Dumas Scarab 377 New Build Electric

[bruceisla]

I have part of this posted in a Q & A thread but, since I have been posting progress pictures, I decided to continue here (and include previous pictures and text).

This a Dumas Scarab 377 kit that has been on my shelf for years. It's about 40" in length and originally designed for nitro. Finally got it down and started an electric build.

[bruceisla]

Transom reinforcement

It's a start .... motor and mount have arrived (from separate sources).

Plywood transom reinforcement .... used the original kit transom piece plus plywood from the kit servo box (box won't be used) .... original plans show reinforcement covering middle third of transom only. Not really concerned about weight since it's just for a leisurely run around the pond and the hull is already somewhat heavy.

[bruceisla]

Noticed an odd offset ...

The cockpit area and the walkaround area surrounding the cockpit are not centered left/right. Functionally it makes no difference but if you were trying to find center by measuring across the top, it has a different centerline than the keel. I'm using the keel for all measurements.

Here's the offset .... the left and right gunwales are about 1/4 inch different. Left is wider than right.

Rails are installed and shortened a bit for electric. Motor mount to rails adapter plates are done.

[bruceisla]

Stern hardware

Stinger and stuffing tube trial fit ... looks good so far.

Stern drilled for turn fins and trim tabs.

Awaiting collet and cooling jacket to align motor/stuffing tube.

[bruceisla]

Changing method of cockpit install

I decided to change the mounting method for the cockpit. The original, due to nitro design, has no sealing of cockpit/hatch to hull. I have decided to build rails around the inside of the deck to allow gasketing of hatch assembly. I'll also use hockey tape but, because the step pads (which are in both the deck and hatch) are "rippled", it will be difficult to seal that area with tape alone.

[bruceisla]

Hatch and cockpit

Still needs to be glassed and coated. View is bottom side of cockpit insert (hatch). Eventually will get some flotation.

[bruceisla]

Hatch/cockpit front retainer

Aluminum "L" bracket bondo'd and glassed to front of cockpit. Bracket slips under a mating piece on hull as hatch is pushed forward. Picture 2 shows the hatch upside down to illustrate where the bracket engages the deck. Picture 3 shows it in correct orientation just before sliding it forward.

[bruceisla]

Motor and shaft trial fit

Trial fit .... pretty close .... need to fabricate the stuffing tube support.

[bruceisla]

Stuffing tube support

Stuffing tube support is in. Resin is cooking off VERY quickly even with reduced hardener. 92f in the garage and no telling what the humidity is .... but it isn't snowing in FL !!

[bruceisla]

Stern hardware .... leak test

Test fit of the hardware .... need some more stainless socket heads. A few tiny leaks that should be fixable with sealant before final assembly.

[Make-a-Wake]

What motor is that.............size, kv? I have a 1984 model 45" Dumas scarab in my Signature............love that old guy!!

[bruceisla]

What motor is that.............size, kv? I have a 1984 model 45" Dumas scarab in my Signature............love that old guy!!

It's a HK KB45-08XL 1600kv Brushless Inrunner
Kv: 1600RPM/V
Weight: 557g
Shaft: 6mm
Size: 77x45mm
Voltage: 36v
Highest rated power: 3528W

I got the water cooling jacket from OSE

Product ID: ham-fei580L-kb45-jacket-v2
Feigao 580L And Kb45 Water Jacket V2

[Make-a-Wake]

I hate to break the news, but that is not a real reliable motor. It's a 2 pole, runs hot and is amp hungry. I'd run it on 5s max and no more than an x442 to keep it from burning things up............it may work there.

I run my 45" with a Leopard 4082 4 pole 1000kv on 6s2p with an x447 and its a sound setup........only gets 37 mph but I like it there as its a scaler.

[bruceisla]

Thanks for the info .... I am aware it has shortcomings. I'll take your recommendation for a prop (the X442) .... sounds like a good place to start. I like the idea of a Leopard but I don't really expect too much from this boat. Thanks for your interest, Bruce.

Mount with new stainless fasteners cut to clear water jacket.

[bruceisla]

a bit of progress

Fabricated the servo mount, installed antenna, installed hull flotation, trial fit of batteries, fabricated wind deflector (solid windshield).