pro10is wrote:
Wow, just stumbled upon this thread today. You've done some very unique mods, very impressive and paradigm changing. Looks like fusioneng now has some serious competition for radical, innovative modifications.
I'm also intrigued, but a bit perplexed, by your bold selection of a 5 HP motor for use on a TI. I recently published a
TI Outboard Motor Application Guide. It never occurred to me to use such a large, heavy, powerful motor for the TI because I felt even selecting a 39 lb (17.7 kg) 3.5HP Mercury was pushing the limit over the smaller, 29lb (13kg) 2.5 HP Honda and Suzuki. Having owned the larger, heavier 3.5 HP Merc I would now not recommend it. I certainly never would have been so bold as to select the 5HP Merc at 57 lbs (26 kg). I would have thought that both the HP and weight would put too much stress on the TI's plastic hull (the TI is rated for only a 400 Watt (0.5 HP) motor).
When unsupported weight is placed on the TI hull aft, a dimple will form on the bottom of the hull about 1/3 from the stern. This may eventually happen even to those who use Hobie Cradles rather than something like PVC pipe supports for a trailer because the weight of the aft end is not well supported, and this is without a heavy motor. With a motor, this might eventually cause hull damage which is why I suggested to everyone using a gas outboard to ensure the motor's weight was relieved when not on the water. Additionally, my 39 lb 3.5 HP Merc caused a considerable list which I found disturbing. At 57 lbs the list must be even more severe. Finally, so much weight aft tends to sink the aft end deeper into the water. If the weight is not balanced up front this may cause fore/aft balance issues.
I'm not saying a 5 HP motor couldn't be used, but I personally would not recommend it. There's a lot of excellent material in this thread to copy, but I hope new TI owners reading this don't copy the use of such a large motor. A 2.5 - 3.5 HP outboard motor is all or more than a TI needs. Even better suited to the TI, the
Torqeedo 403 15 lb electric motor will suffice for most.
Hello Mate!
Glad you like the project. Appreaciated!!
Everyone on the forum has been very inspiring. I learned a lot from reading and looking at all of your builds but I also have a lot of ideas of my own that I have to "put to the test".
So I hope some of my "mods" might interest others.
Thanks for the input about the larger 4-stroke. Very wise words and I am well aware of the stress I will be putting on the TI hull and did take this in consideration when designing the motormount the way I did.
The motormount is securely fastned in the two 75cm (2') long rails on each side of the gudgeon so that spreads the stress a lot. The gudgeon also seems to be rather sturdy. (some areas of the hull is really very weak)
Underneath the rails (inside the hull) two long square tubes acts as very large washers. Everything is mounted with a fair amount of Sikaflex that has a semi-rigid structure so at the end points of the rails/"washers" there is no sharp transition of force/load that otherwise might stress the plastic forming cracks in theese places.
I will off course not transport the TI on the trailer with the 5hp motor mounted. I already have some dimples from the cradles without ever transporting it with the motor mounted. (I will shortly adress this issue, straighten the hull and makes changes on my trailer soon. Pvc tubes seem to be a better sollution.)
The beachweels are mounted ("blocked") togheter with the motormount so when the TI is rolling on the rear beachwheels the hull is not pressed down by the motor at all. All the weight from the motor is transfered directly to the beachwheels. The hull is accually hanging in the 2 long rails when using the beachweels. I will mount a strap to lift and support the hull a little and this will also stabilize the wheels. I am still working on the beachwheel setup/design but I have a pretty good idea how to get it to work right.
The sea conditions must also be taken in consideration when pushing harder on the TI hull with a bigger motor. If its flat all is well but waves and rolling/bouncing gives a lots of extra stress so off course I throttle down a bit. The good thing is... most times when the motor will be used its beacuse of lack of wind.... yup... no wind mostly means calm waters.
So at the moment I am not especially worried about damaging the TI just because of the larger outboard. All seems good.
I have been running for about 5 hours now with 50%-75% trottle (at about 9 knots). No signs of damages on the hull but I will off course continue beeing observant for cracs or deformation. The motormount does not flex ot move around at all so that is a good sign I guess.
As I wrote earlier in the thread (after the first testride), a 2,5-3,5 Hp would be plenty in most cases but I really wanted an engine with external tank, reverse gear and exhaust thru the prop.
Concering the weight, the 10 extra kgs is no issue on the water, the TI can handle the weight if the weight is well dispured as with my setup. The list is accually not bad at all and the hydrofoil wings seem to straighten the TI a bit when using the outboard. The weight is more a "backbraking" problem when lifting the motor on land.
Phew, 10 kilos extra is a lot when logging it over the beach. I will probably make a little cart for the 4-stroke to save my back. I allways attach the motor to the mount when I already got the TI down on the beach or or in the water.
But I fully do agree with you that as a general recomendation a smaller motor is much better choice for most users.
I have seen a lot of examples of motormounts that I would not dare to use even with a smaller motor so good thing you summed it up in the guidelines, very well done!!
I am still messuring the fuel consumption of the motor.It has just been broken in. It seems to use about 1 liter of fuel an hour when going half trottle (~9knots). If I messured this correctly the 12 liter external tank would give me a range of about 110 nautical miles ~200km (125miles) so that would be pretty awsome.
I will have better data in the future once I get the Plotter mounted.
And I am NOT competing with fusioneng!!
(but I appreciate the comment, I am very honoured but do not feel worthy)
That guy has really done amazing stuff with his mods. I will never get the level of experiance and time on the water in the TI as he has.
I just love his double motor setup. How cool is that!!
And his furling jib -wing/spinnaker setup... really awsome!!
I will be looking into a furling jib in the future so I will take a closer look at his build when the time comes.
It sure is fun messing around with theese great kayaks!!
All the best!
/Gustav