One of the most important and vital design tools to create a new cat or tri is the weight/trim spreadsheet. I always use it in tandem with the hull lines program. It’s not that inaccurate to say that knowing how long a boat is does not matter at first. I have my magic hull proportions, and I have weight and payload needed. Ideally, the length is a result. I cannot imagine doing it any other way, but I still encounter builders, even boatyards, who are happy to storm ahead without a weight study. That profoundly amazes me. I know of one professional builder here in my state who prefers to start with hull patterns, and then he freestyles the design from there. Utterly amazing. I even offered one to him for $100 and he declared that he didn’t want to waste his money. (a complete one takes some 10 to 20 hours to flesh out)
Knowing what it will weigh, how it trims, and what it can carry are the most important foundations in any design as I see it. In a series of loops, the hull lines are updated to reflect the excel data. Then the new hull information goes back into excel and tightens that up.
The final hull lines and patterns should only be created after everything else important is designed. Understand that it takes mere seconds to parametrically revise a hull. I know that not everyone agrees with this, but I cannot understand why not.
Vacuum bagging parts with the Space bag has been a mixed scene so far. It is a wonderful concept, but the bags have been failing. I started with the 3’ x 4’ jumbo bags. I am bagging the dome triangles for the lunar lander top. They are ply/core/ply sandwich parts. Recall that the spacebags let me run the vacuum for only a few minutes, not the usual 6 to 10 hours. The first jumbo bag kept the vacuum for 3 days until it failed. The second jumbo lasted an hour and the third was good for about 10 minutes. A smaller XXL bag lasted 2 days, but as in this picture, on a second attempt, the bag would not hold a vacuum. I tested the closable seams and they were fine.
I spoke to SpaceBag and they will send replacement bags. They did say the bags should be airtight when you get them and good for several uses with no problems. I guess I will need to fill up the bathtub to see where the leaks are. I will do a dry run on every bag in the future to test it first. Notice the duct tape on the sharp edges to protect the bag.
A new KHSD 45 has been launched here in Seattle and is now out at Shilshoe Marina. CM plywood/epoxy. I heard it has an extra layer of 34 oz triaxial over everything for good luck. Looks nice Marvin. I do like the color.
Charles, good chance to show everybody the composite brackets. I think best way to make this plywood bow tube work would be for you to cut one or both of them away, then get the correct space between. Then bond and fasten to deck or hull again. Yours would work fine on an alloy tang model.
I will be out of the office J7 through J14. Am attempting to get everyone’s things out before I leave. I will update the 2014 Design Book while out. I will also be working on the 3D models of various projects. I will be in Ft. Lauderdale J8 and J9 if there is anything I need to do there.
Most catamaran bowtubes are alum. or carbon mast sections. Some builders are getting shocking quotes to get these built, so they are considering ply/epoxy bow tubes.
I do urge using the best plywood and do not skimp on construction as this is a mission critical part of your cat.
One thing, ideally the tube end bolt would be not 90 degrees but parallel to the hull. I am assuming the hulls are rigid enough that the delta is not significant enough to upset that pin.
Corners are biaxial roving. The red is biaxial bushing. Blue is triaxial. Yellow is the stainless. There will be cross laminate to hold the triaxial onto to the box.
I got my venturi pump at Fiberlay. I understand that even though they sell them there, the pumps are not on their website nor in their catalog. They are not wildly net savvy there.
So the venturi pumps are called Vacuum Generators. Part number 1807003 at Fiberlay, listing for $110.50. They pull 27″ of mercury at 90 psi on your compressor. They only pull 2.2 CFM so the vacuum bag has to be good. No moving parts. I’m a big fan of mine. Call Fiberlay at 1-800-942-0660 or find email at www.fiberlay.com.
For some reason Richard keeps posting wonderful pictures of his KHSD 63 cat Profligate. And I will keep posting them. Some excitement this month as the Mexican IRS impounded 338 US boats visiting.
I read in Automotive Design magazine about new organic LED lights by OSRAM, osram.com that are as thin as 1.4mm. They will allow tiny cars to have more trunk space as the tail lights will simply be a film attached to the car. They can be programmable also for a variety of lighting schemes. I see a big future for these in multihulls also. I’m sure my multis in the future will have many.
