ML Boatworks RSX380 Outrigger! My first FE wood kit build...

[sammyha]

(A member questions his use of the 1/4 round on the bottom. )

The 1/4 round is not only there because it works, but it also makes the forward part of the center section be flatter as well, AND gives us FE guys what we always need more of...BATTERY ROOM.


(Here he's responding to a question about attaching the rear skis with double sided tape to make them adjustable.)

I don't want people adjusting something that once the design is proven doesn't need moving! The JAE doesn't have an adjustable ski? Crapshooters are not adjustable are they? These are set at 3.25 degrees AoA, just like the front sponsons, which is where they need to be.


(Back to explaining the quarter round in greater detail.)

Yeah, its definitely not an afterthought. Here is the thing, and why I like it so much. It allows me more design freedom. I can arch the top deck, giving my designs some character, not just dead flat from front to back. When your top deck is longer than your bottom deck, you get lift, so everyone else has to run their tops flat as can be, removing "airplane" wing lift. Because of the quarter round, I can effectively increase the bottom side distance, giving me the ability to add the nice, flowing top deck lines that I want to the hull. This ability to add height on the center section of the hull ALSO gives us FE guys way more battery room, not only in height, but it also allows the bottom of the hull to be at zero further forward, allowing for longer packs. It truly is a win win. A windshield wiper blade glued to the bottom...that's an afterthought. It gains you nothing other than stability. With the quarter round, you gain usable features! I also closely measure top deck, and bottom deck lengths on all my sport hydros, and this rigger. It's a key thing.

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[sammyha]

(Here is what I quoted earlier in post #101 about shaving the sheeting and basswood strips to follow the laser cut sponson angles.)

I already made some changes to the sponsons based on a friend in the knows recommendations. Added dihedral to the outside sponson, which I had at zero (not sure what I was thinking, every other boat I have designed has dihedral on the outside..guess I thought riggers didnt need it!) and changed the AoA on the turn fin side sponson. Upped it a half a degree over the outside sponson. This will help keep the turn fin from sucking down on the inside sponson due to its extra drag.

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[sammyha]

(Here is where Mike goes in depth, after one member wants to make some changes during his build to Mike's design, and another member asks Mike if he is concerned about too much lift in his design and also questions the sponson ride surface.)

No, I am actually not concerned. I already cross checked the tub curvature against that of the center section GSX310 sport hydro...same overall curve, Then I checked the sponson top deck curvature vs. the GSX310, this rigger has a good deal less curvature. So, overall, based on previous experiences, this one is more tame. You have to use the quarter round on the bottom tho! That is a key feature, allowing me to design in this much curvature into these hulls.

Remember, this quarter round idea started with Don Ferrette trying to go 100 mph with an 1/8th scale FE hydro. He accomplished that. Scale hulls like the 108 hull he used to set that record, have a LOT of top deck curve, so this quarter round proved effective. Now, you might say, yeah, a big battery heavy scale...Well Scott Liddycoat did the exact same thing the following record trials when he set his record (90+ mph...cant remember) with a nitro setup..much lighter hull...same quarter round idea, with some additional testing proving how to adjust its effectiveness!

I also measured the top deck tub length vs. the lower pan tub length, and the numbers work out where the top deck should pull the hull towards the water, not away. The cowling may have some lift effect, but less than any of my sport hydro cowls due to its overall height, and only 2" width. So overall, I am have thought this out very well.

Next, ride pad width is 1-5/8". The GSX310 is a touch more, and the GP310v2 is 2" at the trailing edge, and almost 3" before the air relief. The sponson deck, and center section on the GP310 is also much more radical than the GSX310, or this rigger.

Now, The JAE 21 is a 1-1/4" sponson width on the ride surface. Yes, that is slightly less than mine..what 3/8"? But, due to that narrow width and lack of non trip, you have to run the CoG way back, or in rough water, the boat tanks. (See a Gas JAE with the original sponsons..disaster) With my more traditional non trip style sponson, you can run your CoG more like a sport hydro, and keep the bow down where it needs to be, and have the advantage of non trips in rough water, which to me..is a huge goal in this project. The huge amount of space in the tub to shift the battery forward or back, gives us a LOT of adjustability.

Next, we have the inside sponson edge upper air trap rails. These, which you have seen me use on tunnels, and sport hydros just the same, have been incorporated into my design of this rigger. This helps air flow come across the sponson deck in a turn, forcing the air to stay on the deck, in turn holding down the inside sponson, instead of letting it come up, being loose, or potentially blowing off in the turn.

Finally, I will discuss the sponson shear outside edge and the front leading edge. You will notice, I have used a double sponson sheer, creating a 1/4" thick shear....same as all my GSX series hulls. You may have noticed this same rounded outside edge on another few hulls, mainly, full size unlimited hydros. Why do I use these? Simple, the rounded edge, just like the rounded nosing block on my sport hydros, helps stop snap blow offs. These slow down the air flow as it enters the sponsons front, or outside edge, effectively keeping the hull stable. Why? The air hits this edge, slows down, and if the boat does get out of shape due to a wave, or wind, it slows down how fast the airflow change from top deck down force, the underside up force. This effectively gives you more time to react, letting off the throttle, settling the hull back down. If you take a look at some other boats out there, and how they blow off vs. a great Video Jesse J did a few years back of the GP335 (the round, blunt nosing block demonstration), you will see how much slower my designs are to "take flight", giving you a time advantage to settle the boat down.

So, as you can see, a LOT goes into these designs. Function is a must, but I have to have some form...or I quit! haha. Simple history tells us, yes...there is a lot of curvature going on, you are right..but the other things I do to the hull counteract that, which is why it is imperative once the design is done, and tested, and works, not to remove things like the quarter round. It is there so all these ideas work in harmony.

I don't usually discuss these ideas publicly, but I figured it was time to share why I do what I do!

But at the end of the day, it may not work. If it doesn't, I already have a backup idea ready, and can design those changes in less than a day. Will I need them..I really don't think so, but if so, they will be done, and I will test it again, and again until I am happy with the results!

I Hope this clarified everything? If not, let me know, and I will do better to answer.

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[sammyha]

Enjoy some great insight into the fertile mind of one of our members!

And maybe get a better understanding of the design and engineering it takes for these riggers to go so crazy fast and yet handle so well.

After I absorbed all this as best I could, I was convinced beyond a doubt I wanted to buy this rigger...

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[sammyha]

Another huge step in the build completed!

Those who have built a wooden boat will understand this video...

https://youtu.be/ZQNfyLnNlUU

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[sammyha]

Making the removable motor mount I sketched earlier in post #88. Had to make some changes(go figure). I'll just roll some pictures...

Setting the angle with a digital pitch gauge zeroed off the counter...

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[sammyha]

Here's one of the changes. The stuffing tube mount is larger than I figured...

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[sammyha]

All the pieces mocked up...

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[sammyha]

Epoxied together and the blind nuts are in...

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[sammyha]

Milled 3/16" wide slots that are .150 deep. The spruce stringers are .200 thick, so the carbon fiber mounts are only raised .050 off the bottom. The tops of the holes in the carbon fiber mount are just below top of the spruce stringers. Should really hold the mounts when filled with epoxy and regain the strength lost from milling the slots...

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[sammyha]

Here's another change from my original sketch. Had to split the front end block to fit around the sponson boom support.

With this design I will have access to the screws from the top for easy motor removal. The stringers will come out with carbon fiber mount and the motor.

Of course the stuffing tube mount will stay in the boat...


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[bhorowitz]

Very nice.

[boatsrnew2me]

just curious ,why the barb on the stuffing tube mount?

[sammyha]

Very nice.

Thank you

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[sammyha]

just curious ,why the barb on the stuffing tube mount?

For oiling the flex shaft. I'm not a fan of it but liked the mount

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