All forms are now cut and aligned.  A recheck of profile points are within 3mm.








Stations 8, 7, 6 and the transom points do not create a fare line.  Does anyone know if this is normal for F15 hulls?  I discovered the comment section is not working and so a message to wymanrt@yahoo.com would be great.  I imagine I will redo this section with a batten and miss the loft points by several mm.  The form is almost ready for lamination work.






The first marking of center-line points measured from the baseline shows they are skewed.  Will have to reset sections of form and remark or rotate baseline reference.  

Moving along I decided to construct the backbone stand alone in the upright or flat orientation (TBD) then build the stations and insert it within them.  The cross members will be added after the initial lamination and shaping and finally trimmed within the shell fairing.  Building base is coming along.  The backbone went through several revisions to where finally the cross pieces (frames and buttresses) are moved to the top of the lamination stack instead of in the middle making the work easier.  A 10 mm cap will sandwich both assemblies.  A few more days of vacation should get the lamination started.

Backbone construction:  Planning to work with African Mahogany for majority of backbone along with Oak for frames and ? for buttresses at four points in the area of the keel flange.  Two frames will be fore and aft of keel centroid longitudinally and one set will terminate near the shroud attachments.  The basic layout still being refined is shown below.  Stiffness of stern area up to rudder attachment is being studied with shell and panels.  Load distribution out from keel attachment along with other stress points; mast, shrouds, jib, etc. will tweak the design before any molds can be setup.


Finished parts waiting for a home.  Still work to do here but at a good stopping point until the hull forms.

If anyone has suggestions on paint I could use some input.  I do not see the need for special anti-fouling or metal paints since it will not stay in the water for more than a day.  Here is my list so far:

1. Pettit Unepoxy
2. Pettit easypoxy
3. Pettit Shipendec Enamel Paint 
4. Rustoleum Oil based enamel
5. Krylon spray enamel

Any comments?, Thanks.

---------------------------------

I ran out of epoxy but it is all ready for glass and fairing.  After that I will give it a coat of paint and store it. Perhaps some more tuning on the keel to clean up the first two layers and prep for storing.  Then the real work gets started, building the back bone and stations but design is still progressing.  I probably will not have any posts for quite awhile.  And it will be time to pay the English for the building right.

November 5:

The router bit slipped a bit last week so adding more material at trailing edge.  Should be able to glass the entire profile by this weekend.













October 30:

The rudder is developing.  It took some time to layout and decide what balance could be achieved while housing the stock and keeping an angle similar to what is used with modern FFs.
Goal:
1. 15-30% balance by area.
2. Rudder stock angle from vertical 6-30 degree.
3.  Rudder center of pressure centered on stock (by area).
Final:  15.4%, 14 degree from vertical, centered by area

The 97/2 plan profile of the rudder shows the airfoil normal to the leading edge of the rudder which is 43 degrees from vertical.  The first method was to stack the profiles with wood blocks and shape it down to the profiles.  I started with a naca 0011 foil which closely matches the plan profile but in the orientation this would develop an ambiguous profile wrt. to actual water flow.  Re-mapping the profile in the direction of flow then plotting the resultant points for a 'normal to leading edge' orientation gave a new profile matched to another naca profile.  Oversize patterns were cut and will be used to rough in the shape with a router suspended across the profiles.  Next step is finish internal shaft and torque pin assembly followed with epoxy glue up of ll parts.

A first layer of epoxy was used on the keel after giving it a better support rack.  Bad news is the keel has a 25 mm twist in it placing the end point of the fin off center laterally.  Will compensate with some shaping and the final mounting hole pattern to backbone.

Keel weighing and drilling

Keel flange is now drilled.  Easy job except the slow steps of positioning the keel safely.  Need to research the method of sealing it with epoxy or paint or whatever.  I imagine epoxy with thickener, sanded out and covered with paint?  Comments any one?  Bolt pattern will have 10x 3/8 bolts.

Made a mistake with the keel right out.  I forgot to add a hole in the base to tune the weight in the future. I wish I had a Carlton drill press now.  But I checked the weight with a lever assembly and two counter loads and averaged 390 lbs. (6.1: 181+/-12 kg, 373 lbs - 425 lbs) so all is well.  

I next moved the keel and hoisted it adjacent to the work bench to gain a good position for drilling.  I would like to finish the keel up to some decent point after which it can store for the future.  I will lay it beneath the base framing that is half built.  Time to figure bolt patterns and sizes.

Rudder and Base

September 25th:
In the last few days I put up the base and developed a rudder plan.  Small and large project work will proceed in parallel so that at night I can make progress without waking the dogs around the neighborhood. The RUDDER should qualify as quiet work.  The design is to take the provided cross section from plan 97/2 of the ruder and scale it within the fore/aft profile.  As the profiles approach the hull they will gradually angle until parallel with the edge adjacent to the hull.

Compared to old pictures of F15s being built circa 1940s it appears I have a relatively stout BASE to setup the station moulds.  I am leaning towards laminating a backbone over the moulds but that could be troublesome with a 4ft wide base.  Only half of the base is setup at this point and I am using it is as a table for laying out the stations profile.  The plans are curious enough with some variations between the loft table and full size station dimensions.  I don't suppose I will ever get this boat class approved but the aim would be strict adherence to the rules.  I will use two layers of 1/8 marine ply formed primarily over a set of stringers on the moulds.  Frames will be laminated and placed densely in high stress area of keel and less so along boat length.  It is not determined yet if steam bent or laminated frames will be used.  The fine frame arrangement on classics as shown in the photo below does not apply.  A recent ffblog page indicated that was the method used prior to epoxies and a large number of small bronze nails visible on the outer surface were driven through each frame.  Also stringers built into the hull are not currently considered, just a laminated frame network and bulkhead panels to carry the load path out from the core to the hull, shrouds, etc.

Keel

The keel arrived and was trucked over from Kona side.  Funny that the location in Hilo is where I stopped by to ask about free pallets to use in mold making.  Well there they are, one stop shopping!!

Lessons learned (not my favorite phrase):

1.  Get advice on shipping.  I saved 300-600 bucks by following suggestions.

2.  Keel does not need a pretty box to get home.  The pallet here was provided by Commercial.

3.  Getting those holes on the flange..well there is a machine shop down the street from the shipper or I rig up the press at home...hmmmm lesson to be learned soon.

4.  Glad I waited on project till this arrived, it was touch and go for awhile.

Shipping costs!!

A rough week with a good ending.  I checked a previous quote for shipping the keel to Hawaii and the cost went up 3x.  I almost keeled over.  I checked further with other carriers and it only got worse.  With prices in the $600.00 range I settled myself by thinking that this is what they charge to ship me to Hawaii and I am self loading.  Things changed with some helpful input from a friend and I am going to ship the mold in a cardboard box, well wrapped.  The casting house said that is fine and that they can strap the finished piece to a pallet and send it off.  A quote for the return pallet came in at $250.00 so the show is on!   If anyone needs a really nice crate for storing a Flying Fifteen keel I have got a deal for you. 

California or Bust!

Finally ready to ship the keel plug to California for casting.  Plan is ship this to the casting house then have keel returned with plug lying on top in this crate.  There is just a bit of extra room.  I suppose someone in the future may need to make one of these so here it will rest for future generations/regattas.  Crate is reinforced across the bottom with oak strips to support 370lb load about its C.G.  Next stop:  California or Bust!

Time to start glassing the form.  I probably do not need to do that for a one time use form but I am looking for some practice before taking on the rudder job.

'It doesn't have to be perfect, it just has to look good.'

Note:  Styrofoam melts a bit with Bondo.  Pour foam does fine.  I have now used 6 different materials filling the form before going to glass/epoxy covering.  These are: Pour Foam, can foam, styrofoam, spackle, drywall filler and Bondo.  Should have taken more time to setup alignment pins and back fill with spare wood blocks.  I ran out of pour foam but managed to empty my shelves of old materials from old projects.  Looking pretty good.  I think by next week I can prepare for a glassing.

A little bit of keel progress today while I try to ignore the good weather and strong winds on the bay.   I will start doing some measurement checks from the base board to get a best alignment between port and starboard halves then insert a pair of alignment pins.  So far all the measurements on the profile have come out fine.  I had a scare the other day thinking I had lost 5mm in stack height somewhere but it is all fine.  Just the sanding of the poly is going to be very messy.

May 5th:  A few days later I have started sanding, cutting and grinding the shape.  I am surprised how fast it is going but regret the use of 'can foam' as mentioned earlier.  It has very low stifness so I will depend on the fiberglass top layer for strnegth in any areas where it was used.  I also revise my opinion of the styrofoam which works very well along with the pour foam.  I will probably test an area of this soft can foam with fiberglass to see what surface pressure it can take so as not to impact the sand casting.  I was warned by Commercial Casting that the sand packing could deform too soft of an area.  After all this work as well I have about 1 oz each of parts A and B of the pour foam.  There are several voids that still need to be filled so I am looking for some other compatible filler before I switch to bondo.  

Followup on the plug work.  Do not use can foam or Styrofoam, even fine grade.  The pour foam is very controllable and manageable and cuts well for shaping.  The others are too soft and make a mess.

So I started on the Port side plug with current success and need to add alignment pins.

Keel work Starboard side:  The keel plug needs to separate along the center line for casting purposes so I have now switched from a 1/2" back board to a 1/4" requiring extra strips to stiffen it overall. The profiles were glued in place and foam added to fill the voids. It is a bit of an experiment and I hope one layer of 6 oz. glass fiber will suffice in the end to make a cast worthy plug. The can foam works quite well but is softer than the 2 part polystyrene pour foam. I use both at this point. I am scratching my head as to why I bought expensive Marine epoxy for this job but next in line (to build experience) is the rudder and that will use it appropriately. This work is getting ahead of itself. I am not sure what the casting house in California will charge but I am hoping for the best. If it falls through I know this thing will look great on top of my Honda Civic. Back to taxes, run silent, run deep.

I laid out the keel pattern on 1/2" ply sheet, the centerline board on which to build the casting plug.  I traced each cross section from the plan (Keel & rudder - lines & templates schematic 97/2) and my trusty helper cut them out.  I pasted them on wood panels and cut those to size.  I will build that up into a 3d structure then fill with polystyrene.  Epoxy and glass will go over that after some fine shaping and bondo work...at least that is the plan.

This is the essence of the F-15, at least from my narrow view 5,000 miles from the nearest regatta.

I finished the keel proposal and request  and submitted it to a casting business in southern California. No word yet but it is a one off strange request.  They did a very fast turn around keel some years back for a damaged boat and they pour in the several ton range daily.

General specification:

Keel Plug:

1. Construction: Plug is to be one part.  Will discuss with you if it needs to be two pieces.
2. Material:  Built up from wood, foam, Bondo and fiberglass.  See figure 1.
3. Shrinkage allowance: 1/8”/foot shrinkage allowance.  
4. Draft allowance:  The shape seems to be well accommodating for retrieval from sand form.  
5. Finish:  Sanded fiberglass.
6. Weight:  Approximately ~30 lbs.
   Shipping dimensions: 2.5’ x 1’ x 7’
   Metal Keel Casting:

1. Construction:  Malleable cast iron.  
2. Material:  Malleable cast iron, Nodular iron both appear to be good toughness without post heat treat.  
3. Finish:  Smooth as possible without incurring additional cost.  
4. Weight:  Expected 370 lbs.
5. CG:  29.5” horizontal, 6” vertical, center-line transverse.  
6. Flange:  I am planning on ½” diameter through holes, 10x eq spc.
7. Shipping method:  TBD - ocean freight.
8. Shipping weight: 400lbs
9. Shipping dimensions: 2.5’ x 1’ x 7’

   

Figure 1:  Plywood sheets, foam and fiberglass plug with same dimensions as finished piece with compensation for shrinkage.

I am putting this log in place to maybe gain input from others.  The plan, emphasize 'plan' is to build a flying fifteen keelboat.  I aquired the plans from England some time back and only now see the window that I might build.  This will be done in coldmolded style. 

I generated a list of all materials, steps and time with costs.  I would like to keep the cost in the 5-7k region for everything.  I hit some obvious road blocks:

Keel:   The first is the keel itself.  This organic shape of 370 lbs of cast iron is outside what I would consider casting with a backyard furnace...oh sorry, Blast furnace.  I made a request to Pin&Bax in UK but no quote has arrived.  The shipping cost might wipe me out anyway.  I am considering a non class keel that matches the horrific 3-500 ft-lb moment arm this thing puts on a hull.  A stack of steel plates torch cut to the shape then sealed in resin....well we'll see, working on that design for now.

Sails:  My living room and dining room just happen to be perfect size for a temporary loft.  And that Kenmore sewing machine I found at the dump actually rams through 6 pairs of levi material.  I am sweet talking the family for that one.  Otherwise a sail set is 1800.00.

Mast:  Need to figure this one out.  I would be game for a wooden mast.

Trailer:  I plan to modify and existing trailer in the future that will do teh trick.  It look necesary to have a trailer that can be backed in to the water with a long rope or chain as it really needs to go in farther than normal.  Our local launch also has a bridge to pass under so rigging will be after that.