Yachts and keel bulb w

[Richard Caughey 1Participant @richardcaughey1]

Yacht keel weight

[Richard Caughey 1Participant @richardcaughey1]

I bought a second hand rc yacht, it looks ok and sails ok but I repainted it today and whilst the hull was upside down I noticed that the bulb weight is not parallel to the deck. Will this cause drag? It looks like it is slightly pointing up to the front Should it be parallel or point up or down front to back? Fore/ aft.

i am not sure i can change it, but if it will help increase speed i am willing to try and change it.

[Tim RoweParticipant @timrowe83142]

Richard

Is this another second-hand RC yacht by any chance? I admire your courage!

Do you know what the yacht is or could post a photo?

Parallel is OK. Pointing down is a no-no and some slight upwards tilt is beneficial. I have just adjusted the bulb of my International One Metre to give it 2.5 degrees pointing up at the bow. The modern IOMs have long and skinny bulbs and the theory (proven by tests) is that when the yacht is heeled and making leeway the bulb is better aligned to the water flow and therefore produces less drag. The limits are considered to be between 2 and three degrees. Below 2 there I insufficient effect for it to be useful and above 3 the drag increases disproportionately when on the run (upright).

Some boats have adjustable bulbs that are set at a very small angle in light winds and up to 3 for heavy weather when the boat will be heeled a lot. I can't be doing with the adjustable bit so plumped for the middle angle.

If yours is only a very small angle then it should be fine. But don't forget upwards not downwards.

Tim R

[Richard Caughey 1Participant @richardcaughey1]

It is not another second hand one, this one I already had, but there are two more yachts in boxes to be built and another second hand built one a kyosho sea dolphin…I think that mrs Richard has admitted defeat on this for now…

so it’s a Victoria that needed some attention. I stripped it down repainted the deck and the hull un it when I noticed the keel weight seemed to be pointing up towards the bow it looked quite a lot up using the deck as the level visually It looked way off, but now I measured it after your comments and it is 2.8 Degrees up, so that would seem to be ok, so I will leave it as is for now….

[Malcolm FraryParticipant @malcolmfrary95515]

A Victoria, when sitting in the water, does not have its deck parallel to the waterline. Since the leading edge of the fin in not vertical to the waterline, this can also give the optical illusion that the bulb is aligned differently to what it actually is. If it has been assembled without any lumps and bumps in the areas where fin meets hull and bulb meets fin, it will be right.

I did, when sorting my Vicioria, find the instrucion manual on line. It was very well hidden in the depths of Thunder Tiger's site. Very useful, full of rigging dimensions that helped me sort out the previous owner's mistakes. Also helps me correct my mistakes.

When running downwind, there is a natural tendency for everything to pivot forward due to wind on the sails and drag on the bulb. With an upward inclined bulb, the pivoting action tends to make the centerline of the bulb horizontal thus reducing the frontal area of the bulb to the water flow, minimising the resulting drag. On other points, the shape and inclination doesn't have any noticeable bad effects. It still out-performs Dragons in light airs, which is satisfying.

[Richard Caughey 1Participant @richardcaughey1]

Malcom, the keel fin was the thing that started me wondering if the previous owner had assembled incorrectly, the fin is not vertical it does angle backwards a little, but on closer inspection there is a slight moulding mark at the top of the fin which kind of looks like it should have been cut off so the keel fin would be at more of an angle backwards and hence level up the keel bulb, any idea what the angle of the keel fin relative to the deck should be?

This also started because in light winds if I end up sailing to close to the wind the boat has a tendency, dont laugh because the previous owner had the same problem…., the boat goes backwards!

[Richard Caughey 1Participant @richardcaughey1]

I think I am going to have to try and take the keel fin off, but looks like previous owner super glued it

[Richard Caughey 1Participant @richardcaughey1]

Ok so 4 hours later….. keel fin off found loads of glue on top of the fin, deck hole in wrong place tube on keel fin rusted on, so all in all badly built in the first place…. what a job just to refit the keel fin into its correct position which it now is. So I now have slightly more angle on the keel fin and the bulb is parallel to the deck….. probably will go backwards even faster now !!!! Just for clarity it is (hopefully was) the only yacht that I have with the « special » reversing feature on, none of my others sailed backwards.

[Malcolm FraryParticipant @malcolmfrary95515]

Not having a reliable way og measuring yer actual degrees, I sat the boat in its stand with the upper end of the fin touching the vertical stand plate. Measuring fromt the bottom of the fin (top of the bulb) to the stand plate gave 23mm.

I've had plenty of occasions where I have misjudged a turn, stalled and found reverse. A handful of reverse rudder usually completes the three point turn and away it goes again. The technique was explained to me by a Laser driver. Being short of a sail, they run into such problems more easily.

Digging out a rusted in fin – got that tee shirt. It come out with the help of a workmate and a hammer and drift. The nasty brass tube was replaced by a fractionally over length thick walled plastic tube, with much muttering, but it did give the deck a bit of camber.

Another trick was to move the mast step forward – undo the rear screw, rotate the fitting 180 degrees, put the screw in its new home, bung the holes with something suitable. I was replacing the Cinese threaded rust with actual stainless at the time. The rudder will benefit from attention – its the same manky stainless shafting in the same brass tube.

[Richard Caughey 1Participant @richardcaughey1]

Malcom, just for info if you are interested, if you have a smartphone you can download an app called precise level that can measure angles quite accurately.

[Malcolm FraryParticipant @malcolmfrary95515]

I've only just been forced into a smartphone, still getting the hang of using it as a phone, never mind "apps". Several years ago, someone said of a smartphone "This is a miserable way to type". He was right.

Using the stand as a measuring jig is probably as accurate a way as any of getting the rake where the designer intended. Just a case of ensuring that the boat is the right way round on the stand, and that it is sitting on plain wood, not padding, to ensure consistency in the measuring. Having the boat as intended, apart from the corrosion issues, gives a very good plaything. I 've been taking mine for walkies round my lake for ten years now, the interest has not waned at all.

Some mods to make life easier –

It helps to be able to drain it easily – I fitted a drain flap at the bow. 65p, you get a free litre of orange juice, look for the se-saw lid rather than the opening flap.

Fitting a leech line to the jib helps

I eventually replaced the arm servo with a drum when the low cost drum types appeared.

I sail in salt water – after two rudder rods corroded away, I fitted a stainless bicycle spoke. And a rubber bellows where it exits the hull.

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