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Thread: 12ft Tunnel Build

  1. #421
    Team Member ice_spy's Avatar
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    I did, I tried many things. The nose dips down and bites in. You then do have to trim up to free the boat of wetted surface. Too less bow down, it drifts and doesn't want to turn. Without 300hp like a F1, you can't dig it right down and expect it to free up so easy. These smaller motors struggle with power. When I had the 50hp on it, you could turn and power out much easier due to the extra torque of the motor. Its a fine balance in these small HP tunnels that I'm still learning. Can talk about it all day in theory, but seat time is everything. Now I want to take my boat out and practise more what we have gone over. Hahaha. Again it's all good to talk about, but the biggest problem I found was other boats wash. It creates extra train tracks so to speak and also pops up up and over making you drift out. I want to go slower to settle thr boat more and turn more precisely slowly.. BUT i also want to test this hull and motor combo agasint the best of them. If I get it set up to take pole.... people are going to start wanting a mold of my boat which I am in the process of talking about getting done as we speak. It could be ( wishful thinking) the next 550 super sports class boat to have .
    The race never stops
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  2. #422
    Team Member ice_spy's Avatar
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    Forge Marine V1 on its way, along with a Mercury Racing TE clever. The prop i was borrowing did not have much blade area, and I believe it was a 19 to 20 pitch the way it performed. It was under 11" diameter also. The higher pitch and the lack of blade area meant there was a lot of slip and not much push exiting the corners. These propellers on their way will perform better, give more top end speed and spool up RPM's faster with a slightly lower pitch. Rumour has it that I will not go any faster, but I love it when I prove them wrong.
    KauE0b.jpg
    The race never stops
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  3. #423
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    Cool, you have a prop coming... Whomever is filming your races for you, "keep them on the payroll" because your video will really be helpful to learn what trim angle and what line through the corners is fastest for your particular boat. Don't follow the v-bottoms thru the corner? Make your own lane that keeps the boat floating.
    Are you using a 12Volt battery for trim? Maybe try three small 6volts in series (18volts) or even a pair of smaller 12Volts for 24V and your trim will react faster. A tap down on the trim when you are reaching your highest speed will make your boat faster (your nose gets high at the end of the straight away).

    Look at the attitude of the fastest two Sport C boats in this video at the start: https://youtu.be/gSTd7khd4zc

    At this point, I'll just be following your thread because you're really getting it dialed in well. Good luck.

  4. #424
    Team Member zul8tr's Avatar
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    The lead tunnels have low AOA which is a good trim for hydro and aero drag control. Too much AOA makes the rear tunnel planes dig and plow plus greater chance of a blow over. Note how they drop for the turn especially #447.
    " Three may keep a secret if two of them are dead" Ben Franklin

    Location: SW Orlando, Fl

  5. #425
    Team Member ice_spy's Avatar
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    This was the 1st time I was able to get some good footage of how the boat performed, although as previously mentioned it looks a lot smoother in the video than what's really going on in the seat, it is definitely a good tuning tool I agree, and hope to get more film every race. I will be sticking to outside pole from now on, to help carry my speed through the corners. I am currently using 12v yes, but the new AU APBA rule amendments have allowed for 24v use for faster trim. This is something I will look into at a later date.
    I was trimming down at top end speeds to make the boat go faster, you are very correct here. Where you noticed the high trim near the finish line , was me just ' showing off ' for the camera, and hoping to catch the eye and pictures from the high quality photographer there on the day 'Quinnos Quickshots' . Everyone loves to see boats out of water, with nothing but the prop touching, however this will be stopped from here on in, as it is not favourable for speed, nor safety. The boat is very predictable at high trim angles, except for sudden gusts of wind, or small waves not seen until its too late. Trim up will only be used to free the boat exiting the corners as I have been.
    Thanks 25XS, I do appreciate your input and any help to achieve better results. I too can't wait to dial the boat in further, improve my cornering and go faster down the straights. I believe the propeller is the last key now. My friend just dropped off 2 of his props that I am going to try and get on the water today to test. An early quicksilver chopper I , and an unknown clever. The more props I can try now the more specs I will know to ask Ron for another propeller. I have had great results from Ron Hills props so far, although the props i purchases before and the one that Ron sent me winning a competition on BRF, were more dialed in for my previous engine, a modified 50hp 3 cyclinder. My friend who does not wish to give me all his race secrets, is keeping a modified ( thinned and re-shaped ?) Ron Hill 4 blade close to his heart, and will not give me the specs or pictures yet... He did say he would let me test it at a race meet one day in the near future, and if it performs on my boat as good as his claims then I will be ordering one of the last ones from Ron. He said he is clicking over 65mph with this prop. I am very keen to see what he has done to it, and show Ron for R&D.
    Here is the 2 props I will be testing today.
    KcR7B1.jpg
    KcRYEF.jpg
    I will report back with the results. My other two props will be here in the next couple of weeks.
    The race never stops

  6. #426
    Team Member ice_spy's Avatar
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    Tested the small clever, it was only 10.5" x 18p. Revs were good, acceleration not bad, however it maxed out quickly at 7k rpm and only 84kph. This prop is also the first prop I have used that induced alot of proposing. Weather it was bow lift or stern lift I could not tell, except I could not trim out of it. It held the corners very good, and held the RPM's too. Unfortunately is way to slow for top end speed. Yet to test the chopper 1 next, I do have a chopper 2 I tested before, however it also lacked too end speed.
    The race never stops

  7. #427
    Administrator Ron Hill's Avatar
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    Default Signature Four Blade Propeller 11.25 X 18 Semi Cleaver for 40-50 Tohatsu

    Might make a good Tohatsu 40 HP prop.
    Attached Images Attached Images
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  8. #428
    Team Member Chad Morgan's Avatar
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    Nice work building this boat mate, looks the goods and was a great read thanks.
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  9. #429
    Team Member Dvdracing's Avatar
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    Default 18hp & 30hp

    Last edited by Dvdracing; 01-07-2021 at 05:42 PM. Reason: Title

  10. #430
    Team Member ice_spy's Avatar
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    fMq0hu.jpg
    fMqlIe.jpg
    fMqap9.jpg
    Some recent photos of Alter Ego @ 7,000rpm + around the race circuit. Lifted the motor approx 20mm higher and have to retest all my props again. The chopper seems to be the best all round prop so far. What works and gives top speed out on the waterways testing, is no comparison to using the prop in race conditions. So while the chopper didnt initially didn't give the best numbers testing , on the race circuit it performed well.
    The race never stops
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