Bladerider Foil Mods

I’d like to get a new set of foils for MB1, but I can’t quite justify that expense at the moment.  That being the case I looked at my current foil package to see if I could modify it to improve the overall performance.  I’m currently running a home-built front foil designed by Gui and a Bladerider rudder foil.   I’ve considered cutting the tips of Gui’s foil, but I’m not going to go there quite yet.  That leaves the Bladerider rudder. It’s clear that the current trend is for symmetrical rudder foils and the stock Bladerider foil is far from symmetrical.  I looked at the foil shape and decided that it should be possible to make the foil more symmetrical by modifying the trailing edge.  Below is a typical NACA section that is pretty similar to the Bladerider rudder foil.  This foil really has a lot of ‘flap’ which can’t be very fast for high-speed sailing and probably produces a lot of drag at all speeds.  The red line shows what kind of section you’d end up with if you removed part of the trailing edge.  

 

This section looked quite a bit better to my eye so after a bit of checking to see how much carbon was in the trailing edge of the foil I simply took a large file and removed about 3mm of the trailing edge.  Then I thinned the bottom side of the edge to remove more of the ‘flap’ and repainted it.  What I was left with was a foil that still isn’t symmetrical by any means, but it is far more symmetrical than it used to be.

So far I’m really happy with the performance.  It may not have quite as much low-speed lift, but also seems to have less drag.  The largest benefit I’ve seen so far is that I don’t need to adjust the pitch of the rudder as much when going from an upwind mode to a downwind mode.  Previously it felt like I needed to decrease the pitch on the rudder when going downwind to keep the boat from getting uncomfortably nose-down and then increasing the pitch again when I turned upwind.  Now the boat feels much more stable in pitch on all points of sail.   It also seems like the foil is less prone to cavitation.  So should you take your stock Bladerider foil into the shop and grind it down?  I’m not going to go that far yet, it could turn out that grinding this much off the trailing edge weakens the foil, but I do think it improves the overall performance.  So if you have an old Bladerider foil laying around that you don’t mind breaking, it’s may be worth the 30 min it takes to modify it.

Pimp My Moth

Decided to bring some bling to my moth experience by upgrading my ride. I'm talk'n Cadillac Escalade yo!   And chech out the cute young thing at the wheel.  Don't be hate'n when I pull up in this bad boy at the next moth event.  Peace.

It's Alive!!

For all of you that have been wondering what the fate of Mothball 1 was, well here she is, fully repaired and sporting new tramps.  The repair of Mothball 1 was actually fairly easy.  After cutting out all of the crushed plywood I just made some new plywood backing plates and epoxied them in place, then re-attached the mast stump and cut more plywood to fill in the gap.  To make sure it never fails there again I reinforced the whole area with carbon and then added a forward facing compression strut (as suggested by Phil) to take the forward loading from the mast.  When I was designing the boat I never really imagined the amount of forward pressure at the mast stump from the vang so I'm not really surprised that it failed there.  All in all I’m pretty happy with the repair.  I took the boat out to do a shakedown cruise yesterday and everything worked well.  Now I need to do a few extra mods and repairs that I forgot about from last summer and I should be ready for the season.  Maybe my next project should be a new dolly?

Dude, where’s my stump?

 I was planning to show you guys the photos of all the cool improvements I’ve made this year.  Ride-height adjustor, new gantry, stuff like that, but now I have a new moth chronicle to relate.  I went out sailing early this morning because the forecast was 10-15 diminishing by noon.  I rigged up the boat and it looked like it was starting to blow pretty good on the water.  I was ready to try and get some good numbers on the GPS.  I headed out and started sailing downwind.  The wind was a bit puffy and I instantly was sailing 15-18 kts with good control.  As I made it down the lake farther the wind started to pick up more.  I sailed down the lake for about a mile and then came back up to meet some family members who where sailing my way on keelboat.   I pasted them going upwind and then bore away again in a big puff.  This one was really strong.  The GPS log put me at 20+ knots for over 60 seconds with a max speed of 23 kts, my new personal best.  The boat handled fairly good but I decided to work my way back upwind in the big breeze.  Upwind was pretty hard, by now it was blowing 25-30 steady and I was having a hard time getting the boat going into the stiff breeze.  I sailed back to the marina and took a break hoping the wind would settle a bit.  About an hour later I headed back out.  The breeze was down a bit, but pretty steady around 20 with some good waves.  I was sailing downwind at about 18 kts and stuffed the bow into a wave, it didn’t seem like a bad impact but the terrible crunching sound told a different story.   The boat flipped over and I instantly knew something was very wrong.  I righted the boat but the rig was clearly down.  Looking forward the reason became instantly clear.  The mast stump was completely gone, just a jagged hole remained in the top of the boat.  The rack struts just hung in space.  I wasn’t too far from shore and the wind was blowing me that way so I wasn’t too worried about being stuck in the lake.  I swam the boat toward shore and watched helplessly as the mast which was now bouncing in the waves on the unsupported racks breaking the joints.  It took some effort to keep the gaping hole on the top of the boat from taking on water and filling the forward tank.  Finely I got to shore and started taking the boat apart.  Shortly after my family came along looking for me and we stacked all the broken parts on the deck and started back to the marina.

After taking everything apart and looking at the broken bits I’m happy to say that Mothball 1 will sail again, but not this season.  The racks should be easy to fix and there wasn’t much other damage.  Thankfully I didn’t lose anything.  The remains of the mast stump were held to the boat by a small guide and the tiny line for the ride-height adjustor.  The stump had failed by compressing forward into the deck.  I should be able rebuild it and reinforce the area to take the massive loads that I’m starting to put on the boat.   All in all it was a good day.  I’m just glad I didn’t get hurt or sink, but mothing season 2012 is now over :(

Time for an Upate

Where has MB1 been this summer?  Well sailing actually.  So far this year I've logged over 100 miles on the foils.  The boat is working great and I'm starting to feel pretty confortable at the helm.  My tacks and jibes still have a long way to go, but I'm pretty sure that I could race the boat now and not make a fool of myself.  I'll post some more info about the mods I've made this year over the next few days. 

As a moth sailor all I can say about the flying AC72s is Fuc$ Ya!

Stainless, Brass, or Carbon?

I’m in the process of building a new gantry out of carbon.  It looks really good (pics soon), but I’m planning on upgrading my rudder pin in the process.  Right now I’m using a ¼” stainless pin which has worked fairly well, but I’ve bent it several times so I don’t think it’s really up to the task.  For a replacement my choices are 5/16” stainless, brass, or carbon rod.  Stainless is the most obvious choice but it seems like brass may work just as well and is far easier to work with. My other choice is a solid carbon rod which would be way lighter than the metal rods but I’m not sure if it would be up to the task.  Carbon would also be able to flex without bending and could shear off without damaging the rudder.  Any advice?

Space Moth

I was looking at Google Earth yesterday and realized that the satelite photo of my area had been updated.  It was clearly a summer photo and the lake was busy so it must have been taken on a weekend.  After a bit of searching I found Mothball 1, unfortunately I wasn't sailing.  The boat was under its cover in the rigging area, so I must have been getting ready to sail.  Can you find Mothball 1?