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-   -   Lifting Seams (http://www.rib.net/forum/f8/lifting-seams-5293.html)

Colin F 18 June 2004 12:06

Lifting Seams
on my avon, the seams on both sides of the boat, that face forward where the rear cones are attached have started to lift.

my question:

is it just a case of dry it, clean it, degrease it and put the rubber glue on that is in the repair kit, or is it a lot more complicated than that??

hope the wealth of knowledge here can help


quinquarimarine 18 June 2004 14:02

Seams trick

The problem of the forward facing edge of seams is obviously due to the water pressure on the seam and is a well known problem. For that reason we have now switched to one piece "seamless" tubes (the seam is longitunial and inside the boat)

Re glueing and doing a good job of it should be OK. The real trick though is that if the water is still catching the raised edge then apply a small amount of gel superglue, feather back with glass paper, apply more super glue, sand ... repeat etc so as to create a smooth edge. Works wonders and was advised to me some years ago by a tube maker who believe that Avon came up with this trick. Do remember that impact forces on tubes/hull etc in a heavy sea at speed can be in the region of 25-30 tonne/sq m so a small raised surface is itching to come away.

The good news is that on well-made tubes the outer seam is simply that - an outer seam. The main force is the inner seam which is helped to hold in place by the air pressure. This leads to sound advice of keeping tubes under pressure in the winter as otherwise the inner seam can deteriorate. Caution though to all - do not igore a failing outer seam as it is still part of the tubes integral strength.

In you case I am not sure whether Avon fit an inner seam on the cone as this can be difficult or rely upon the fact that the cone pushes against a smaller hole.


Quinquari Marine

jwalker 18 June 2004 14:07


...is it just a case of dry it, clean it, degrease it ...
Nope. If you do that it will lift again in not too long a time. I'm not familiar with the tube attachment on the Avon but, if it is similar to other boats, you may need to lift the end of the tube to hull strip, put a piece of hypalon under that edge and take it rearwards enough to overlap the lifting edge at the cone. That way you will have no forward facing edges to pick up.

It amazes me that any manufacturer cannot see what is likely to happen to a forward facing edge which constantly drags through the water. (Drag being the operative word.) It does make one question their brain power.

Colin F 18 June 2004 16:17

thanks chaps, i'll give the gel superglue series a go first of all. As jw said, it does seem a daft idea to put a forward facing edge where the water force over time will start getting behind it. What makes it worse is that this boat runs on the tubes all the time at the rear so it's constant pressure.

I'll let you all know how i get on with it.



Colin F 18 June 2004 16:26

on the other hand
this boat is only 4 years old and i notice on avons website.....

10 Years transferable, no-qibble written fabric Guarantee and 5 Year seam Warranty is your assurance of our commitment to quality.

in my eyes at least this is the start of a seam failure. how do people think i stand with this? :eek:

quinquarimarine 18 June 2004 17:21

With regards to the warranty I think that as a very devoted comapny Avon would repair any defect without any question. Alas though it will be RTB which could involve much effort on your behalf and maybe an hours work by Avon. Obviously in case of warranty you should consult them first prior to diy warranty repairs so as not to void your cover.

In respect of JWs reluctance to such a repair I can confirm that it has worked many times but at the same time accept that a "deflection angle" of fabric can help. This however is not realy practical on all external seams such as bafle seams and hence the super glue method. Again we have used this on large commercial ribs and in cases where a tear patch may be 5ft long.

JW is correct about his coment on the naievety of seams in the first place. To date it has been driven by the cost of hypalon as it requires a greater length on "seamless" tubes. Some companies though have balanced the benifit of seamless taking into account the strength and the quicker manufacter time against the material cost. An example is Humber who have introduced such on the 10m range with an increased hypaolon thickness to go with it.

Seamless seams will though have a taper, though marginal, towards the bow. This needs due to standard widths of hypaolon.

As a very final point we supply our own vessls will a repair kit as all do. To help though preglue your patches as this will speed up and enhance an on board repair. Also do carry superglue as under damp conditions you may be able to effect a temp repair where hypalon glue fails. On top of that some wooden or rubber plugs (as carried on liferafts) with some gaffer tape may help (rip-wan-winkle and all that !!)


Quinquari Marine

jwalker 18 June 2004 17:36

I'm not so fussed about the forward facing edges forward of the stern because they are not subjected to too much punishment but the ones at or near the stern are a different matter. Humber were actually guilty here. My Destroyer had a widening wedge shaped section as the rear strengthening/protection but it stopped short of the cone seam by about 25mm. Just dopey. My present Humber is the same but at least they have joined the cones to the inside of the tube so it's not too bad. Why they couldn't have extended the patch 50mm, only they know.

John Kennett 18 June 2004 18:10


Originally Posted by quinquarimarine
For that reason we have now switched to one piece "seamless" tubes (the seam is longitunial and inside the boat)

Is that standard now, or do Humber build your boats to your own spec? If so, does it add much to the cost?


paul tilley 19 June 2004 12:53

you may have the start of a major problem cones are normally joined to the main tube with an overlap joint with internal and/or external tapes but some manufacturers use a butt joint when the outter tape lifts you sometimes loose the complete cone . in your case try avon for warrenty claim if no luck reglue and sikaflex or supaglue leading edge or lift attatchment strip and fit alarge triangle of fabric to cover the leading edge of the strip. the best option is to have tubes with out separate cones as on scorpions and some of the tubes i build

quinquarimarine 21 June 2004 15:49


Originally Posted by John Kennett
Is that standard now, or do Humber build your boats to your own spec? If so, does it add much to the cost?


At present it is on the latest 8.5 to 11m models that we spec but it was evolved by Humber themselves. I guess its advantages will result in an application to the smaller models.

We have supplied 5 10m models with seamless tubes and they certainly do the job. Other smaller benefits include easier cleaning, more space for fixings (handles etc).

There is no additional charge on the bigger models at present as is the increase to 1500 hypalon.



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