Online metal shops and my Monitor

[GBR3068]

Two reasons for posting this:
1. I had a problem with chafe on my Monitor steering lines. Needed a custom metal bracket.
2. Used one of the online metal shops and built the part in 316 for $15. Hate to think how much it would cost anywhere local. I really think this changes the game for maintenance. Not the first time I've used these services, I have also built things like alternator brackets and pulley spacers, but posting this Monitor design as a simple example to give you the idea and perhaps get you started.

Here was the problem. My Monitor steering lines rub against the backstay. See first photo. (By the way some may notice I am not using the Scanmar blue/white Dyneema, I use Petzl orange/white PUR see, for example, https://colinhaley.com/nugget-1-the-petzl-purline/ I think the Petzl Dyneema sheath is more chafe resistant, we'll see). By making the plate you see in the photo the pulley can be moved enough to stop line chafe.




Solution: I used Inkscape (free drawing program) to draw a part and an online service (I used SendCutSend but there are several). Cost was $15 in 316 stainless.



I've attached the files. You draw in vector graphics or .svg then export and send a .dwg file. Both are in the attached ZIP (no way to attach the raw CAD files).

 

[BobJ]

This is timely - thanks! I've completed my pattern and will confirm it on the boat tomorrow. It's a piece about 22" long (x2) and in keeping with Surprise!'s appearance standards, it has a long, sweeping curve to its top edge that would be a challenge to draw in software, even if I knew how.

I plan to send S-C-S a full-sized pattern and pay their fee to convert it to a CAD file before machining.

 

[GBR3068]

You can make in a cheap material, say ABS or acrylic plastics, before you commit to something harder to work, like stainless. I've done that a few times. Start with cardboard, move to a plastic intermediate before making multiple metal finals. You can easily file or shave the plastic intermediate to fit exactly and form a master.

 

[BobJ]

Great idea, and I could also see approx. how they'll look.

I wish SCS offered polishing. I have the stuff to do it if the parts come back smooth, but that's a big "if." I'll also need a plate welded on the bottom.

Here's the project:

 

[BobJ]

Getting back to this... SCS will create a CAD file (which they retain) and then give me an estimate for the plates. But they don't do electropolishing - any local recommendations for that?

Or if I get a CAD file made, there are other sites who will quote on the spot, and some do the polishing. Any recommendations to have a 2D CAD file made from my template?

I'm still trying to avoid dropping the big bucks at the boatyard.

 

[breezetrees]

Getting back to this... SCS will create a CAD file (which they retain) and then give me an estimate for the plates. But they don't do electropolishing - any local recommendations for that?

Or if I get a CAD file made, there are other sites who will quote on the spot, and some do the polishing. Any recommendations to have a 2D CAD file made from my template?

I'm still trying to avoid dropping the big bucks at the boatyard.

If you trace your template onto graph paper and annotate critical dimensions like hole spacing I could cad it up for you, it’s a simple shape to trace with splines I think.

 

[GBR3068]

Here's a pretty good overview of what you need to do and all the "lingo" and "buzzwords" https://www.scan2cad.com/blog/cad/convert-paper-patterns/#online-converters You could use Scan2CAD free to try it https://www.scan2cad.com/free-trial/

I use Inkscape. It was pretty easy to learn once I had some examples. Curvy shapes are pretty easy by just adding points and tweaking the "handles" that each point has to adjust the curviness of the lines running through them. Plenty of videos online, you just have to wade through the garbage ones like anything else these days. Its a very useful boat maintenance skill to have, I think.

Stepping into unknown territory but I "polish" my stainless by hand. The cost for polishing is more time than materials I think. I wouldn't say I go to a mirror finish but it looks OK to me. The parts I polished before install were mostly flat which makes things a lot easier. On some I started from bar stock which has all kinds of printed markings on it and is basically dull. I just used an angle grinder and 3M pads and discs. On the really dull stuff I started with a conical flap disc but the stainless you get back from an online shop is already pretty shiny so you wont need that initial step. If you really want a mirror finish I think you can still do this by hand, just search on "polishing stainless steel" and you'll find all the petrol-head and biker videos that show how far they go. Now you mentioned electropolishing and thats way out of my wheelhouse but do you want to do this because you think it will give you a better polish or because you want to improve the passivation? If the latter then (at the risk of igniting a flaming thread) what I use is Wichinox https://marine.wichard.com/en/stain...ntenance/passivating-paste/wichinox/part-9605 I use this because it has phosphoric acid (and thats what they usually use in electropolishing plus electricity of course) and its a gel, so it sticks. You have to use it carefully, not leave it too long and carefully wash it all off with water, but it passivates (and cleans off any discoloration, rust, etc.) better than anything else I've found.

Also dont forget that you can bend the metal from online shops. This changes the way I think about making parts, I'm not saying you should change your design but as an example you could bend flanges onto your bow roller sides and eliminate the need for welding the bottom plate. Just as an example. The online shop capability has definitely changed the way I make parts for my engine for example.

I attached some examples (picture below, zip file attached) that you could practice with and some (like my alternator bracket) you could even use a starting point.
1. Alternator bracket. For Kubota engines such as Universal and Beta Marine. This is a weak spot on all these engines as the bracket mounts to the thermostat assembly, If you break the existing structure usually cobbled together with spacers on both types of engine you are in for a world of hurt as you have to take the whole timing cover off.
2. A tabbed washer that I use on bolts so I can tie a safety wire to the washers so I dont lose them on install and removal.
3. Pulley for Kubota, Universal, Beta Marine.
4. Spacer with an extra hole to allow you to grab and tie to each of several spacers so you dont lose them.
5. A rigging plate. Use this on my shrouds to keep halyards from whapping on the mast.

 

[BobJ]

Thank you, Breeze and GBR (both Mikes I think). GBR, I've used Winchinox and plan to use it on the old plates, to which the new plates will be bolted. This should discourage crevice corrosion between the plates. The electropolishing process should do the same for the new plates, while removing foreign materials left from machining. Once I have a CAD file, I can use an online shop that also does electropolishing. I found that using the spline tool in their free software was frustrating, and I really want to get that curve right.

I'm thinking 3/16" SS will be hard to bend, and would leave a radius that won't fit tightly to the old anchor roller assembly. The challenge with this project is that the anchor roller, deck plate and headstay tang slot are one integral piece, which is hard to access from inside the boat with that big anchor locker between it and me.

I appreciate your suggestions.

 

[GBR3068]

Here you go. This is an SVG and DXF file in the zip attached that are pretty close to your template. I also put in the JPG file I created from the image you posted (and that bitmap is in the SVG and DXF file and will need to be deleted before submission, I just left it there so you can see how close I am to your template currently). You should be able to play around with this and get pretty close. I put two approximately 3/8" holes where you wanted them, but you'll need to copy and re-size or create new holes for your 5/16" mount holes. Watch the units because the template was in pixels and I just converted to inches. I don't have any easy means to judge your dimensions, so just scale it. For your first attempt I'd try plastic.

 

[BobJ]

SendCutSend is indeed remarkable. I uploaded the DXF file last Thursday and the parts arrived yesterday: $104 w/free shipping. The bottom plate added another $41. The plates match the drawings precisely. Big thanks to Breezetrees for the DXFs and PDFs, and to GBR for the advice.

I'm waiting on a wider roller, the Wichinox and the welding and polishing.

 

[GBR3068]

Very nice! I hesitate to tell you what that would have cost at the local boatshop, but my PO had a small alternator bracket made that cost over $1k. Let us know where you decide to get the welding done. It was not easy for me find job shops for 316 stainless. I'd be curious if they use TIG or MIG, what gas, and also if they have any concerns about distortion. I dont think you are high precision here, but I think it will distort.

The Wichinox is expensive if you have a lot of stainless on the boat. Wichinox is 25-50% H3PO4 (according to the MSDS at https://marine.wichard.com/en/stain...ntenance/passivating-paste/wichinox/part-9605 ). I've now started mixing wallpaper paste and a cheap phosphoric acid stone cleaner (Rust-Oleum does one with *exactly* the same 25-50% concentration, wouldn't be surprised if its the same source) and it works a bit better because you can control the stickiness. I just have to be careful.