45" Dumas Scarab

[Ken_NJ]

I'm typically a scale boat builder and I usually go for older boats. I wanted to build a FE boat from the offshore powerboat days of the 80's since I would watch the boats at the Benihanna Grand Prix off of Point Pleasant NJ. A friend recently gave me this Dumas 45" hull, so my goal is to build something that resembles Betty Cook's Kaama. I've been posting questions in the Q&A forum, figured I would start a build thread and see what other help I would get here. I'm a slow builder and procrastinator so bear with me on this.

I'll be keeping a continuous photo blog here unless I figure a better way for it: http://s11.photobucket.com/user/ken_...tml?sort=9&o=0

Here are some previous models I built. I'm no slouch when it comes to detail. The Miss Belmar is scratch built, 54" long and powered by 4 Dumas 12v motors with 4 props of course. The USS Marlin is a highly modified kit.
SS Miss Belmar: http://s11.photobucket.com/user/ken_...ideshow?sort=9
USS Marlin: http://s11.photobucket.com/user/ken_...0Marlin?sort=9
USS Marlin pool test: https://www.youtube.com/watch?v=IjELKbpJNfk
Complete USS Marlin build: http://www.rcgroups.com/forums/showt...ghlight=marlin

This is my goal.
wc-cook-0011sm.jpg

This is what I am working with.

[Ken_NJ]

Ordered this hardware from Hobby King, should be here Monday.

Motor: http://hobbyking.com/hobbyking/store...dProduct=42488
ESC: http://hobbyking.com/hobbyking/store...rless_ESC.html (did not order)
Batteries: ESC: http://hobbyking.com/hobbyking/store...dProduct=20676
And a charger.

Power will be 8S2P.

[Ken_NJ]

I have a lot of work to do on the hull. I have to make a new hatch-cockpit as the original one does not fit my plans. I also have some divits I need to fill in the the deck that where for railings I will not be using. I hope only to have to paint the black areas and leave the white areas alone. Between the divits and some other spots I need to fill with white Gelcoat. Anyone good with Gelcoat? A friend gave me this Evercoat paste but the paste is green and I need to add a lot of white pigment. Also, the arrow in the one picture the deck was not secured to the hull evenly. There is a noticeable bend in the deck. I think I might have to leave that alone.Any suggestions?

[lenny]

From what I hear that esc has some issues,
I think you would have been better off with the seaking HV130a esc.
As for the cells,
The normal blue turnigy 40c would have done the job.

[Ken_NJ]

Hi Lenny,
Does it? Brushless and Lipo is out of my comfort range. But building a boat is not. I feel like anything that I might order will have an issue.

I just checked my order, looks like I left off the ESC.

[srislash]

I think white pigment is your best bet if you don't want to paint it.

If I remember correctly you did not have the original cockpit right Ken? If so I would be interested if you would part with it.

[Ken_NJ]

I'd have to add a lot of pigment to overcome the green. I made a sample, it's in the previous pics I posted. From what I found, at $25 a can, I only need a teaspon's worth. Unless I Gelcoat the cockpit.

I do have it. If I don't cut it up for the replacement, it's yours. Let's wait until after I have the new cockpit done.

[lenny]

Yes the Aquastars are not very proven yet and has problems,
If you look on the discussions you will see zeeek1 and that is AKA ray schrauwen from on hear.
You just need to do little more home work and ask about stuff before you buy.

[srislash]

I'd have to add a lot of pigment to overcome the green. I made a sample, it's in the previous pics I posted. From what I found, at $25 a can, I only need a teaspon's worth. Unless I Gelcoat the cockpit.

I do have it. If I don't cut it up for the replacement, it's yours. Let's wait until after I have the new cockpit done.

Cool thanks Ken.
BTW that motor is a Proteus relabeled for HobbyKing and same for the ESC but it is called Swordfish elsewhere. Like Lenny stated, not proven but I have not heard anything bad either on them. You are not likely going to be pushing this too hard anyway, correct?

[Tbauer]

Your the master scratch builder, some really awesome work you have done, very impressive..... Do you sale them or they just for you? Just awesome

[Ken_NJ]

No problem srislash. No not pushing hard. This is for fun, no competition or anything like that. Wanted to keep costs down that's why HK. I know this will cost over $1k. I'm looking at this boat as have two processes, the mechanical and appearance.

For the mechanical I still need the running hardware, ESC, 1/4 flex and all the hardware mounted on the transom. Batteries and motor will be here any day. ESC recommendations? I know a Stinger is the way to go. I started a thread over in the Q&A forum, I'll ask here. What about a submerged drive setup, where the flex cable comes out the bottom and goes to a transom mounted strut so the propeller is always below the water surface?

For the appearance I have to start on the Gelcoat repair, hatch-cockpit and paint. I've worked with polyester and epoxy resin before but not Gelcoat, so any help is appreciated, otherwise I'll just hammer away at it. For the hatch my LHS ordered 1/16, 3/32 and 1/8 aircraft plywood for me. I'm not making a mold for this so it's going to be a one-off hatch with plywood construction keeping it as light as possible. Probably be using polyester resin (don't care about the smell) to give the hatch a finish. If white rattle can paint does not look like the white Gelcoat, then maybe I'll have to buy that $25 can and pigment. I'll start using construction paper to get the lettering on the hull side designed. The graphics I plan on getting done from Callie Graphics once I know what I need.

[Ken_NJ]

Your the master scratch builder, some really awesome work you have done, very impressive..... Do you sale them or they just for you? Just awesome

Thank you for looking at those pictures, and for the compliment. I do not sell them, they are for my fun sailing with other club members. I added a link to the Marlin build on RC Groups and a pool test.

[Tbauer]

I love scale builds and have looked at a lot, yours are right up there with the best. I don't know if your retired, but if you are or when you do and need extra cash, I know you have seen what those can sale for. Yours is easily up there bud, keep up the great work, I am jealous, I wish I had the patience to do that kinda work. Very time consuming indeed. = )

[srislash]

Well y'know, these were originally designed with submerged drive in mind. You won't need such a big prop with full submerge. I will ask how many cells you plan to run before aiming you in the ESC direction.

[Ken_NJ]

Thanks again Tbauer. Not retired yet and like I said, I'm a slow builder and procrastinator, so they can kill your building time.

Srislash, since this hull is probably from the 80's, don't think they had surface drive in mind back then. I'd like to go submerged. Batteries will be here Monday I hope. Ordered 4 5000mAh 4s batts for 8S2P.

[lenny]

I found a HV 130a seaking with free shipping hear.http://www.aliexpress.com/item/HOBBY...687251393.html

[Ken_NJ]

I not familiar with brand names in this area. Hobbywing, Seaking? All the models I built was with stuff I had on hand from years ago. (Marriage and kids interrupted the model boating life but that is over now). So I guess the China stuff is what everyone uses? You wouldn't say to get a 130A esc if it wasn't the right one. How do you judge 130A?

[srislash]

I not familiar with brand names in this area. Hobbywing, Seaking? All the models I built was with stuff I had on hand from years ago. (Marriage and kids interrupted the model boating life but that is over now). So I guess the China stuff is what everyone uses? You wouldn't say to get a 130A esc if it wasn't the right one. How do you judge 130A?

I would look t the motor recommended wattage, then divide by the volts you are going to run. That will give you the amps. In this case 5280 watts / 33= 160 amps. I am pretty sure the controller is rated at 130 amps at its max voltage capacity. Meaning it is good for 6300 watts or better.

That is how I go about it anyway. If the budget is in mind this should be a knock off or Hifei Swordfish ESC http://hobbyking.com/hobbyking/store...ooled_ESC.html

I believe Hobby king just buys in mass and rebadges this stuff much as Walmart does.

[Ken_NJ]

In post #2 I listed a 200 amp motor that Lenny pointed out the HK comments indicated that 200 amp model was questionable. I see no negative comments about the 240 amp one. It is more pricey, then again this is not a cheap hobby.

I have all of the original Dumas parts, instructions and all. I attached a pic of the Dumas drawing of the section of the drive area. If I went submerged, not sure how far below the hull the shaft should be.

[srislash]

Ken that motor rating is at 10s in 'Y' configuration(129amps) or 6s in Delta configuration(229amps). I think for 8s in 'Y' configuration 200 amps should be safe.

I just thought of another more reputable option http://keithbradleyboats.com/product...s-200a-hv-esc/ Not sure where else you can find these but Hifei Swordfish are good. That is why I recommended the HK 240 one there. I have the Hifei version and it has been good for years.

[srislash]

Can I add in here Ken that you can prop up and push way past those stated numbers or you can prop down and never see them.

[Ken_NJ]

So with any of these motors I would be OK? For the motor I was told use the delta config as that would give me more torque? In delta, the motor would be at 38k rpm's. In wye it would be 21.5k rpm's. I'm learning on the job here. And since the motor is a 56mm I guess any 56mm mount will be OK? Something with good support.

Swordfish 200amp: http://keithbradleyboats.com/product...s-200a-hv-esc/ $199.99+
Aquastar 240amp: http://hobbyking.com/hobbyking/store...ooled_ESC.html $215.99+
Seaking 130amp: http://www.aliexpress.com/item/HOBBY...687251393.html $149.90

Boat work...
There is a section of 1/8 plywood that Dumas supplied that needs to be secured inside the transom. They call it a transom double, can be seen in the drawing in post #19. That required lots of shaping to get it to fit. I also sanded the inside transom with course sandpaper in preparation for fiberglassing it in. My can of fiberglass is old and sealed itself shut so have to pick up another can and some white coloring agent. Will posts pics when I have some more work done.

[iridebikes247]

http://offshoreelectrics.com/proddet...ef-HBC0240L-CW

You will fall in love with this esc, in your setup it will stay ridiculously cool like below 90 degrees. I ran run 4 of these escs sometimes demanding environments, sometimes not. They always perform flawlessly. I would not go with that turnigy 130 esc that motor you've got is big, it WILL spike.

Remember you're running a big can motor in a less efficient hull that motor will pull some amps on a spike. Its $250 for that esc and you'll have it for a very, very long time. When it comes to big motor setups you have to be careful and the price jump to a sf240 will be well justified.

As Shawn was saying that motor should pull some 6300 watts and the esc is capable of it, just depends how close you want to get to the max. the sf240 has been known to handle 10,000 watt spikes without an issue.

[Ken_NJ]

Oh boy, that was the first esc I had on my list, then started trimming things down as the spreadsheet costs were getting way to high. But I know the esc is important investment. No matter what I do I'll be going over my budget.

Great advice on this forum, and as many people there are you will also get that many opinions.

[iridebikes247]

I mean other guys have had luck with the seaking 130 and lenny seems to have found the best deal for it, you could definitely give it a go.

[twissted]

If cost is a issue then look at the HK 180 esc. It will do the job. Up to 6s. This must be a fast build for you. Looking at the builds past. I'm surprised it not a 1/6 hydroplane or something with more detail. Your skills are more than the sum of these parts!

[srislash]

Oh boy, that was the first esc I had on my list, then started trimming things down as the spreadsheet costs were getting way to high. But I know the esc is important investment. No matter what I do I'll be going over my budget.

Great advice on this forum, and as many people there are you will also get that many opinions.

You won't go wrong with that ESC.

[lenny]

ken how wide is you 45" hull at the transom ?

My thinking is that this sport scale build is for sport and fun running,
At speeds of 50 mph tops at some times.
And if this little motor,http://www.atomik-rc.com/V700-Marine...er-1100Kv.html
On 6s and a T180a esc can move a 58" cat to 45mph gps and still keep temps in check,
Than why would it not work even better in a 45" V hull if the boat is trimmed out right.

Also this is a nice setup in a 40"Vee but not sure on what speeds he was getting.
https://forums.offshoreelectrics.com/...tte-40-quot-6s

[twissted]

This is up for grabs on ebay.
save you some money.
http://www.ebay.com/itm/new-warehous...item1e8890d83b

[Ken_NJ]

The boat is 13.5" at the center, 14" at the transom. The transom height is about 5 1/4" at the V. That's all I'll be running this for..... fun! I'm committed to the Turnigy motor, will be here tomorrow. Toss up on the ESC! My hands are on my head. Have to order this tonight to get going.

That outdrive would be a very nice touch since the original ran with Mercruiser outdrives.

I bought this little brushless boat NIB from a LHS fro $150 before Christmas. He is selling out. Put 2 NiMH 5000 mAh packs in, ran about 20 minutes. Bought it so I have something easy to throw in the car. Ran it first time this afternoon, took some getting to use running something fast compared to my slow scale boats. That was fun, can't wait to get this done.