Hornet F1 Upgrades - "Build"

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Hi All;
Like a few people out there, I purchased an F1 Hornet as an entry boat for my first tunnel hull. I thought I could get a season out of it before doing many mods, but I learned quickly from others shared experiences that this was not going to happen. This boat needs some serious upgrades. So here is what I have done to mine to make it a reliable runner which will give me reliable running. Competitive? Well, we will have to wait and see.
I have included photos and explanation of my thought processes as we go along. I will add posts here until the whole story is finished.
Feel free to send me questions you may have.

Enjoy!

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Here it is as it arrives. I have included more detailed photos of mine out of the box.

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Here are the radio box, receiver, motor, ESC, servo, and outboard leg with all included parts. This motor is good for N class at best, more like a micro boat. The prop shaft is 1/8". The leg is some sort of plastic/poly with two bearings but no "keeper", so if you break the flex shaft you lose your prop and shaft.

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More Pics

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Original Motor Mount

Here is the original mount for the outboard leg.

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The electric motor mount

This is the original motor mount for the electric motor. It does have 25 mm mounting bolt spacing. I will be reusing this for my build.

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The original cowl

Here is the original cowl. I really want to keep a scale look so I will be reusing this for sure. I hate those awful-looking outboards with motors and wires etc sticking out everywhere. It ruins the look of the boat in my opinion.

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Here is the unmodified hull.

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This is the original leg. Pay attention to the top "plate". I will need that for mounting the cowl, so you can see where I glued the two halves together to hold them for the next step. I used "Seals-All" which will allow me to get the two halves apart again later.

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Here you can see how I cut the top "plate" off the original leg. First I made a rough cut with a basic hacksaw so I had easy access to the inside corner just at the bottom of the plate. Then I used a dremel tool to cut the inside edge and get the top plate off the leg.

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Here is the leg I will be using. Yep, you guessed it, a K&B 3.5 I got on eBay. You can see how I used the plate off the original leg as a mount for the cowl. I drilled the existing K&B threaded holes out to make clearance for the screws used from the original leg to hold the motor adapter/mount on. I figure if I go with a metal adapter later (if the poly one wears out or whatever) I can use bolts rather than the K&B cap screw design.

In hindsight, I recommend you just buy a new complete outboard leg from Mecoa. It'd only be 10-20 dollars more and you'd have a brand new everything (flex, prop shaft, etc).

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The bottom of the cowl has to be cut a bit wider to allow for the wider K&B body. You can see the cowl with one half cut for this. Then the drive shaft hole and the 25mm motor mounting screws have to be moved back exactly 1/2 the width of the original drive shaft hole in the original motor mount/adapter. This is because the K&B leg has it's flex shaft coming up that distance further back than the original leg does.
Again, the dremel with a rotary rasp worked well on the main hole, and the two 25mm apart holes I measured the distance back and re-drilled.

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Here you can see how I just flipped the plate over which I cut off the original leg so that a nice flat surface was mated to the top of the K&B leg. Then, drill the existing motor mount holes in the poly plate out so that the legs of the motor mount sit down and mate right against the aluminum K&B surface rather than sitting up on the poly plate. This does two things; keeps the motor down that little bit further so it fits inside the cowl for height, and, makes the mount more solidly held in place since it has "webs" on the mount's legs which sit flush against the poly plate exactly when the bottom of the same legs mate against the aluminum K&B leg.
Then I mounted the motor to the adapter, and he adapter to the leg, using all the original screws.
Note that the brass flex adapter is not the one I will be using. I left it on to test the height when it was all mounted. It was perfect.

Oh yes, the motor I will be using is the one which came in my Surge Crusher. It is a 3660, 1900kv brushless. I will also start with the prop from the surge crusher and see how that goes.

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These pics show how I used the original cooling pickup on the K&B leg. I opened up the aluminum just above where the original tubing exits the side of the leg, in order that the cooling tubing can exit the leg straight up inside the cowl when mounted. The tubing will run through the cowl into the boat. through the ESC, and back into the cowl, through the motor jacket, and then I drilled an exit hole in the top rear of the RH cowl half as a telltale to indicate good cooling flow when I am running the boat.

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All my research told me I should ditch the teflon stuffing tube in the leg and use brass (durability and better cooling of the flex shaft/tubing so less chance of over-heated spots resulting in shaft and/or tube failure). A 1/4" brass tube is the correct size. You will have to bend the brass tubing. It is harder than say copper so you can kink it or flatten a surface if you don't do it correctly.You will have to anneal it to do this. I used a hotplate out in my garage rather than my wife's kitchen stove (haha). I didn't have a tube bender tool or anything, so I used a tomato juice can. It is the correct size to give you the radius you need, and it also has grooves which would help avoid flat spotting the inside surface of the tubing bend. Several heating and bending sequences later, I had a reasonable section of this 12" piece of tubing to fit the leg okay.

Oh yes, you can see how I used a spare flex shaft from one of my other boats inside the brass tubing to help prevent kinks. It worked really well, and did not damage the flex any.

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Strengthening the hull. Although I thought this hull looked pretty good, (thin and light but lots of angled shape at the transom), I thought I'd do some strengthening anyway.
First the bow; I used polyurethane based expanding foam insulation (Great Stuff), and did not do it all at once. I put two drink straws together with the dispensing tube and taped the joints so I could reach all the way to the front of the two sponsons and also the nose. I the first laying in, I did the front of the sponsons back to the about the nose and I did a baseball sized blob in the nose. My advice received told me not to put in too much at one time in order for it to expand fully without stressing the hull. In a worst case you can crack the hull or break a seam open. I waited a day then with a shorter straw I did the second and final batch. This really toughened up the thin hull at the front of the boat. During races the pickle forks hit the buoys or heaven forbid, another boat,and I wanted to strengthen these areas up. This type of foam did the trick very well. The foam is not only flotation but hardens up like glue nearly and is a closed cell foam so it won't retain water.
The other area to strengthen is the transom. I laid in some strips of fiberglass cloth around the bottom below the wood mounting piece and towards the stern so they add some strength there, and I added some pieces near the top of each side of the board which also go around the corner for strength. Finally I laid in pieces to strengthen each side of the radio box area down onto the top of the inside of each sponson so that should add strength too. All these strips overlapped a bit. I don't think transom strength will be an issue now, if it ever was anyway.

One other thing to redo at this stage is the battery board. For some reason it comes built off centre. I don't know why but it just does. So I made a new foundation piece and used fiberglass resin to mount it to the bottom of the hull, then later I re-glued the board back in, in the centre.

The other thing to fix here was the position of the battery mount. It comes off centre on purpose by design, but I don;t know why. I made a new foundation piece and bonded it in with resin while doing the fiberglass, then later I glues d the board back in, in the centre of the boat.

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