Paul D Posted August 26, 2004 Report Share Posted August 26, 2004 I have an auxiliary engine bracket that Adam kindly swapped for a fishfinder. I am having a dilema though with regard to installing it on the back of the boat. The Orkney 520 is double skinned and I can fit the top bolts through the transom, however, the lower bolts will be inaccessible I think, as they are behind the seat which contains the fuel tank and is behind the double skin ( if that makes sense ! ). Is there a bolt which you do not need to gain access to the rear of ( in a same way as plasterboard screws ? ).. anyone had a similar problem. Any solutions ? Help !! Quote Link to comment Share on other sites More sharing options...
Newboy Posted August 26, 2004 Report Share Posted August 26, 2004 Can't you just use large seld tapping screws? The fixing at the top is 'tension' and the fixing at the bottom is 'compression', it doesn't have a large pulling force on them. If you really want large locking typed bolt, just trade fixing suppliers they have all sorts of plasterboard type but much larger. Quote Link to comment Share on other sites More sharing options...
Afishionado Posted August 26, 2004 Report Share Posted August 26, 2004 I have an auxiliary engine bracket that Adam kindly swapped for a fishfinder. I am having a dilema though with regard to installing it on the back of the boat. The Orkney 520 is double skinned and I can fit the top bolts through the transom, however, the lower bolts will be inaccessible I think, as they are behind the seat which contains the fuel tank and is behind the double skin ( if that makes sense ! ). Is there a bolt which you do not need to gain access to the rear of ( in a same way as plasterboard screws ? ).. anyone had a similar problem. Any solutions ? Help !! Paul there is a type of building/engineering plastic plug that acts as the back stop for fitting things to an inaccesable void. They are made out of plastic and look like an ordinary wall plug. If you are in no hurry I will bring one over next time we meet. The ones I have are huge, they may do but I need to know the width of the interior void. If mine are too large getting smaller ones is simple. By using them you can safely use S/S self tappers (must be 316 grade S/S or A4) because they will coil up into a bunch that locks against the back of the void. Mad Mike Quote Link to comment Share on other sites More sharing options...
Adam F Posted August 26, 2004 Report Share Posted August 26, 2004 Indeed their are several type of fixing available - and they are pretty strong. They have to be for fixing shelves etc to stud walling. However I would be dubius about using them to fis the bracket - no matter how strong they are. Even a small aux. engine still weighs quite a bit, add the forces of the engine working and it bouncing around on the road, and over time, I'm not convinced they would hold. Cant you just use a super long bolt through both skins with massive washers? Quote Link to comment Share on other sites More sharing options...
Afishionado Posted August 26, 2004 Report Share Posted August 26, 2004 IMO yes they will hold. Newboy is right in saying that the top bolts will take the weight and are in 'tension' , and the bottom fixings will be in 'compression' therefore will have to cope with only about 25% of the fixing strength required. However if you want to be belt, bracers and jockstrap then use S/S 10 or 12mm studding with dome head nuts on the outside and nylock on the inside. The studding comes in 1M lengths so you cut off what you need. Beware of overtightening and crushing the two skins together. Mad Mike Quote Link to comment Share on other sites More sharing options...
Bob F Posted August 26, 2004 Report Share Posted August 26, 2004 Hmmm...in normal operation, I agree that that the top bolts will be under tension and the bottom bolts under compression, but IMO, when you are trailering, the aux bracket and engine get bounced around a hell of a lot, which will cause tension on the bottom bolts, also. The same applies when the boat is being tossed around at sea. I would secure the bottom bolts to coupe with both tension and compression. Have a look at other 520's and see how they have secured the aux. Bob F. Quote Link to comment Share on other sites More sharing options...
Paul D Posted August 26, 2004 Author Report Share Posted August 26, 2004 Had a closer look at the gap between the transom and the seat. There is hardly any gap between the two at all. Therefore, I think I will be able to drill through the lot and pass the bolt through into the seat. This will mean the skin will have been pierced, but it is not that bad as the seat will be intact so if worst came to worst and the outer hull was leaking water due to some horrendous event it would at worst leak into the fuel tank area under the seat ( through my fixings ) but the inner skin would still be intact. ( Hard to explain bu I know what I mean ! ). Quote Link to comment Share on other sites More sharing options...
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