DPV Construction Begun

[Larry Horne]

Attached is the propulsor for my DPV. Its a Minn Kota 55# thrust lower unit and draws 45 amphes. As you can see I have disassembled it to determine which parts I will us and which not. I plan to upgrade the motor's seal points (O-rings and gaskets)

I will provide Step-by-Step construction photos but it will be a slow process due to other obligations.

I plan on using a composite construction technique to hold the weight to a minimum. I have collected PVC in 6, 8, and 10" diameters and solid surface material but all weigh too much in my opinion.

Battery is the next decision............it drives the diameter of the body which drives construction technique.

[/ATTACH]

The propulsor is a KIPAWA #358 three blade prop for the Minn Kota.

Cost to date:

Motor: $125
Prop: $40

Larry

 

[Nostromo]

Just curious, have you given any thought to the benefits of a variable pitch prop? Also, will there be a clutch to allow the prop to be hand stopped in a runaway motor situation? Just a few safety issues to think about. In any event, best of luck with your project.

e.a.e.

 

[Larry Horne]

Nostromo,

Your points are well taken and were thought about. I'd attempt to put a VP Prop with clutch into the system if I weren't trying to do this as economically as possible. The Apollo's clutch and prop assy costs in the area of $350...............the benefit of VP would be an advantage and I understand the safety of the clutch but on my MkI I'm going to try the 3 blade trolling upgrade and see how it goes.

Another option would be to use a soft shaft pin to link the motor shaft to the prop, something that will shear easily say if I shove a dive knife in the prop.

Thanks

 

[Nemrod]

I don't think weight is a problem since I think you will find it to bouyant most likely and any reduction in weight will require ballast thus negating the composite materials lightness. Have you calculated volume so you can figure bouyancy of the empty container (hull) and then calculate required ballast such as the batteries and motor and material weight etc to arrive at a length/diameter that is suitable for your requirments? N

 

[ShoalDiverSA]

Larry,

You may want to consider adding a DIY clutch assembly. You would need two clutch plates, which should be do-able in a machine shop (it *LOOKS* simple) and some cup washers to set the clutch pressure.

Silent submersion have step by step photos. I really did not want to link to a manufacturers site, but I can't find the sketch of the Oceanic clutch assembly that I used to have.

Cheers,

Andrew

 

[Larry Horne]

Nemrod,

I'm concentrating on the dry weight that I have to handle on the beach and boat, my back sucks. You are correct in your assessment regarding volume and bouyancy. I may have mislead you slightly. I am not going to use any foam core in the composite except in the end cap on the stern, everywhere else will be approx 1/8" fiberglass and formed and few voids, one of the benefits of laying the glass for the body is that I can make it as thight as possible. I plan to determine battery size today which is looking to force the body to be around 8" in diameter and 16" or so long. I do plan to weight the system for slightly negative buoyancy and balance. I'll weight the items as I assemble but I estimate the motor assy to be around 10# (this thing is a beefer, heavy duty windings and a lot of torque, we'll see if its too much) and the batteries are specing out at arund 40# so you can see that even though the weight is negated in the water, it builds rapidly dry. For reference the Apollo DV weight is 40# dry with battery. I'll run some numbers once I get the battery sized. Good comment!

Andrew,

I'd seen the SS clutcha nd VP prop assy from my research. The clutch is easy as long as I have the length on the out put shaft or the room on the prop to modify to receive the extra thickness of the clutch............I've had the SS assy printed out for a while, once I get things mocked up, I'll see how much distance I have on the shaft and/or prop hub. Good comment.

Please keep the ideas coming.................design is still on paper.

 

[Nemrod]

Larry, the specified weight of my Teknas is 48 lbs. They are about four lbs negative. I have only dived it a few times but one thing I learned way back from previous adventures is to carry an emergency float. What I am using now is a safety sausage. I am planning to carry two. They are so small and compact they will not add much complicatiion. I can attach one to the scooter should it fail or flood and that leaves me still with one for myself. Those little nylon finger spools and some brass clips should complete my scooter rig. If the scooter fails in real use then the sausage can be used to float it or at least to mark it's watery--er--resting place.
As to a runaway motor, what if you used two triggers, both would have to be pulled to complete the circuit. If one switch welds/jams or relay welds then releasing the other will break the circuit. A clutch would be nice but maybe not a requirement at least in your first try. Mine never had a clutch but the Teknas do. N

 

[Larry Horne]

Batteries and Resin System Selected

View attachment 26181

View attachment 26182

View attachment 26183

Ok, today the batteries (yes two (2)) and resin system were selected.

Rechargeable Sealed Lead-Acid Batteries (mock-ups shown in photo). These batteries are normally used for mobile vechiles such as wheel chairs.

The batteries drive the body's diameter and dictate total weight. I have chosen Power Sonic PS-12330, 12V 35AH with dimensions 7.8"L X 5.2"W X 7.07"H (over terminals) with a modest 26.5 lbs each. The 7.07" height over terminals means the diameter of the body has to be 9" so I've elected to use a 10" diameter body.

Estimated cost of the batteries are $70.00 each but there is one thing to consider with these rechargable sealed lead-acid batteries is the charging system you have to "recover" the batteries from a greater than 30-50% discharge. Conventional 12V battery chargers are not capable of bringing these batteries back from a deep discharge............ie running them totally dead. This type of cycling will reduce the batteries useful life considerably...........So the charger runs $140 and a small "maintance charger" (often called Battery Minder) runs $50. I have used these trinkle chargers before to maintain my airplane battery and it has more than doubled its life, so worth the eventual investment.

Resin and hardner system.
I have chosen the West System (parts 105 Resin and 205 Fast Hardner). This is the product of choice used my many of my "buds" building composite aircraft such as Long-Easys. It offers better workability and strength than normal fiberglass resin and hardner. Not cheap........$60 for the pint shown in the attached photo.

Comments and suggestions welcome.

 

[Larry Horne]

Nemrod,

Comment on floatation system is excellent. Right on the money. Will incorporate.

As far as the dual switch system. Your correct there too but I add they are a pain in the a*@. I have a Sea Doo Dolphin with the two trigger switches and I find myself always trying to use it one handed in order to say check my guages or computer and of course it will not run with one hand off so I "tie wrapped" one of them down.......so guess what.....single reed switch embedded in the handle with magnet in glove. I'll bet the odds on this one until something changes my mind during operations.

As for the clutch, I agree with you, nice idea but I got thinking about it and that system works off of a spring which loads the clutch. I'd have to extend the shaft to allow for the room required for the spring and hopefully size it correctly where it applies enough force to maintain engagement but weak enough to allow the clutch to disengage when the prop is bound........too much design, buying one already fabricated and adapting it to the motor shaft would be easier but raising cost considerably.

Well off today to the craft shop for 10 and 12" foam discs and the rubber shop for sourcing O-rings.

I have to determine how to end-load the motor into the stern tube, seal and afix it. Right now I am thinking about designing the tube's diameter to be about 1/4" greater than the OD of the motor casing. Use several (2 or 3) O-rings (est 1/8" dia) forced between the tube and the motor casing with valve packing material wedged between the O-rings. The very end of the tube and motor casing would then be sealed with a flexible polyurethane sealant. Sounds like over-kill but this is one of the few entry points that I cannot control with clamps.

Keep thinking about it this for me. Still time to make design changes.........

 

[dannobee]

You can get your epoxy from these guys if you need more. West works, but it's really expensive.
http://www.uscomposites.com/epoxy.html

Also, you'd probably want foam that's rated for epoxy/fiberglass resins, and is more dense (I think the stuff that you have is craft foam?). Aircraft spruce has some.

http://www.aircraftspruce.com/menus/cm/foam.html