I think now that David T was right to declare the "stability testing" with the rigid "passenger" invalid. I’ve started doing it all over again, with revised estimates for build weight, and a different way of allowing for the huge discrepancies in "over weight” of the models. I think we need to look at proportionality - and also, any additional weight should be added to the midship section, not perched on a rowing thwart.

I am doing four static tests on each model.

- 1. A righting moment versus heeling angle (stability curve) for each dinghy model in its current over weight form. (Percentage overweight is stated in each case.) These will be represented by an
**orange line**.
- 2. The same again, but with additional weight (a strip of lead flashing) spread around the midship section, to bring each dinghy up to the same level of over weight (250%).
- This (250%) might sound a lot, but it is the only way I can try to make a level playing field. Most dinghies improve their stability with extra hull weight, and it is not uncommon to load real dinghies up to 400% or more, of the empty designed displacement. These graphs will be represented by a
**grey line**.
- 3. The same again, without the additional weight, but with the addition of a quantity of water in the hull equal to twice the weight of the hull, to look at the free surface effect on stability. There will be some surprises here. These graphs will be represented by a
**blue line**.
- 4. A simple test in which a concentrated weight is applied near the gunnel, to see how much weight is required to bring the gunnel down to the waterline.

Dinghies which do not have full buoyancy will lose stability when the gunnel is immersed, and the line graph quickly decays to zero. Those with full buoyancy will have a wider range of stability.

Here are the first four, in no particular order(click to enlarge):

That's right - *General P**urpose Dinghy* is more stable swamped than dry - much more - not that I can imagine how it could ever be flooded, as it retains stability beyond 80 degrees of heel, floats high on its side tanks and will recover virtually dry.

above: *GP Dinghy* at 80 degrees, dry and still has stability

above: *Sibling Tender* at 45 degrees, flooded but still retains some stability

*The whole project has got a bit out of hand and is taking “messing about with boats” to a rather ridiculous level, so please do not use these absolute figures to compare dinghies, rather it is just an interesting exercise to look at the effect on stability of weight, shape, beam, buoyancy tanks, free surface water, etc.*