Small boats and ballast

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Hello lads n lasses.
In a bit of a quandary at the moment. I'm more used to sailing boats with lids on, but for the time being, the Achilles is ashore, whilst I concentrate my efforts on potting and long lining. The boat I've got is an open 18' fibreglass coble with a 9ish hp Johnson 4str outboard.
This outboard pushes the boat up to about 7.5knts, but to be honest, it feels like its past its displacement speed, and is just digging a hole in the sea; theres loads of wash, and the bows are pointing skywards. This doesn't feel or look right at all. Current thoughts are..
lighten load at back- stick on my suzuki 6 (25 kilos against 40 kilos) or even more drastic find a century plus (I know, but I love the things)
Move to a forward steering position but this will bring complication and clutter- I like simple in my boats
Consider using ballast.... I dont like this idea in principle ( I like my boats to be 'floaty') but as well as adressing the above question of trim, the boat at present feels like it could have more grip in the water...
Any thoughts on the matter would be great..
Cheers John.
 
Certainly 7.5 knots is well past hull speed - about 6 knots for an 18' hull.
Have you thought of/tried a tiller extension allowing you to move your weight forward and still helm? It would be my first step.
 
It's not unlike the situation we all suffer when using a solid dinghy/outboard single-handed. You are exceeding the displacement hull speed and getting stuck near airborne, trying to mount your own bow wake - exciting but counter-productive. You must be using quite a lot of fuel to maintain the situation, whereas throttling back will save fuel without any significant loss of progress. It certainly helps to stow as much heavy gear in the bow as possible and a tiller extension to allow you to move to the centre thwart would be a great improvement. That would at least help stop the bows being thrown up by every ripple.

If you are willing to go a little further, a simple whipstaff steering arm with ropes and pulleys would allow you to adopt a forward steering position during extended periods, but move back to the engine for manouvreing!

I used to have a heavy dinghy and underpowered engine so I would lock the steering, move forward and steer by weight shift for the half mile trip through open water to the boat. Don't try that near obstructions as the reaction is slow and only shapes up a rough course!

Rob.
 
I don't think it's going to plane, so I think you are just trying to go faster than the boat wants to be going.
I would make sure the bow is properly in the water at rest, but not bother with trimming down more than that.
A mate of mine uses an old bit of broken windsurfer mast as a tiller extension for his outboard, it's about 6ft, light, stiff and the right size! The more rigid plastic drain pipe (40mm?) is a second best. You don't need to steer much at top speed, and it just slips off for close quarters. A bit of bungee stops it coming off on its own.
 
I agree, theres no intention of planing the boat or breaking any speed records, I suppose the main thing I want is for the boat to be trimmed at sensible (4-5 kt) cruising speeds; at present, as soon as its put in gear, up goes the bow. Favoured option to me is to use my Suzuki six; its lighter, economical, and probably has plenty power. The main thing I was interested in is what folks think of the ballasting issue to achieve the correct trim. As the coble is very pinched at the stern , theres not masses of buoyancy there compared to the bows.
 
Have you exhausted the tilt range of the outboard?
I would try it with the motor fully down, so it is trying to lift the transom a little.
You could try adding a wedge to the bracket to increase this perhaps?
 
Beware the leverage exerted by a prop a long way down with a relatively powerful engine; I know someone who ended upside down with a dunked engine due to that.

I was once on an Orkney Longliner, a similar boat I think ? - and when beam on in about F4-5 inside Langstone Harbour it seemed very near its' limits, certainly had our attention; I think some ballast secured low down on the centreline amidships or a little forward would have helped.
 
Seajet said:
Beware the leverage exerted by a prop a long way down with a relatively powerful engine; I know someone who ended upside down with a dunked engine due to that.

I was once on an Orkney Longliner, a similar boat I think ? - and when beam on in about F4-5 inside Langstone Harbour it seemed very near its' limits, certainly had our attention; I think some ballast secured low down on the centreline amidships or a little forward would have helped.
Click to expand...

The leverage on a longshaft engine near caught me out once. The clamp screws were a bit corroded, so it wasn't tight enough on the transom. The engine nearly climbed off the transom as I turned on full lock. Not clever, but you've got to learn when you're 16!
 
Similar boat to a longliner; a yorkshire Pebble 18' version; theres certainly no way of tilting the engine further without surgery, and as this thread goes on, I think the idea of a smaller, lighter, engine may help a lot. I was prompted to start the thread after reading a post on a sea angling site, where one chap mentioned his 16' Pebble, and how well it went with a 15+ horse engine on and trim tabs??
As I stated, I'm far more bothered about getting a good stable trim than blasting about the place!
Oh, and thanks for all your comments!
 
I'd thought of these Ken, but I cant see them doing what I want at the speeds I'll be doing. May look at ballasting issues re previous threads and the comments about the orkney boat; whilst mine is to some degree designed around the Yorkshire coble, it certainly lacks the mass of a heavily built wooden boat.. hmmmm.
As I said my natural inclination is to steer away from putting heavy things in my boat, but am I talking nonsense in this respect? I suppose coming from a sailing perspective, heavy weights have tended to be unwanted.


Oh hang on, Im talking b@77%cks; the Achilles has a dirty great chunk of iron under it..
 
I had the same quandry with my 15ft boat (in the avatar). As you can see steering from the stern at 6 knots it was far too nose high.
I had the added problem that even with a longshaft motor the prop would come out of the water if I moved to the centre of the boat.
I solved it all by cutting a notch in the transom to lower the motor and installing remotes to steer from the middle of the boat (it already had steering)
I was also against adding ballast, but settled on 25kgs of decorative gravel in a sealed plastic bag from the builder's merchant (£2.50).
This way I could move it about to get the trim correct.

My 5hp 4 stroke powers it at 5 knots at slightly above tickover and 6 knots at a bit opened up. As you say, if I try a lot more throttle there is a lot more noise and vibration but no more progress.


Philinsmudger1.jpg
 
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Around here, there are a lot of small (sub 20ft) sailing boats used as purely river motor cruisers. Their hull forms are not ideal for the same reasons yours is not. Some friends have a 20fter with a 40hp, clearly over powered for the limit of 5kts. But, to counter the wt. the original owner fitted a ss plate. Sort of trim tab, but fixed and goes around the lower part of the leg. Such a plate could be adjusted until you got the result you wanted. Not an answer for your ballast question, but my feeling is to avoid extra weight.

What about those 'Dolphin' wings/flippers that attach to the cavitation plate?

Re the previous reply about a whipstaff to get you forward. How about a cable run to a fore and aft steering lever on one bulwark with the O/B tiller hooked on by a bit of small chain to a pin. Quickly put on for cruise, equally quick to detach for close work.
DW
 
Lakesailor, that avatar is about right.
Whipstaff idea may be well worth trying, just needs a bit of lateral thinking.
Has anyone been in this situation, added ballast, and considered it a positive move in terms of not only trim, but general 'feel' on the water?
 
OK, a bit of drift here. But in the early 70s, a couple of friends had tuned Hillman Imps. Bit prone to wander in X winds. Usual cure was a sack of spuds in the front boot. Looking at the developments on the track, we cooked up some early 'air dams' for the front ends. Worked a treat, and releast the spuds for the food chain.
Hence my suggestions for trim, rather than weight, solutions.
DW
 
OK, might give it a thought Downwind, or try knocking something up over the weekend.
Sunday Ill try a lighter engine, and if thats the wrong tack, Ill put some thought to it.
Cheers John.
 
Fins...

I'm not any sort of expert, but FWIW I have hydrofoils (Dole-fins) on my 14' Fletcher's outboard and they do work very well for me. They were already fitted when I got the boat, so can't compare to what it was like without them. Most other similar type vessels I've seen however push up and over the 'bow wave' phase whereas mine rises up onto the plane level and pretty much unnoticed. They are said to provide stern lift which is what you appear to need and would be a cheap fix. I would add however that they are clearly not the answer to all problems and can make the boat unstable at higher speeds - although it doesn't sound like you want to go fast enough for that to be an issue! My Fletcher has a 30hp and maxes out at around 22kts - at that she shows no sign of any instability. From what I've researched, I think you need to be closer to 50kts to start triggering 'chine-walk' and thus I wouldn't fit to a boat capable of those speeds. :)
 
His boat is a displacement boat and won't get onto the plane.
Whilst trim tabs may improve the boat's trim they are using the engines power to overcome the tabs' drag, which is a waste of fuel.
 
Small power boats

Back in December I was asked to return a dinghy about 13ft long 15HP Honda on the back. The trip was about 1.5 hrs by water. The dinghy was a light weight Aluminium with tiller control. I found the trip horrible.
I had difficulty getting my body far enough to one side for comfortable control of the tiller without the boat leaning to one side. I had to sit near the middle (athwartships) and then like the OP at any speed the bow rose too high making the boat more longitudinally unstable. This boat is an extreme case and would have been happier with 6 people on board but going slow.
I realised why we go for steering wheel and remote control on even small boats. By contrast the same trip a few weeks earlier in a centre control RIB was just so comfortable.
The dinghy I found so uncomfortable was used as a coaching boat for rowing so I find it hard to understand how the coach could work for several hours I know I would complain. For storage (they had 8 of these) the motors were removed and hulls stored on their side in a shed. So any complexity would make it difficult.

Anyway to the OP I would want to consider wheel steering. Or at any rate a tiller extension. Try to keep the boat level at all speeds but I don't think ballast a good idea. Just be wary that small boats overpowered can capsize often bow over stern in a wave so be careful. good luck olewill
 
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