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#48206 - 04/28/05 04:59 PM Formula 16 mast design  
Joined: Jun 2001
Posts: 9,582
Wouter Offline
Carpal Tunnel
Wouter  Offline
Carpal Tunnel

Joined: Jun 2001
Posts: 9,582
North-West Europe
Here is a Formula 16 mast design for the aluminium superwing section that I made using what works from the Taipan design and improving what didn't work so well. Most things were tried on my own mast and those experiences have been used to fine-tune it once more.

[Linked Image]

This mast design is fully F16 rule compliant and allows a mainsail to be downhauled to max 8.1 mtr. The boom is pretty low and I really don't think anyone would want to put a longer luff mainsail on a doublehanded F16. You would make your crew really mad. All distances are measured from the bottom of the mast section, excluding the thickness of the mast foot plate. My mainsail has a luff of about 7900 mm and during the REM-race 2004 in 20-25 knots of wind I downhauled that all the way down to my boom fitting. That is a 200 mm stretch and is also the very max my (unintentionally shorter)downhaul system allows. I initially designed my downhaul system to a 150 mm max downhaul as that was given to me by Taipan sailors. However my cascade downhaul system can produce significant more pull and so I pull an extra 50 mm out of my luff. My downhaul internal system bar is at 1420 mm instead of 1500 mm and I don't know why I made that mistake when building up my mast. But still during this REM-race we could completely depower my rig to the point that we both set on the luff hull comfortably in 25 knots of wind when we had to wait for a large fishing vessel to pass.

Due to various reasons my current mainsail fits just within this design, but next time I think I will order a mainsail with a slightly shorter luff length. I'm thinking about 7850 mm when untensioned and 8050 when fully tensioned. If anybody considers shortening the luff even more than they should place the sail feed gap higher as well. At 7850 mm untentioned the foot of the mainsail will only just pass the bottom part of the sail feed opening. Any shorter and it will hang on this point when downhauling.

My mast rotation is placed on the mast foot plate, is sheeted of the trampoline and I'm very happy with that. I would not consider sheeting the rotation arm of the boom on a spinnaker boat. I think that is inferiour and needless expensive, but it will be to much to explain why here. On A-cats and F16's without a spi I can see advantages of a boom sheeted rotation system increase.

Standard Taipan sailors should take into account that my main beam sits 25 mm higher on my hulls than their mainbeam. Therefor I have 20 + 25 = 45 mm more clearence under my boom near the mast and relative to the trampoline then they have. Especially under spinnaker I appreciate this increase in boom height near the mast. My boom therefor hangs more horizontal then on the Taipans as my clew is still in the same place. I did alot of research on the boom height on spinnaker boats and found that you really want it to be 500 mm of the (tensioned) trampoline at a location is about 300 to 500 back of the mainbeam. When Hoisting, retrieving or flying a spi you really can not expect your crew to work with a boom that is lower than that. Blade (homebuilder) builders should be able to use this very mast setup very succesfully as long as they move the sail feed up by 30 to 50 mm. The boom height will be perfect for them.

I general I'm very happy with this mast. It look really clean with the rotation arm on the mastbase and the internal downhaul system.

I can warmly advice AHPC fitting for the mainsail hook, boom fittings and hound fittings. I use 390 mm proctor spreader arms and I can advice those warmly as well. Set these up at their minimal length (390 mm) and with 50 mm rake as the minimal starting point. Increase rake if you sail in strong winds often and the rig needs to improve its gust response a little. I still have to measure prebend. Will post that later. I use 3 mm 1x19 stainless wire for my diamond wires and these do their job beautifully. I really see no need for using dyform wires here. As tensioners I use two small turnbuckles that are fitted to the mast base plate This plate sticks out a little and I drilled two holes in it (as AHPC does as well) I bought two threaded forks and put these through the holes with the threading point upward. To this I screw the turnbuckles. The other side of the turnbuckles take the threading that is pressed on the wires. Easy, effective, inexpensive. Right now AHPC has copied this approach on the Capricorn F18's. I stole this idea from Phill Brander. At least I saw what looked like this in one of his picture and I thought :"that is smart, I want to have that". To Taipan sailors with the old system; I can tension or detension my diamond wires without taking my mast of the boat OR having to take the diamond wires out of the spreader arms. This makes adjusting the tension and prebend between races a WHOLE LOT easier.

[Linked Image]

If you are using the AHPC mainsail hook fitting as well AHPC's mainsail welded shackle and ring and the distances specied above than your mainsail will hook and un hook like a dream when you use a headboard and have the eye that takes the fitting at the spacing shown in the picture below. (upper bearing surface eye about 30 to 35 mm back from inside bolt rope)

[Linked Image]

Push up sail users need to look no further. Halyard users will need to fit a little block as shown in the next picture.

[Linked Image]


For the halyard coming out of the bottom of the mast I currently use a small opening in the mast groove just below the sail feed gap (pretty close the the internal web of the mast) as the Stealth design does and that works, but I still want to show everbody the solution the Mark Woudenberg has implemented on this Taipan F16.

[Linked Image]


The spi gate is best build as shown below :

[img]http://www.catsailor.com/bb_files/48628-AHPC_Mast_nbsp_gate.jpg[/img]


And the internal cascading system is build as follows :

[img]http://www.catsailor.com/bb_files/48629-Typhoon_F16_downhaul_full_diagram.gif[/img]


Don't forget to bend the lower lip of both exit blocks leading the downhaul line into the mast and riveting this to the mast base plate instead of the mast itself. Don't look at the picture of my mast as I did it wrong. Look at Mark Woudenbergs picture. Although you can do it my way and use either the rotation arm or a ronstan cleat base to raise the cleat to the right height relative to the exit block. In my case I find that cleating the downhaul is now very easy on my boat. because of the line being pulled downwards a little towards the exit block. Right now I don't consider swivel cleats at all. I don't need them and it would make my mast only more complex than I would like.


That is it. It is now public domain knowledge. Spread the news.

Wouter

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Last edited by Wouter; 04/28/05 05:31 PM.

Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
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#48207 - 04/28/05 05:04 PM Re: Holding pic 2 (no message) [Re: Wouter]  
Joined: Jun 2001
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Wouter Offline
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Wouter  Offline
Carpal Tunnel

Joined: Jun 2001
Posts: 9,582
North-West Europe
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Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#48208 - 04/28/05 05:06 PM Re: Holding pic 3 (no message) [Re: Wouter]  
Joined: Jun 2001
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Wouter Offline
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Wouter  Offline
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Joined: Jun 2001
Posts: 9,582
North-West Europe
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Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#48209 - 04/28/05 05:13 PM Re: Holding pic 4 (no message) [Re: Wouter]  
Joined: Jun 2001
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Wouter Offline
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Wouter  Offline
Carpal Tunnel

Joined: Jun 2001
Posts: 9,582
North-West Europe
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Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#48210 - 04/28/05 05:19 PM Re: Holding pic 4 (no message *) [Re: Wouter]  
Joined: Jun 2001
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Wouter Offline
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Wouter  Offline
Carpal Tunnel

Joined: Jun 2001
Posts: 9,582
North-West Europe
.

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Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#48211 - 04/28/05 05:21 PM Re: Holding pic 5 (no message) [Re: Wouter]  
Joined: Jun 2001
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Wouter Offline
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Wouter  Offline
Carpal Tunnel

Joined: Jun 2001
Posts: 9,582
North-West Europe
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Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#48212 - 04/28/05 05:25 PM Re: Holding pic 6 (no message *) [Re: Wouter]  
Joined: Jun 2001
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Wouter Offline
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Wouter  Offline
Carpal Tunnel

Joined: Jun 2001
Posts: 9,582
North-West Europe
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Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#48213 - 04/29/05 09:49 AM Just got around to measuring prebend ... [Re: Wouter]  
Joined: Jun 2001
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Wouter Offline
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Wouter  Offline
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Just got around to measuring prebend , bloody hell, I'm really starting to enjoy this "chairman on the backburner" bit !

Finally I can get around to doing some work on my own boat.

I have a Redhead sails mainsail (Ian Markovitch) and I've gravitated to 40 mm spreader rake (using 390 mm arms = longer than Taipans) and 26 mm prebend. I feel I still need a fraction less prebend. So I'll be turning my prebend to 23 mm. I also feel to depowered when sailing with a crew so I will be increasing my rake to 50 mm and loosen my diamonds to get back at the 23 mm prebend. I feel that will be a good setting for my sail. NOTE; when you have standard AHPC spreaders (350 mm long) than the rake numbers need to have 20 mm deducted. So my 50 mm rake is equivalent with 30 mm on a standard AHPC build Taipan 4.9 mast.

All you guys with different sails I advice you all start with 50 mm rake (when using 390 mm spreader arms) and tension your diamonds to 25 mm prebend.

Ohh, before I forget prebend is measure with mast perfectly on its side supported at base and tip. Then a very light line (I use 1 mm wipping line) is tight of the the top runs underneath the mainsail hook fitting and down to the gooseneck (boom) fitting on the mast. I also passed underneath this fitting and is then tensioned. So in effect the line touches the outside of the mast at the mainsail hook and gooseneck fitting. Make sure your mast is perfectly on its side even a small amount of say 30 degrees rotation is enough to have the prebend swing about by 3 mm = 10 %

To fnd the best trim for your mast and sail combo I advice that everyone looks at the trimming tips as found on the Taipan class website :

AND look at their sails while sailing. It should be possible to have all telltales stall and stream at the same time but steering up and down. If the top and bottom telltales do this but not the middle ones than your prebend is wrong. This can be solved by either increasing rake or increasing diamond tension. Rule of thumb :

Do you feel powered up or even flighty ? then reduce rake and increase tension.

If you feel lacking in height and power despite strong winds then you need to increase rake and reduce wire tension.

Wouter





Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#48214 - 03/23/06 06:51 AM Re: Formula 16 mast design [Re: Wouter]  
Joined: Jun 2001
Posts: 9,582
Wouter Offline
Carpal Tunnel
Wouter  Offline
Carpal Tunnel

Joined: Jun 2001
Posts: 9,582
North-West Europe

Corrections.

After having sailed with this mast design for 2 seasons now I give a short update on its design and present you with my experiences.

First the updates :

In the diagram it says :

5600 mm ; upper diamond tangs ; to lowest contact point on the mast, place on scribed line.

I had my sidestay hang up on this fitting 2 times in the past 2 years. This is partly due to the fact that I'm using large forks on my diamond wires, I had no choice they didn't have any other. However this shows that the given measurement is a bit tight when not using all the preferred components (small narrow forks). So if anybody is not using the T-ball end terminals or the really narrow forks then move this point another 20 mm down on the mast. This should be enough to prevent any mishaps while not changing the mast behaviour in any significant way.

So new measurement 5880 mm

Moving up the hound fitting by 20 mm will have the same effect but is expected to make more of a difference in the overall behaviour of the mast. It'll make the top of the mast stiffer; heavier crews may even prefer that. I'm sailing at 145 kg and this mast feels properly powered up when doublehanding.


Also, as per direct advice of Greg Goodall himself. Don't place the rivet holes directly on the scribed line (as was given in the design earlier). There is a case of one mast where the diamond wire fitting split the mast along the scribed line. No other reports have come in to this effect in the last 10 years so it is probably a freak accident, but it is better to be safe then sorry. Ergo drill the holes of the upper tang fitting next to the scribe line (on the rear part of the mast) and have a few mm clearence between them and the scribe line. MY mast has to last minute modification and all other measurements in the plans are able to work well with this modification.

The loop that is thrown over the mast top and hangs of the mainsail hook fitting works very well. This loop is part of the spinnaker hoist system. There is no reall wearing down of the loop on the hook fitting on my boat. I'm using a 2.5 mm 300 kg dyneema line and that one has hold up over 2 years now with 6 months per year full influx of UV. This appears to be the bottom limit and when I replace the line I'm going to that with a thicker one. However it is dependable enough and will remove the need to dril holes in the top of your mast. Here the less holes the better I say.

Boom height is one of the best mods I made. It is spot on. High enough to make quick crew work possible and low enough to get the full 8.1 mtr luff of the mainsail as allowed by the class rules. Use this setup is my advice.

The use of the 12:1 internally 3-staged cascading downhaul system is definately the way to go. It is the best system available and the superwing seems to want a 12:1 system with low friction.

I really do appreciate the turnbuckles on my diamond wires. I don't adjust them enough to warrant the use of a large single turnbuckle setup on the front of the mast. BUT I do adjust the tension often enough to make the "only a threaded terminal and nuts" setup as found on standard Taipans impractical. With the last setup you'll need to detension the wires (take the mast down and take the wires out of the spreaders) in order to adjust the tension. Big pain in the neck. With the displayed setup I can adjust the tension with the mast stepped and even with the mainsail hoisted. I have not really encountered any problems of the turnbuckles fusing. This despite remarks but other sailors/builders. I did grease them up pretty well with silicone grease.

The fixed downhaul cleats at the bottom of the mast seem to work very well, despite the fact that they are not swiveling. They work well enough for me to NOT consider replacing them with swiveling ones. If swiveling ones are desired then the given mast design can be used UNALTERED with these swiveling cleats. Just remove the cleats from the mast plate and have two swiveling cleats mounted upside down on the mast, say about 100 mm vertically above the microblocks (exit blocks) in the wall of the mast. Now just lead the downhaul line through these blocks and voila you now have a swiveling cleat setup that works well. (Thanks Tony Jenkins for this idea)


Now the last bit of info. Get a mainsail halyard. Don't listen to A-cat sailor saying that they can push their sails up easily and so you should be able too. I'm convinced they can on their carbon masts with mainsail that have only little luff round, BUT on the alumnium superwing mast with the F16 doublehanded luff round you'll appreciate a halyard.Push up sails will work well when they are new and during the first season after that they won't. So get a mainsail halyard system.


That is it. I think this concludes the F16 mast design from my point of view. I know of no modifications that would make this mast design better for an averaged sized doublehanded F16 crew. So you Blade F16 homebuilders this is the design you want.

Best of luck,

Wouter




Last edited by Wouter; 03/23/06 07:01 AM.

Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands

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