Swallow Yachts Association
Swallow Yachts Forum => General Discussion => Topic started by: Peter Cockerton on 21 Sep 2013, 10:07
-
Whilst out on Rutland yesterday on a steady run i took some readings from my paddle driven log to see the difference the outboard, rudder, and centreboard made to my speed through the water. With outboard, centreboard, and rudder down i was making a steady 4.3 knts i lifted the outboard and speed increased to 4.8 knts. Outboard down again and centreboard up 4.6 knts, about the same with centreboard down and rudder lifted to horizontal.
With the outboard raised i still get a fair amount of turbulence in the outboard well, the lamelia if thats how you spell it is still in reasonable shape so i want to look at a way of reducing further the turbulence to reduce drag.
Anyone else considered this and have any ideas on creating a simple but effective method way of shuttering the outboard slot.
-
I made and fitted a plywood filler for my outboard well last winter as the flaps had largely broken up over the last few years. It is just plywood (painted White here) fitted into the hole and held down by a pivoting cross bar. Three isn't much room under the raised outboard to either place it our remove it, but it works quite well. I got quite adept at using it after a while and I use it most of the time, but if I am just out for a drift around the harbour I often don't bother. It its mainly useful when going fairly fast. I made it because I didn't fancy replacing the flaps. That seemed to involve a lot of funny glue.
-
Julian
Thanks for sharing that idea with me, fairly straight forward and it works, with the turbulence affect removed if not the flow disruption under the boat do you notice any positive affects on the boat speed or any other aspect of the boat behaviour.
I note you comment on the amount of space and the filler being a little akward to get into place can you see it being possible to install a couple of channels front and back of the opening which rise partially curved vertically to hold a flexible piece of shutter material which could slide over the gap and when you want to use the outbaord be pulled up away from the opening, just a thought.
Thanks again
Peter
-
Hi Peter
I originally planned to have the filler split in in two lengthways and hinged on either side, but there isn't room under the engine to fold up even half an infill panel. My installation is also a bit more complicated in that I have the transponder for my depth sounder fitted in the starboard side of the well, where it gets in the way of the infill when trying to put it in. The infill has to go in from starboard to get under my engine. But I found practice helps speed up the process. The trickiest part is fitting the infill accurately in place. You would think is is easy, but it isn't, and the panel is buoyant, which means it really has to be forced down into place.
Performance wise I really don't know. I use it because it makes the boat quieter and a bit drier. If you are really flying along in choppy water, a lot gets thrown up through the well. At low speed I don't think it makes much difference (but raising the engine does, that is a real drag). At high speed I noticed that the transom is largely out of the water and the back edge of the well is in the open air, so there isn't all that much drag. But I must be nearly planing at that point. Slightly slower and I am sure there is some drag. I'm planning to stick with the arrangement for next year, but might see if I can modify it a bit to make it more self aligning in the hole.
-
Just to make details a bit clearer, here are a few photos showing the various stages of my outboard well infiller, including what the underside looks like when you take the existing flaps off. One side effect I hadn't expected, but like, is how my outboard works. Before I could only turn it very slightly side to side, so couldn't use it for steering. The cavitation plate hit the plywood holding the flaps in place. When I removed that plywood cover and the flaps, there is more clearance so that I can turn the outboard 90 degrees either direction, which can be useful for manoeuvring around marinas etc. The copper covered lump in the bottom left of the well is my through hull transducer. The two on either side of the hole are plywood clips the cross bar squeezes under. It is a doddle to fit when there is no engine, and not when there is. I had to plane the handle down to half the initial thickness to be able to fit it in. I didn't anti-foul the infill, because I take it out on the mooring, so there is no growth on it.
-
Julian
Thanks for the photo's it shows perfectly how you implemented the idea, it also shows that you have removed I would think totally the water flow disturbance from the outboard well opening. I understand that you removed the installed "lamellae" (again if that's what it’s called) because yours was damaged, mine is ok'ish so I intend to keep mine in place but shutter of the inside to reduce the flow of water into the well and then see what that does to the boat speed.
Many thanks for all your postings.
Peter
-
Hi All,
I wonder if any of you have found a method of removing the glue/gunk that is used to fit the shutters to the hull.
Guess what I am about to do ?
-
I'll be very glad of suggestions for an efficient safe way to remove the Laminae goop, which I suspect is Sikaflex.
On a similar adventure I resorted to a very sharp chisel and plenty of sticking plaster for me and gelcoat repair for the boat.
If anyone is thinking they might join the Turtle Club (I'm already a member, along with some much more eminent persons) they should note that blanking off the outboard well also stops water flowing out freely if the boat is swamped. The speed of water exiting depends of course on the fit of the plate but the chances are that if the boat is swamped it will not be fast enough. Some water can exit through the sump self-bailer, if it is open, and water will exit through the rudder port in the transom but only to the height of the port.
In my experience (all hard-won) opening the main ballast tank hatch quickly transfers the water to where it should have been in the first place - the ballast tank. However, remembering to do this and finding time to wrestle with a submerged, probably stuck hatch cover (especially if not vented) takes a lot of focus and/or adrenalin.
Matthew
BR20 Gladys
-
All good points. Is suspect that the gloop is construction glue as it is cheaper, but in the end it is a moot point. I have also resorted to using a sharp knife to remove the stuff and as of today I still have ten fingers :).
I have not finalised my design for a plug but think that I will either include some form of hatch or make it simple to remove in the event of an application to join the Turtle club. On that matter I wonder if these events have been written up so that we may all learn from them.
best wishes
Simon
-
For capsize titillation tales see Who dunnit? thread.
Matthew
BR20 Gladys
-
Now the Turtle Club is a group of privileged young American ladies, who even on their backs, are incapable of improper thoughts.
-
To contribute to the different ideas, I made the installation as shown, in case excess turbulences would slow me down in a race- not the case so far- . It opens and closes well . Obviously it requires space in the well and the engine (Yamaha 5 HP) has to be fully horizontally lifted to flip the cover up or down.
___________________
Catchando Bay (BR#48)
-
Has anyone ever considered some kind of flexible water bag that would extend over the well when inflated (with water?) on the same principle as those kids whistles that unroll in front of your face! It's one of those wild ideas that I would like to explore one day.
-
That's actually a good idea, but I think an inflated buoyancy bag (full of air) would be easier to use and just as effective, if not better.
-
Here's another solution (?) to outboard well turbulence: I've been busy doing some rough carpentry over the winter and have made a set of "outboard" doors to pug the gap, so to speak.
See them at:
https://www.dropbox.com/s/c4tkqwgkujnh7uz/Outboard%20doors.mp4?dl=0
So far (one test sail) they seem to work quite well but it was fairly calm.
AS you can see from the vidieo, the aft part of the well has been permanently filled in (about 150 mm of it) as Julian has done with his well. The mid portion is fitted with a pair of rectangular "doors", hinged along the outboard sides by means of stainless steel tubing with matching external / internal diameter. The width and length of the opening is such that the propeller and outboard shaft column will pass through when raising and lowering the motor.
The forward end of the well is left open, with a keyhole shaped slot. The outboard shaft slides through the narrow bit of the keyhole as lowering / raising takes place and the round bit of the keyhole allows the motor to the turned to provide some thrust steerage.
The doors are opened and closed by means of control lines, lead forward either side of the engine. If they work OK, they'll be on display at Mylor (otherwise they'll have been ignominiously removed and replaced by the flaps.
There's one downside I have foreseen and chosen to ignore. If you drop something in the forward part of the well, it's gone for ever......
-
Oops. Forgot something. This link takes you to a cross section sketch of a door, showing down the pull up pull down strings work.
https://www.dropbox.com/s/0iqmja8ensudx7v/Outboard%20doors%20section.jpg?dl=0
-
OOPs Opps. Just realised that the links in the last two post blew the security of my DropBox folders so you'll find they no longer work.
Here are valid links:
To the video of demonstration of the doors
https://www.dropbox.com/s/1anaktfy5bv6v4o/Outboard%20doors.mp4?dl=0
To the sketch section of a door :
https://www.dropbox.com/s/ze59q4ptz89slc7/Outboard%20doors%20section.jpg?dl=0
I think these should be secure.
Sorry
-
Here (below) is my wooden solution to outboard well turbulence misery in my BR20. Not quite "bombs away" but still fairly effective and similar to Julian's infill on the previous page. I was prompted to devise this because my Venetian blinds/lamellae were falling to bits and the well turbulence was increasingly noticeable.
Because of the exceptional length of my Torqeedo propellor blades, I need the entire length of the well opening for raising and lowering the motor. On the other hand, when the motor is raised, the well can be closed off completely, with the hinged forward flap lowered and locked down. I have filled in some of the less than watertight gaps around the edges with Sugru.
Probably the most watertight solution was proposed by an erstwhile prolific contributor to the forum. His description is no longer available but I think it involved making a fibreglass cast of the well opening and then using polyurethane foam to fill the cast, with Moss Rubber tape to seal around the edges. He also had a self-bailer set into the infill, so that water was removed from the well at a faster rate than it could leak in around the edges.
-
I have modified my outboard well plug, but don't have photos at the moment. I found that it was really difficult to force the big piece of ply into place against the inflow of water when I was moving. It is surprisingly powerful and it could only be done from one side, due to the engine being in the way. I have cut it in two, with the larger, rear section being fully lift-outable, and the smaller forward section being hinged on one side, so permanently fitted. This arrangement is much easier to close and has an added advantage. When the engine is down, the forward section is left open, but the rear section can be reinserted, which improves flow when motoring. I don't usually bother with it if just motoring out of the marina, but if I am going a long way I often shove it in.
-
Just found a photo, which I hope is clearish. Everything is covered in something similar to Coppercoat, which was interesting to apply...
-
Nothing quite beats the convenience of the original lamellae. My wooden infill is a bit of a struggle to install (even with the boat stopped) but has a big grab handle on the top to help the process. On the other hand, I don't need to swap it about very often. Like Julian, if I'm only motoring a short distance, I don't bother with it. All-day sailing is a different matter and when it's fully in place it certainly helps to lift the stern.
-
I have put a lot of effort into streamlining Gladys's bottom. This has included making a sealed outboard well fairing similar to Julian's but with a 6 mm ply external plate that over the lamellae and fairs in with the battens holding the lamellae in place and a hefty internal plate bolted through the lamellae to the external plate with a rubber seal around the fiberglass edge - a sort of lamellea sandwich . The space between the inner and outer plates containing the lamellae filled with water but the volume was small. This was successful at fairing in the lamellae and more importantly adding buoyancy to the stern that lifted the transom out of the water. But it took some effort to install each time and negated the use of an outboard - but not having a motor was another ploy for increasing buoyancy in the stern. I have used this system in SailCaledonia and Swallow Boats raids. Luckliy I have kindly friends willing to give the engine-less Gladys a tow when needed. Perhaps they will be justifiably less friendly now the nasty competitive motive behind my no-motor policy is known.
The most important thing to be aware of is that sealed outboard wells prevent water from quickly evacuating from the boat if the cockpit swamps. The tiller hole in the transom provides some escape but not quickly enough if the boat became suddenly and heavily swamped. I fitted a small removable hatch to quickly drain the outboard well but lying prone facing the stern to open in a crises is probably not a good thing to do. As I have mentioned before, opening the main ballast tank hatch to move water from the cockpit floor to the ballast tank, where it should probably have been anyway. If the cockpit swamps and the ballast tank is full then the traditional frightened man bailing with a strong bucket is probably the best option.
Andrew (the sailing master) suggested a close fitting foam block in the outboard well which is a good idea but I have not got round to developing a substantial fixing to hold it down and stop it floating out of position.
In cruising mode I thought it would be fun to have a perspex infill so that I can watch the rocks wack my rudder as I hit them. It was satisfying to make but with an effective seal the disturbed water on top of the perspex made the glass-bottomed boat concept useless except when stopped in very calm water. Making a seal, with an effective clamp to hold the plate down and yet easy to remove for the outboard to operate has defeated me so far.
As Graham says, lamellae are the most convenient solution. After a few years use though they can distort and droop. In desperation I have used a hot airgun to soften centreboard gasket plastic material plastic and to my surprise and delight the laminate meekly returned to its original shape without further persuasion.
Matthew
BR20 Gladys
-
Slightly off topic, but I have always felt that Daisy Grace was a bit low at the stern. Certainly, with more than one crew, there seems to be too much water sloshing up into the cockpit floor from the outboard well. I have tackled this by reducing the ballast in my stern tank (Baycruisers have two tanks, one under the cockpit and one under the fore berth.) At first I did this with a buoyancy bag, shoved in through the tank cover, but this season I have pushed in several slabs of expanded polystyrene, which I haven't tried on the water yet. The idea seems to work, and reduction of ballast had not noticeably affected stability.
-
Hi Julian,
Last year, and continuing into the future, I've had a buoyancy bag in the aft ballast tank of a size calculated to displace 26kg of water - being the weight of the 12V lead-acid battery I have situated under the "bridge deck" directly forward of the ballast tank. The effect is to move the cg of the ballast slightly forward and to render the lead acid battery "weightless" as far as calculating the extra weight that I've added to Seatern! I was a little worried about the bag moving about in the ballast tank, particularly since I sometimes sail with the tank empty, but it stays in place and, as Matt pointed out, it can't move far because of the baffles in the tank.
Having seen how well the buoyacy bag stays in place in the tank I'm wondering about following up your suggestion earlier in this thread for a air filled bag to seal the outboard well.
Incidentally, I'm also planning to keep the fuel tank installed at the forward end of the side locker in future, again to move weight forward in the boat. Lifting the transom can't be bad and it may even decrease turbulence in the well.
Peter
-
To contribute to the different ideas, I made the installation as shown, in case excess turbulences would slow me down in a race- not the case so far- . It opens and closes well . Obviously it requires space in the well and the engine (Yamaha 5 HP) has to be fully horizontally lifted to flip the cover up or down.
___________________
Catchando Bay (BR#48)
Guy
Have you tried this out on the water yet, does it keep the turbulence down in the well, does the leading edge of the filler lift at all as I guess it's not held down tight to the hull.
The design with the opening and closing controls looks good to me and easy to operate without having to spend time with my head down the well and as a consequence the boat steering all over the place whilst helm unattended. Does the well still fill with water or is it fairly watertight, have you put any method of sealing the infill to the hull when closed.
Appreciate response as i'm looking to copy your idea.
Peter
-
Attached yet another solution found as shown at the end of this video: a sliding cover closes the well on a Thunderbird.
https://www.offcenterharbor.com/videos/ben-seaborns-fabulous-thunderbirds-badass-family-boat-racing-cruising/
___________________
Catchando Bay , BR#48
-
Hi Peter,
I read your message today only.
The system is not watertight. It mainly eliminates turbulences. No sealing, water can still come in but remains there with no flushing which is the main purpose. The cover is kept closed by fixing the lines on clam cleats.
Sorry for the late response.
__________________
Catchando Bay BR#48
-
Reviving this thread after several years. It’s more of a technical than general question but the thread was originally posted to the latter section.
Having removed my lamellae years ago, I have used a plywood infill to plug the outboard well hole at water level and reduce turbulence, whether motoring or sailing. A new eProp Spirit electric motor with a wider shaft means that the old infill no longer fits at the front end, so I have made a new one, again from 12mm marine plywood. I can see quite a lot of daylight around the sides of the cover at its aft end, through which fountains of water and other evidence of turbulence will undoubtedly flow.
My question is, what is the best way of reducing the gaps, which in places are at least a couple of mm wide? I used Sugru to reduce gaps on my previous cover, which worked reasonably well but was expensive and tended to flake off over time. I’ve thought of using Sikaflex or epoxy but don’t know how to keep the filler stuck to the edge of the cover while remaining free of the the perimeter of the outboard well opening. Special (or standard) masking tape until the sealant cures? I’ve also thought of gluing strips of laminate to the edge of the cover and then sanding them down for a better fit but then will they split off when used roughly? And I’ve also considered gluing slot strip around the underside of the edge of the cover. However, the cover is already quite difficult to manouevre into position under the skeg of the tilted eProp and slot strip would make it even more so.
All suggestions gratefully received.
-
Would you not be able to thoroughly coat the edges of the well with a release agent which according to West System videos could be highly burnished Simoniz wax and then use epoxy filler around the edges of the plywood infill? Of course you would have to be careful the shape of the set filler doesn't lock the plywood infill in place.
Might be wanting to do something similar eventually so interested to see how you get on!
BRe 047 'Whimbrel'
-
Graham
Not being the proud owner of a hole in the bottom of my boat (filled, part time only, by an outboard), I can only generalise. There are now widely available (e.g. see Amazon) 'cyanoacrylate activators' which, used with superglue, enable almost everything to be glued to almost everything else. And they work. Last year I wrote up (somewhere else in the forum) using one of the first available in the UK, which actually came from Poland, to stick thin PTFE sheet to polypropylene webbing - two of the most previously no-no substances you could think of for gluing together purposes. A year on, they remain firmly fused to each other, and look to be inseparable for the long term, bless them. A few weeks ago I used 'Xpert Activator' + superglue to stick rather thicker PTFE sheet to two-pot-painted surfaces when re-assembling my repainted kick-up rudder: again, perfect result, and a rolls-royce smoothness as the rudder blade swings up and down.
Using this new glue technology, I was wondering whether you could find some sort of pliable plastic sheet to stick round the edge of your cover, slightly over-filling the hole and bending upwards round the edges, to keep most of the splash below the cover. The right degree of bendability would be critical. It might work even better if you reduced the size of the infill to leave a deliberate gap, now filled with your flap-valve material and even with a plastic edging strip along the free edge to improve the seal. The point is that you can now stick almost anything to anything else.
Just a thought, hope it helps. I think 'gluing' has been quietly revolutionised, and the possibilities are endless.
Michael R
-
Ray, Michael,
Thank you for your suggestions. Ray’s use of the term ‘release agent’ sent me down a Google hole which gave me all sorts of interesting results. Here’s a clear Swiss explanation of what epoxy won’t stick to https://acrylgiessen.com/en/what-does-epoxy-not-stick-to/. This led me to sheathing tape which in turn sent me to eBay. And it turns out that I already have some in my shed. Described as sheathing tape, an obviously very specialist item, it costs £12.99 for a roll. The exact same item described as Gorilla clear repair tape (which I already have) is £8.50. The power of marketing!
I’ll use Gorilla tape to make a mold in the gap between the outboard well perimeter and the ply infill. I’ll then fill the mold with epoxy, which will only adhere to the infill. Wait for the epoxy to cure, peel away the tape, lift out the infill and the gap should be thoroughly closed, with a bit of luck. I’ll post before and after photos here in due course, whether a success or failure.
Michael’s cyanoacrylate activator looks to be interesting stuff and is now very widely available. You can get a tube of superglue with a can of activator for £4.98 from Toolstation.
-
Graham,
Try on a lash-up first before the real thing?
-
Definitely!
-
I haven’t got around to closing up the gaps around my infill yet but can report that in its existing state, it improves speed by around 0.25kn compared to having no infill at all. Measured while doing 4kn with the eProp.
-
I have removed the Sikaflex and replaced the flaps however I think there is now a better option available. I have attached a PDF which shows the current arrangement on my BC23 whereby the flaps are sandwiched between the hull and a section of marine ply which is screwed into the hull. The main problem being to maintain the integrity of the hull during the removal of the Sikaflex. Chiseling away at the Sikaflex is no fun!
The PDF also shows the arrangement on a BR17 however I do not have all the detail. It would appear that a plastic infill is used in some way, perhaps the flaps are glued to the underside.
Does anybody know how the plastic infill is used and whether it is an item which can be purchased, perhaps from Swallow Yachts?
Regards,
Whistling Kite BC23