WTC Saddles

[mylo]

Hey all,

I'm trying to design some WTC saddles for my VIIc/41. I like to work with MDF for it's ease of shaping, but it's water resistant properties are less than desirable. Will a coat of West System Epoxy (same stuff the hull is made from) over these MDF saddles work to waterproof them, or is this just asking for trouble down the road ? MDF + Water = Bad News, that's a given but does MDF + Epoxy + Water = No Problem ??

Thanks,

Mylo

[PaulC]

Hi Mylo,

I've used a plywood

Hi Mylo,

I've used a plywood thrust bearing bulkhead sealed with epoxy in a boat for a number of years and have had no problem.

However, today I would use it as a master, make a mold, and cast it in urethane -- because I can. At the time I built the boat in question I didn't have the necessary experience.

[mylo]

Paul,

I was wondering about

Paul,

I was wondering about that.

Urethane.....again my ignorance is going to shine through....how does urethane differ from two part plastic resin (the stuff I have been casting my other parts from) ? ....is it the same thing ? Do you have any pics of the product you use ?

What are you using for a thrust bearing ? My prop shafts are going to be 1/4" diameter x 3' long to reach the WTC. I need the bearing to act as both a thrust and steady bearing which will be mounted in a bulk head at about the half way point. Is this an idea, or should the thrust bearing be mounted closer to the WTC / closer to the props ?

Thanks,

Mylo

[PaulC]

Mylo,

What you use is the

Mylo,

What you use is the same thing I'm talking about: a urethane casting resin. It may be called different things but the end result is the same, a cast plastic part. Lately I've been using the Task 2 material from Smooth-On. It has a little bit longer working time, cures into a very tough material, and comes in small quantities (quart kits). The only drawback I've found is it is very sensitive to humidity -- which we have in abundance on the Gulf Coast.

I have a bulkhead with a flanged 3/16" oilite bearing in it which receives the thrust from a wheel collar on the shaft. The set-up you describe sounds very good. The bulkhead should work fine for shaft support and thrust.

[corsaire]

Hi,

I like using 1/4 inch

Hi,

I like using 1/4 inch polycarbonate as bulkheads, it's strong and impervious to water, I like using Plumber's Silicone to secure them to the
FG hull, it works very well for me. I also like using flanged oilite bearings, but I've read somwhere here that RULON bearings are even better due to the almost zipo friction factor. See pics.

Brian

[JWLaRue]

Mylo,

What diameter will your dive

Mylo,

What diameter will your dive module be? When I built my OTW Type VII (1/32nd scale) it turned out that I did not need any saddles to support the WTC. I simply used a series of three small rubber pads along each side of the open keel as foundations for the dive module. This raised it up enough so that the top of the ballast tank was at the surfaced waterline.

Of course, I did need to add two sets of tie down straps to hold the WTC in place.

-Jeff

[mylo]

Jeff,

The WTC is going

Jeff,

The WTC is going to be 6". I prefer the idea of having a rigid mount for the WTC and have the thing seated in there. I've made the masters and am about to pour the molds. I'm going with the resin castings for these things as well as the thrust / steady bearing aft bulk head as well as a fore support bulk head. I like the idea of pouring the castings to ease duplication as well, the resin machines very nicely for any bearings/supports/screws, etc., etc. that may have to be done to the bulk heads and of course, is not going to have the potential for any water problems as MDF would.

Does anyone have a link for those thrust bearings ?

Thanks,

Mylo.

[JWLaRue]

Mylo,

Understood.

Just to be clear for

Mylo,

Understood.

Just to be clear for others who might be interested, the way that I mounted my dive module is rock solid. The WTC rests on the rubber pads, which in turn rest on the inner surface of the lower hull, and is held into place with a pair of custom-made brass straps that include a tool-free means to remove the straps and the module. See the photo below:



Done this way, one can pick up the sub by grasping only the dive module....that hull and WTC are not going to separate!

-Jeff

[mylo]

Jeff,

I really like that

Jeff,

I really like that clamp setup you have. I would like to use the same thing, except have that clamp somehow mounted to the saddle so that the clamp sucks the WTC down in snug into them. The "tool-less / quick release" system you have there would be nice.

Mylo

[JWLaRue]

Mylo,

If I understand correctly.....the ends

Mylo,

If I understand correctly.....the ends of the straps are anchored on the inside of the saddle tanks about at the middle. This exerts good, downward pressure on the dive module, which is what makes it such a snug fit.

I don't have a photo of it, but the strap ends are wrapped around a piece of brass tubing and soldered. To securely mount the strap, I epoxied onto the inner saddle tank wall brass tubes that are located on either side of the strap end. A stainless steel pin (1/8" diameter) is slid through one anchor, through the strap end and into the other anchor.

Hope this text description makes sense!

-Jeff

[manowar]

Mylo,

Get your Oilite or Rulon

Mylo,

Get your Oilite or Rulon bearings here: http://www.smallparts.com/products/desc ... bb-fbb.cfm
They have many, many other useful items such as specialty o-rings and seals.

If you want to order Canadian go with]http://www.bcbearing.com/[/url], More expensive, but it'll be faster and work out to be the same price because of customs' saving and shipping.

Joel

[corsaire]

I just have to add

I just have to add that be careful when ordering Rulon bearings from
Small Parts, when I did the batch/pieces I got weren't precisely 3/16" ID as ordered, there was a little play in it, which it didn't on the oilites, so I ended up returning the Rulons and using the oillites I already had. Perhaps I was just unlucky to get a bad batch. But I'd rather order from Mc Master either way double check that you get a perfect snug fit on your SS shaft.

Brian

[pirate]

Mylo,
Another nice material to make

Mylo,
Another nice material to make the WTC saddles out of is sheet PVC. You can get scrap pieces from a sign shop, or whole sheets even. Also available at plastics wholesalers, but they may make you buy whole 4' x 8' sheets. Most places will cut for you for a price too though.

Pete

[mylo]

Many thanks for the input.

I've

Many thanks for the input.

I've casted the saddles out of plastic from molds made out of rubber using an MDF master. They turned out very nice.

Mylo

[kazzer]

I simply go to a

I simply go to a hardware store and buy the connecting sleeves that fit over plastic water pipes. I cut the saddle from them, add a stainless nut and bolt to secure to the hull and provide a Sub-driver (WTC) locating pin, then glue in place a VELCRO strap with buckle.

If you find a little wobble in the saddle, place a small amount of Epoxy putty

http://www.caswellplating.com/aids/quikwood.htm

under the saddle just prior to tightening down, and it will form wedges underneath.

Finally, glue the Velcro strap outside the saddle, and you have the simplest/fastest cylinder holding system out there!