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fixed carbon bowsprit


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#1 golfinaspen

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Posted 27 November 2012 - 10:55 PM

Interested in adding a fixed carbon bowsprit to my Ben 25 (platu). We have been flying assym's from the pole with good results, especially in light air, but a sprit would make sail handling much simplier given the tippy nature of the boat when it blows. Does anyone know who makes such custom equipment?

#2 Vela Sailing Supply

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Posted 28 November 2012 - 03:41 AM

Assuming that you want to keep the option of sail the boat under One Design configuration with too much hassle, I suggest to install a Forte Carbon bowsprit. They are simple and easy to install, as well as remove when you want to bring the boat back to its original layout. For a boat like the Platu 25, a 2" ID carbon sprit will do the trick. The way Forte builds this tubes oriented for use on a 50/50 ratio (supported/unsupported lengths): ie. If you want a 3 ft bowsprit from the stem to the tip, then you need a 6 ft. tube. Keep in mind that this sprit will work for an asymmetrical spinnaker not for a code zero (you need to add a bobstay for a code zero to compensate for luff rope/halyard tension).

Here are some shots of how it looks like:

Posted Image Posted Image

We carry the small kit at $1,559 including:
• Carbon sprit painted clear.
• Harken loop and outboard cap.
• Your choice of aft mount: Saddle or removable deck eye.

Feel free to email or call us if you want to talk about this and the options.

Rod

#3 golfinaspen

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Posted 28 November 2012 - 03:51 AM

Boat is not in OD configuration as it sails PHRF and there is no OD competition in the U.S. It uses assym chutes carried on the OD pole which greatly improves handling and reaching performance. Replacing the pole with a fixed sprit is the concept.

#4 golfinaspen

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Posted 29 November 2012 - 05:03 PM

Found it, GC Marine in Richmond CA made a custom fabrication for a sister ship. Check out www. gcmarine.net and the showcase tab for details. Looks like a beautiful job.


#5 sos

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Posted 20 December 2012 - 08:08 PM

Found it, GC Marine in Richmond CA made a custom fabrication for a sister ship. Check out www. gcmarine.net and the showcase tab for details. Looks like a beautiful job.



I've sailed that boat. Worked really well and I can't speak highly enough about Gills, great guy and dose great work

We found you can use an M24 kite quite well.

#6 Soley

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Posted 21 December 2012 - 03:59 PM

I assume you are ready to buy new kites as well as buying the sprit as your current assyms will not work too well on the new configuration.

If melges 24 kites fit that would be very nice! Have you thought about going the retractable pole route? You could have two settings, half pole out for A3 and full pole out for A2 and A1. It maybe less expensive to retro fit the boat for that.

#7 golfinaspen

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Posted 23 December 2012 - 12:58 AM

SOS please tell me more about the performance of Black Sheep with the sprit. I seems that M24 sails would be too long on the luff. Gilles thought that a shorter sprit would well and not need a bob stay especially sice we now lead the tack line down and under the deck via a bolt hole in the forestay chain plate on the bow.

Solely, we have considered a retractable pole but the internal reinforcement of the tube would be considerable since the boat is quite skinny up front . A fixed sprit is a straightforward solution. The LIS PHRF. Committee uses a similar rating formula based on TSP/J and a sprit about 3.9 feet would allow the boat to sail at the bareboat 120 rating. I think Black Sheep has sprit about a foot longer. We will need a new runner but the existing reacher would still work.

The Platu is a giant killer in light air but when the breeze picks up it is a handful downwind so getting rid of the pole is a project worth exploring. We have also followed with Interest the development of the Donovan GP 26 as another horse for the course on Long Island Sound.

#8 garrett818

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Posted 23 December 2012 - 04:24 AM

One thing to keep in mind: In heavyer air a longer sprit will balance the boat better than a short one.

#9 golfinaspen

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Posted 24 December 2012 - 07:11 PM

Garrett818 - good point, center of effort of the sailplan moves forward something that we have considered but not with precision. At the moment we are looking to get the length and new sail area into a band that does not hammer the rating the way the pole + asyms do and give us an improvement in boat handling.

Ryley - agree, no doubt the local PHRF committees look to each other for solutions to "loopholes". The interesting point is that LIS uses the same rating criteria for both fixed sprits and retractable poles so long as the chute is tacked on the centerline. PHRF LIS also has a multi-part screen for chute size so one possibility could be to tax heavily based on sail size, primilary mid-girths on runners and not so much sprit length. One would think that the handicappers have sufficient data with the J boats of various sizes but the conversions are one-offs, hence the issue. I think we are with a band of =/- 6 sec/mi and would live happily in that range if we get a boost in handling. One screwed up jibe with the pole eats up that delta very fast.

#10 golfinaspen

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Posted 17 April 2013 - 01:27 AM

IMG_0524_small.jpg

 

Here is picture of the GCMarine sprit for Black Sheep before it was fitted to the boat.

here is the business end.

IMG_1118_small.jpg

Still considering a similar setup but probably more of a TP52 type sprit since we need only one jack line.



#11 clamslapper

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Posted 18 April 2013 - 08:35 PM

Assuming that you want to keep the option of sail the boat under One Design configuration with too much hassle, I suggest to install a Forte Carbon bowsprit. They are simple and easy to install, as well as remove when you want to bring the boat back to its original layout. For a boat like the Platu 25, a 2" ID carbon sprit will do the trick. The way Forte builds this tubes oriented for use on a 50/50 ratio (supported/unsupported lengths): ie. If you want a 3 ft bowsprit from the stem to the tip, then you need a 6 ft. tube. Keep in mind that this sprit will work for an asymmetrical spinnaker not for a code zero (you need to add a bobstay for a code zero to compensate for luff rope/halyard tension).

Here are some shots of how it looks like:

image_bowsprit01.jpg image_bowsprit02.jpg

We carry the small kit at $1,559 including:
• Carbon sprit painted clear.
• Harken loop and outboard cap.
• Your choice of aft mount: Saddle or removable deck eye.

Feel free to email or call us if you want to talk about this and the options.

Rod

 

 

Makes the foredeck look pretty nasty. 



#12 Left Hook

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Posted 20 April 2013 - 07:19 PM

IMG_0524_small.jpg

 

Here is picture of the GCMarine sprit for Black Sheep before it was fitted to the boat.

here is the business end.

IMG_1118_small.jpg

Still considering a similar setup but probably more of a TP52 type sprit since we need only one jack line.

That is sexy as all hell...



#13 golfinaspen

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Posted 13 November 2013 - 09:59 PM

Here is a picture of the sprit mounted on the bow of Black Sheep, looks great.  We will build a TP52 style sprit with a single tube using a single tack line that exits the sprit and then goes  through the stem head and aft below to cam cleat mounted on the companionway ladder. This will keep the deck clean and allow the pit person to operate without shifting position.

Attached Files



#14 Christian

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Posted 13 November 2013 - 10:52 PM

Seriously????????????????   that is a more than average clumsy solution - and about half the length needed.  Come on you know better Rod!

Assuming that you want to keep the option of sail the boat under One Design configuration with too much hassle, I suggest to install a Forte Carbon bowsprit. They are simple and easy to install, as well as remove when you want to bring the boat back to its original layout. For a boat like the Platu 25, a 2" ID carbon sprit will do the trick. The way Forte builds this tubes oriented for use on a 50/50 ratio (supported/unsupported lengths): ie. If you want a 3 ft bowsprit from the stem to the tip, then you need a 6 ft. tube. Keep in mind that this sprit will work for an asymmetrical spinnaker not for a code zero (you need to add a bobstay for a code zero to compensate for luff rope/halyard tension).

Here are some shots of how it looks like:

image_bowsprit01.jpg image_bowsprit02.jpg

We carry the small kit at $1,559 including:
• Carbon sprit painted clear.
• Harken loop and outboard cap.
• Your choice of aft mount: Saddle or removable deck eye.

Feel free to email or call us if you want to talk about this and the options.

Rod



#15 rantifarian

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Posted 14 November 2013 - 03:40 AM

Seriously????????????????   that is a more than average clumsy solution - and about half the length needed.  Come on you know better Rod!

 

If OP wants to have it easily removable, cheap, etc, it isnt a terrible option. We used a similar setup alloy dick on our trailer sailer to fly the 48m^2 chicken chute when it was averaging above 25 and couldn't use the rotating pole for the bigger chutes. As he said in the note, it is designed for a 50/50 length ratio, so just buy the size you need.

What is wrong with it?



#16 Christian

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Posted 14 November 2013 - 07:30 AM

It is a honking big monstrosity built for a 35 foot cruiser - not a 25 foot almost-sportboat

 

Seriously????????????????   that is a more than average clumsy solution - and about half the length needed.  Come on you know better Rod!

 

If OP wants to have it easily removable, cheap, etc, it isnt a terrible option. We used a similar setup alloy dick on our trailer sailer to fly the 48m^2 chicken chute when it was averaging above 25 and couldn't use the rotating pole for the bigger chutes. As he said in the note, it is designed for a 50/50 length ratio, so just buy the size you need.

What is wrong with it?



#17 schoonerman

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Posted 14 November 2013 - 02:50 PM

I always have like this option for adding a sprit. Happens all the time on SC52's. The tip of the spin pole lives in the outer collar and simply slides out to fin in the more forward deck chock. This also doubles as the Sym Pole. Obviously you have to reinforced the crap out of the pole (should/must be carbon)



#18 Foilman

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Posted 03 April 2014 - 06:38 PM

IMG_0524_small.jpg

 

Here is picture of the GCMarine sprit for Black Sheep before it was fitted to the boat.

here is the business end.

Attached File  CCI_C&C115_Bowsprit_2.JPG   221.23KB   65 downloads

 

A shorty we just made for a C&C 115

 

Phil



#19 golfinaspen

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Posted 05 April 2014 - 05:23 PM

We made the decision to have GC Marine build a sprit for our Platu 25, First Tracks.  The sprit will be shorter than the one they designed for Black Sheep so that we fit within a rating band on LIS for fisprits.  It will be 3.33' so that TPS = 11.9.  This should result in no change for the distance rating ( 114) but improve the W/L by 6 sec/mi to 120.

 

The design will closer to a TP 52 style with a G10 plug at the outer end for the jackline to exit. Since the boat used asymmetrical chutes off the pole and the jackline ran under the deck, this configuration will match well. Attached is a picture showing the jackline entering the bow. We eliminate the pole, foreguys and afterguys that should make jibing much easier.

 

The band has been made using Black Sheep as a "mold" and fitted to our bow. See picture of the band in frame. Differences in dimensions were noted and will be  taken into account when the sprit fabricated.

 

Gilles is now in the process of  finalizing the design and construction will shortly commence.

Attached Files

  • Attached File  bow.jpg   61.68KB   94 downloads


#20 golfinaspen

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Posted 05 April 2014 - 06:16 PM

The first picture shows the band after it was removed from Black Sheep.  The frame is needed to maintain stability and the geometry. It was shipped to us and fitted to the bow of our boat - picture 2. We, measured the differences in dimensions, both sides and also marked the location of the exit hole in the bow so that the tackline path can be ascertained and incorporated into the design .

 

A new VMG A1 chute has been ordered from Quantum.

Attached Files



#21 golfinaspen

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Posted 15 April 2014 - 07:00 PM

Attached are pictures of the sprit being laid up, vacuum bagged and the result. Reinforcement, joining to the band and finishing are the next steps. 

Attached Files



#22 SoAPieceOfStringWalksIntoABar...

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Posted 16 April 2014 - 01:32 AM

Did a couple fixed sprits a few years ago, here's how the bigger one went together:

https://picasaweb.go...412600420980721

#23 SoAPieceOfStringWalksIntoABar...

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Posted 16 April 2014 - 03:18 PM

Attached File  DSCF0776.JPG   195.23KB   77 downloads

 

ugh, bad link. this one works:

https://picasaweb.go...it?noredirect=1



#24 tootall519

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Posted 16 April 2014 - 07:48 PM

Too short. should go 4' to 4.5' out from J is you want to go downwind.



#25 SoAPieceOfStringWalksIntoABar...

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Posted 16 April 2014 - 08:43 PM

so 4.7' is ok?  :rolleyes:



#26 golfinaspen

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Posted 23 April 2014 - 01:57 AM

Further progress - band and sprit have been joined - see attached images.  Next step is fitting and fairing. At the boat we will add a G10 tube inside the bow for the bobstay and splice 1/4" aramid  through the tube to fix that end of the bobstay.



#27 golfinaspen

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Posted 23 April 2014 - 01:58 AM

here are the images

Attached Files



#28 golfinaspen

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Posted 08 May 2014 - 12:38 AM

Sprit completed by GC Marine - see attached images. It came in at about 6 pounds and is beautifully finished. Installation is next. We will reinforce bobstay thru hole and holes for both mounting bolts with G10 tubing and fill as needed to get exact fit. New Quantum A1 is also in hand for the season. 

Attached Files



#29 golfinaspen

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Posted 10 May 2014 - 08:35 PM

sprit installed - initial fit was flawless and mounting was straightforward.   The proportions and contour are a perfect match to the lines of the boat. Time to go sailing.

Attached Files



#30 8:07 to New Haven

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Posted 11 May 2014 - 12:56 AM

Oh my god that looks amazing. I'd love to get out on that sled!

#31 Code 2

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Posted 11 May 2014 - 01:42 PM

congrats golf - looks great.



#32 golfinaspen

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Posted 17 August 2014 - 09:29 PM

My buddy Dave Irish in Harbor Springs MI sent along the attached images of his old Mumm 30 USA 2  " Surprise"  now sailing out of Marblehead as INDRA.  Among the modifications is the addition of a fixed carbon sprit.  The work was done by Kenny Harvey, Harvey Rigging in Marblehead.  The boat looks simply beautiful and lethal.

 

Our experience so far this season with the Platu 25 First Tracks is that the sprit modification is a true game changer. Handling and speed downwind is amazing 

Attached Files



#33 Savage 17

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Posted 18 August 2014 - 02:02 PM

My buddy Dave Irish in Harbor Springs MI sent along the attached images of his old Mumm 30 USA 2  " Surprise"  now sailing out of Marblehead as INDRA.  Among the modifications is the addition of a fixed carbon sprit.  The work was done by Kenny Harvey, Harvey Rigging in Marblehead.  The boat looks simply beautiful and lethal.

 

Our experience so far this season with the Platu 25 First Tracks is that the sprit modification is a true game changer. Handling and speed downwind is amazing 

I know the boat has been very successful in Marblehead especially with the 6 sec credit for the bowspirt!



#34 Graciousj100

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Posted 18 August 2014 - 08:58 PM

Assuming that you want to keep the option of sail the boat under One Design configuration with too much hassle, I suggest to install a Forte Carbon bowsprit. They are simple and easy to install, as well as remove when you want to bring the boat back to its original layout. For a boat like the Platu 25, a 2" ID carbon sprit will do the trick. The way Forte builds this tubes oriented for use on a 50/50 ratio (supported/unsupported lengths): ie. If you want a 3 ft bowsprit from the stem to the tip, then you need a 6 ft. tube. Keep in mind that this sprit will work for an asymmetrical spinnaker not for a code zero (you need to add a bobstay for a code zero to compensate for luff rope/halyard tension).

Here are some shots of how it looks like:

image_bowsprit01.jpg image_bowsprit02.jpg

We carry the small kit at $1,559 including:
• Carbon sprit painted clear.
• Harken loop and outboard cap.
• Your choice of aft mount: Saddle or removable deck eye.

Feel free to email or call us if you want to talk about this and the options.

Rod

Any reinforcement needed below to compensate for compression on the deck?



#35 Christian

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Posted 19 August 2014 - 03:02 AM

My buddy Dave Irish in Harbor Springs MI sent along the attached images of his old Mumm 30 USA 2  " Surprise"  now sailing out of Marblehead as INDRA.  Among the modifications is the addition of a fixed carbon sprit.  The work was done by Kenny Harvey, Harvey Rigging in Marblehead.  The boat looks simply beautiful and lethal.

 

Our experience so far this season with the Platu 25 First Tracks is that the sprit modification is a true game changer. Handling and speed downwind is amazing 

I know the boat has been very successful in Marblehead especially with the 6 sec credit for the bowspirt!

Yeah I saw the cert - seems like a bit of a gift - maybe a good rating bandit..............



#36 richiec

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Posted 19 August 2014 - 04:49 AM

The Mumm30 looks awesome. Bet it goes like hell as well! Beautiful.



#37 golfinaspen

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Posted 19 August 2014 - 08:06 PM

The PHRF handicaps for a sprit generally have rating bands that are a function of  TPS/J, so the trick is to keep the sprit length right at the limit for one of those bands.  For the Platu we remained level at 114 on the distance rating ( same as with the class over length pole) but  were given +6 on W/L  for a 120 rating same as the base rating for the boat.  The theory, which seems to be correct, is that with the sprit you cannot  sail as deeply downwind on a square run as with a pole.  The advantage is in light to moderate air when the pole would still be on the headstay.  I think the rating is about right. Also, boat handling is much, very much easier when you eliminate the guys, pole lift and pole.



#38 Savage 17

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Posted 20 August 2014 - 01:37 PM

right... but how can you get a credit for increasing you spinnaker size 30%..... which was the case with the Mumm. Yes, I understand you can't square the pole and go directly downwind, but the boat sails in Marblehead, MA which is usually light air.

 

I'm glad it is working out for your boat. Yes, bowspirt makes crew work much easier....

 

Now you just need to go masthead with your Spins!



#39 golfinaspen

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Posted 22 August 2014 - 03:43 AM

More information from INDRA - sprit was made by Jeff Kent of Composite Solutions.  North did the sail design.

 

On our Platu 25, Quantum was closely involved in the spinnaker design.  We were cautioned ( as was INDRA by North) that the sprit can be too long and the A - sail too big for the boat. In the case of the Mumm the spar was designed for masthead chutes, in our case it was not. We could have lengthened the sprit ( greater penalty) and lowered the aspect ratio of the A1 but the boat is rather tippy and Quantum's advice was to design a VMG downwind sail that the boat could easily carry with the correct flow characteristics,( i.e., not a huge bag flying off the sprit) over the useful range of the sail.

 

That proved to be solid advice - bigger is not necessarily better. 



#40 Left Hook

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Posted 29 August 2014 - 04:16 AM

Where have you been racing FT? Haven't seen y'all at Tuesdays or any weekend regattas. Saw the boat near crab shell the other day. 



#41 golfinaspen

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Posted 01 September 2014 - 09:05 PM

Left Hook - thanks for the note.  We knew this year would be lean due to arrival of co-skippers baby in June. Sailed the SYC Double Handed Regatta. Day sailing during the week to avoid the power boat mess at the entrance to Stamford Harbor on weekends and that's it. Tuesday nights were out given the distinct possibility of long motors home ( FT is "powered" by a 3.5 hp outboard) after races had called near Lloyd's Point several times in the past.

 

We will  move the boat to Cedar Point YC in a few weeks and sail the season out from there; that will be the new home going forward and hopefully bigger fleets are in the offing in that locale. 



#42 Left Hook

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Posted 04 September 2014 - 07:55 PM

As one of the members who says "CPYC Needs More Racers!!!" WELCOME!!!

 

Come do Cheese Race! we'll be there on the 45



#43 Kenny Harvey

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Posted 19 November 2014 - 11:29 PM

right... but how can you get a credit for increasing you spinnaker size 30%..... which was the case with the Mumm. Yes, I understand you can't square the pole and go directly downwind, but the boat sails in Marblehead, MA which is usually light air.

 

Thanks everyone for the compliments on the Mumm.  Its been a fun project.  There are a bunch more pictures on the team's facebook page: https://www.facebook...139514542730860

 

Regarding kite area with the fixed bow sprit, the current area is only roughly 10% bigger than the one-design kites.  100 m2 vs 89 m2. 



#44 Savage 17

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Posted 20 November 2014 - 02:05 PM

right... but how can you get a credit for increasing you spinnaker size 30%..... which was the case with the Mumm. Yes, I understand you can't square the pole and go directly downwind, but the boat sails in Marblehead, MA which is usually light air.

 

Thanks everyone for the compliments on the Mumm.  Its been a fun project.  There are a bunch more pictures on the team's facebook page: https://www.facebook...139514542730860

 

Regarding kite area with the fixed bow sprit, the current area is only roughly 10% bigger than the one-design kites.  100 m2 vs 89 m2. 

Kenny great job with the boat!!! It looks great and has done very well!!!



#45 golfinaspen

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Posted 20 November 2014 - 07:02 PM

Beautiful renovation and upgrade. I sailed on that boat when it was " Surprise" owned by Dave Irish. Dave treats his boats as thoroughbreds and spares no expense to make sure they look beautiful and go very fast.  I'm sure he is happy to know that the current owner feels the same way.

 

BTW on our little 25 we did not max out the A1 - shape is more important than size in the under 10knot regime the sail is used.



#46 Ryley

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Posted 21 November 2014 - 04:20 PM

right... but how can you get a credit for increasing you spinnaker size 30%..... which was the case with the Mumm. Yes, I understand you can't square the pole and go directly downwind, but the boat sails in Marblehead, MA which is usually light air.

 

Thanks everyone for the compliments on the Mumm.  Its been a fun project.  There are a bunch more pictures on the team's facebook page: https://www.facebook...139514542730860

 

Regarding kite area with the fixed bow sprit, the current area is only roughly 10% bigger than the one-design kites.  100 m2 vs 89 m2. 

how long is the sprit as %J? The rating would indicate 10% but in the pictures it looks longer than that.



#47 Kenny Harvey

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Posted 24 November 2014 - 01:59 AM

 

right... but how can you get a credit for increasing you spinnaker size 30%..... which was the case with the Mumm. Yes, I understand you can't square the pole and go directly downwind, but the boat sails in Marblehead, MA which is usually light air.

 

Thanks everyone for the compliments on the Mumm.  Its been a fun project.  There are a bunch more pictures on the team's facebook page: https://www.facebook...139514542730860

 

Regarding kite area with the fixed bow sprit, the current area is only roughly 10% bigger than the one-design kites.  100 m2 vs 89 m2. 

how long is the sprit as %J? The rating would indicate 10% but in the pictures it looks longer than that.

40% of J sprit length.  You should be able to view the 2014 cert on the PHRFNE.org website. Under PHRF-NE (2014 and prior) the one-desgin Mumm 30 pays for a 130% pole with the 54 rating.  +9 s/m for removing the pole and going to a sprit with the same STL and -3s/m for additional 10% sprit length bringing the rating to 60 in PHRF-NE.  Shoot me an email if you want some more details.



#48 i550sailor

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Posted 24 November 2014 - 03:19 AM

right... but how can you get a credit for increasing you spinnaker size 30%..... which was the case with the Mumm. Yes, I understand you can't square the pole and go directly downwind, but the boat sails in Marblehead, MA which is usually light air.

 

Thanks everyone for the compliments on the Mumm.  Its been a fun project.  There are a bunch more pictures on the team's facebook page: https://www.facebook...139514542730860

 

Regarding kite area with the fixed bow sprit, the current area is only roughly 10% bigger than the one-design kites.  100 m2 vs 89 m2. 

Nice!



#49 Ryley

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Posted 24 November 2014 - 01:08 PM

 

 

right... but how can you get a credit for increasing you spinnaker size 30%..... which was the case with the Mumm. Yes, I understand you can't square the pole and go directly downwind, but the boat sails in Marblehead, MA which is usually light air.

 

Thanks everyone for the compliments on the Mumm.  Its been a fun project.  There are a bunch more pictures on the team's facebook page: https://www.facebook...139514542730860

 

Regarding kite area with the fixed bow sprit, the current area is only roughly 10% bigger than the one-design kites.  100 m2 vs 89 m2. 

how long is the sprit as %J? The rating would indicate 10% but in the pictures it looks longer than that.

40% of J sprit length.  You should be able to view the 2014 cert on the PHRFNE.org website. Under PHRF-NE (2014 and prior) the one-desgin Mumm 30 pays for a 130% pole with the 54 rating.  +9 s/m for removing the pole and going to a sprit with the same STL and -3s/m for additional 10% sprit length bringing the rating to 60 in PHRF-NE.  Shoot me an email if you want some more details.

Yeah, I saw the cert. I'm not going to comment on it here any more because this thread's supposed to be about the Platu, but I'm guessing we'll be discussing this particular situation in the near future ;)



#50 crashtestdummy

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Posted 24 November 2014 - 03:34 PM

Looks like it will be 51 with the rules that were past last week

#51 Ryley

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Posted 25 November 2014 - 02:11 PM

Looks like it will be 51 with the rules that were past last week

Fine.. or 42 if you believe the intent of the original rule. But again.. Platu. I want to hear how it goes with the new sprit. :)



#52 Roleur

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Posted 10 December 2014 - 06:43 PM

All,

 

I'd like to join the group of retrobowspritists.  I think it would make our Schumacher 28 more fun to sail and light it up quite nicely as the current standard spinnaker is quite small with a fractional hoist.  After talking to sailmakers and Jim Antrim about size, shape, and ratings, it seems that I only need a 3.5' extension.  Anything longer does not match well with the ISP (again fractional hoist).  At 3.5' my JSP would be identical to a J/80 (13') and my ISP would be 6" less.  We are about 500 pounds lighter than the J/80 and 2 feet longer, so I think that is where I want to be.  

 

I love the idea of the bolt on GC Composites type sprit, but can't wrap my head around the cost.  Spending $5k for a sprit on a $30k boat seems "not most smart".  That brings me back to the Selden or Forte deck mounted sprits like Rod posted above.  I know it has aesthetic issues, but I wonder if a little customization couldn't mitigate that substantially.  First since I only need a sprit that is 4' in front of the mounting bracket it only needs to extend 2' aft, so 6' total.  It doesn't need to retract and would have a bobstay.  My thought is, instead of the typical round brackets, that I would mold many layers of fiberglass sheet, 18" wide, shaped over the tube, with flanges to bolt the think to the deck.  The idea is to help the arrangement blend into the deck.  You could still walk on it, paint it the same as the deck, or black, and put some non-skid on it.  Forte can make me a custom diameter and length tube for the this application for a quite reasonable few hundred dollars.  

 

Comments?  

 

4720539_20140527102405346_1_XLARGE.jpg&w



#53 CazzaRanda

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Posted 11 December 2014 - 08:22 AM

No please, don't do it... That boat is a beauty and a tube on deck would kill the look (I'm gladd the hoyt boom is gone). When you bought her, I was ready to step in if you had not closed the deal. If anything else fails, crowdfund the GC sprit as a memorial to Carl... I'll chip in 50 bucks. Seriously. 



#54 golfinaspen

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Posted 11 December 2014 - 06:25 PM

Roleur - some thoughts:

 

You certainly started at the right point by talking to designers and sailmakers but do some sample calculations at different values of TPS/J for the local PHRF ratings bands for fixed sprits. We went through that exercise on First Tracks before arriving at a desired sprit length as a  function of rating.  I think Indra did the same on the Mumm 30. You will find and a fraction of an inch of sprit length will save you on the rating by fitting just inside one of the handicap bands. 

 

Also, consider whether your mast can handle the loading of a full hoist chute and whether the boat has enough stability. Since you are in essence designing a new downwind sail plan look at all options.

 

Our Platu 25, with all the improvements, is probably worth about the same as your boat but the money spent on a quality sprit is well worth the cost. We looked at a full hoist ( the Mumm already has it) but concluded that stability was a big issue so we stayed with the fractional hoist. It was the correct call.

 

 Looks aside ( the Selden or Forte while functional is just ugly and not for a racing boat) but the engineering that goes into design to take the loads makes all the difference. The band itself because it wraps up to the hull-deck joint and has a conformal flange takes the vast majority of the lateral and twisting loads as well as all the downward loading at the aft end of the sprit.  The bolt is essentially for mounting although it is backed with G10 tube. The geometry of the sprit was likewise chosen to insure stability while reducing weight.  The foredeck is perfectly clean, nothing to trip over, no holes for leaks. Yes, it was pricey but worth every penny in terms of a beautifully functional addition to our boat that really amped up the fun factor and made the boat a keeper.

 

 You can certainly eliminate the band/integral sprit and use a thick wall over-sized tube strapped to the deck in some fashion but I think in the end you will look at your beautiful boat and think that it was compromised.  GC Marine did a  super job for us and I would recommend them without any reservations. But, if you want to save, my advice is to look for a local company or guy experienced in carbon fiber fabrication and work with him on the project and help along in the measurements, trial fits and the like. It is a great off-season project and this forum has a lot of data. Look also at other sprits, like on the C&C 30, Farr 280 and Bolt 37 for ideas. Happy to discuss further - good luck.



#55 Roleur

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Posted 11 December 2014 - 06:43 PM

Golf,

Thanks for the input. We did evaluate the rating changes of different sprit lengths and also a longer pole for a larger sym. We would maintain the fractional hoist, so no concern regarding the mast. Our righting moment is slight less than a J/80, but for most conditions where we sail that isn't a concern and when it is we would fly a smaller kite.

In the end, the rating is secondary. Fun is the primary goal. There is no question an asym would be more fun to sail shorthanded and that is how we like to sail. I'm certain we could sail the boat closer to its potential with an asym shorthanded.

The sprit comes down to a choice between aesthetics and cost. I wish it didn't, but I haven't solved this dilemma. In our case we have roughly $20k to spend to prepare this boat for racing to Hawaii in 2016. If cost wasn't a factor I would have just bought a J/88 and been done with it. As it is, we are a two boat owner trying to maximize the fun factor.

#56 golfinaspen

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Posted 11 December 2014 - 09:16 PM

Roleur - the asym off a sprit is most assuredly more fun and a lot safer than jibing a conventional chute on a pole.  As I mentioned, the fun meter maxed out once we made the  change.

 

Another thought - the sprit length you are considering is very close to the one we had GC Marine build for us. You could call Gilles and  see if he still has the tooling to duplicate it or give him your budget and see what he can do for you. You can easily build a mold for the band to match the  contour of your bow and he can take it from there.  Contact info for GC : 415 533 2915    Gilles@gcmarine.net

 

good luck



#57 WoobaGooba

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Posted 12 December 2014 - 04:33 AM

Roleur - some thoughts:

 

You certainly started at the right point by talking to designers and sailmakers but do some sample calculations at different values of TPS/J for the local PHRF ratings bands for fixed sprits. We went through that exercise on First Tracks before arriving at a desired sprit length as a  function of rating.  I think Indra did the same on the Mumm 30. You will find and a fraction of an inch of sprit length will save you on the rating by fitting just inside one of the handicap bands.

 

How are you performing these "what if" rating evaluations?



#58 Roleur

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Posted 12 December 2014 - 01:03 PM

So, more details...

The rating I'm primarily interested in is the PCR rating for Pacific Cup. That is derived from the NorCal downwind PHRF rating. Jim Antrim is a naval architect and the "owner" of the NorCal downwind rating / PCR rating. He is on the NorCal PHRF committee. I gave him the information on the boat and he put it through the rating formula. Importantly, he isn't guaranteeing the actual rating, but the relative difference between the configurations should hold. We compared my current spinnaker, a sym with a 120% pole, and asym with a 3.5' sprit, and a sym pole equal to the length of the J + 3.5' I didn't go beyond 3.5' because the sailmaker I contacted (Terry Flynn at Quantum) that specializes in J/80 / J/70 type sails (he's the current J/80 North American Champ) indicated that with my fractional hoist I couldn't go beyond 3.5' or the chute would be too wide and not efficient. It turns out that 3.5' makes my ISP and JSP almost identical to a J/80.

As a far as the ratings, we found that a 120% J pole and a 3.5' sprit have the same rating, within 2 seconds/mile. A longer pole equal to J + 3.5' rated about 11 seconds faster than the previous options. The 120% J pole is a very simple mod and would be really effective racing to Hawaii. Unfortunately, it is clear that a sprit and asym would be a far better option for our local sailing where we do really short legs, multiple laps, and lots of gybes because it is both shifty and narrow. A sprit would be more fun too, there is absolutely no doubt about that. My wife and I could go out in 20+ and blast around double-handed with an asym. With a pole we aren't so sure as there isn't a lot of run off room in our lake if you have issues.

#59 WoobaGooba

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Posted 12 December 2014 - 01:09 PM

OK thanks. Interesting. You have very knowledgeable guidance, one person that sits on the committee

#60 Left Hook

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Posted 12 December 2014 - 06:02 PM

No please, don't do it... That boat is a beauty and a tube on deck would kill the look (I'm gladd the hoyt boom is gone). When you bought her, I was ready to step in if you had not closed the deal. If anything else fails, crowdfund the GC sprit as a memorial to Carl... I'll chip in 50 bucks. Seriously. 


Gotta agree with Fabio on this one. I have a soft spot in my heart for Schumacher boats and anything you're suggesting would ruin the look. 5k seems steep no matter what the so start shopping around and seeing what you can get.

From a financial standpoint a well done sprit will absolutely increase your resale value and make the boat more attractive to buyers should you decide to move out of it at some point. On the flip side, fucking around with a half assed option will conversely decrease the value as owners look at how they'd need to "undo" what you've done.

#61 Christian

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Posted 12 December 2014 - 06:39 PM

No please, don't do it... That boat is a beauty and a tube on deck would kill the look (I'm gladd the hoyt boom is gone). When you bought her, I was ready to step in if you had not closed the deal. If anything else fails, crowdfund the GC sprit as a memorial to Carl... I'll chip in 50 bucks. Seriously. 


Gotta agree with Fabio on this one. I have a soft spot in my heart for Schumacher boats and anything you're suggesting would ruin the look. 5k seems steep no matter what the so start shopping around and seeing what you can get.

From a financial standpoint a well done sprit will absolutely increase your resale value and make the boat more attractive to buyers should you decide to move out of it at some point. On the flip side, fucking around with a half assed option will conversely decrease the value as owners look at how they'd need to "undo" what you've done.

I trust you haven't bought and sold a lot of boats.  The sad truth is that you pretty much NEVER recoup the cost of upgrading a boat.  Sure you might have more fun but treat it as a write off because that is almost certain to be what happens



#62 Roleur

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Posted 12 December 2014 - 07:12 PM

I mostly agree with Christian, however, there is some possibility that a well done conversion to an asymmetrical would actually increase the value, or at least increase the number of prospective buyers.  I wouldn't count on that, but I think it is fair to say that in today's market given two identical otherwise cool boats, one with an asym and one with conventional kites, most people would choose the asym boat.  Resale value is far from my mind right now though.  Boats make no financial sense from day 1.



#63 Left Hook

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Posted 13 December 2014 - 01:43 AM


No please, don't do it... That boat is a beauty and a tube on deck would kill the look (I'm gladd the hoyt boom is gone). When you bought her, I was ready to step in if you had not closed the deal. If anything else fails, crowdfund the GC sprit as a memorial to Carl... I'll chip in 50 bucks. Seriously. 


Gotta agree with Fabio on this one. I have a soft spot in my heart for Schumacher boats and anything you're suggesting would ruin the look. 5k seems steep no matter what the so start shopping around and seeing what you can get.
From a financial standpoint a well done sprit will absolutely increase your resale value and make the boat more attractive to buyers should you decide to move out of it at some point. On the flip side, fucking around with a half assed option will conversely decrease the value as owners look at how they'd need to "undo" what you've done.
I trust you haven't bought and sold a lot of boats.  The sad truth is that you pretty much NEVER recoup the cost of upgrading a boat.  Sure you might have more fun but treat it as a write off because that is almost certain to be what happens

So you woulda paid the same amount for Wanda if all her mods were done half assed and shabby looking?

#64 Christian

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Posted 13 December 2014 - 03:32 AM

So you woulda paid the same amount for Wanda if all her mods were done half assed and shabby looking?

Off course not - but that has nothing to do with what wrote:  go ahead and do mods to your boat if that makes you enjoy it more - BUT - if you think it will significantly increase the value of the boat you are dreaming.  Maybe you will get a little more for the boat but you will (unless in extremely rare cases) recoup the cost of the modification



#65 Trov„o

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Posted 13 December 2014 - 08:52 PM

I mostly agree with Christian, however, there is some possibility that a well done conversion to an asymmetrical would actually increase the value, or at least increase the number of prospective buyers.  I wouldn't count on that, but I think it is fair to say that in today's market given two identical otherwise cool boats, one with an asym and one with conventional kites, most people would choose the asym boat.  Resale value is far from my mind right now though.  Boats make no financial sense from day 1.

 

this!   ;) 



#66 gone

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Posted 14 December 2014 - 02:59 AM

I believe you will hate yourself every time you looked to the fordeck of that beautiful boat if bolted a tube of glassed a hump onto the bow.

If you set up a string drop on that new asym, that two handed bombing around with the wife will be QED.

Aesthetics aside, the points made earlier about tripping or snagging things is worth the additional cost.

#67 Kapteeni Kalma

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Posted 14 December 2014 - 05:38 PM

The Platu pictured has certainly the right look and execution. Rare for production boat which is touched.

#68 golfinaspen

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Posted 14 December 2014 - 07:04 PM

yes, we feel the same way, the sprit looks like it always  belonged on the boat. Even on the trailer for this winter ( with the obligatory protector up front) it is correctly proportioned and a beautiful fit.

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#69 Left Hook

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Posted 15 December 2014 - 04:15 AM

Legitimately looking forward to you joining the fleet next year man!



#70 Reht

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Posted 15 December 2014 - 04:34 AM

That poor monkey is going to freeze this winter!

 

Nice seat for it though, at least it has a shnazzy spot to watch the winter...



#71 Roleur

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Posted 15 December 2014 - 06:37 PM

I get the aesthetics comments, but in fairness they are a bit overblown.  First, the boat currently has a 9' aluminum spinnaker pole adorning the deck for all to trip on.  Aesthetically and ergonomically a deck mounted sprit is no worse than what is already there.  

 

Also, I find it funny that one of most liked boats on SA are the Pogos with?  You guessed it...

 

 

1_medium.jpg

 



#72 solosailor

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Posted 15 December 2014 - 10:03 PM

porky



#73 Shorthanded

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Posted 16 December 2014 - 01:07 AM

We build this stubby prod for my SR33...use it for a code 0.  I'm kicking around the idea of building a 4-5 foot prodder, but a pretty serious financial commitment for the asyms which would all be masthead.  Overall, this one wasn't too difficult to build.

 

A few pics in action - http://boatpix.zenfolio.com/p856707523  

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#74 gone

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Posted 16 December 2014 - 02:22 AM

I know there are different strokes for different folks and the Pogo 30 fills a niche but I would not be caught dead during a Viking funeral on a Pogo 30...

#75 golfinaspen

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Posted 16 December 2014 - 02:22 AM

There are numerous examples of poles mounted on the deck, the Antrim 27 being a common one. Since you have been in touch with Jim it would be interesting to find out if, given the choice, he would build that boat today with a fixed sprit.

We approached the task as trying to really upgrade the boat in sailing handling and performance but the " look" was also a consideration. Having completed the exercise I would have to rank the new appearance of the boat as right up there with the other considerations. It's like buying a new car off the lot with the wrong color just to save some $$$. Thereafter, every time you look at it you think, "... I should have waited and bought the silver one...". Go for the fixed sprit, you will not have any regrets.

#76 WoobaGooba

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Posted 17 December 2014 - 09:10 PM

I know there are different strokes for different folks and the Pogo 30 fills a niche but I would not be caught dead during a Viking funeral on a Pogo 30...

 

Your issues?



#77 Animal Kingdom

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Posted 18 December 2014 - 01:32 AM

I put a Selden 72mm deck-mounted sprit on my FC-8 last winter. We fly a slightly cut down M-24 kite, and took a 6 second hit for it. Don't know if we're faster, but it's way more fun and is easy to sail shorthanded. Total cost was around $600 and it took about an hour to install. WRT aesthetics, the sym spin pole doesn't look any better lying there on deck as you said. If you're worried about resale, it'd be very simple for a new owner to remove the hardware and fill a few small holes. It's been a great way for us to get into asyms without a huge investment.

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#78 SailMoore1

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Posted 10 January 2015 - 03:22 PM

i am sure the deck mounted sprits are functional. But they just do not look good on the bow of the boats. Whereas the custom carbon fibre sprits look great. Like most things you get what you pay for. For give me if I missed it. Anyone willing to share the budget for a custom sprit for any of these 25 - 30 foot boats?

#79 Roleur

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Posted 10 January 2015 - 03:49 PM

$3k min. Some of those shown here are in the $5k range. A deck mounted, off the shelf, carbon sprit is close to $1500.

#80 golfinaspen

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Posted 12 January 2015 - 01:19 AM

Yes, Roleur's estimates are accurate based on our experience. You will also need to factor in the cost of at least one new chute, unless the new dimensions closely match an existing asym boat like a Melges 24 or J80. For our Platu, the conclusion was that the boat was a keeper and the investment for a custom carbon fiber fixed sprit was well worth the bump in cost.

 

Either way you go, there is uniform opinion that the boat becomes a lot easier and more fun to sail. Our experience to date is that it is also overall faster and safer.



#81 Schnick

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Posted 12 January 2015 - 07:00 PM

If you have some skills,,,

 

My buddy built this one for his Humboldt 30 out of two windsurfer mast tips, a bit of carbon to wrap around the end.  I'd be extremely surprised if it was in the thousands of dollars.  It looks like it belongs and projects further than a Selden-type unit would have.

 

Attached File  Manana prod.jpg   158.49KB   54 downloads

 

It also pops off with the removal of 6 bolts.



#82 us7070

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Posted 17 January 2015 - 05:45 PM

it's not such a big deal on little boats, but once you get to 40ft or so, it gets harder to retrofit a fixed sprit and keep the ability to have an anchor on the bow when you want to cruise

 

the deck-mounted sprits are much easier in this regard



#83 movable ballast

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Posted 03 February 2015 - 05:54 PM

Great topic.

 

I have played with both 4.8ft (140% of J) and 2.4ft (120% of J) sprits on my Capri 30 using a J105 A4 chute for both configurations. The long sprit makes a huge difference balancing the normally heavy helm of the Capri downwind by moving the downwind CE significantly forward but the rating rules in San Diego puts me in a fleet with very few participants, a retracting pole and bobstay is needed to better distribute the loads. The short sprit can be fixed (deck or bow mounted), keeps me in my current fleet and lessens the rating hit a bit.

 

So I while I like the longer sprit better I will probably go with the shorter one due to the local rules. We are normally at the front of our fleet it will be interesting to see if the rating hit for the conversion affects our results.



#84 SA Lurker

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Posted 03 February 2015 - 07:02 PM

Roleur- What did you decide? Lovely boat, BTW.



#85 golfinaspen

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Posted 03 February 2015 - 07:42 PM

Movable Ballast, quick question - with two different sprit lengths  which luff length best fits the A4 from the J105?  It would seem that if the shorter sprit  is a better fit, the sail would have a tighter luff given the stretch with the longer sprit and  conversely if the longer one is better the sail would have a slack luff on the shorter sprit.

 

We sized the sprit to fit just inside the TPS rating band and built a new A1 sail to match those dimensions.  We still carry an AP assym from the old configuration but it is short on the luff and used only when it blows. 



#86 Roleur

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Posted 04 February 2015 - 01:08 AM

Roleur- What did you decide? Lovely boat, BTW.

 

Good question.  We now have a sprit and an asymmetrical and IT IS awesome.  Started with a used J/80 spinnaker just to confirm things were working, but earlier this week I ordered a new AIRX 600 spinnaker from Quantum that is designed specifically for our boat and dimensions.  

 

So, what did we do?  Well, simply put, I ignored all of the comments and did what made the most sense to me.  This decision was influenced by the fact that despite wanting a fixed sprit, we ended up keeping our boat in the water most of the time and our slip won't accommodate a fixed sprit.  Also, when originally built, the boat had a carbon Hoyt boom {shudder}.  Talk about an abomination cluttering up the foredeck.  So much for the logic that an on deck sprit was an insult to Carl.  That ship sailed during the design phase.  It turns out that the Hoyt boom included a 6' long straight piece of carbon tubing.  Ah, ha!  Cut off the 6' piece and now I got's me a bow sprit.  Grabbed some Selden deck brackets, some G10 for top and bottom backing plates for the deck and put it all together.  Total cost was around $300 including all the hardware.  Fully retractable.  Extends 4' beyond the forestay.  Functionally perfect.  We went from not being able finish in the same time zone as a J/80 due to slowness downwind to finishing in front of the J/80's 7 out of 7 times and correcting out ahead of them 5 of 7 times (we owe them 21 seconds/mile).  And that is with an old ill-fitting kite.  It really couldn't have worked out better.  

 

21jdiqa.jpg

 

28tgcgi.jpg



#87 movable ballast

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Posted 04 February 2015 - 08:17 PM

There is only 11 inches difference in the rig luff length between the to sprits. For a class J105 A4 the shorter sprit is actually a better fit at 114.5% sail luff length ratio. The long sprit reduces the luff ratio to 112.2 which is a bit short for an A4 but not horrible. An Class A2 is right at 111.2% with the short sprit so that is also a better fit with the short sprit.



Roleur

 

Looks awesome! love it.



#88 movable ballast

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Posted 04 February 2015 - 08:21 PM

What was your rating hit for the conversion?



#89 SA Lurker

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Posted 04 February 2015 - 08:43 PM

Appears to be a nice clean install, Roleur.

Trust you reinforced the deck amply beneath the attachment points...



#90 golfinaspen

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Posted 04 February 2015 - 08:56 PM

Roleur - looks like in the end the got the best of both worlds - a huge performance boost at a bargain price, hard to achieve.  You may have set the benchmark for low cost conversions !!! The G10 could well have been the most expensive piece but it is really needed to take the compressive load.

 

 Good call on saving $$$ for a new chute, when you get that new Quantum sail, it will be lights out, especially in that light air reaching shown in your image.



#91 CazzaRanda

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Posted 04 February 2015 - 10:00 PM

Looks good Rol, can't argue with function and cost... that boat is still a looker! 

 

Cazza



#92 Roleur

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Posted 04 February 2015 - 10:25 PM

What was your rating hit for the conversion?

 

TBD.  The boat is currently on Lake Travis in central TX which operates it's own PHRF location.  Our original rating was 96 compared to 117 for a J/80, 93 for a Melges 24, and 111 for Tripp 26.  That was with a symmetrical and standard pole.  We literally could not finish in front of the J/80's.  That was a provisional rating though and understandable given a one of a kind boat.  Now with the asymmetrical the results are already looking quite reasonable, but the conditions haven't been stellar for getting a real gauge.  Rating hasn't changed yet.  The typical change for our area is a 6 second hit.  I will be mystified if they drop me to 90.  Owing a J/80 27 seconds/mile?!  We are 500 pounds lighter, 2 feet longer, same upwind and downwind sail area, slightly less righting moment.  Same weight as a Tripp 26, 2 feet longer, similar keel, less upwind sail area (they have a genoa), and they fly a symmetrical on a 3' turbo pole.  We owe them 15 seconds.  

 

The boat never had a PHRF rating before I bought it last September so there are very few race results to look at in the symmetrical configuration.  

 

For racing to Hawaii, which is the real goal, we never had a rating with the S-kite, so no real comparison, but Jim Antrim on the PHRF committee ran some numbers and I think our rating dropped 20 seconds/mile with the conversion.  Something close to that.  The catch though is that the s-kite rating would have equated to much higher than a 96.  It worked out to something like going from 110 to 90.  Pac Cup rating is heavily influenced by displacement and downwind sail area.  



#93 Roleur

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Posted 04 February 2015 - 10:30 PM

Appears to be a nice clean install, Roleur.

Trust you reinforced the deck amply beneath the attachment points...

 

Also, TBD.  I think I did.  I over drilled, epoxied, and redrilled the holes so that epoxy could act as a compression ring, then put big G10 plates on the top and bottom.  The key though is that the tack ring is attached directly to the bobstay.  That means there is no upward force on the sprit.  Only compression.  We haven't had strong breeze yet, but we've had some very reachy conditions and managed to wipe out and flog the kite hard once.  So far so good.  



#94 Expression

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Posted 04 February 2015 - 10:50 PM

Roleur: I really like your solution-- am considering doing the same to my 30' custom boat.  One question... how does the bowsprit pole retract and not interfere with the front hatch?



#95 Roleur

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Posted 05 February 2015 - 12:55 AM

Express, I made sure the G10 plates above deck were thick enough to clear the hatch (well, I tell myself that is what I did). It does overlap the hatch by about 9", but a) we rarely open the hatch because we launch the spin from the companionway and B) to open the hatch you can easily just push the sprit forward so it clears. No issue really. If I wanted I could limit the retraction so it doesn't overlap. The sprit would stick out a foot. There is no rule against that.

#96 golfinaspen

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Posted 05 February 2015 - 04:19 AM

Roleur - after we sailed for a while it was amazing to see how much the loading on the arimad bobstay required re-tensioning because the sprit is loaded primarily in shear laterally and upwardly. I don't think you can eliminate these forces which are greater than the compression loads on the sprit. Even if the tack ring attaches directly to the bobstay, the bobstay itself as shown in the dock image passes upward through the end of the sprit. That presumably transfers the majority of the upward bending load to the bobstay but does not eliminate all loading on the tube. At that points of contact where the bobstay passes through( hopefully bevelled with a stainless ring or grommet) at a minimum there will be a lateral force from the sail transferred to the outer end of the tube. Any deflection to leeward is constrained by the wall thickness and diameter of the tube which is why a Selden retractable tube seems so much larger than other geometries used in fixed sprits. At the same time this same force acting in shear tends to pull out the retaining rings at the aft end of the tube. That is, the tube is acting like a crowbar, the longer the extension the greater the moment arm and load. In the case of a fixed sprit, that load is taken up by the band affixed to the bow and there is considerable surface area to bear the force. In the case of the retaining rings mounted on the deck the load must be borne by the reinforcement where the bolts pass through the deck. So after you have sailed in stiff conditions for a bit you may may want to closely inspect the G10 for any evidence of crazing.

#97 rantifarian

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Posted 05 February 2015 - 05:31 AM

The shallow angle on your bobstay will make it more difficult to keep it tight too. Was there a reason to mount it so high? We had a similar setup in alloy, and the bobstay require re-tensioning a few times as the splices set in a few big blows



#98 Roleur

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Posted 05 February 2015 - 11:53 AM

Rant, the bobstay is always tight because it passes through the sprit and is attached to the tack ring, so the kite load pulls directly on the bobstay. We may have retighten periodically, but the only downside if it stretches is the tack ring raises above the sprit.

The SS ring on the bow was already there, for I don't know why. Seemed reasonable to try and utilize it. We'll see if the location is okay.

Golf, that is my assessment as well. The bending moment is very small, compression very large, creating shear at the deck brackets. I'm confident the G10 will rip through the deck before the G10 fails. It is quite thick. All together it seems quite solid. Time will tell, if it is strong enough. Each G10 plate is roughly a 4" circle. Two on top, two on the bottom. 3 bolts per bracket.

#99 SA Lurker

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Posted 05 February 2015 - 04:19 PM

That's ~1.5SF of G10 bearing surface per bracket to distribute the loads.

What's the composition of the original deck?



#100 Roleur

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Posted 05 February 2015 - 05:06 PM

The deck (and hull) is 1/2" closed cell Klegecell foam with 11oz carbon on each side and 4oz glass on the top/outside.  It is very stiff and very light, but not the toughest structure.  The skins are not very thick so you could puncture the skin easier than you might expect/want, but it is very, very stiff.  Honestly, I have no idea how the thickness and weight of cloth compare to other boats.  Is that crazy thin, crazy thick, or normal?  I have no reference.  

 

I may have not explained it correctly.  There is just one 4" circle sized G10 plate per bracket on each side of deck.  2 plates per bracket.  

 

I still don't know how much the boat weighs.  The original plans say 2800#, but that was for a glass boat (and how accurate were the plans).  The carbon/foam construction certainly weighs less, but no one that I know, including the builder, knows how much less.  I call it 2700# until I can get it weighed.  






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