Building foiled rudder question.

[5monkeys]

Hi Folks,
    Working on a foiled rudder here. I have ripped a mix of poplar and some other unidentified hardwood from the garage. Into 1 1/8" strips. I'm rotating them 90 degres and gluing them together. In an alternating pattern like butcherblock. My question is should I use tight bond (cheap and easy) or epoxy (messy and pricey)to glue it up?

[philb Junkie19]

Hi Keith,
I held off on giving an opinion seeing that you already started and hoping someone more knowledgable about poplar, would respond. I would be cautious using it. I know that it is used for interior trim or outside where it is not exposed to the weather. Here in Maine it is also used to make OSB 4x8 sheets, basically chipboard. They can swell and weaken when wet. I don't know if that is relevant to milled strips. Not sure which tightbond adhesive you are looking at. I don't think any of their common water resistant glues are meant to hold up regularly immersed.

I made a centerboard out of spruce like you describe and glued it up with epoxy and long clamps but never tested it. The boat also had a keel and was sailing ok without a cb when I sold the boat.  Over the past thirty years I used a lot of epoxy. It's great and hateful stuff. It would be good for gluing up your pieces but shaping will make a lot of dangerous dust if it is not fully cured.

Phil

[crazycarl]

all woods will rot when left in a dampened state, some just rot slower than others.   generally the denser the wood, the slower it is to decay because it's natural ability to keep water out.  this must be considered because if the fiberglass covering is cracked or breaks from an impact, water will seep in. 

this is a project where every fall i move my rudder to the shop to foil it, and it never happens.  i have several options available in my shop.  a piece of 4"x14"x9' red cedar, 40 board feet of IPE, and a 4"x24"x4' piece of high density foam.  (not cushion foam) the foam would be the easiest to work with.  it can be shaped with a surform file and takes fiberglass and epoxy well.  however, it also absorbs water over time.  the IPE, or ironwood as some call it, is the most durable, but also the hardest to work.  carbide tooling is necessary and screw and nails holes must be pre drilled.  the stuff is so dense it sinks.   the best adhesives i've found are epoxy and gorilla glue.  i will say that i replaced all the outside teak on my first boat with IPE, and 10 years later it still looked as new.  then there is cedar.  lightweight, easy to work, and has rot resistant properties.   white oak has been used in boat building for centuries, but it's also expensive.  another, cheap alternative is pressure treated lumber.  when dried, it is easy to work and will last decades exposed to damp conditions.  however,  getting a glue to adhere to it can be tricky. 

i also have a moderate supply of teak.  because of the natural oils in teak, it too is hard to glue together, but it also makes it the most rot resistant.  to glue teak, it must be thoroughly washed with acetone to remove all the surface oils.  of course doing so will defeat the use of using teak for it's rot resistance.  also, teak's price alone will deter one from using it for anything but decorative cabin moldings.

if i ever foil my rudder, i'll use the IPE and foam.  i have carbide tipped bandsaw blades and a 6"x80"  horizontal sander to do the hard work.  the IPE will only be at the leading edge and bottom for impact resistance.  the foam will be glued to the aluminum rudder blade and shaped before everything is covered in fiberglass. 

i will have to check my stock from when i had my pattern shop.  i may still have sheets of carbon fiber and kevlar.

good luck and keep us posted with pics!

[5monkeys]

Hi all,
   Gentlemen, Thanks for the feedback. I've only cut the strips at this point as I'm on travel for work this week, but should be home Friday night. I must confess there is a bet of experimentation involved here and perhaps frugality has bled into cheapness. I'll try to be careful of that.
I probably should mention I currently have 2 rudders, one is badly pitted and corroded. This is the one I intend to use  as the core. If this goes all wrong I still have a good rudder to save the sailing season. I suspect that pitting will only assist in providing grip to the "glue".  while, I don't want to spend a fortune on this project, I don't want to guarantee it to fail either. So, I think I'll use thickened epoxy to glue up the strips, then put heaters around it, and allow it time to cure.

this is the tentative plan after that...

Once cured I'll plane it flat

Then I'll cut the plank in half..
Route a 3/16" relief out of the "inside" of each to accommodate the 3/8" rudder blade.

I saw on duckworks where a gentlemen had made a jig with plywood to manage using a router to shape the blade like a 3d printer head...I plan to do the same.

once shaped I'd use thickened epoxy to glue the two halves to the cleaned aluminum core..

I will probably wrap the entire creation with a layer of  cloth and epoxy to help seal and protect the wood.

If it looks terrible, I'll paint it.. if it looks cool, then I'll have to protect it with something else (I don't know what yet).

[brackish]

As a long term woodworker I would actually advise against using solid wood or glued up panels of different species for the rudder,  You will have to deal with glue adhesion issues, differential expansion issues, and potentially cross grain glue up issues depending on design.  I would go with carved foam with glass epoxy coating or alternatively a wood frame covered with 1/4" Okoume or Meranti plywood which should bend to the form then glass epoxy with the appropriate fairing.  Full disclosure, I haven't done this just know how unstable solid wood can be.

but to be specific as to your question, I would use Titebond III as long as you plan to cover the finished unit with glass/epoxy.  Epoxy really prefers some gap on glueups, hard to do with a hard clamp.  I would avoid teak or any oily wood for the the project, does not glue well, Smith's Oak and Teak epoxy would be my only choice for that.

[brackish]

going off topic a bit but interested in adding to knowledge base.

"i will say that i replaced all the outside teak on my first boat with IPE, and 10 years later it still looked as new".

Did you finish it and if so what did you use?  How often refinish? Does it change color over time? Curious as I have never worked with it, it is not locally available.

[bruce]

I used a similar approach to foil my rudder, attaching cheeks to the stock rudder as a core, so I'll put my 2 cents in in case there's something useful for your project. I was using a NACA 0012 profile with a 12" chord, so the maximum thickness was about 1 1/2". Two 3/4" cheeks was just right.

Like brackish, I have 40 years of woodworking experience. I wanted to use a material that I could shape using tools I had on hand, but durable in the marine environment. 3/4" Starboard planks fit the bill. I found a 24" x 30" piece on eBay, enough for both cheeks, for about $50.

I haven't seen the router jig at Duckworks, but the dado head I had on my table saw did something similar. By tilting the dado head and adjusting the height I could rough out the cheeks. The same could be done with wood, of course. There was some final shaping, but hand planes, files, and abrasives took care of that. The biggest problem was the static charge that would build up working the plastic, shavings stuck to the tools and had to be cleared frequently.

Once I had the cheeks fit to the core,  I temporarily mounted the rudder to see how things were going. The rudder had picked up 9 lbs. in weight. My intention was attach my rudder uphaul to the small triangular tab you can see on the core in the second photo, but the weight and balance were off. My solution was to attach bars to the core, creating a lever to attach the uphaul to. Whatever you do, check the weight.

Starboard can be welded, but my experiments with what equipment I had on hand were not encouraging. Rather than rely on an adhesive, I elected to use FH nylon machine screws tapped into the starboard cheek. I filled and faired the countersunk FH screws in the port cheek with hot melt adhesive toned with white pigment. I wasn't going for a perfect match, just to make them less noticeable. I trimmed the screws where they emerged on the Starboard cheek flush.

We dry sail, so I wasn't overly concerned about water that may enter between the cheeks and core. Caulking the seams, or cutting drainage channels in the cheeks next to the core could be considered. I wouldn't use Starboard if I wanted to encase the rudder in fiberglass, I doubt it glues well, but it would be fun to investigate the structural foam boards on the market.

[5monkeys]

Thanks for all of the great feedback!

I'm just adding the duck works article to the

https://www.duckworksmagazine.com/09/howto/foils/index.htm

[crazycarl]

going off topic a bit but interested in adding to knowledge base.

"i will say that i replaced all the outside teak on my first boat with IPE, and 10 years later it still looked as new".

Did you finish it and if so what did you use?  How often refinish? Does it change color over time? Curious as I have never worked with it, it is not locally available.

i finished it with tung oil.  i cannot remember if it was 'cooked'' or raw.  i bought this from a boat building shop in upstate new york while on a motorcycle tour.  the old man who sold it to me swore by it.  i only applied it once.  unlike poly, oils don't flake when aged.  i let it go to see what would happen.  the dark color did fade a bit, but not so much as to make it noticeable to others.

as for the IPE, i had just purchased 1,000 board feet of pattern grade mahogany when the foreman of the hardwood company asked if i had any interest in exotic woods.  i didn't, but thought i'd take a look.   he wanted $100 cash for as much as i could take that day.  i overloaded my F250, filling the bed and the ladder rack.  it was long, slow drive on back roads from milwaukee.  i didn't arrive at the shop until well after dark and then it took some time to unload and stack the wood. 

i made mallets from the lignum vitae and sanding blocks from the rosewood.  from the walnut i made a gerstner type toolbox to a gentleman's specs for his gun cleaning supplies, and turned bowls and chalices to sell from various woods.  most of the other woods i sold for a hefty profit, but no one wanted the IPE because it was too difficult to work with.  i have a nice piece glued up and sitting in the lathe now.  i intend to turn another striker for carving.   

i have a 20" surface planer and after sending a couple IPE boards through, the HS steel blades have to be removed and sent out for sharpening.

[bruce]

i had just purchased 1,000 board feet of pattern grade mahogany when the foreman of the hardwood company asked if i had any interest in exotic woods.  i didn't, but thought i'd take a look.   he wanted $100 cash for as much as i could take that day.

"100 bucks, I guess I can do that..."
Sweet deal!!! They must have really been tired at looking at that stuff.

[crazycarl]

I like the starboard, this has me thinking.  Not something I'm use to.

[CaptK]

I am a wood butcher, but I used to make a pretty mean surfboard, and while I didn't make the first foiled rudder, the one I did make was a loong time ago ('02, '03 or so...?) and I used foam. 

The very first, "test" version was just to see if 1) it made enough difference to work, and 2) be worth the work it took to make. It did on both counts. It was simply pink EPS household insulation foam shaped to a NACA foil and then lightly glued onto the blade and wrapped in aluminum tape for a modicum of strength. Made it thru a couple of short trips as a proof of concept. I then made one of the same foam, but glassed, and in two halves intending to mount it permanently on the regular AL blade.

I don't recall the hows and whys now, but during that time Joel Santarone of what was then called "IdaSailor" got in touch and I gave him my research and numbers and he tooled one with an AL spine and Starboard for the body/foils. The first one, the spine material was a bit thin and bendy as it turned out, but the second one Joel took care of that and it wound up making a world of difference in the performance of my CP-23.

The starboard (or other UHMWPE) works better than foam because it is tougher, easier to keep clean, and being denser, easier to drop properly into position than the foam version. I had to push the foam one down, end even 'locked' into place it would work up after a bit. You will not be able to get glass to stick to the Starboard, and it doesn't need it anyway. Last, be prepared for a HUGE difference in how your CP handles with the new rudder.

[5monkeys]

I see that the wood on hand may not be ideal, perhaps I'll make some non-marine project out of it then.

I do have some 2" rigid foam insulation leftover from another project (Polyisocyanurate Rigid Foam Insulation Board) I could try and shape that. It's not starboard, but it is on hand and is easily shaped (maybe too easily).