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Bertram31.com General Bulletin Board
Re: Ethanol and replacement tanks
Posted By: Russ Steffler In Response To: Ethanol and replacement tanks (Capt Bob)
Date: Saturday, 8 April 2006, at 12:23 a.m.
Thanks to all who have e-mailed me regarding your questions related to fiberglass fuel tanks, and the ethanol question.
Based upon the number of enquiries I have received (all apparently originating from topics on this busy forum... and suggestions that I visit this site) I have decided to respond here rather than send out numerous emails to those who have approached me directly with this enquiry.
I have been involved with the composites industry since 1967. At that time it was a relatively 'new' material... was inexpensive... and provided engineering opportunities previously unheard of... An innovative material which seemed to be the "answer" for so many "problems"... A 'cure-all' solution ... :-)
One of the 'problems' we (in the marine industry) have discovered with metal fuel tanks (disregarding corrosion problems in the marine environment) was the inherent weakness of the weld joins, as compared to the strengths of the sheet metal.
As we all know a yacht (boat) is subject to extreme flexural conditions, and there are two ways to get around this. Either make the ship / yacht / boat so stiff that is does not respond to the movements... or develop methods to allow the 'boat' and its components to 'move' within certain design parameters ---
in other words composite materials are ideally suited to the marine environment due to their high tensile elongation strengths. This property allows composites (FRP / 'fiberglass') to shift with varying stresses without suffering from material fatigue.
This 'fatigue' in the metal world is known as 'metal fatigue',
Everyone recognizes the fact that if most metals are 'bent back and forth' along the same stress line, that metal will begin to develop hair-line fractures within the molecular structure of the metal which eventually lead to cracks or fractures along that stress line. Weld zones are particularly susceptible to this fracturing (not so much in the weld itself but in the immediately adjacent sheet material).
This is the main advantage in using FRP for applications in the marine environment, because composites have far more tensile strengths that metals and can 'flex' to accomodate shifting loads or stresses innumerable times without developing these flexural cracks... within certain design limits and based upon proper laminate engineering designed to fit the requirements.
In 'theory' FRP sounds 'perfect'.
In practice, over the years, we have discovered a number of other 'problems' related to composites (at least the resins we were using in the matrix years ago).
With the ever changing and advancing world of adding new chemicals (such as... to fuels), we found that some of these chemicals had adverse effects on the resin formulas we were using years ago.
This is a 'problem' we discovered years ago (in the pacific northwest) related to fiberglass fuel tanks.
The original resins we used at that time were impervious to most fuels. However, as they changed the formula of the fuel mix {by adding chemicals which were not a concern originally), this altered the resistance capabilities of the resins we used to use (most of which were polyesters).
It took us a number of years to determine that the tanks installed 20 - 30 years ago were built with resins which were NOT resistant to some of the new chemicals being added to the fuels and over a slow period of years the original tanks began to 'break-down' microscopically under the influence of some of these chemicals.
The use of vinylester resins has been developed (specifically over the past 10 - 15 years) to address this problem.
This has partly been due to research into the area of osmosis (boat-blisters), but the development of vinylester resins have also been discovered to have an added advantage in that these are resistant to numerous chemicals which were not in wide use 20 - 30 years ago, (such as ethanol).
Some have approached me to ask if the old tanks could be 'opened / cleaned / sanded / and have a barrier-coating of vinylester applied to the interior of the tanks to correct this problem with the original tanks.
To be honest, I can not say for a fact that this would (or would not) work.
In theory, it sounds feasible, but one drawback / question I would have in this regard would be HOW certain we can be of ASSURING that we have completely removed the ethanol contamination from the surface of the original polyester resin?
IF this contamination is not completely removed (by whatever process applied), then I would not feel safe in guaranteeing a proper bond between the vinylester barrier coating and the original polyester.
I do know that the reverse materials engineering works... (that is - I can apply the vinylester barrier as a base coat, and then apply a polyester back-up laminate and be assured of a proper bond)... but I personally could not guarantee that the ethanol contamination would be sufficiently addressed by any method to assure a proper bond between a vinylester barrier coating applied to the original polyester.
I hope I'm not being too technical and am trying to keep my comments to a basic common sense level.
Chemical engineers (which I am not), would have to study and examine the question of whether a proper bond could be achieved by 'cleaning' the original tank (by whatever method), in depth... before I would suggest this method.
It might work for a few years, and then one might find that the bond breaks down, and suddenly one could find themselves with the same (or worse) problem.
As I stated to one respondent, I worked with a company subcontracted as representatives of the Bertram series way back in the late 60's / early 70's... but am no longer intimately familiar with Bertrams (as many of you are)... so I certainly could not fabricate replacement tanks from memory.
The ideal situation would be to have (here at my locale) an original tank which I could use to fabricate a replacement mold and then the costs of each individual tank would be less than having to custom design a number of different tanks.
Alternatively... Photos of the tanks 'in situ' (as well as after removal) along with precise measurements and configuration details would assist me in designing individual replacement tanks.
As we are discussing 'business' here, I do not want to be 'spamming' this site to sell fuel tanks, so this will probably be my only post here. My apologies to any who might consider this post as spam - as I previousl said, I just thought with the numerous enquires I have received on this question I would provide the above information on this forum (as opposed to sending out numerous duplicate emails to answer the same queries).
To those who have previously emailed me, I have your queries on file, and if you can send photos (jpegs only) along with proper measurements, I would be happy to attempt to fulfill your needs.
If I can be of any further assistance please feel free to contact me through my website ... www.foxxaero.com
Best regards ... and fair winds.
Russ Steffler
Foxxaero Marine Technologies
Victoria BC Canada
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