Chocks for Lanerboy.

[colhel]

I caught with Shawns thread last night concerng his dinghy chocks. A PM followed by a phone call was followed by some machine time today.
This is still very much a prototype and your opinions and ideas are actively sought. The idea is that they will not need to be held in place with self tappers but will be secured a large dome nut which will also act as a water trap so no water will leak into the lazzerette

Picture1 shows how they look from above looking down onto the deck.

Picture 2 shows the keyholed plate and the plate to take the eyebolt, on the back end you might be able to see the thread on the back, this will fit through a a hole in F/G. In this case the thread is 1 1/4" x 1mm so depending on hole saw availabilty we can use either 32mm or 1 1/4" diameter.

Picture 3 shows the keyholed plate and the dome nut assembled with the acetal washers in place. The F/G will be sandwiched here.

 

[DinghyMan]

I like the large dome nut approach, much better than self-tappers or similar

It may be that the sealant will be strong enough to prevent any turning motion but might they need a pin / couple of pins on the outer keyhole section down into the F/G to ensure that they cannot turn at any time?

 

[jfm]

I caught with Shawns thread last night concerng his dinghy chocks. A PM followed by a phone call was followed by some machine time today.
This is still very much a prototype and your opinions and ideas are actively sought. The idea is that they will not need to be held in place with self tappers but will be secured a large dome nut which will also act as a water trap so no water will leak into the lazzerette

Picture1 shows how they look from above looking down onto the deck.

Picture 2 shows the keyholed plate and the plate to take the eyebolt, on the back end you might be able to see the thread on the back, this will fit through a a hole in F/G. In this case the thread is 1 1/4" x 1mm so depending on hole saw availabilty we can use either 32mm or 1 1/4" diameter.

Picture 3 shows the keyholed plate and the dome nut assembled with the acetal washers in place. The F/G will be sandwiched here.

Very nice Col (as one has become accustomed to, having seen your work a few times ). Much nicer than the laser cutting that was being discussed in the other thread. Also the laser cutting discussion didn't deal with the need for water seal (maybe the plan was to weld a little box on the back of the 6mm plate - I dunno) but I didn't want to sound like broken record on that because I'd already mentioned it earlier.

A few quick comments:

1. In picture 2, the "cup nut" ie the left-most of the 3 s/s machined items, has an internal thread, right? I cannot see it in the pic

2. Teaching to suck eggs here, but installing these needs a 2inch hole saw to cut away the 6mm of teak only, then a 32mm holesaw right through. Remember to do the 2 inch holesaw cut FIRST!!!

3. Personally I would not use the washers. I'd just bed things down both sides onto polyurethane adhesive. I wouldn't want the sponginess that the washers give, and I'd want the polyu to seal the end grain of the teak in the 2inch holes, as water can sit in there for ever. But each to their own on that

4. I would have turned the top flange to a thickness 2mm greater than the thickness of the teak, and turned a 2mm x 45deg bevel to take the edge away. This is how I have always done mine. This makes the chocks stand uplifted 2mm off the teak deck which allows a little air gap for the teak to dry. I put 50x4 s/s strip on the bottom face of my chocks too, so I've got s/s sitting on s/s. I weld the mushroom (that will mate with the keyhole) onto this strip (weld on the far side, so as not to create a filet weld), and the other end of the strip sticks out beyond the teak chock providing a tab with a 11dia hole for the "Colhel M10" knurled knob/screw that holds the chock onto the boat

5. You can drill a small hole into the big nut and make a tool to tighten/untighten, or machine a couple of flats, but that is perhaps not really necessary because these things are fit and forget

6. What's the thread on the tapped hole? M10? I have a few of your lovely knurled knobs left over so can post you back 2 of them if that would help (?) (You'll remember Fairline's M8/M10 mix up, leaving me with surplus "Colhel M10s", which I'm happy to donate back)

Anyway, good going!

 

[lanerboy]

That is looking very good Colin you obviously know what you are doing, I do like the idea that JFM has suggested regards sitting them 2mm higher than the teak with a bevelled edge as like John states it will let air through and will be stainless sitting on stainless allowing the teak to dry underneath as i also I like the idea of having stainless on the bottom on the chocks.

Once these are fitted I will not be removing them so again I will sit it on some sort of adhesive to seal everything and make it 100% water tight

The quality looks really good Colin and I cant wait for you to finish these I think the way you have designed them to fit and secure in place is very clever indeed

Cheers Shawn

 

[jfm]

some sort of adhesive

Sikaflex 291 or 291i in black, or 3M 3200 black.

You could alternatively use Sika 292 or 3M 5200, but only if you're 100% happy you never want to remove these items, because 292 and 5200 form a very strong bond.

I'd suggest not to use any of the Sika products with DC in the title - 290DC is the main one. These are deck caulking and too wobbly/rubbery for this job.

 

[lanerboy]

thanks John we have black sikaflex at work I will check the spec of it

shawn

 

[colhel]

DinghyMan, thanks for posting. I did think about dowelling but with a tightened mating surface of 2" diameter I didn't think it was needed. However if it can easily be modified if neccessary.

Very nice Col (as one has become accustomed to, having seen your work a few times ). Much nicer than the laser cutting that was being discussed in the other thread. Also the laser cutting discussion didn't deal with the need for water seal (maybe the plan was to weld a little box on the back of the 6mm plate - I dunno) but I didn't want to sound like broken record on that because I'd already mentioned it earlier.

A few quick comments:

1. In picture 2, the "cup nut" ie the left-most of the 3 s/s machined items, has an internal thread, right? I cannot see it in the pic

2. Teaching to suck eggs here, but installing these needs a 2inch hole saw to cut away the 6mm of teak only, then a 32mm holesaw right through. Remember to do the 2 inch holesaw cut FIRST!!!

3. Personally I would not use the washers. I'd just bed things down both sides onto polyurethane adhesive. I wouldn't want the sponginess that the washers give, and I'd want the polyu to seal the end grain of the teak in the 2inch holes, as water can sit in there for ever. But each to their own on that

4. I would have turned the top flange to a thickness 2mm greater than the thickness of the teak, and turned a 2mm x 45deg bevel to take the edge away. This is how I have always done mine. This makes the chocks stand uplifted 2mm off the teak deck which allows a little air gap for the teak to dry. I put 50x4 s/s strip on the bottom face of my chocks too, so I've got s/s sitting on s/s. I weld the mushroom (that will mate with the keyhole) onto this strip (weld on the far side, so as not to create a filet weld), and the other end of the strip sticks out beyond the teak chock providing a tab with a 11dia hole for the "Colhel M10" knurled knob/screw that holds the chock onto the boat

5. You can drill a small hole into the big nut and make a tool to tighten/untighten, or machine a couple of flats, but that is perhaps not really necessary because these things are fit and forget

6. What's the thread on the tapped hole? M10? I have a few of your lovely knurled knobs left over so can post you back 2 of them if that would help (?) (You'll remember Fairline's M8/M10 mix up, leaving me with surplus "Colhel M10s", which I'm happy to donate back)

Anyway, good going!

(1) yes there is an internal thread.

(2) understood

(3) The washers are only 1.5mm thick and the only reason I made them was i thought if the the underneath of the F/G was a bit rough it may take some of the stress. On the rear (underside) of the keyholed plate I machined a face groove to allow an O ring to compress and form a seal, you can't see it in the picture but do you think this would help?

(4) Shawn is supplying some eye bolts. We can rotate the plates so all the eyes line up as we don't need to fix the plates in a certain position due to having no self tappers. Hope that makesense. Are the knurled nuts used to hold the chocks in place when you're underway?
Regarding the upside down mushroom, I was going to machine this and the fixing plate as one item and then the whole unit can be self tapped into the teak.

(5) two flats is the plan. The OD of the nut is 50mm and the internal thread is 1 1/4" so arounfd 35mmA/F.

(6) M8

(7) it's a bulldog clip as used on Russian transport aircraft

Thanks for your input John

 

[jfm]

DinghyMan, thanks for posting. I did think about dowelling but with a tightened mating surface of 2" diameter I didn't think it was needed. However if it can easily be modified if neccessary.





(1) yes there is an internal thread.

(2) understood

(3) The washers are only 1.5mm thick and the only reason I made them was i thought if the the underneath of the F/G was a bit rough it may take some of the stress. On the rear (underside) of the keyholed plate I machined a face groove to allow an O ring to compress and form a seal, you can't see it in the picture but do you think this would help?

(4) Shawn is supplying some eye bolts. We can rotate the plates so all the eyes line up as we don't need to fix the plates in a certain position due to having no self tappers. Hope that makesense. Are the knurled nuts used to hold the chocks in place when you're underway?
Regarding the upside down mushroom, I was going to machine this and the fixing plate as one item and then the whole unit can be self tapped into the teak.

(5) two flats is the plan. The OD of the nut is 50mm and the internal thread is 1 1/4" so arounfd 35mmA/F.

(6) M8

(7) it's a bulldog clip as used on Russian transport aircraft

Thanks for your input John

Ah, good stuff.
3. I wouldn't use an O ring there. I just prefer to deal with the random rough F/G surface using 291 or 3200 which dries pretty hard. You need the polyU adhesive on the deck side anyway, so seal the end grain of the teak or it will be wet forever. So, each to their own, but I'd dispense with the washers and O rings.

4. Ah I like this - very nice! It always used to annoy me that they deck rings wouldn't line up! BTW, I never use self tappers. I have tapping grade aluminium blocks moulded into the GRP lay up then drill and tap from above, and use c'sunk set screws with hex socket heads. Looks pukka and "aero"
On my chocks I use mushrooms/keyholes at one end (the aft end) then I use the tapped M10 holes and your knurled nuts at the forward end. The stainless steel 50x4 strip projects out to allow me to use the knurled knob. So I don't just use the mushroom/keyholes. I like it set up that way because removal is quick and easy but both ends are locked down and can never come out if I don't want them to. Remember mine get submerged a metre with the hi-lo platform. You can set up chocks other ways of course; this is just my personal preference

6. Haha, you and Fairline and your love of M8 Mine are M10 so no good!

7. Ah, right oh. I'll give it a try then. The ball bearing grips the paper I guess? Very clever! But wait a minute - did you make it Col, seriously?

 

[jfm]

Here are pics of mine. One end is held by an M10 knurled knob and the other end is held by the mushroom/keyhole but you cannet see that. The teak chock has a 50x4 or 5 strip under it, attached with woodscrews and gripfill

The last pic shows the tie down eyes I use. These are not cupboard or hatch handles; they are made for this job. The just shut flat on a hinge pin; nothing to unscrew. Made in uk but tbh I don't know by whom.

 

[jimmy_the_builder]

The last pic shows the tie down eyes I use. These are not cupboard or hatch handles; they are made for this job. The just shut flat on a hinge pin; nothing to unscrew. Made in uk but tbh I don't know by whom.

These?

http://www.monitormarine.co.uk/mini-pad-eyes.php

 

[jfm]

These?

http://www.monitormarine.co.uk/mini-pad-eyes.php

Yes indeed. Well spotted! The owner of the company, very nice chap, came by my boat at BMYS 2013 and told me about them, and explained they use 17-4 grade s/s for the hinge pin, for extra strength

 

[colhel]

Thanks John, your picture is very helpful. This project is very much a learning excersise for me and any help along the way is much appreciated.

I did have a couple of thoughts today regarding the keyholed plate being raised slightly above the teak. The first thought was to make the plate with a step, this is where it gets hard to explain btw, if Shawns teak was 5mm thick i could make the top (the bit you see from above) about 60mm in diameter but this part would be a flange of around 2mm, on the back would be a step of say 50mm at 5mm thick and then the threaded portion as in the pic. This way you could clear 50mm diameter of teak and the 5mm could be tightened down leaving the 60 x 2 on top of the teak which would hide the holesaw cut.
I also made the upside down mushroom which I've photographed the right way up so in fact it's just a mushroom the right way up but upside down. ..as you can see I've transfered you bevell idea onto this part, which may make it possible for the keyhole plate to fit flush? The idea on this component wood be to secure this to the chock with woodscrews through the plate. Hopefully with this picture taken in natural light it's a bit clearer, however my photography and presentation could probably do with improving. You should be able to see the face groove I mentioned for an O ring which I'd like to try before sealant just in case it actually works

View attachment 40290View attachment 40291

 

[lanerboy]

Colin regarding the mushroom I was thinking it should be a nice snug fit so the length of the stem only wants to be slightly longer than the thickness of the part it will be fitting into as my idea is that the chocks will just be held in place with a tight snug fitting mushroom

After reading this post though I am wondering if we could do something like JFM has done with the knurled knob?????? by using this it will not matter if the mushroom is not such a tight fit as the knurled knob would secure the chocks whilst I am launching and recovering but with this method I would need to fit an extra fitting in the bathing platform for the knurled knob to screw down in to.

I like the idea of the overlap to hide the 50mm hole saw cut but I would like it no thicker than 2mm and with a bevelled edge as I done want to be stubbing toes on it lol

I am sure jfm will be along to give us his input later regards this but after looking at his pictures do we need to have the keyhole at both ends of the chocks or could we have a keyhole fitment at the aft end and then a knurled knob at the other this way it would give me a way of locating the aft end of the chocks then secure them in place with the knob this way I still only need 2 fixings for each chock

opinions please

Edit whoooops just re read jfm post with the pics and he has done it how I have stated above I think ??? unless I have read it wrong

 

[colhel]

I've been racking my brains trying to think of how we can do without extra mountings and the knurled knob. Making the mushroom a tight fit that's tight enough to stay in place could make it a pain to attach and remove as the contact area is very small and metal to metal isn't very grippy. On (possible) solution would be to have an adjustment screw going all the way through the chock so the mushroom could be pulled up tight. Another way would be have a screw that when tightened would lift the hole chock thus tightening the fixing, but this feels a bit bodgy and could damage the teak unless it was protected, in wchich case we may as well use knurled knobs.
Another thought (and one I think may be worth considering) is rather than have a round mushroom, make it almost rectangular so when the chock is slid into place you then twist it 90 degrees to lock in.

 

[lanerboy]

Colin I cant visualise how we could fit the chock then turn the whole thing 90 degrees to lock it in place

what is the reasoning for not wanting to use the knurled knob on the one end and a mushroom on the aft end of each chock this way I still only need 4 fixings in the bathing platform a mushroom fitting on the aft end to locate that end of the chock then a knurled knob the other end which tightens down in to a thread fixed in the bathing platform at the other end of the chock, this way its secure both ends but is locked into place with the knob so it cannot become detached and one simple undo of the knob and the whole chock slides off to be stowed away

keep thinking

 

[colhel]

Just to let you know in case you're wondering why this thread has stopped. Shawn and I had a chat yesterday and decided we'd hold fire until he has the teak chocks made and we'll meet on his boat and proceed from there.
John, those spare knobs may come in useful after all

I guess the next stage will be to drill a hole in a fairline, something I'd never thought I'd do but gives me a feeling of excitement and fear at the same time

 

[Jurgen]

Col, I should point out at this stage that I have NO TOOLS capable of drilling holes in my hull should you become bored at any stage on Saturday lol

 

[colhel]

I'll bring some. I could with a prsctice first

 

[Nick_H]

I have chocks held in place with upside down mushrooms in keyhole plates as you are envisaging, and fwiw I wish they were just straight pins as Hurricane has suggested.

You don't gain anything from the mushrooms when the tender is on the chocks, because the weight and straps secures everything firmly against the deck, but if I ever did need to cruise with them in place but no tender (can't think when i'd need to do this), then they're not secure enough that one end couldn't bounce out, so i'd remove them anyway, which is a bit more awkward because you have to line up the holes. I think removing them could be a real pain if you try and allow an interference fit on the shoulder height of the mushroom. The keyholes also give them the opportunity to move around a bit laterally when underway, which is no big deal but they look a bit untidy at odd angles.

jfm needs them secured to the deck because he has a lowering platform and they'd float away, but on a fixed platform I don't see the point.

 

[colhel]

That makes sense Nick. An idea I discussed with Shawn yesterday was to have the mushrooms on the outside of the chocks, where JFM has his knurled knobs, and a pin on the inside which would be held in place by the weight of the tender. Regarding easeof fitting and wobbling, I've machined a bevell on the upper plate whicj allows the mushroom to attach easily to the keyhole but also allows a closer fit. But I do take your point. I can't see Hurricanes post.