Cheap, Down and Dirty Mailbox

garren · Oct 4, 2013

OBN said:
How much sand was moved on this adventure in the amount of time you worked it? And thanks again for sharing...

I was really impressed with how much material this moved. I don't think we ever ran this more than 5 minutes on each hole and it would go from knee deep to chest deep with low RPMS. One spot must have been softer, because the hole was neck deep. It was hard to tell the diameter of the holes because this area is "lumpy" and tangled with timbers from the wreck.

garren · Oct 4, 2013

ScubaFinder said:
Nice work Garren, I wish I still lived in Dallas so I could go with you, I miss the alligator-less rivers of Texas. While I love your blower design, you might consider looking into deflector plates as well. Weld a 24" x 24" plate of steel onto your mounts at a 45 - 60 degree angle and it will deflect the propwash down as well, they work great in shallow water. I also had a 6" PVC elbow fitted onto my Evinrude 9.5 and once used a 4" PVC elbow on a SeaDoo. Both worked great in the shallows while I was a 1715 fleet subcontractor. My mount looked just like yours, and I used big hose clamps to hold the PVC in place. I love anything McGuiver-ish, keep it up and keep us posted. This thread is inspiring me to make a new one for my Evinrude. :-)

I wish you could go with us too. We need somebody that knows what they're doing!

The deflector sounds interesting. I'm going to look behind the shop and see if I have a piece of plate that big.

AUVnav · Oct 4, 2013

Late to this party, but I have been using 14" to 18" PVC pipe for the mailbox. I will try to explain the box, as I dont have any pics right now.

Near the prop, to adjust the flow/vacuum with speed, there are 1.5" round holes drilled. A piece of a bend flange has similar configuration of holes, and is banded over the holes in the pipe. This way, by rotating the flange, the holes will partially or fully line up, thus allowing to regulate the flow with engine speed.

The greater the radius of a simple bend, the more head loss, so 2 45 degree bends are used, with a 24" section of pipe between them, This gives quite a few degrees of freedom on the nozzle, so you can work an area without having to move the boat.

There are several pieces of the final downard section of varying lengths, depending on conditions.

Here is a very slick trick on the final, I have heat welded two ridges inside the pipe, they are 2 inches high, and arc slightly inward. what this does is create a vortex, concentrating the water into a tighter jet. You can also buy the ones meant for cars and attach them as well....

Difficult to explain, but perhaps you get the idea. (sortof like turning a 2 liter upside down, then giving it a slight swirl, and look at the concentrated flow)

I will get some diagrams of the design up in the future, but dont have access right now.

garren · Oct 4, 2013

AUVnav said:
Here is a very slick trick on the final, I have heat welded two ridges inside the pipe, they are 2 inches high, and arc slightly inward. what this does is create a vortex, concentrating the water into a tighter jet. You can also buy the ones meant for cars and attach them as well....

I like that vortex idea!

Jason in Enid · Oct 4, 2013

Yes, that is a very interesting concept! Just make sure your vortex runs the same direction as your prop or you'll be fighting against yourself.

AUVnav · Oct 4, 2013

Yes, that is a good point that I neglected to mention.

The combination of venting and vortex can be tuned to eliminate caviation as well. While it seems counter-intuative, the right placement of venting in the initial stages, tends to draw even more water into the system.

With the vortex, you will find a huge increase in velocity. this will allow you to throttle back the motor quite a bit.

Jason in Enid · Oct 4, 2013

AUVnav said:
While it seems counter-intuative, the right placement of venting in the initial stages, tends to draw even more water into the system.

With the vortex, you will find a huge increase in velocity. this will allow you to throttle back the motor quite a bit.

Not counter-intuitive at all! I can't believe I forgot about that. It's the same thing we do with hydraulic gold dredges, a high pressure water jet into a tube pushes all the water in it and draws even more water that just the original water jet.

OBN · Oct 4, 2013

I like the vortex idea....... :thumbsup:

And I'm impressed with the amount sand moved.
Question, Would a less stable anchoring be good for clearing out just a hole? Where the boat itself squirms around some, clearing more of an area out. And I noticed, I think, near the end of the video the wash is more of an angle then straight down, did you get the same results, a hole. Thanks again Joe

garren · Oct 5, 2013

OBN said:
I like the vortex idea.......
And I'm impressed with the amount sand moved.
Question, Would a less stable anchoring be good for clearing out just a hole? Where the boat itself squirms around some, clearing more of an area out. And I noticed, I think, near the end of the video the wash is more of an angle then straight down, did you get the same results, a hole. Thanks again Joe

Towards the end we actually loosened the anchor ropes and fanned the back end of the boat back and forth...but it was hard to tell if we had a round hole or an elongated hole because the bottom is so lumpy in this spot...and the timbers are jumbled up too..

Digg Mo · Oct 6, 2013

Okay! The cold weather is over for now. Time to get the mailbox back in to the water! :skullflag:

AUVnav · Oct 8, 2013

The double 45 acts as a hinged joint, allowing the boat to stay anchored, and the wash to be directed by the diver.

The pipe extends in front of the prop as well, with a 2 and foot foot section option.

Trez · Oct 8, 2013

Going with the title of the thread...I have to ask
Has anyone tried making a Blower from ADS pipe? I would think it would be cheap, easy to work with, can be angled, smooth wall or perforated, various sizes.
Just curious as to the many reasons why it isn't used more often, I am sure there are obvious reasons :icon_scratch: