DELRIN KEEL BLOCK

Hello lift-keelers. After crane out I see that the delrin block mounted at the back of the keel box has split. Fair enough, the ocean floor did leap up and attack me a few times this year. I’ve replaced the block before, it’s not the easiest of jobs. Before I carve another piece of dense plastic delrin to replace the split block, I am asking myself if there could be an improved solution.

I believe this block has two functions
- provide a slot to guide the rear edge of the keel as it is raised and lowered, and keep it aligned fore and aft when underway
- protect the fibreglass at the back of the box from impact damage from the keel’s trailing edge should the keel strike an object

For the first time in my experience there is a small chunk of damaged fibreglass as the keel split the delrin block then travelled a little further. With its V shape to guide the back of the keel, the delrin block is likely to split on impact and has done so several times in the past. I’m leaning towards an experiment. To improve shock absorption I am considering using a hard rubber insert in place of the delrin. Something along the lines of a home brewing rubber bung is very dense and might give better impact protection. It may also be easier to carve to fit the hole. It would have more friction against a rising or lowering keel though I think the front keel roller takes most of the pressure.

Have you tried an alternative to delrin at the trailing edge of the keel block? What are your thoughts about a rubber alternative that would compress then return to its normal shape?

---

This is where the suggested topic separation of the 26/27 from the 275 makes sense.
The mass of your 275 keel obviously makes the difference here as so will the profile of trailing edge and block.
I made a pair of replacement blocks for our 26/27 MK2 the other winter although it was only really the aft block that was severely worn,having lasted though for about 30 seasons of sliding and grounding - so perhaps not susceptible to splitting in the same way.
I did though make a cast of each block so as to be able to progressively 'scribe' it in to the correct beddding profile ,using blue chalk dust as a marker.The aft mould wasn't worth saving but the forward mould is shown here.
I also see that there are instructional You Tube videos of casting e.g. Urethane .
Perhaps there are possibilities here ? casting in some material rather than the tricky task of paring away a rubber block ?
Peter

Hi Peter, Ken,
fwiw I replaced the blocks in Artemis (P27) a few years ago using solid PTFE bought on ebay as an 'off cut' block.
I have access to a bandsaw so shaping the blocks was fairly easy once the varous angles had been accounted for. The only problem so far is that the keel becomes very tight when fully down - so I guess a little fettling could be in order. The original blocks were nylon or similar so using PTFE was not too different.
They seem to protect the boat hull well - but still damage the rear of the keel when grounding which seems to happen regularly on the east coast - Harwich harbour seems to have a drying patch in the middle and the bars of both Alde and Deben have all modified the keels aft profile. Our club has facilities to remove the keel at same time as lowering the mast so repair can be effected at home in the warm and dry.
rgds
Chris

I replaced the [fractured] block on Dark Star [P275 No 36] a few years ago. I have tried to be careful since then!

I didn't think of the idea of taking a cast of the pocket the block fits into. Speaking to Chris [previous post] it sounded as though his block didn't have the same sort of 3D geometry mine had.

I made the block from some 20mm thick Delrin. I used a lot of templates of the pocket opening and base, with profile gauge sections fore & aft, athwartships, and on diagonals to help shape the block. It took a lot of fiddly sanding to finally get it to sit home.

---

Thank you for your advice and encouragement. I was back at the boat fitting in as much maintenance as I can before lockdown starts. Looking at my split delrin block, I think it will always be prone to splitting. After carving a V slot to allow the keel to travel there will never be much thickness remaining at the back. So I decided to try something new. The delrin is mostly still there at the sides so I left it in place, split. I fashioned a small rubber bumper from a rubber home brew wine cork and used gel coat filler to hold it in place at the back of the slot. It’s not very big so the keel should still lower ok. I then filled in the remaining small gaps between delrin outer and the hull using more gel coat filler. At the end of next season we will see if it worked.

In summary I am now using the delrin only for lateral guidance and rubber for bumper protection.

While I am here I can report a good outcome at the front of the keel. Two seasons ago I replaced the front keel roller, at the bottom leading edge of the keel slot, with a stainless steel roller. The reason for this was frustration with the way that the plastic roller always developed a flat and therefore no longer rolled. After the second season the new stainless steel roller still rotates freely and is perfectly round. There is no sign of galvanic action.

---

While I am here I can report a good outcome at the front of the keel. Two seasons ago I replaced the front keel roller, at the bottom leading edge of the keel slot, with a stainless steel roller. The reason for this was frustration with the way that the plastic roller always developed a flat and therefore no longer rolled. After the second season the new stainless steel roller still rotates freely and is perfectly round. There is no sign of galvanic action.

Ken,

Pleased to hear that the S/S roller is a success. Do you find any damage to the leading edge coating on the keel, particularly over the last 300mm of downward travel of the keel? I'd be interested to find out whether the S/S roller is better from that point of view too.

Regards

Dick

---

Dick,

Thank you for your interest. Great keels lift alike. When Vol-au-vent is craned out each year, I am always surprised at the relatively decent cleanliness of the keel. That said, while the paint at the sides is always in good condition, with no fouling, the leading edge paint does get patchy, with some paint being rubbed away by the roller. The interesting point is that the leading edge end of season condition seems to be the same whether a plastic or stainless steel roller is fitted. The plastic roller always developed a flat and anyway failed to rotate by end of season. While the paint is a bit bumpy, there is no flat worn on the leading edge of the keel. It looks normal and the stainless roller continues to roll. If you can hold on until October, I can send you some pictures of the keel leading edge 😀.

While I am here and we are talking keels, did I previously mention a new approach to the trailing edge buffer block? I don't remember so let me explain. Last year I again managed to split the plastic block that guides the rear of the keel and protects the fibre glass at the rear of the keel box from impact damage. Strictly speaking it was the boat that caused the damage, not me, but let me continue. On this occasion not only did the block split but there was light fibreglass damage as well.

I had two new thoughts

• First, shaping a new plastic block and bolting it in place is a very tricky job, best avoided if possible

• Second, given the thickness of the back of the block, between split and fibreglass, I have a feeling that any impact will always split the block and do some degree of damage.

What to do? The side cheeks were still in place, swivelling a little in the enlarged space after the rear of the block split. Eureka, the way forward was clear. I cut a home brew rubber cork to fit in the space at the rear and jammed it into place. This will provide a little shock impact and is not brittle, so it might survive a light impact. I then used filler to fill remaining void and secure it into place. My memory is vague but I think I did this before relaunch in late 2020 so will be able to gauge its efficacy at the end of the 2021 season.

Will there ever come a time when lift-keelers reach complete satisfaction and stop looking for improvements? I don't think so.

Fingers crossed for a sunny summer season,
Ken

---

Keel news and tips

Let me share my recent experience of keel modifications and servicing tips.

STAINLESS STEEL KEEL ROLLER - WORKING WELL
Two seasons ago I replaced the delrin keel roller that is located at bottom of the hull by the leading edge of the keel. You may recall that I switched to a stainless steel roller after finding the delrin roller always developed flats and then stopped rolling. With the boat recently craned out I am pleased to report that

• The roller still spins freely and has no flats, and I’ve simply applied more lanolin grease
  
• The leading edge of the keel shows no signs of wear
  
• There is no sign of galvanic corrosion anywhere
  

I know of another P275 that also switched from delrin to stainless. Unfortunately on that boat the spindle that is the axis for the roller became detached on one side of the cheeks. This lead to an evil sound while raising and lowering the keel. Also, the bore through the roller was not central. This double error was really bad luck.

AFTER KEEL BUFFER - WORKING WELL
When the hull-level delrin guide split yet again during 2020, after the seabed suddenly attacked Vol-au-vent, I decided it was time for a rethink. I’m pretty sure the thickness of the plastic at the rear of the keel is way too small to prevent any impact damage. The block is really there to guide the keel laterally. It is going to split almost every time there is a grounding. So instead of carving a new block I applied filler at the sides of the remaining delrin block to secure it in place. At the rear of the slot where trailing edge of the keel would impact, i carved an old rubber wine-making cork to fit the hole and then also secured that lightly with filler while leaving the rubber exposed and facing the trailing edge of the keel.

With much apprehension, I recently inspected the area, knowing we (OK, I confess, I) had run aground again this past year. I’m pleased to report that the rubber is still there. It cushioned the blow and stayed in place. I did not have to do any maintenance in this area during our period ashore.

KEEL EYE BOLT TIP - A NEW TECHNIQUE
I have mentioned in the past how I easily remove and tighten the two keel eye bolts. I have a stout long metal tube with one end deformed in a vice to make it into an oval shape. I lower the tube over the eye and, using a tommy bar through the higher end of the tube, twist and release the bolts. It works well.

I remove the shackles from the eyes before lowering the tube over the eye. This year I was in a pickle. Last season I’d changed one of the shackles that goes through the eye that does all the lifting. Oops, the shackle pin was a tad undersized and the pin had bent. It refused to come out. In a moment of desperation I laid the shackle flat against the top of the keel and attempted to lower my tube over both the eye and its attached shackle. To my relief, it worked. With the eye and shackle at deck level I was able to release the shackle. So if you can’t get your shackle to undo, try bringing it out while still connected to the eye. Do apply Coppaslip grease to the eye bolt threads to make for easy removal next time.

KEEL ELECTRIC WINCH NOT LOWERING - ALL WORKING AGAIN
I had reported earlier this year that my Dutton-Lainson winch was happy to raise but would generally only lower if immediately following a burst of up. Peter from Zephyr thought it might be dirt on the brake disk. I did look and didn’t see anything obvious but am happy to report that, without any intervention, it has come back to life and is now fully functional again.

Life must be boring with a fixed keel 😀

---

Hi Ken.
Your experiments with the keel roller raises some interesting points. Bill in the manual always recommended coating the roller in grease, however I believe that this may be the reason for the roller developing flats. I believe that the grease might pick up and trap sand and debris which causes the roller to seize on the spindle. With water as the lubricant, Delrin and stainless is the ideal bearing, so I would suggest no grease

Now your stainless roller on a stainless pin is not an ideal bearing and possibly needs the Lanolin grease, but with the same risk of trapping sand, although obviously it does appear to be working so far.

My ideal solution would be to enlarge the hole in the stainless roller and fit a Delrin liner to run on the spindle without any lubricant, other than the water.

Just a thought,

Peter (Zephyr)

Hi Peter, thank you for your suggestions, just as I was feeling relaxed about my keel setup…😉. Points taken and noted. Of course the reason to fit the stainless steel roller was precisely because the delrin roller always developed a flat and ceased to roll. It was a ‘stiller’, not a ‘roller’. I confess that I did not think about the consequences of having a stainless steel roller on a stainless steel axle. The lanolin I apply is for general lubrication in that area rather than specifically for the axle, and is certainly not intended to attract debris.

What to do? As the boat is afloat until autumn this year I can defer my thinking until later. I’m tempted to leave things be until the roller potentially stops turning freely as that would be a good time to remove the roller and ask my friendly welder to inset a liner for the roller. Thanks again for your suggestions. I will spin the roller carefully at next crane out and make an assessment.

---

Hi Ken, I have made a new front roller for Sophia's keel for Peter Lowry, as his roller was eccentric and being stainless, had worn a flat on the lower part of his keel. I made the new roller using a shaped Delrin roller on a 12mm s/s shaft and with an Oilite bearing push fitted into the Delrin. It will be interesting to see how that fairs when he lifts out and the end of the year.

---

Hi Martin, I like your idea of using a porous bronze Oilite bearing in the roller, these are my favourite 'go to'bearings! However it will be interesting to see if there is any reaction with the stainless shaft in salt water. The axles on my launching trailer are also bronze on stainless and I did wonder if there would be a problem but so far apart from a bit of green discolouration they appear ok, but they are not permanently immersed in the water.
As an aside many years ago I was involved in the manufacture of circulating pumps for central heating systems and initially we did use porous bronze on stainless shafts. However whilst most were ok, occasionally some would pick up and cause rapid wear, so we changed to carbon bearings. This resulted in a large quantity of the bronze bearings being scrapped, some of which I 'acquired' and I have since been putting to good use renovating the seized drums on our electric winches. You never know when things will come handy!

Peter (Zephyr)