Plate boat

[Fisherfriend]

Was looking at a few recently and one that I really liked I noticed on both topsides between the top and bottom side strake things it has like dimples running parallel in perfect straight line around every 200mm from the back up to around the the driver seat position. They clearly look like some design thing as there painted over and you don't notice them in pictures.
What are they?

[ranmar850]

Likely just where it has been stitched inside. The more expensive boats fill them with bog before painting to try to ( and fail to ) emulate the finish on a good FRP boat

[Fisherfriend]

How do you mean stitched? This is a totally smooth plate side boat, what would they need to bog?

[Funchy]

Got any pics?

[Dignity]

How do you mean stitched? This is a totally smooth plate side boat, what would they need to bog?

Plates that are spot welded from inside is what I took from that

[Fisherfriend]

I figured it out. It is indeed from the gunnel tack welds. Never really noticed them before

[tunaticer]

Every alloy boat has them, some hide them more than others.
Tack welds should never be left in a boat, they should be stitched or fully welded depending on location and design.
Tack welds left after manufacture are a stress point with poor strength.

[ranmar850]

Just as an example, Australian Marine Masters, who claim to build a top-notch aluminium boat, admit to having up to 4mm of bog in places, to get a smooth finish.

[Fisherfriend]

These were stitch welding marks not tack welded my mistake above. 4mm of bog is something I never considered. What part of there boats do they do this

[Noelm]

Bog is used in lots of boats, when a weld is ground flat, it leaves grind marks, these are skim coated or high build primer is used (depending on the depth) welding from the inside can cause imperfections on the outside, lots are filled to look pretty when painted. So, depending on the build, plate boats can be bogged, or top notch work will be left as is most of the time.

[Fisherfriend]

Bog is used in lots of boats, when a weld is ground flat, it leaves grind marks, these are skim coated or high build primer is used (depending on the depth) welding from the inside can cause imperfections on the outside, lots are filled to look pretty when painted. So, depending on the build, plate boats can be bogged, or top notch work will be left as is most of the time.

Thanks for the explanation. Most of the boats I been looking at do not grind there welds. What is the reason for grinding them, do they just look that bad that they rather grind and paint?

[ranmar850]

It depends on where the welds are. The body filler can be used to smooth out the sides, even where no grinding is need, or in painted, easily-seen areas, they might want to make it more aesthetically pleasing. This could apply to the inside of the cabs, for example, radiussing all the joins and corners. Not as likely to use it out on deck on stuff like longitudinal welds of side pockets, or vertical welds on frames.
If it is somewhere really neat welds are needed, without grinding, they are more likely to TIG, rather than MIG. Slower, but much tidier.

[Noelm]

Small intricate welds are done with a TIG, but, long welds are usually done with a pulse MIG that creates a TIG looking weld, but, less distortion/heat and way quicker. Some welds are not ground off, because grinding can weaken the weld at times, and often the weld is neat and not visible to the overall boat appearance.