[PSUBS-MAILIST] Minn Kota C2 vs Riptide

Sat Jul 13 09:14:13 EDT 2019

 Tim,I can tell you from experience that having the same motors on both sides does not mean the sub will defiantly travel in a strait line.  I would not spent the money to match the exact thrust.  I would replace the guts of the dead motor first, if it travels wierd then replace the other to match.  Or buy Alec's motorsHank
    On Saturday, July 13, 2019, 6:21:20 AM MDT, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Hi Tim,
I have two never-installed Minnkota 74lb lower ends, which I bought years ago but never installed because I changed the design to 101s. They can run on either 24 or 36 volts, and were the salt water version. Let me know if you could use these, I can surely sell them for less than you were quoted.
Best,Alec
On Fri, Jul 12, 2019 at 8:38 PM T Novak via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

It is time to re-motor the SportSub.  Currently it has 42lb thrust Minn Kota motors, one corroded and unusable, the other working well.  Locally I can pick up the Endura C2 40lb for $250, or the Riptide 45lb for $400. The Riptide is marketed for salt water use.  Has anyone any advice as to whether or not the Riptide is worth the extra $150? The extra 5 pounds of thrust is not relevant since the hull is far from hydrodynamic efficiency and I would just us more battery power to go no faster. The thrusters must have the same thrust rating, so I need to get two new.

Tim

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of hank pronk via Personal_Submersibles
Sent: Friday, July 12, 2019 5:57 AM
To: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] Foam preperation

Brian, thats' a good plan.  The cheapest way to gain buoyancy is to remove weight if possible.

Hank

On Thursday, July 11, 2019, 6:44:00 PM MDT, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote: 

Hi all,

                   I think I'm going to do another test with that foam.  This time I will encapsulate it with epoxy and fiberglass and drop it down.

  My sub is going on a serious diet.  I'm cutting out a significant section of the upper ferro-cement area and replacing it with epoxy fiberglass which will be bonded to the ferro-cement.  It will be a bit different shape, but the whole area is underneath the fiberglass shell so it won,t really look any different with the shell on.   I always though I could compensate for that weight by having flotation cylinders there but I just didn't control the thickness of the ferro-cement and it probably should have been fiberglass all along anyway.  The bottom of the ferro ballast hull will still be the the existing hull .  It will be a lot of weight that I'll be losing.  Maybe 1,500 lbs, if the section I cut out is any indication.  

Brian

--- personal_submersibles at psubs.org wrote:

From: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] Foam preperation
Date: Mon, 8 Jul 2019 23:17:21 -0700

Alan,

             Yes it's puzzling the mechanism at work allowing it to take on water.  It could be that the small bubbles of foam that make up the matrix of the foam itself are simply not strong enough to handle the water pressure.  But it's interesting that it can take a rated pressure ( parallel applied pressure) and not be crushed but then on the other hand will absorb water.  From the look of it you would never think that water would penetrate it, the outside of the foam seems nonporous.  Might be instructive looking at it under a microscope.  

Brian

--- personal_submersibles at psubs.org wrote:

From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] Foam preperation
Date: Tue, 9 Jul 2019 16:57:52 +1200

Brian,

I am wondering how it absorbed water, seeing it's a marine product.

Do you think there may have been a break down on a microscopic level through

the water being forced in under pressure.

Anyway, good that you got a result. Imagine if it had absorbed water more slowly

so that it wasn't detectable in the short time that you tested it.

Alan

On 9/07/2019, at 1:43 PM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Bad news,  the test piece that I dropped down to 900'  , it didn't crush , but it absorbed water.  So it lost a lot of its buoyancy.   

Brian

--- personal_submersibles at psubs.org wrote:

From: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] Foam preperation
Date: Fri, 28 Jun 2019 16:15:09 -0700

Alan,              I've done one small test piece so far and it did give off some heat.  I'm planning on doing a larger piece that I'm going to drop in the ocean, it will be interesting to see how that goes.  I'm more inclined to pour larger amounts for a couple of reasons, first I think you get a better and more accurate mix of the A and B, and also where I'm pouring into my cavities I don't want to inadvertently seal off areas that I will not be able to get to to complete the pour.  So I'd rather error on over pouring a bit so I have foam pushing out the vent holes.  

Brian

--- personal_submersibles at psubs.org wrote:

From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] Foam preperation
Date: Sat, 29 Jun 2019 09:18:40 +1200

All,

as we are talking about testing this for General Psubs use I'll elaborate

on something I mentioned earlier.

In the product specifications below it mentions that in the setting of this product

the temperature is critical, & that temperatures below 75 degrees F will make a

denser product. One would assume that temperatures above 75 F would make

a less dense & hence weaker product. 

With 2 part chemical reactions there is generally a heat produced & this is 

exponentially greater the thicker the pour. I used to use casting resins for art

& they would get very hot on thick casts.

If this were the case then filling any large voids in one pour may cause the

centre of the material to be a lot weaker than the outside.

To check this we could ask the rep about thick pours, do a thick pour & cut it

in cross section to see if it is less dense in the middle or stick a heat probe in

the middle of the pour to check for an increased temperature.

   - All expansion rates and times given are temperature critical. Temperatures below 75 degrees F will lower the expansion rate therefore requiring more foam. Ideal working temperature is 75 to 80 degrees F or above.
   - Accurate measuring of these products is extremely critical.

Alan

   - All expansion rates and times given are temperature critical. Temperatures below 75 degrees F will lower the expansion rate therefore requiring more foam. Ideal working temperature is 75 to 80 degrees F or above.
   - Accurate measuring of these products is extremely critical.

On 28/06/2019, at 11:04 PM, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Not my forte, but given the hardness of this product when cured is there really an expectation that it is going to deform in a visually measurable way and spring back into shape from a depth test?  Seems like it's more likely to either structurally fail or not with obvious non-elastic results such as cracks, cavities, etc, hence the weight test to see if it absorbs water.  I'm thinking the dunk test from the sailboat is a good first start.

The cost of this product seems to be on par with trawler floats from a pound to pound buoyancy perspective but it has the advantage of allowing custom shaping.  I'm interested in the results.

Should we invest in a small amount of this product and put it to some more rigorous pressure testing?

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