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Middle of Tramp STBD Side is Pulling Out of Slot

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Good day from New Zealand. This post is primarily for darcy1945, as I saw an intimidating post from Jan 2022 and Dec 2023 about how to fix loose rivets on the metal strip holding the tramp in place. Darcy stated there was only one way to fix this problem, and it must be complicated/difficult as he said for the two pers to phone him. I suspect, but don't know, that the difficulty is that there is a metal strip inside the hull through which the rivets pass through to give the tramp fixing the necessary strength.  Perhaps only replacing the middle 4 rivets can be done without the same problems????  Would using Monel rivets give extra strength?

The photos explain my problem.  It is a Mk1 Maricat and I hadn't sailed for 2 years, but in Nov 2023 I noticed the tramp had pulled out and so I took it off and put it back in.  I went for a sail a few days ago with my wife and noticed the tramp had pulled again.  We had a second sail that day and it didn't seem to get worse.

Tramp 1.jpg

Photo 1.  Inside the two lines show where the tramp has pulled out. This is roughly in the middle of the tramp, fore and aft.  The rivets are evenly spaced, aside from the arrowed rivet.  I wonder if that was an attempted fix by a previous owner?

Tramp 2.jpg

Photo 2.  The tramp has been removed.  From the start of the ruler to approx. 360mm the metal strip is a bit 'spongy'.  Pressing down on the edge, or lifting it with the ruler results in the strip edge moving, perhaps 1mm.  Outside these distances the strip is firm.  It is clear from the photo that the strip has been bent up.  The rivets still seem firm, but I have no doubt that there is slight 'stretching' of the rivet to allow the strip movement.  Although the strip seems to have lifted a bit to the right of the right-hand line, the tramp is still firmly clamped in place there.

Bolt Rope.jpg

Photo 3.  This is the bolt rope.  It seems to be 8mm measured with a ruler, and 7mm by digital calipers (compression?), and so I'm not sure what it actually is.  Perhaps going up a size would help keep the tramp in place?

Tramp Overview.jpg

Photo 4. An overview of the tramp in case anything can be learned from it.


Darcy1945; you mentioned the rivets are 3/16 x 3/4 in.  We don't seem to have inches for our rivets, at least in Mitre10 and Bunnings over here.  Something I have, which I have measured, might be close enough.  It is what is sold as 6-10.  When measured the rivet diam. is 4.8mm, the Grip (max. thickness of material to be clamped) is 16mm, and the shell length of the rivet is 21mm.

[6-10 is decoded as: 6/32in = 3/16 = 4.8mm, and 10/16in = 5/8in = 16.0mm.  Whereas 3/4in = 6/8in which is slightly longer.]

Any help is appreciated.

Regards John

Edited by jbcoop
Adding measurements.
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To check that you have the right length, drill 1 of the rivets out of the storage compartment first, drop a rivet in and check that there is adequate protruding.  To move the rivets you need to buy a thin parallel punch, cut it down to about 20 mm (Otherwise it will bend), punch out the steel mandrel and your drill will cleanly remove the rivet. This is a common problem, the rivet heads corrode and break below the flat alloy strip. I check this with the tramp tensioned, by pressing down on the tramp with the fingers my other hand on the rivet head. You will find your idea is only a quick fix and other rivets will break and cause the same problem. Bunnings sell the tramp track for about $30aus, 3m lengths. Give me a call if you are going to do the mod (You need the flat track to come off in good condition, so it can be used as a template. 0243591729.


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Thank you for your reply. I would like to explore the situation a bit more and so I hope you will be willing to try to answer my questions.  I will give you a call if necessary.  (And this extended post may be helpful for other people in the future.)

On finding out what size rivets to use I noted the following.  There are 5 tramp rivets penetrating each storage locker.  The photo shows the problem stbd side and you can clearly see the metal strip underneath, with the rivets just poking through.  Note, on the good port side I cannot see the metal strip and the rivets seem to be flush or a bit inset.  I assume the strips were glassed in during the build and then holes drilled from the outside for the rivets.  Therefore, the strip is there on the port side, I just can't see it because it has been covered with more glass than was the stbd side, as seen in the photo.

Questions below.

Tramp Inside Strip.jpg

1.   I assume the thickness of the parallel punch must be that of the steel mandrel or thinner?

2.  If I replace everything, are you saying I need to use the old top strip as a template for the drill holes in the new top strip?

3.  You mention not damaging the old top strip.  Is it difficult to remove because it has been glued on?

4.  I'm keen to just replace the bad rivets and take my chances on others failing later.  Do you see any problems with these steps?
          Remove the problem rivets.
          Hammer flat the bent top strip.
          Remove a further rivet each side that are likely to have been stretched from the hammering.

5.  If the steps in 4. work, wouldn't that mean I can just continue along replacing each of the other rivets without having to replace the top strip at all?

5.  I couldn't understand this sentence. "I check this with the tramp tensioned, by pressing down on the tramp with the fingers my other hand on the rivet head." Do you mean this is how you check for loose rivets?  Please explain what you are doing and what you actually see when you do this?

Once again, thank you for your reply, and hopefully you will be able to answer my questions.

Regards, John

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Update on Replacing Rivets

As Darcy has stated, the 6-8 rivet is easily long enough for the shell of the rivet to protrude clear of the glass layer over the inside aluminium strip. 6-8 (3/16in x 1/2in) has a shell thickness of 4.8mm (3/16in) and shell length 18mm (1/2in).
Over time the steel mandrel in the rivet rusts and falls out. This allows the aluminium shell to deform, letting the aluminium strip lift and the tramp to pull out.
If the mandrel falls out there will be a hole into the hull letting in water. If the mandrel hasn't fallen out yet, a loose rivet can be found by pushing down on the strip and feeling it move.

The Steps I Took to Replace Some Rivets While Leaving the Strip in Place
1.  Removed the tramp.

2.  The tramp had pulled out of the middle section of the strip, bending that part of it, so I hammered the strip flat again.

3.  I intended to leave the strip in place and so I needed to replace all suspect rivets, which included all rivets out to either side of the bent section of the strip. Of interest, on the good tramp side, the hull had been mysteriously taking in water in the rain. On checking, I found that I could poke the 2mm parallel punch right through several of the rivets.  Obviously, that was the source of the leak as the mandrel had already fallen out.  These rivets were also replaced.

4.  I drilled out the top of the rivets with a 10mm drill, stopping before reaching the aluminium strip.

5.  With an old wood chisel I knocked off the top of the rivet, leaving the remainder flush with the aluminium strip. (I found a cold chisel was damaging the aluminium strip, whereas the wood chisel sliced through the aluminium head like butter using gentle taps with a small hammer.)

6.  For those rivets where the steel madrel was still in place, I used a 2mm parallel punch to knock it through, then did step 7. [Darcy recommended shortening the punch to 20mm to reduce the chances of it bending. I reduced it to 15mm, but it was still bending. I eventually realised that most of my mandrels hadn't rusted enough to be punched out.  For these rivets I either tried a 2mm nail punch, if the mandrel was near the surface, or went straight to step 7.]

7.  I drilled through the middle of the rivet using a 4.5mm drill. If the mandrel was still in place I drilled down to it, and then did step 8. (The holes for the rivets on my Maricat are 5mm, so 4.5mm protects the sides of the aluminium strips from damage.) If the rivet started to rotate in the hole when drilling, I went to step 8. Note, I broke two 4.5mm drills because they jammed in the rivet. Setting the battery drill to 'screw' and '15' allowed the drill clutch to slip first and drill #3 to survive.

8.  I used a 4mm parallel punch to knock out the remaining bit of the rivet. (If the mandrel was still in place, I was able to use a 2mm nail punch, not the parallel punch, to knock it, and the rivet, through after I had drilled down to the mandrel.)

Everything looked and felt good so I reassembled the tramp.  See next post   😖

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After climbing on board, the tramp started to pull out just inside the forward line drawn on the strip.  Removing the tramp again I found that the aluminium strip was still flat, that is, it hadn't bent up and that the rivets still seemed firm when levering the strip gently with a screwdriver.  I couldn't think why it had pulled again, unless the bolt rope had shrunk a bit in that section.

This time I removed the good side of the tramp to compare strip 'spongyness' and noticed that on this side the gap between the strip and the boat was narrower than on the failed side.  I then ran a 3mm drill along the slot in the failed side and it entered the gap for almost the entire length.  On the good tramp side the 3mm drip wouldn't enter at all, but a 2.5mm drill could.

Could my problem be the gap is too big for a bolt rope that has shrunk after many years in the sun?

If so, is it an easy solution to get a bigger bolt rope sewn in on the failed side?

Regards all,  John

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Thank you Darcy.  I will keep that suggestion in mind.  It could certainly be the boltrope deforming due age, since it wasn't a problem up until a year or two ago.  Meantime, the tramp is at a local sailmakers to sew another layer of cloth around the boltrope.  I will try that first to see if that gives the necessary bulk.  (And will re-reinstall a few of the rivets where the tramp pulled again in case any rivet shells were stretched etc.)

Regards, John

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Darcy knows best!  How many times has that been said on these forums I wonder?

I re-reinstalled the three rivets around the last tramp pulling.  I used Darcy's method to remove the mandrel and it was so easy.  After one or two taps with the 2mm parallel punch I heard the mandrel bouncing off the hull.  Then I used the 10mm drill followed by the chisel.  So why was it so difficult for me to remove the mandrels the first time?  I'm thinking the rivets were too short and the mandrel head had pulled into the bottom aluminium strip when the weak point in the mandrel sheared.

Anyway, the problem side of the tramp has another layer of cloth sewn over the bolt rope and the tramp refitted on the yacht.  I walked all over the tramp while the yacht was on the trailer and there are no signs of the edge pulling.  Hopefully this problem is now solved.

Thanks Darcy for all your input.


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