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Old 12 December 2006, 15:24   #1
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A very cunning tube repair idea

Regular listeners will be aware of one of two little tube problems I have had over the last few months and probably think (sorry - if its any consolation I am a lot more bored with it than you....!)

Another interesting possibility has presented itself so I thought I would share the idea in case it is useful to anybody

A guy here had a similar problem a few years ago with a Tornado rib and I was talking to him this morning. I had been told he bought inner tubes but apparently not. The idea he came up with was to get a new "proper" tube section made up the same length as the aft chamber with a blank end on one end and a normal tube cone end on the other.

Humber made it for him out of hypalon just as you would make a normal tube, then he cut the end off the old tube, slid the new "hypalon sausage" up inside the remains of the old tube, inflated it and it was held fast by the air pressure, the overlapping edge of course is a trailing edge so no problems with the water flow, simple but brilliant

He said he could have glued around the trailing edge (and that was the original idea) to secure the sausage inside the old tube but he never got around to it as it never moved. The inflation valve was built in to the end cone when the sausage was made, so he basically never had to do any tube gluing at all just chop the end off the old tube, stuff the sausage in and blow it up, 5 minute repair.

There seems to be another benefit which is that the aft chamber is now basically double thickness so any damage to the outer layer of hypalon (the original tube) will have more or less no effect at all on the new inner part - so it adds a full sized wear patch in effect

There is still a light at the end of the tunnel if my ham fisted attempts at gluing fail he said it cost a few hundred quid to have the sections made but is pretty much guaranteed to solve the problem.

Just wish I had spoken to him a month or two ago and I could have had the bits here by now
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Old 12 December 2006, 15:44   #2
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It would need to be exactly the right diameter to prevent a longitudinal fold but it does sound a better solution than sticking an end cone onto a tube of rotten hypalon.
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Old 12 December 2006, 16:35   #3
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Quote:
Originally Posted by BogMonster View Post
Regular listeners will be aware of one of two little tube problems I have had over the last few months
Correct - 2 little tube problems: Port tube, and starboard.

Mr Walker: I have a feeling that it could be a bit oversize, as the hypalon will stretch a bit as it's inflated (and the now-outer tube would tend to hold that in place.) Not way oversize, of course, lest the fold thing happen, but a bit would serve to secure it in the old tube better (though personally, I think gluing would be a far better idea.)

Interesting solution, though.

jky
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Old 12 December 2006, 17:49   #4
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wish id thought of that
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Old 12 December 2006, 17:58   #5
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wish id thought of that
Something else for your product range Paul

If idea no. 1 fails I'll be back to you for a quote for a set of these

The bits you sent should arrive this Saturday then it is out with the scissors over Christmas!!

The brilliant bit is that I bet it is almost always the rear sections of the tubes that fail first because it has got to be them that takes the battering, so you could do it to almost any RIB to prolong the life of the existing tubes for a few hundred quid.
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Old 12 December 2006, 18:28   #6
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i think i may have two customers already ,i will quote them tomorrow
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Old 13 December 2006, 05:12   #7
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What a cracking idea
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Old 13 December 2006, 05:14   #8
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i think i may have two customers already ,i will quote them tomorrow
If you're doing a quote anyway can you forward it to me so I have a rough estimate? Depending on the price I might order a set as a backup so next time it goes flat I can get my 12 inch carving knife out and wreak my revenge while the steam is still coming out of my ears

I have been thinking about the options and I think I'd probably develop the idea slightly and rather than put the inflation valve on the cone end I think I'd try and put it where the original valve was located. I'd cut a circle out of the old tube (maybe six inches in diameter) to get rid of the old valve and poke the new one through the hole. It would be a neater solution and easy to secure in place - deflate the sausage slightly, squish a bit of glue in around the new valve (between the two layers) and blow it up hard till the glue dries. It would also remove the possibility of the inside of the old valve chafing on the sausage.

The only bit that would probably show it wasn't original to anybody that looked closely is that the rubbing strake wouldn't go round the sausage but I suppose if you were bonding the sausage into the old tube around the outer end, you could probably even re-stick the strake to it as well. The only difficulty then would be fixing the sausage if you did put a hole through both layers with something sharp because you'd have to take it out again...
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Old 13 December 2006, 11:47   #9
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I like the idea, but for the gemini industries inner tubes do much the same thing, and would be quite cheap for the two rear chambers. I think I only paid about £ 300 for the whole of a 5m Tornado. As you insert them through a tiny slit in the old tube, they are encapsulated by the old tube, and fill it well.

I like the idea of separating the protective functions of the outer skin from the air-keeping function of the inner skin. However, the valves do look a bit budget on the inner tubes.
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Old 13 December 2006, 12:47   #10
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Would there be cause for concern regarding the baffles in the adjacent tube? It could be possible for there to be a gap between the new inner and the baffle which could put strain on it - a bit like fully inflating 1 chamber with the next one empty.
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Old 13 December 2006, 14:33   #11
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Would there be cause for concern regarding the baffles in the adjacent tube? It could be possible for there to be a gap between the new inner and the baffle which could put strain on it - a bit like fully inflating 1 chamber with the next one empty.
I believe the idea is that you inflate the sausage to a slightly flaccid state (ooer) then stuff it in till the end hits the baffle between the sections and then blow it up, so the baffle should be mostly supported by the end of the sausage I think. When I chop the end off my dud toob to stick the new end in that Paul made for me, I'm going to measure the distance back to the baffle so I already have the measurement without opening the tube, if it looks like I need to order the sausages!

I suppose you could say that if the baffle isn't man enough to hold the air pressure of a fully inflated tube then it isn't going to be much use if you get a puncture (same situation - full pressure fighting no pressure) which defeats the object of having sectioned tubes

There seem to be some concerns about the Gemini type inner tubes chafing on the inside of the tubes because of their thin construction, I think I would rather have a full-strength hypalon tube even if it were more expensive. Damn I'd even fit concrete tubes if it was the only way to stop the thing going flat
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Old 14 December 2006, 05:58   #12
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gemini inner tubes

Here's some recent correspondence I've had with Jack at Gemini. Interesting point about the old valve damaging the new inner - I'd cut out the old valve just to be safe:

1. The bow on my Delta is high and very pointy when compared to other RIBs - will the 2 inner tubes for the nose deform enough to completely fill the existing tubes when they squash together?
A. Yes they will fill perfectly.

2. How do the inner tubes work with the inter-chamber baffles in the existing tubes i.e. one tube may end up with a convex end as expected, but it's neighbour may as a result have a concave end with strain on a crease?
A. Each inner tube has to be installed overlapping the next one by about 20cm, They then blend into each other.
This is why you measure the chamber from the seam where the baffle is attached to the next. This works out to be the length plus 15%.

3. Measuring which lengths to order will be an estimate based on where the existing baffles are. Is it better to order the inner tubes slightly larger than estimate (and risk folds)or slightly smaller (and risk stretch)?
A. Longer is essential, creases have no bearing on the tube life, it is not a problem.
I would recommend the 0.68mm thick tubes which are the standard price on the web site, 1mm. have to be shaped to be a perfect fit.

4. How do you know where to cut the hole for the valve?
A. The valve is in the middle of the inner tube, same for the hole in the boat, the midpoint of the chamber the tube goes in.

5. Any issues with patching the insertion slit to minimise the risk of the slit extending?
A. You can put a strip of fabric over the cut and glue it at the top and bottom, leaving a "hand hole" for future use if . for example the tube is punctured.
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Old 15 December 2006, 09:53   #13
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would it not be better to make a 700mm long insert with valve in the cone ,put this in the end of the old tube glue up and inflate in place . as long as the old valve is far enough forwards in the rear chamber you have now added an extra chamber each side of the rib and fixed the cone end problem .
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Old 15 December 2006, 14:15   #14
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would it not be better to make a 700mm long insert with valve in the cone ,put this in the end of the old tube glue up and inflate in place . as long as the old valve is far enough forwards in the rear chamber you have now added an extra chamber each side of the rib and fixed the cone end problem .
Another good idea, will do some measuring and I might go for that though I do like the idea of the whole thing being removable in the event of any problems and also having a double layer of hypalon all the way down the aft chambers.

A seven chambered RIB would be verging on unsinkable, in fact I might even re-name it Titanic II. Then again maybe not...

I also thought of another idea which is that if you put relief valves (which I wish I had fitted) in the new sausages, and blow up the sausages first then the middle chambers and then the bow chamber, you would have some overpressure protection for the whole lot because the relief valves in the sausages would blow off at (say) 5psi and then the baffles would deform to reduce the pressure in the forward chambers.

Lots of options anyway, which is lots more options than I had a week ago
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Old 15 December 2006, 14:29   #15
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A seven chambered RIB would be verging on unsinkable, in fact I might even re-name it Titanic II. Then again maybe not...
Stephen, your tempting fate again
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Old 15 December 2006, 15:41   #16
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Stephen, your tempting fate again
Yep. Forecast says 50 knots of wind tomorrow, after the champers bottle bounces off the tubes in the renaming ceremony I might go out for a spin and see if I can make it fly straight
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