A Caravan forum. Caravan Banter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » Caravan Banter forum » Caravan, Motor Homes and Camping Newsgroups » UK Caravanning
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

UK Caravanning (uk.rec.caravanning) A forum for the discussion of caravanning undertaken by residents of the United Kingdom, whether in the UK or abroad. It encourages the interchange of views on the merits of models of caravan, makes of tow car, accessories, caravan sites, caravan clubs, and other related topics. The term caravan is to include trailer vans, motor caravans and trailer tents.

mastics



 
 
LinkBack Thread Tools Display Modes
  #1 (permalink)  
Old August 11th 03, 07:40 PM posted to uk.rec.caravanning
ken
external usenet poster
 
Posts: 136
Default mastics

Hi,
Can any-one enlighten me on the mastics used on the corner joints of a
motorhome and the best way of removing the excess where it has squidged out?

Ken


Ads
  #2 (permalink)  
Old November 26th 03, 08:49 AM posted to uk.rec.caravanning
John
external usenet poster
 
Posts: 1
Default mastics

On Mon, 11 Aug 2003 18:40:58 +0000 (UTC), "ken"
wrote:

Hi,
Can any-one enlighten me on the mastics used on the corner joints of a
motorhome and the best way of removing the excess where it has squidged out?


I haven't used mastic on caravans but I've used mastic (silicone
rubber) on leak-proofing pressure gauges for years.

There are some important things to know about it. They come in both
acid-cure and neutral-cure types. You can recognize the acid-cure
(acetic acid) types by their strong odour of vinegar. Acid-cure types
generally provide a more secure bond, but they do tend to corrode some
metals while setting (unless you can provide plentiful ventilation to
prevent the vapours from lingering).

Preparation of surfaces prior to application of mastic is important,
because the mastic clings best to very clean, somewhat porous
surfaces. Also, its not good enough to merely overlay the surface with
a bead of mastic. The mastic should be actively worked into both
mating surfaces. Take a pointer from the space shuttle programme. When
space shuttle Columbia was first carried aloft on the back of its 747
carrier aircraft, many of its insulating tiles fell off. The tiles had
simply been applied to the craft by pressing them into a filling of
mastic. Subsequent research demonstrated the need to "work" the
surfaces together, actively smearing the mastic into the pores of the
surfaces and keying a much better seal.

If you have an existing situation which is leaking, don't expect a
good repair by merely squirting mastic against the offending joint.
Water will find its way through it, sooner or later. You have to
either (a) lift the entire panel, clean the joining surfaces
thoroughly before mastic rejointing, or (b) design a form-fitting
flashing that fits the whole faulty joint, and mastic-seal that entire
flashing to the original surface.

Don't take too long over the application time. Especially in warm
conditions, mastic begins to set quite quickly. Get the stuff on
quickly, give it a good working into position, and then immediately
wipe off any excess with a rag. Complete the job in stages; only apply
as much in each area as you can complete within say 3 minutes.

While the mastic is setting, don't disturb or distort the area of
jointing, or you can work stress lines and air bubbles into it,
producing a joint that might leak. Give it at least 24 hours for a
full set.

Basically, nothing dissolves mastic once it has set (but then, that's
one of its big advantages). The only way to get excess mastic off
after it has set is to cut it off with a very sharp knife (and it
never looks as good as it should afterwards).

Mastic, when properly applied, is brilliant at leak-proofing, and can
absorb moderate vibration and shock without breaking the seal. I
started using silicone rubber compounds to seal front bezels and rear
covers of pressure gauges for liquid-filling them 24 years ago. Since
then, many of those gauges have returned for calibration to date, with
no leakage problems.
 



Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT. The time now is 08:00 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.Content Relevant URLs by vBSEO 3.0.0 RC6
Copyright 2004-2019 Caravan Banter.
The comments are property of their posters.