a 1/8 id and the other will just slip over the first tube. Cut two pieces of tubing from the firsts tubing with the 1/8 id to act as bearing supports. Then cut two pieces of tubing from the larger tubing about 4 inches long.

Side the 1/2" smaller tubing in the end of the larger tubing and solder in place. Make sure not to get solder inside the inner tubing. Then remove the motor and the coupling from end of the prop shaft. Slide the larger tube over the tubing that you now have in the hull as far as it will go and solder the end of the tubing to hold in place.

Once all the soldering is done make a brace support for the end of the stuffing box about 1/2 back from the forward end of the stuffing box to prevent the stuffing box and shaft from whipping.


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