Sea Sled Performance: Qualitative Analysis

Well, there no research of any kind to suggest that an inverted deep V would be any improvement over the flat bottom sled. And there are very few made. Baeckmo made about half of all the ones I know about. He carried the A aft. Marcus Lee made a dozen. His are flat. Robin has 1. It has a shallow A. So there's hardly a trend one way or the other, and no comparison between the 2.

Naturally I'm not saying the absence of proof is proof of absence. Carrying the tunnel to the transom may be desirable. Or not. But @Mr Efficiency refers to flat bottomed boats being necessary to carry old engines and hulls because of the weight, and lighter boats, with modern components being faster in V form. I would like to point out that massive load capacity is a desired feature, not a flaw or failure of design. If I had to make the boat incapable of meeting the SOR, so that it was faster than a boat meant for nothing other than empty speed, my money and time would be very poorly spent.

 

And there is the difference between meeting an SOR and chasing your hearts desire...come what may..

 

I hope that didn't sound testy. I'm putting everything I've got into my sled. The idea that I made a mistake that I can't fix, makes me very anxious.

 

The ribs are all healed ? Say hello to your helper over there DC, she is certainly bringing things to fruition sooner.

 

Darn. I'm really running in a circle with my hair on fire. @baeckmo must be thinking:"Siiigh... DC has posted again. Let's see what he misunderstood this time."

My conundrum is this:
There's a tremendous amount of anecdotal description going back over a century saying they are really fast, don't pound, don't exhibit a transitional resistance hump, and carry massive loads. But the only tank testing ever done says the opposite. I'm trying to reconcile all this. I'm not going to assume that everyone who ever had direct experience of them, from the 1915 editors of The Rudder, to Marcus Lee, whom I spoke to at tremendous length in the last few months, is liar or an idiot. But as @baeckmo pointed out, neither were the fellows who did the 1955 tank testing.

And of course, I've bitten off so much, I'll either swallow or choke, so I have a huge investment.

 

But there are also anecdotal reports of just the opposite in performance characteristics.
I don't think anyone is a liar or an idiot but that everyone's experience is different
under different conditions and circumstance.
Perhaps the most telling to me is to watch those old videos of SeaSleds at speed in varying conditions.
At any rate, consider letting the history go and focus on the present and getting your dream in the water.
Not much you can change now anyway short of getting out the chainsaw.
Run with what you've got and lets make some of our own videos to add to the pile.
Carry-on.

 

I'll just point out that I don't think much of what you need that boat to do seems dependant on the possibility of sea sleds being high-performance machines anyway.

My guess is that at speed in big water, it'll be a rough ride. Have you ever been in a workboat that didn't slow down in rough water, though?

Like every other boat, it's a compromise. You will have load carrying capacity that could only be beaten by an actual barge. You will also have a boat that can run fast in reasonable conditions. You will probably not have a boat that would be a better offshore racing machine than an Apache. Don't worry about it. To do what you need it to do, it doesn't have to prove that the Hickman concept is better than every other compromise. Don't ask it to be all things. Ask it to be a good, safe, dependable workboat that can turn out speed when you need it to, haul a ton of gear and people, and burn less fuel than a deep V with equivalent carrying capacity, while costing less to moor and drafting only a fraction of what a deep V does.

I think you're letting your mental mission drift into "prove every Hickman sea story to be perfectly accurate."

They don't need to be. You're doing great. Get her on the water. She'll do what you need.

 

@cracked_ribs you have summarised my thoughts as well absolutely with your post above.
I think you nailed it totally.

 

Thanks Mr Efficiency. They are healed as they will ever be. Seem to be permanently half way there. Didn't help that a week later, I blew about 20' of 2' high foundation wall full of rebar apart with a 15# sledge hammer. But the only other person on site was my Padawan, Beverly, and she's slender as a runway model, and 6 months pregnant. So it was me. There was some discomfort.

I'll say hi! to my Sweet Anne. Anyone who drops by for a visit will meet her.

 

I agree entirely. And of course Serenity will my favorite boat, whatever she does.

 

And that's the issue with subjective anecdotal evidence versus quantitative tank testing.
...and then having to take off ones rose tinted glasses for the sake of ones sanity!

As noted above.. it matters little what is or is not correct. If this is your boat and the boat you want.. who cares whether is slams a bit more or is not as fast as you want?

If it does what you want.. then job done.

That's design.. every boat is unique in that sense and where far too many people get tunnel vision into selecting one attribute of a design, out of many in the design of a boat, and using it to justify XX or YY claim about said boat.
A successful design is greater than the sum of its individual parts... and very very rarely defined by one single attribute.

As such... if it ticks your boxes... who cares what others think or if there is a tank test report criticising the ride etc.
That's true for any boat.. criticism is easy, anyone can do it... one only has to read the comments by many of the familiar posters on this forum to know that!

Relax.. chill out.. and enjoy the experience that you are creating for yourself. ..and for many reading your build thread

 

Thanks everyone. I've managed to recover some chill, as @Ad Hoc recommended. A thousand thank you's to @baeckmo for the fascinating info. Sorry about the misquotes. I've rewritten the more egregious of my misunderstandings.

@baeckmo , you mentioned instumentation to measure the performance of my boat. When it's in the water, I'd like to do as much testing as possible. Anyone have any notions how we might do this?

 

Well frist of all, what is it you wish to measure/test?
But before you begin this task, you require a datum. So, when you have finished building the vessel - completely - you need to know its weight and KG.
The first part is easy... you can have 4 calibrated load cells positioned under the vessel...this will give you weight and LCG.
This can then be confirmed (hopefully - but not so easy on small vessels) via the draft marks you place on the hull side, now you also have a set of hydrostatics.
The VCG...that may be a bit more tricky for you... but we can talk you through that one later.

So,check list:
1 - weight of boat
2 - LCG
3 - VCG

That is your starting point. Because then you can now start to add consumables (fuel) etc and add it to your lightship values which you now have.
And then.. what tests you wish to do shall dictate how you perform them and what equipment is required.

Now you're getting into the nitty gritty side

 

Nitty gritty! That's good with yogurt.

Performance at power to weight ratios between light-as-possible, and barely afloat. Response to rough seas, both under power and adrift. I'm wondering about @Mr Efficiency 's pounding concerns.

But data that other folks can use is my goal.