Thread: GIS X or Raid Special

As far as a GIS special for Raiding that is stretched 10%. That is dead easy if only basic information is needed and all structure is borrowed from the Goat. There would never be any building instructions for such a boat, but should be a sensible extrapolation from the Goat Plans.

The current mid seat would have to move back a bit and the fore seat fitted in in front of the centrecase. Will need a second FIN type centreboard for rowing that won't come up beyond the case height.

MIK

MIK

Originally Posted by Joost

My thoughts exactly!

The Multimono skiff is fast (compared to the smaller raid boats, not to an OZ 18 ft skiff), but that seems to be more due to its size (long waterline, water ballast, massive sail area and many people on the oars) rather than that the boat is an impressive feat of designing or engineering. And due to the size (and weight) you need a big crew to handle her and to make it go fast in all conditions.


I would like to think that most (if not all) raids are won by the crew who can keep a good pace during the whole duration of the event regardless of weather conditions and whether sailing or rowing. In other words, you need:

• a proper all-round sail&oar boat; and,
• an all-round experienced crew that knows the boat well and is able to both sail and row the boat hard and fast in all conditions (this might even be more important that no. 1)!

The way I conceive the GIS is the following: the GIS is a boat predominantly designed for sailing (it is after all advertised as a simple sailing boat on MIK’s site!) that actually performs very well under oars without the designer having made any true concessions to its sailing qualities.
In other words, it is in fact very much an all-round sail&oar boat (and therefore a good raid boat), but its rowing qualities seem to be more of a byproduct, though a very welcome one, than that the designer had them in the back of his mind when designing the boat. But please correct me if I am in the wrong here MIK!

It wasn't the plan. However the reason is that my starting point were two racing boats I had spent a lot of time in.

The NS14



the following isometric is before the hulls went REALLY narrow underwater



The NS14 is for two adults and doesn't have much sail area - 100 square feet (9.3sq m).

So the performance comes from reducing every aspect of drag. Rig, hull, foils, wave impact.

The other class was the Australian Sharpie - another low drag boat that sails even with the much more powerful Flying Dutchman and is fractionally faster than the 505.



So the GIS is focussed on less all round drag within the context of being a flat bottomed hull. Note the NS14 isometric above. If you look at the widths of the waterlines - the dark blue curves are the hull sections, the Goat is not too far different, but a little more conservative with a narrower stern.

So .. the sailing performance is based around less drag .. which also helps out the rowing performance.

to come up with a lightweight flat bottomed skiff that would truly “upset” the European raiding world in the hands of a competent crew (and I am pretty sure it would also perform very well in an event as the Texas 200 as well!) but would still be a great sailboat without having made any concessions???

Joost

The small simple light low-drag way seems very sensible. Problem is getting enough stability - so it does put a premium on people who do know how to sail well!

Best wishes
Michael

Hello MIK,

Thank you for your extensive explanation of the low drag principle that forms the basis of the GIS design. I really appreciate the feedback regarding the starting point and the design principles as it helps me to better understand how the boat performs.

The past few days I have spent a lot of time assessing the Goat: it will be hard to do any better for all-round performance in this size.

More reviewing, thinking, measuring and rough calculations have led me to the following conclusions:

1. I really don't want to build a bigger boat!

2. I don’t want to make any permanent changes to the current layout of the GIS. I just love that big cockpit for sailing, and for cruising one row station is more than sufficient. Wringing out the last bit of speed under oars is only required when raiding.

3. Oregon pine and fittings have been ordered for the new L-shaped boom and construction should start in a week or so. I am looking forward to fine tuning the rig and test sailing. Toe straps will be fitted as well the coming 2 weeks.

4. Could the following be a solution for faster rowing with a crew of 2 when raiding:

Detachable/foldaway seats aft of the mid seat and in front of the centerboard case.

This set up would give an approximate 110 cm’s distance from front end of aft rowing seat to the front end of the forward rowing seat. These seats don’t need to be long (i.e. go from side to side) as they are only used for rowing. The aft seat can use the mid bulkhead as support, the front one the front end of the centerboard case. My gunwales allow for easy incorporation of another 4 oarlock sockets at the appropriate places to ensure 300 mm’s distance from end of seats to mid of oar lock sockets.

I have reviewed the study plans of Iain Oughtred's Tammie Norrie: rowing stations seem to be some 110-115 cm's apart. Looking at the range of motion with the oars when rowing from the mid seat, this should allow sufficient space for proper rowing in tandem configuration for the GIS as well.

The challenge will be to come up with a nifty design for these seats: they should stow away easily, don’t mess with the current layout, not require too many amendments/reinforcements to the current structure and easily come off the boat when not in use. It will be interesting working out this concept and to find a good solution.

Best regards,

Joost

Joost,

I suspect that having a second rower at the front will push the nose of the boat too far down for efficient rowing. Maybe moving gear to the back of the boat might compensate or the main rower only using the back section of the middle seat?

Wonder if a small fin with a seat on top could fit in the centrecase for rowing and the mid seat extended backwards in the middle - maybe a fold down extension? Or a box that sits on the floor. Or a seat that hooks into rudder fittings on bhd #3

I think you need to get the boat into the water and see how the weight distribution works out.

MIK

Talking low drag.

Another wonderful website is the one for the National 12 in the UK.

The National 12 is also a restricted class like the NS14 with a moderate sail area.

The NS14 does have a measurement that prevents the boats from getting too narrow underwater, but I don't think the 12 does.



They have a page that shows the evolution of the boats too.
http://www.national12.org/boats/inde...n=list_designs


Michael

Originally Posted by Joost

Hello MIK,


3. Oregon pine and fittings have been ordered for the new L-shaped boom and construction should start in a week or so. I am looking forward to fine tuning the rig and test sailing. Toe straps will be fitted as well the coming 2 weeks.

]

Hi Joost

By L-shaped boom do you mean the boom PDR style? If so, what do you see as the advantage of that design over your current boom?

The inverted L.

It is a new boom design we are trying out on the RAID. Less traditional, but a lot stiffer so is more suitable for loose footed sails.

It comes from the T shaped wooden booms from when the NS14s (above) used to be much more homebuilt than now.

The T section is excellent for dealing with lateral and vertical forces. However it is not very compatible with a balance lug. I was trying to work out how to improve the resting of the boom against the mast.

So ... you saw the inverted L boom here first!

Knowing how often things have been thought up and forgotten in this boating thing it is hard to know whether I am revisiting old territory ... but it is a nice solution for a loose footed balance lug.

The RAID41 inverted L Boom.

We will need pictures from Brian of the rigged boat to see how it looks, but it promises very good interaction with sail controls too.

Unless Joost beats him to the punch!

MIK

Originally Posted by Boatmik

Wonder if a small fin with a seat on top could fit in the centrecase for rowing and the mid seat extended backwards in the middle - maybe a fold down extension? Or a box that sits on the floor. Or a seat that hooks into rudder fittings on bhd #3

I think you need to get the boat into the water and see how the weight distribution works out.

Hi MIK,

Yes, this was my exactly my line of thinking that I tried to put into words: one small seat in the middle hooking ont bhd #3 and one seat on top of the front part of the centrecase. Otherwise I would be worried about the weight distribution as well and the space required for rowing.

Anyway, I will try out next outing how this works out with regards to the entry of the bow and the release at the transom.

Joost

Why not do a removable fore-aft beam seat like on Bolger's Nymph. Then you can adjust the trim just by moving. Maybe even clamp on oarlocks (rowlocks) that can be adjusted to different positions?

It doesn't always have to be a high tech solution

Mr Kirtley,

this is an excellent solution!

A fore and aft seat that drops over the centrecase and extends forward and aft enough for two rowers to find their balance points!

It could run from in front of the case to behind the mid seat.

I think this is the one that has potential - and it can be removed completely when not Raiding.

MIK

Michael

Just a 300mm wide seat up the middle of the boat. Could even be padded for comfort and stability by gluing on some foam used for cheap camping mats.

Doesn't need to be boxed in like this.

If you wanted to get really fancy, you could even add some tracks for sliding seats.

haha!

The goat without sliding seats and one rower is already outclassing all but two of the boats in its division!

MIK

Originally Posted by Joost

I have reviewed the study plans of Iain Oughtred's Tammie Norrie: rowing stations seem to be some 110-115 cm's apart. Looking at the range of motion with the oars when rowing from the mid seat, this should allow sufficient space for proper rowing in tandem configuration for the GIS as well.

Joost

My rowboat Drake has the tandem positions separated by 48" and it is great...a couple inches closer wouldn't hurt. The single rowing seat slides out of the way when tandem and slides back into place for solo rowing. Moveable seats is the key to making a boat row with two OR with one.

Clint