moving speed & depth transducers

[mikehoyt]

A number of years ago I purchased a Raymarine ST40 Bi-Date Speed/depth/log instrument that comes with two thru-hull transducers.

Due to the layout of the inside with a shallow bilge and the intake and outflow thru hulls for the head that had been installed forward I installed these thru hulls port and stb beneath port & stbd settees as close to centerline as possible beneath these settees. The problem is that when the boat heels more than say 15 degrees either the speed or depth transducer stops working.

The diagram below illustrates the bottom of my hull and shows approximately where the existing thruhulls for the marine head and the transducers are located and where I can move them. The locations available are limited by a depth beneath the floorboard of less than three inches between settes and in head area. Where I have indicated is under the vee berth behind the water tank whereas the head thru hulls are fwd of the water tank.

diagram at http://fulltilt2pics.angelfire.com/thruhulls.GIF

The transducers are sealed with 3M 4200 I believe.

My plan is to remove them and then fill the holes using West or East system epoxy grinding a tab angle both inside and outside the hull.

I would start by placing plastic wraop on the outside of hull held in place with tape. Then I woudl move inside and put a layer of cloth just larger than the hole in place, followed by glass matt the sise of the hole followed by glass cloth increasing in diameter (2 layers) over the matt. I would then saturate with resin (I would use fast hardener) and then move to the hole on the other side and repeat.

After a suitable time period (maybe an hour?) I would go outside, remove the plastic wrap and apply two - three layers of cloth and resin on each hole. Not sure how to stop it from dripping but suspect plastic wrap and tape could be used to hold in place.

Repeating this process of alternating between inside and outside I would build up the patch to the thickness of surrounding hull. Then wait 24 hours to cure and apply thickened epoxy witha sandable filler (probably west 407) to build up to a smooth surface - sanding with 80 grit and Random orbital sander. Also inside.

Any comments on transducer locations? Will the flow over fwd head thru hulls affect in any meaningful way?

Any comments faults with patch plan?

What does epoxy need to be overcoated with before applying bottom coat (Micron CSC)? Inside I would use a primer and then a bilge paint.

Thanks

Mike
Full Tilt 2

[sailingdog]

Originally Posted by mikehoyt

A number of years ago I purchased a Raymarine ST40 Bi-Date Speed/depth/log instrument that comes with two thru-hull transducers.

Due to the layout of the inside with a shallow bilge and the intake and outflow thru hulls for the head that had been installed forward I installed these thru hulls port and stb beneath port & stbd settees as close to centerline as possible beneath these settees. The problem is that when the boat heels more than say 15 degrees either the speed or depth transducer stops working.

The diagram below illustrates the bottom of my hull and shows approximately where the existing thruhulls for the marine head and the transducers are located and where I can move them. The locations available are limited by a depth beneath the floorboard of less than three inches between settes and in head area. Where I have indicated is under the vee berth behind the water tank whereas the head thru hulls are fwd of the water tank.

diagram at http://fulltilt2pics.angelfire.com/thruhulls.GIF

The transducers are sealed with 3M 4200 I believe.

The image isn't there. This is what I see when I click on it:

My plan is to remove them and then fill the holes using West or East system epoxy grinding a tab angle both inside and outside the hull.

Grind to an 8:1 bevel or thereabouts if possible.

I would start by placing plastic wraop on the outside of hull held in place with tape. Then I woudl move inside and put a layer of cloth just larger than the hole in place, followed by glass matt the sise of the hole followed by glass cloth increasing in diameter (2 layers) over the matt. I would then saturate with resin (I would use fast hardener) and then move to the hole on the other side and repeat.

After a suitable time period (maybe an hour?) I would go outside, remove the plastic wrap and apply two - three layers of cloth and resin on each hole. Not sure how to stop it from dripping but suspect plastic wrap and tape could be used to hold in place.

Repeating this process of alternating between inside and outside I would build up the patch to the thickness of surrounding hull. Then wait 24 hours to cure and apply thickened epoxy witha sandable filler (probably west 407) to build up to a smooth surface - sanding with 80 grit and Random orbital sander. Also inside.

I would use at least three or four layers on the inside, and the same on the outside. Don't over saturate the cloth... just wet it out enough so that it turns transparent... laminates are stronger and lighter if they have a higher ratio of glass to resin—as resin itself is fairly weak and heavy. Get rid of the air in the laminate as well. Good fiberglassing should appear almost transparent...it is glass after all. If it is whitish or cloudy...it still has a lot of air trapped in it. After it cures, it should have a nice greenish translucent appearance.

Also, if you're using West System... don't forget to scrub the cured laminate with a scotchbrite pad and rinse heavily with water... If you don't the amine blush will prevent the thickened epoxy filler from bonding properly. Don't use microballon filler, use chopped glass strand instead. The microballon fillers will absorb water—chopped glass won't.

Any comments on transducer locations? Will the flow over fwd head thru hulls affect in any meaningful way?

Turbulence may affect the depth transducer's ability to function properly. Most depth transducers are recommend to be installed aft of center.

What does epoxy need to be overcoated with before applying bottom coat (Micron CSC)? Inside I would use a primer and then a bilge paint.

Don't forget to scotchbrite scrub and rinse the epoxy to remove the amine blush, then sand to roughen the surface a bit. Use Interprotect 2000E as a primer, then paint with your bottom paint.

[Hartley18]

A number of years ago I purchased a Raymarine ST40 Bi-Date Speed/depth/log instrument that comes with two thru-hull transducers.

I have been seriously considering purchasing one of these once I get enough pennies saved up (maybe Christmas?)... but the thought of two holes in the hull rather than just the one offered by more expensive "triducer" setups has made me hesitate a bit.

I'm still hoping that someone will invent an cheap GPS unit the same size that will do speed/depth/log and tell me where on earth I am in one handy little gadget. Anyhow, when it's working, how do you find it? Is it as good as the spec sheet makes it out to be??

--Cameron

[mikehoyt]

Sorry about the link. Apparently you have to cut and paste it into address bar of Explorer. Not sure why I could not upload pictures duirectly. Possibly fiewall issue.

Thanks for the point about chopped glass vs micro balloons - I would have missed that.

The ST40 unit is great if you do not need to have it tied into a series of repeater displays, etc... In our cockpit even the smaller numbers are clearly visible from aft end of cockpit. (you can toggle between large depth, small speed and large speed, small depth). The unit is reliable and at $349 cdn a very affordable device. Remember if using GPS that GPS is speed over ground vs speed over water - can be important if currents, etc... at play and esp if doing any racing. I have heard of display issues with Navman (LCD dies) but not of any with Raymarine ST40. I have had no problems with the display units and they are easily removed for winter storage...

Location. Now they are about 1.5 feet either side of keel and behind and to the side of head thru hulls. Also beside keel rather than in front of keel. No problems with depth interpretation here - just not so sure if behind the thru hulls for head (2 feet) if this will be a bit bad or a lot bad.

As for how do I like them (more or less answered above)... My boat is for sale. The very first thing I would buy on a cheaper replacement boat is this same instrument. In marine terms is an outstanding value. The only one I would consider in its place would be the more expensive ST60 or Tac Tic but then again we are talking of value. Note that I have also the ST40 wind and without the seatalk cable you can just connect the two yellow wires and get the same thing... ST40 wind is OK but not as good in relation to other products as is the bidata.

Mike

[sailingdog]

Mike-

Trust me...the photo uploading issue isn't your machine.

Glad to help.

[KeelHaulin]

The best way to repair a hole IMHO is to taper it on the outside and patch from the outside. A layer of roving can be bonded to the inside as a starting point. It's more difficult to do but the resulting patch will be much more resistant to being "pushed in". The angle of the taper you grind should be generous (several inches on all sides) to maximize the bond surface area and minimize delamination.