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Bigfoot00

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Hi i'm new to the site and have a project about keel bolt sealing washer and i posted on another part of the forum help where i was told to post here.

here's the full question please help

The drawing entitled "sealing washer for keel bolts states that the washer is required to be made from a "good quality rubber". it also quotes an obsolete reference to a specific material "dTD 625".

A) Investigate a range of suitable materials from which component could be made. You should use at least 3 different sources of information, for example, electronic (internet CD-ROM), paper based and "expert" recommendation. Identify what information you found from each source. Outline the difference between the suggested materials and the reason for your choices, including their appropraiteness for making the component.
 
I am intrigued. My immediate reaction is 'sealing washer for keel bolts!?' All my experience has been with bolts that 'hold on' the keel to the bottom of the boat (to put it crudely. Hence there is a bit of a weight/strength thing going on and the whole thing should be tight - which is generally not the place for a rubber washer. The next thing is that a washer in this situation is primarily for spreading the load rather than sealing although since the keel bolt goes through a hole in the bottom of the boat I admit, of course, that there is a sealing issue and the whole lot is to be squigged up with goo.

Does A suggest that this is a project about how to research rather than sealing your keel bolts? If so and you want to understand about rubber, have a search on the web - sealsdirect.co.uk has some useful background info on nitrile and neoprene etc. If this is about sealing your keel bolts, tell us a little bit more about the boat, keel config etc because its certainly different to me
 
i don't think the examers know anything about boats

I do have a boat i'm only 16. The question is for my school project and as the question asks for expert opinion i thought i could maybe find a expert here, but all i get is use sealer
 
Indeed keelbolts should be close fitting and tight as possiable imagin having a flexable rubber seal between keel and hull.

When i did a keelbolt(awful job) i put butal rubber on the bolt after the first few cms as it went down, down into the keel, Dident leak either!!!
 
The reason you get sealer as an answer is that the question you've been set doesn't work - washers on keel bolts are not there for sealing but are there to spread weights. However, to tell someone who set the question that they are wrong never succeeds. So how about a sentence pointing out that washers are for spreading weight not sealing and then trying to answer what you think you are being asked. Are you being asked to research different types of washer, sealant or rubber. If its the first then the washer ought to be as big as possible/practical in order to spread the weight/stress over as much area as possible. Typically in a 30 ft yacht, these bolts are going to be 1" or more in diameter and the nut is going to be done quite tightly. The washer should be the same material as the bolt and nut to prevent any adverse corrosion. In a marine environment, mixing metals will lead to corrosion and is to be avoided. If you want more on this aspect, people have written books about the subject and a search on the web on it will probably delivery some interesting results.

Sealant. There are lots of different types butyl rubber, polysulphide, silicon etc that can be got from a tube. Have a look at B & Q. Before all that sort of thing came along people with boats used pitch, red lead putty and white lead putty etc. Generally all pretty hazardous materials by todays standards.

Rubber. Well in a marine environment nitrile and neoprene are the most common I guess. Both are pretty resistant except that neoprene gets attacked by diesel - nitrile doesn't. Since most yachts today have diesel engines if you were going to stick a rubber washer on your keel bolt then I would say it would say it should be nitrile (the most expensive of course). You can get it in various thicknesses. If you were going to use a rubber washer for sealing purposes you are going to need a metal washer on top so that the nut when tightning doesn't chew up the rubber - but then of course we wouldn't be using one here as I said before.

Hope this helps! If you want a picture of old keel bolts all rusted and corroded (because the sealing had failed after years of use) and their nice new replacements send me a private message with your e-mail address and I'll attach one or two for you.
 
Hi to fix my last post i don't have a boat

How my class is on this website ( thank to the teacher) so we all need more information please
 
the reason you cannot find the material DTD 625 is because it no longer exists in this form. its a very good quality rubber, made from australian yukka tree, very expensive and mainly used in the aerospace field. For fabrication of rotary seals used in contact with heavy mineral and diesel based oils. Not suitable for use with petroleum based fuels, light mineral oil or grease derived from them. its usualy a light pink colour. it would be suitable for keel bolts. if a keel bolt needed a rubber washer and you had very deep pockets.
 
I have been watching this with interest & curiosity, the only contribution I could think of was to put a rubber sealing bung in a recess in the keel to seal the end of the keel bolt. Obviously the material chosen would have to have durability and a shape to allow it to remain in situ for extended periods. In common with most I was fixated by the idea of heavy dangly bits of metal held up by bolts tightened to silly torques and introducing squidgy bits into the mix was not sensible or desirable.

I then started to service my keels at the w/e. The Atalanta has twin lifting keels attached to the main bulkhead via large steel plates on the side of the centreboard case and three bolts to each keel. These bolts protrude via steel tubes into the cabin and are below water level. One bolt acts as the pivot and the other two are used for braking. The keel bolts use grease in the tubes to prevent water ingress and an accurately cut tubular rubber seal. The bolts are regularly adjusted to prevent the keels slopping around and to contol how rapidly they descend on lowering. Tightening the bolts also slightly compresses the seal. In principle each bolt tube works like a stern gland or the seal around the moving shaft of a hydraulic ram. If you picture a complex way of fitting and sealing the centreboard pivot bolt on a dinghy using flanged tubing it may be easier to visualise. Fairey heritage would suggest the use of an aero spec rubber but I believe they are now a neoprene compound. I have the drawings but the scanner is shot. I can fax if req. PM if needed.
 
I'm doing an aerospace engineering Avionics course at the Newcastle college and i'm looking for someone who can help-me with my assessment. The question is about a material i can use in place of DTD 625. I already know that DTD 625 is a very expensive rubber material used by nasa. I should be grateful if someone give me some useful information and an expert opnion over what alternative material i could use in place of DTD 625. my emai address is: franklintavares7@hotmail.com
 
im also doin the assignment mensioned earlier, all your help has bin great and i was just wondering if you have anything to say about metal washers just for comparison
 
Re: btec national award level3 keel boat washers

i have been looking with interest at the threads and as a tutor i am able to confirm the following. It is obvious that Edexcel that have set the question know nothing about keel bolts or boats at all.
There is no wrong answer to the question set.
You will be marked on the following

Speaking, technical language, tone and manner, listening, impact and use of body language.

From the research you have undertaken, what have you found? that is where the marks come from, not whether or not you have used the right type of rubber but from the presentation of your answers.

As for you boat enthusiasts, you really should consider yourselves experts, thankyou for the help you have given.
 
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