Blade F18 Project

G'day All,

Most of you may be aware of the BF18 & the platform stiffness results that have made their way into many dicsussions & arguements on this and many forums on catsailor.

All the BS aside, the BF18 is very rigid & under any measurment scenario is much more resistant to torsion than any other catamaran that I have laid eyes on & tested.

Having owned & raced both the Reg White & Marstrom Tornado, I can tell you there is a marked differnce in the performance of the two boats when racing in a sea way. It is like chaulk & cheese. Dont Get me wrong the Reg White is a very well made boat, but the Marstrom is streets ahead in the construction department.

Given the experience from the Two Tornado's, we identified several areas on the Blade F18 that needed attention during the construction & this was not just targeting the hulls. The major areas of concern were the beam size & cross sectional area, how the beam is attached to the hull & its bedding & how well the load from the beam is transferred in to the hulls.

We used an oval section ( 150 x 100 x 3mm wall thickmess) beam that was double bolted to the hull at both sides of the hulls (ie// there were 16 bolts instead of the usual 8 bolts), the beams were fully bedded into the hull to the half way point of the beam. ( the bedding is very important as we conducted a torsion test before full bedding was complete & the torsion results were reduced by 300% once bedding was fully completed). The beam bolts were connected to some serious glass layup that continued in to the hull sides for maximum connection.

The hulls them selves were fairly standard using 4mm ply with stitched glass both sides, 4mm ply frames every 330mm & 4mm ply subdeck.

Generally there is no rocket science here, but just common sense as we knew that the F18 is a heavy bugger & we taylored the construction of the beams & hulls to suit the class rule. F18 rule suggests a manufacturer can get away with 45kg per hull & still be on min weight.

Now building a F16 to 25kg per hull will be little more challenging while keeping the platform rigid.!!

I have attached a photo of the BF18 on its first day on the water & will dig out some of the construction photo's over the next few days.

Marcus

Hi Marcus,
Nice Pic! I'm amased that you guys built the 18 with 4mm ply as I would have thought you'd get better stiffness with 5 or 6 and still be under weight. Or is the bending the problem with thicker ply?.

Also if you've got to drop 20kgs then where will that go from (apart from the obvious extra 2ft)?

Would like to see more of your 18 and 16 construction photos as you get round to it.

Cheers Phil

Phil,
A more appropriate question would be how do you put 20kg extra into each hull apart from the extra 2 ft. and make sure all the extra weight contributes to increased strength and stiffness.
That has a long answer and to answer that fully you really need to compare the two sets of plans.
4mm ply was used because it was just what was needed to meet all the objectives of weight, strength and stiffness given the selected glass laminate.

The Blade F18 is very very stiff compared to the other F18s measured. Marcus has all the numbers as he peformed the comparative measurements.

Regards,
Phill

OK, how are you guys bending 4mm plywood to form the round bottom of the hulls? Do you do only one half, (port-starboard) then put it together like a clamshell? Do you cold mold it over a framework of bulkheads or steam it or cut it into long strips or what? Not that I'm going to try it myself, just curious.

Matt McDonald has made molds for the Blade 16 and is making them of glass. He may also start work on a F18 after he gets the f16 up to speed.

Timbo,
I went through quite a few different ideas and a number of trials when trying to work out how to put a really modern hull shape within easy reach of the home builder while still building from ply.
If you're really interested in how the shape is achieved send me an email and I'll send you a couple of pics.

Regards,
Phill

So I take it there's a glass layup over the ply as well as just taping the joins?

I believe the timber T4.9s are not fully glassed over which would make a fair weight difference.

I'd be interested in seeing you're construction pics Phill maybe a future posting for all to enjoy!

Cheers Phil

Phill, I checked out your web site with the construction photos. Very nice! So, do you finish with a layer of glass over the ply or just paint it with epoxy paint?

Timbo,
It depends on the boat.
If you're talking about the F16 just a layer of 3oz on the deck is all that is required.

If your talking about the F18 it has a layer over both deck and hull.
What web site are you referring to, you may have been looking at photos of building a Taipan.

Regards,
Phill

Yes, I think it looked like a Tai Pan. You must also put some kind of epoxy or paint sealer on the inside of the hulls, to keep the wood from soaking up water, right? I'm not going to try to build a cat but I would like to build a small, square, sail boat for my kids to play on, that's why I'm bugging you!

Timbo,
Your not bothering me. I have been trying to get people to build their own boats for years that's why I put up the web site.
If you want just email me your phone number. I'll give you a call and answer any questions that you may have about building.

Regards,
phill

What is you r website phil, I would like to see it.

Phill's site is at
http://www.geocities.com/phillbrander/

Has some good info on different building methods, though some links to photos didn't seem to work for me yesterday.

Cheers Phil (with one L)

My apologies about the site.
The photos were all stored in albumns on Yahoo that were
linked to from the web page.
Something changed a while back that means I have to completely rebuild the site so people can access the photos. This job has been a long time coming and is not complete.

Phill, I'll email you when I get home. I'm on the road for a week. Thanks. Hey, do you know any Quantas Pilots that fly to Los Angeles? I would love to get a ride down there. I met a few in Tokyo but they didn't sail!?! (I thought ALL you guys were sailors!)