Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 25

Thread: Sport C tunnel boat

  1. #11
    ExperiMental BYOBoat's Avatar
    Join Date
    Jan 2014
    Location
    Warrenton, OR
    Posts
    34
    Post Thanks / Like

    Default

    Since the expert's here, I have another question. Any ideas on how long to keep the sponsons straight, compared to what TBDP predicts for wetted length? Right now I've taken my lowest corner exit speed, added a little to that wet length, and then started the bow curve. I suspect longer sponsons will help in rougher conditions. I'm also trying to keep from dragging too much over the water when the boat comes out of the corner with little positive trim. I'm sure handling is affected but prop height and setup should keep it manageable.
    mini tunnel boats for sport, now an experimental Sport C added to the fleet.

  2. #12
    AeroMarine Research Jimboat's Avatar
    Join Date
    Nov 2004
    Location
    Canada
    Posts
    44
    Post Thanks / Like

    Default

    Quote Originally Posted by BYOBoat View Post
    Since the expert's here, I have another question. Any ideas on how long to keep the sponsons straight, compared to what TBDP predicts for wetted length? Right now I've taken my lowest corner exit speed, added a little to that wet length, and then started the bow curve. I suspect longer sponsons will help in rougher conditions. I'm also trying to keep from dragging too much over the water when the boat comes out of the corner with little positive trim. I'm sure handling is affected but prop height and setup should keep it manageable.
    BYOBoat - it sounds like you've got a pretty good handle on using TBDP to optimize your performance. Good job! I think you're on the right track with the ideas you're following in your explanations above. I presume that when you say "straight" sponsons, you mean the "flat" aftward section, prior to where the sponson bottoms must curve up to meet tunnel roof and deck height? TBDP will tell you what the sponson wetted lengths will be throughout the velocity range. Water conditions can wet more area inadvertently, however. Longer sponsons will certainly be more forgiving in rougher water, but are exposed to unwanted wetted area (drag) in the lighter water. It's a compromise based on what you think your most frequent operating conditions are likely to be. If you utilize longer "flat" sponson lengths, another alternative is to increase deadrise further forward.

    If you want to discuss, just give me a call anytime.

  3. #13
    ExperiMental BYOBoat's Avatar
    Join Date
    Jan 2014
    Location
    Warrenton, OR
    Posts
    34
    Post Thanks / Like

    Default

    TBDP is an awesome tool. So far it's predictions and actual boat response have been really similar. The program is so much easier/quieter/cheaper than grinding and sanding!

    The boat runs much better now. It isn't stuck to the water at corner exits any more. Top speed is a little shy, but corners and accelerations are better.

    Currently my center pod (it's sticks down about 1" from tunnel roof) matches the tunnel angle inc of 1deg. Tunnel height is 6". I'm wondering if that is contributing to my current porpoise challenges from about 39-48mph? I don't really want to cut it down and expose more of the gearcase to spray. My prop height is good for straight and corner rpm, I still have cooling, and handling is just enough to prevent spinouts. The program shows porpoise should reduce consistently from 33mph on. It's difficult to tell but I may also have a very slight hook in the aft end of the pod. I forgot the GoPro so I didn't get footage of the transom today. I assume the pod is well above the water but may be seeing a lot of spray?


    Sent from my iPhone using Tapatalk
    mini tunnel boats for sport, now an experimental Sport C added to the fleet.
    Likes Jimboat liked this post

  4. #14
    ExperiMental BYOBoat's Avatar
    Join Date
    Jan 2014
    Location
    Warrenton, OR
    Posts
    34
    Post Thanks / Like

    Default

    Another question, does anyone know how much HP a good Sport C motor really makes? Or even better a typical OEM motor at racing rpm's, and full HP when race prepared?
    mini tunnel boats for sport, now an experimental Sport C added to the fleet.

  5. #15
    ExperiMental BYOBoat's Avatar
    Join Date
    Jan 2014
    Location
    Warrenton, OR
    Posts
    34
    Post Thanks / Like

    Default

    Fixed a little sag in the tunnel aft end from initial build issues. Also adjusted the center pod bottom to be parallel with keel line instead of tunnel 1* angle. Boat is running better. Still have some porpoise at 40-47mph range. Moving weight aft calmed it down but still an issue. Down wind is worse than up. I don't have access to a prop with more bow lift at the moment, but I'm gonna try changing setback next day it's not raining and blowing.


    Sent from my iPhone using Tapatalk
    mini tunnel boats for sport, now an experimental Sport C added to the fleet.

  6. #16
    Team Member MN1's Avatar
    Join Date
    Nov 2004
    Location
    Bourbonnais, IL
    Posts
    489
    Post Thanks / Like

    Default

    Here's a Sport C boat I designed and built. It was a lot of fun. I learned a lot building and modifying it.
    I used the information from this boat to build a SST - 60 boat which won the 2012 OPC National Championships and set the 1/4 speed record for the class.
    I used the TBDP for both boats.
    Mark N
    Attachment 61863 Name:  FB_IMG_1493606424413.jpg
Views: 162
Size:  48.5 KB
    Attached Images Attached Images   
    Thanks Jimboat thanked for this post
    Likes Jimboat liked this post

  7. #17
    Team Member DeanFHobart's Avatar
    Join Date
    Feb 2005
    Location
    Lake Sammamish, Washington and Indio, California
    Posts
    337
    Post Thanks / Like

    Default

    Quote Originally Posted by MN1 View Post
    Here's a Sport C boat I designed and built. It was a lot of fun. I learned a lot building and modifying it.
    I used the information from this boat to build a SST - 60 boat which won the 2012 OPC National Championships and set the 1/4 speed record for the class.
    I used the TBDP for both boats. Mark N
    Really cool and great stuff. For some of not in the know could you explain in layman terms how the TBDT program works. What does TBDT stand for and what are the variables?

    Thank you very much.
    Dean Hobart

  8. #18
    Team Member zul8tr's Avatar
    Join Date
    Oct 2008
    Location
    Orlando, Fla
    Posts
    684
    Post Thanks / Like

    Default

    Jim Russell's TBDP Tunnel Boat Design Program explained here, left click on the detail pages on the right for further insight:

    http://www.aeromarineresearch.com/tbdp6.html

    Also lots of good articles here as well
    “Extraordinary claims require extraordinary evidence” Carl Sagan

    Location: SW Orlando, Fl
    Thanks Jimboat thanked for this post
    Likes Jimboat liked this post

  9. #19
    ExperiMental BYOBoat's Avatar
    Join Date
    Jan 2014
    Location
    Warrenton, OR
    Posts
    34
    Post Thanks / Like

    Default

    I think I've seen pictures of the red Sport C. It had the tunnel extended forward later on? How did you pick your CG? I'm not showing enough CG affect in TBDP to pick a location, hence the cockpit cutting and moving aft once already.

    Adding 10lbs to my boat's stern reduced porpoising, but my CG is already way aft. Using a GoPro I could see water separating a few inches in from the chine on the sponson bottoms like it needed a lift strake added. I changed the bottom to the blue line below, and besides gaining a little speed most of the porpoise went away.

    I see a lot of Tomcats and GrandPrixs with mild to aggressive lift strakes added by owners. Aeromarine articles suggest lift strakes tend to reduce top speed. The F1s and RJ boats don't seem to have any.



    Sent from my iPhone using Tapatalk
    mini tunnel boats for sport, now an experimental Sport C added to the fleet.
    Likes Jimboat liked this post

  10. #20
    Team Member
    Join Date
    Dec 2004
    Location
    Toronto, Canada
    Posts
    227
    Post Thanks / Like

    Default

    Nice to see a picture of Sammy Miller's #7 SST 60. Sam passed away and we miss him.

    We started in Sport C in 1992 when the class first appeared in Ontario Canada. We were totally all new to the class and there was no one that had Tohatsu engine knowledge, boat set up or prop info. We only had a APBA rule book and the class record sheets. We purchased a Mirage TOM CAT 2 from Wayne Worthy [his sons]
    Here is what we did have:
    - a 14 year old boy who could flat out drive a boat on the edge
    - a boat builder Rob Scythes who was a superior craftsman
    - a prop guy named John Beer who was an artist
    - a dad who had been racing since 1964
    Circle racing is about Lap ET time not straight line speed. Acceleration, cornering speed and especially exit speed out of the turn are MOST important.
    We never had the opportunity to have a Mike W. motor or any professional engine build.
    We focused on the boat set up and the prop selection.
    You drive a Sport C WOT all the time. Never back off because it takes too long for the boat to get back up to speed. No need to trim in on the turns either.
    Properly set up the boat will spill enough air on entry into the turn. Just trust the boat.
    Many add 4 to 6 inches of set back to carry the nose. Problem is the nose flies up on entering the turn. We never added set back.
    You DRIVE the boat into the turn and thru the turn.
    Here is what we did to the boat:
    - we straighten and corrected all the flaws in the hull. There were many!
    - we reworked the tunnel with a wedge panel to provide more lift to the stern Big improvement!
    - we added a series of 3 steps on the sponsons to help it thru the turns. Boat was QUICKER thru the turn.
    We tested again and again making small changes in the boat set up and reworked MANY props. We took a year.
    We ended up with a very competitive boat that was easy and predicable to drive.
    Thanks Ron Hill thanked for this post
    Likes Jimboat, Ron Hill liked this post

Page 2 of 3 FirstFirst 123 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. 89 stoker sport tunnel.$1500.00
    By 84 stoker sport in forum Boats Up to 25'
    Replies: 1
    Last Post: 06-23-2013, 07:24 PM
  2. wanted sport c tunnel
    By luisoque in forum Boats Up to 25'
    Replies: 1
    Last Post: 07-31-2012, 01:14 PM
  3. 88 stoker sport tunnel
    By d.jones in forum Motors and Powerheads
    Replies: 2
    Last Post: 03-04-2010, 05:42 AM
  4. 2001 Stoker Sport Tunnel
    By whiteworks in forum Motors and Powerheads
    Replies: 0
    Last Post: 03-18-2008, 06:41 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •