Deflate the tubes for long distance towing?

headdamage · 02 May 2015, 08:48

I'll be towing my 440 Hurricane to the West Coast and back this summer. It is going to be about 5800 km round trip. Would it make sense to deflate and tie down the tubes for this sort of trip? I'll be driving over some mountain passes and deflating removes any expansion risk, the 440 doesn't have pressure relieving valves. I'm also thinking that the deflated tubes might be more aerodynamic behind the tow vehicle.

Johnscubanut · 02 May 2015, 17:57

I think you have answered your own question really. Yes, I agree with you, let the tubes down, secure to stop any flapping. They may well burst otherwise up in the mountains! Save some fuel due to less drag in the process! Enjoy your trip!

Andre · 02 May 2015, 18:16

Quote:

Originally Posted by headdamage

I'll be towing my 440 Hurricane to the West Coast and back this summer. It is going to be about 5800 km round trip. Would it make sense to deflate and tie down the tubes for this sort of trip? I'll be driving over some mountain passes and deflating removes any expansion risk, the 440 doesn't have pressure relieving valves. I'm also thinking that the deflated tubes might be more aerodynamic behind the tow vehicle.

Pump out all the air this way the tubes won't flap but keep the bow chamber inflated

Trimix · 02 May 2015, 18:19

I dont think it will make an aerodynamic improvement. Your driving at towing speeds and its following you.

Id leave them pumped up (perhaps a bit soft if your really going over a high pass).

Saves flapping about, saves having to secure them down, saves having to pump them back up again.

I towed my boat to Corsica and left them pumped - Id not bother letting them down.

Todd Grimley · 02 May 2015, 21:14

It won't be oversize, so it is better around for the tubes to stay inflated. No matter how well you secure them they will start to chaff somewhere! Check the pressures at the passes. Road grime can be hard to clean off where the creases in the deflated tubes are for some reason.

jyasaki · 03 May 2015, 00:22

I leave the tubes just firm enough to hold shape (and verify by looking for a little bounce in the mirrors.) Going cold to hot or changing altitude calls for a check every now and then (on a tow from the SF Bay Area to Tahoe, I ended up stopping more than half a dozen times to release pressure, and once after the pass on the way down to Tahoe to put air in.)

jky

Bigtalljv · 03 May 2015, 01:04

Altitude is a bigger issue that heat in my opinion. Driving in CA is normal to be 50 degrees and foggy at the coast but 110 degrees 30 minutes inland

Going to Tahoe I saw a much bigger changes in pressure with altitude than with the heat.

Better safe than sorry

Jason

jyasaki · 03 May 2015, 20:37

Agree, Jason, but I've also left home in sub 50 degrees, and drove through Santa Rosa at 110; tubes will overpressurize if taut to begin with. Which is why I always lower tube pressure before trailering (unless starting out in the evening.)

jky

headdamage · 06 May 2015, 20:02

I have talked to an engineer at Hurricane and he said that deflated towing was fine and that it would be better than towing with the tubes under inflated.

willk · 06 May 2015, 20:12

My advice would be to use a pump to remove all the air from the sections. While they collapse, fold them up into the GRP carrier section (where they are attached) and secure them with ratchet straps or similar covered with pipe lagging or another soft material. Tie in the cone ends with soft rope running loops. It removes all the issues with heat, altitude and flapping. It also makes for a much more manageable package on the road.

In this job, an electric pump is your best friend!

jackreno · 24 July 2015, 03:54

How much more pressure can it be when going say from 1000 ft to 6000 ft above sea level, anyone know.

The reason I ask is I have a open stacker trailer, jeep on bottom and rib boat on top, cant get to boat while traveling so is 2 lbs air pressure ok in tubes while traveling to higher elevations..

Bigtalljv · 24 July 2015, 04:48

Elevation is a big change. I didn't have a gauge but going down they go from full to completely flat and floppy. I would deflate as much as possible or maybe leave the valves open.

ShinyShoe · 27 July 2015, 09:14

Quote:

Originally Posted by jackreno

How much more pressure can it be when going say from 1000 ft to 6000 ft above sea level, anyone know.

The reason I ask is I have a open stacker trailer, jeep on bottom and rib boat on top, cant get to boat while traveling so is 2 lbs air pressure ok in tubes while traveling to higher elevations..

Going up will be fine. Pressure drops as you climb and temp usually falls too. However if you pump then up at 6000ft to 2psi and come down to 1000ft you will find they will increase in pressure - if temp stayed same maybe about 0.3-0.4psi increase. But temp likely to increase too...

Poly · 27 July 2015, 09:39

Quote:

Originally Posted by ShinyShoe

Going up will be fine. Pressure drops as you climb and temp usually falls too. However if you pump then up at 6000ft to 2psi and come down to 1000ft you will find they will increase in pressure - if temp stayed same maybe about 0.3-0.4psi increase. But temp likely to increase too...

Me thinks you are wrong. When we talk tube pressure we are talking relative to atmosphere, so a drop in air pressure actually increases the apparent tube pressure.

JamesF · 27 July 2015, 10:15

Atmospheric pressure is typically about 14.2 psi at 1000ft and 11.8 psi at 6000ft. So the tubes' gauge pressure would increase by 2.4 psi as you climb.

If you have 2 psi in the tubes already, that could be enough to take you over the limit.

jackreno · 29 July 2015, 22:50

So 1 to 1.5 psi should be my max if ever going up in elevation just to be on the safe side, would not want the pressure in tubes to be to low so they wont flap in the wind..

It should also get colder as going up so that will also help keep the pressure down.

FJR1300 · 30 July 2015, 04:17

Many RIBs are tested for 15 PSI minimum and should not cause any damage, of course if the elevation or higher temperature is the new norm then they should be deflated 3 psi.
Best to check with your RIB manufacture to confirm max tested and rated PSI.

Sonar · 30 July 2015, 08:45

Or you could fit automatic release valves and the problem is sorted.