Jump to content

Foiling, how heavy is too heavy?


Recommended Posts

I have a 1990 OD 14 made by Ontario Yachts. It has the old style daggerboard trunk. I have some raw materials and plenty of time on my hands and want to see if I can get it to foil. The boat weighs about 170 lbs dry and the combined crew weight will be just short of 300 lbs, bringing the grand total to 470 lbs. I've read Nacras weigh 310 lbs without crew, but those foils are far more efficient than what I will be able to make. I know it won't be easy, but could I make this foil? If so, I want to try making t-foils to replace the daggerboard and rudder. The daggerboard trunk is big enough that I can rake the centerboard back and forth. I think it would be more practical to do that than to try to rig up a wand and a flap. If anyone has any thoughts on this or is pretty certain it won't work please chime in.

Link to post
Share on other sites
23 minutes ago, jamesmalcolm said:

I have a 1990 OD 14 made by Ontario Yachts. It has the old style daggerboard trunk. I have some raw materials and plenty of time on my hands and want to see if I can get it to foil. The boat weighs about 170 lbs dry and the combined crew weight will be just short of 300 lbs, bringing the grand total to 470 lbs. I've read Nacras weigh 310 lbs without crew, but those foils are far more efficient than what I will be able to make. I know it won't be easy, but could I make this foil? If so, I want to try making t-foils to replace the daggerboard and rudder. The daggerboard trunk is big enough that I can rake the centerboard back and forth. I think it would be more practical to do that than to try to rig up a wand and a flap. If anyone has any thoughts on this or is pretty certain it won't work please chime in.

Anything can be fitted with foils and flown in the same way that anything can be fitted with wheels and driven. As with both, mass negates performance, unless it is being used towards the production of horsepower. Right at centerline, it isn't doing that for you. It will work, but it might work less well than it did as a floater. 

DRC

Link to post
Share on other sites
10 hours ago, jamesmalcolm said:

If I start I think I'll do more harm than good.

I hate to be cynical but I think I fixed it for you. Don't think: foiling=faster. It isn't. Think: costless reductions of drag and increases in power to weight ratio=faster. Simply putting T-foils on an OD14 will almost certainly make it slower.


DRC

Link to post
Share on other sites
2 hours ago, Dave Clark said:

I hate to be cynical but I think I fixed it for you. Don't think: foiling=faster. It isn't. Think: costless reductions of drag and increases in power to weight ratio=faster. Simply putting T-foils on an OD14 will almost certainly make it slower.


DRC

True, but I think the object isn’t necessarily speed, the object is to foil

Link to post
Share on other sites

This is an interesting concept.    We have an OD14 as well, and a UFO foiling dinghy.   The OD14 is heavy for its size (compared to modern skiffs), but it is tough and if you have the Gran Prix rig and decent sails,  you are working with a lot of horsepower.  So I believe that the rig has enough power to get the boat up on foils if you have fairly well executed foils.  More hull weight means more force needed for lift, which means more drag as well.  But you are correct, foiling in and of itself is pretty fun, and even if you are not going as fast as a purpose built super light foiler, you still have decent speed potential. 

My biggest concern would be the difficulty in sailing this craft with centerline T foils.  Sailing the OD14 with the Gran Prix rig is a reasonable challenge for most dinghy sailors.   For good skiff sailors, its a pretty forgiving boat, but for those without skiff experience, the limited initial stability combined with the significant sail area make for a tough learning curve.   Once powered up and with both  folks on the wire, it gets much easier.   My concern would be that keeping the heel angle in the sweet spot with two people on the wire would be challenging and exhausting.   Both sails are pretty large.   I know on the UFO and Moth, you are working the mainsheet continuously to maintain a slight windward heel.   The same level of active trimming on the I-14 would leave me crushed in 15 minutes (yes, I could use more gym time).   On the other hand, you have the ability to adjust your personal contribution to righting moment instantaneously and continuously on the trapeze, so perhaps it may be easier than I think.   The idea of popping its enormous chute while on the foils is downright terrifying to me, but if you can pull it off, I'm sure it would be an epic ride!   

There have been a few one of boats built with twin trapezes and centerline foils.   I'm sure they are listed on other threads here and you can find them on youtube.   All look challenging to build and sail.   If the challenge excites you, go for it!   Post updates.   For every project's nay-sayer, someone out there actually goes out and DOES it.   There was a great looking Laser foiling conversion that was done in Maryland last year.  

Good luck!   Doug

Link to post
Share on other sites

@JulianB experimented with a Foil config with the foil between a board/strut each side of the hull. I don't know where they go to with it, but the config might be a bit more boat friendly and easier to make for the OD14. I think pretty much anything will fly, given big enough foils, at least downwind. Faster round the track than a standard boat is a bigger challenge.

Link to post
Share on other sites

We went Canard, rather than Tractor configuration

That allowed us to use a H foil rather than a T foil.

This was 2009, BTW, and yes we achieved far high CoL's than say Bora was getting on his moth or Luna Rosa.

JimC is dead right, anything will fly, the issue is keep it from not flying until you hit a higher speed.

Top speed tends to be 3 x takeoff speed, dose not really matter if its a 787 or a moth or a F111.

So if your chasing max speed, then you want a high Take-off speed.

We have recently done the sums WRT the 49er, it goes up wind and is very tight racing at 12 knts, (VMG8.4knts) we may get to 14knts if we foil but VMG wont increase much.

Style of racing will completely change, cost will double and in light air, and 70% of sailing happens in light air, it all goes to shit!

Downwind the numbers are even worse.

49er will probably remain on it's arse for a while yet!

For all sorts of reason, if the 49er or a variant went foiling, and mostly for safety reasons + structural, Canard makes so much more sense than Tractor.

 

Link to post
Share on other sites

Julian makes some interesting points. 

Foiling monohulls that aren't designed for foiling is about doing it for the fun and anything can be made to foil. There are a range of poissibilities. Besides Julian's 49er and the R Class, try looking at the foiling Cherub in the UK.

The light wind issue is real in most foilers. Even in the highly efficient A's, the foiling A's struggle against the non foiling boats upwind although it is close. Once out on the trapeze upwind, the boat feels good and works well as a non foiling boat. I am not sure there is any way of achieving this on a monohull. This leads to the push to get foiling early, which becomes interesting due to Julian's speed comment. Downwind on the A we get foiling in 5-6 knots of breeze if you are good enough, but you still need to get some decent boatspeed to achieve that. I think the Moths are similar, and narrow hulls with power from wings and overall beam helps, again why a conventional mono might struggle. 

 

As for max speed being 3 times take off speed, I suspect Julian is in the ballpark here, but there is more than meets the eye. For instance, we are struggling to hit those top speeds downwind with the A, although we are now able to sustain higher speeds in less wind than we used to. We used to need 18-20 knots to hit top speed while we can now do that downwind in about 12-15 knots. What we have found is a surprising turn of speed upwind that everybody thought was impossible.We all thought 18-20 knots would be the max, but we are now getting 22-23 knots and going about 3-5 degrees higher than the non foilers. There is even a low mode that reaches 25 knots, but it doesn't gain anything VMG wise. The truth be known, it is terrifying going upwind at those speeds and 27-28 knots downwind feels "cruising" all because of the perceived apparent wind, and the fact I stil struggle to stop safely when going upwind!

So back to monohulls. Part of the fun and the journey is in the development, so give it a go. Don't try to be radical. Enough people have done things that work, so choose your system, learn as much as you can about it and do it! Good luck.

  • Like 1
Link to post
Share on other sites
8 hours ago, SimonN said:

Juli

 

 

8 hours ago, SimonN said:

So back to monohulls. Part of the fun and the journey is in the development, so give it a go. Don't try to be radical. Enough people have done things that work, so choose your system, learn as much as you can about it and do it! Good luck.

So T-foils might not be the solution for dinghies. Better to do as the A-cat and go for surface piercing foils instead. 

Link to post
Share on other sites
6 hours ago, revintage said:

So T-foils might not be the solution for dinghies. Better to do as the A-cat and go for surface piercing foils instead. 

It's a tough one. Without lots of development, you don't really know what would be best. In monohulls, it is clear that T's can be highly developed and produce excellent results, as with the Moth. But let's not forget that it has taken years of refinement. With Cats, everybody said that the A Class "Z" foils wasn't the way to go, that they had speed and control limitations. However, being forced down that route by the rules, we have been surprised at what has been achieved to the extent that we now believe we have the best option for top level cats. In many ways, we should never have started from where we did but if we hadn't, the boats wouldn't have been as good as they are today. We got lucky.

Bringing this back to monohulls, who knows where foils would be if the same amount of effort is put into some of the alternatives to T foils as has been put into Moths and A's. The most commonly used top A Class foil is the Z27 and while some of the 27 iterations never made it passed the drawing board, it gives an idea of how much development has been done. The Moths are similar. Look at the development of both the foils and the control systems. In both cases, the development has been driven by a set of rules and a strong class following. One of the problems that I see is that alternate solutions aren't continually developed - maybe Julian's canard is the real future for monos. Maybe it is something else. the question is who is going to go through 20+ iterations to get there when there is no commercial reason to do so. What you end up with if you are not careful is a boat like the Nacra 17 which is defined by far from ideal foils. The boat could be so much better with foil development.

  • Like 1
Link to post
Share on other sites

I think we have to divide foilers in different segments.

The first ones are the development classes, like A-class with Z-foils(surface piercing) and Moth(T-foils), where the refinment of foils are part of the competition. Their findings have done much for the spread and interest.

Then there are the one design classes where Nacra 17 is one of many, asking the crew to be acrobatics to even get around the course.

About monohulls it seems to be that the DSS variants, are what commercial forces are hoping for. Surely not high speed foilers, but they are probably easy enough for anyone to sail.

For those who wants to experiment and learn, T-foil modifying a conventional dinghy can not be easiest way to begin, especially with two onboard.

Link to post
Share on other sites
On 5/6/2020 at 1:16 AM, SimonN said:

What we have found is a surprising turn of speed upwind that everybody thought was impossible.We all thought 18-20 knots would be the max, but we are now getting 22-23 knots and going about 3-5 degrees higher than the non foilers. There is even a low mode that reaches 25 knots, but it doesn't gain anything VMG wise. The truth be known, it is terrifying going upwind at those speeds and 27-28 knots downwind feels "cruising" all because of the perceived apparent wind, and the fact I still struggle to stop safely when going upwind!

Wow, 20+ upwind!?

What's a Moth's upwind target speed?

Link to post
Share on other sites
On 5/10/2020 at 4:25 AM, Liquid said:

Wow, 20+ upwind!?

What's a Moth's upwind target speed?

We need to be careful this doesn't become a pissing contest. To start with, straight line speed isn't what's important, it's VMG. Stories say the top Moths are now doing about 21 knots upwind in the right conditions, so maybe a little slower on the clock but what is more interesting is tacking anglesI have seen data on this, but the reality is that it all depends on conditions - both sea state and wind speed. Then you really need to add in tacking. I think if you got the top Moths and top A's together (something we would love to do up at Lake Macquarie and might happen fairly soon), it would then depend on exact conditions. I suspect that if you take all conditions together, the Moth is a bit quicker than the A, but I think there are a reasonable range of conditions where it would be really interesting and that I would not like to predict the winner.

More on the VMG. One thing we have learnt is that there is a difference between top speed and best speed on the race track. We usually see our highest speeds downwind when not trying to beat another boat, and when it is 2  more boats, the speeds go down This is because downwind you can go high and fast or lower and slower. You can drop a lot of speed if you are going 15 degrees lower than the other boat. We have seen training days where the downwind speeds are "only" 25-26 knots but when somebody does a run on their own, they are suddenly closer to 29 knots.One of our fastest sailors trains on his own in Perth, and regularly gets over 30 knots but when up against others at events, he is seeing more like 25 knots. I suspect the same is probably true with the Moth.

The real thing to marvel at is that there is a choice of boats to go at what seems, on reflection, crazy speeds. Just think about upwind. I started sailing in the 1970's and spent a significant portion of my life sailing boats that go 4-5 knots upwind. Then came the skiff revolution and I found myself sailing 49ers at 12+ knots upwind. Most forget what a jump that was. Now we have seen that leap again with foilers. 13 years ago, the Moths had a roll of honour for those who had cracked 20knots+. I think when I first did that it was blowing 18 knots and I did 23 knots out of control and made it into the top 10 speeds. Now, if I sail and i don't hit 23 knots, it's probably a disappointing day. Sure, speed isn't everything but how far we have come in what seems like a fairly short period

  • Like 2
Link to post
Share on other sites

Seemed a simple question...

Not a dick size contest! I could care less which configuration goes to windward faster or why! Just surprised those are your speeds..

Back sailing a B3 14er, our target was 9.25ish for best VMG. But that was nearly 15 years ago...

 

Link to post
Share on other sites
10 hours ago, Erwankerauzen said:

Do you think it is relevant for a foiling windsurf too ?

 

NO, the issue is weight, so a moth or a windsurfer, if you stack the worst that is going to happen to you is you may get hit (unlikely) by a foil attacked to something 20-30 kgs.

A 49er if your on foils,

#1 you want to make sure you won't be in the path of the foils, so if say a trap wire/ring/hook breaks then you don't fall into the path of the rudder attached to say 140kgs of boat and another 80ks of the remaining crew member.

#2 most likely "stack" is a nose dive, so if you have a Canard, the front foil is likely to be 3m underwater, the main foil is likely to be at WL but 2 m way under the boat.

& #3 structurally, H foils can be pin jointed, so you don't end up with bloody big hubs/T-joints, and those bloody big hubs all = drag.

#3 ii) is that H foils tend to end plate far better, so you can get far higher CoL's and AR (Aspect Ratio) laws tend to lend themselves to reducing CoD's.

Windsurfer/moths are light enough that the compromise is way to the left (T foils)  but a 49er all up weight is 290-300kgs plus they regularly do 12-14knts up-wind and 26-28 knts down-wind on their bottom,  so much higher potential takeoff speeds, so far smaller H foils with far higher CoE and lower CoD's make far more sense.

Link to post
Share on other sites
On 5/18/2020 at 10:27 AM, Bruno said:

There was an experimental 14 foiler at 2006 worlds, poms, might talk to them.

The thought of adding full foiling to a 14 boggles my mind.

That boat is already hard to sail, fast and fun enough!

 

I think it would be weird to sail a 14 and not skip/bash off the top of waves... 

Link to post
Share on other sites
  • 2 weeks later...

Thank you JulianB for your crystal clear explanation, it is very rational & consistant

and sorry for very late reply , recreational CFD was a bit on the back burner these last months.

I would notice that on the video posted by FastYatch, these foilers monohull demonstrate great stability.

Simon's remarks regarding A's & Moths performances would deserve a dedicated thread, a kind of "open source" polar datas for these high performace boats.

I have been told datas exist for Moth, while for A-Cat, prohibited on-board electronics does not make it easy. (AFAIR, Only USA 230 has kindly and regulary provided us with some A-Cat polar figures)

I will stop here as it is a bit off topic.

Thanks & Regards

  • Like 1
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...