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| Ideas in designing TBOAT MOD VP Bottom?? http://ww.w.hpbc.ca/viewtopic.php?f=20&t=4723 |
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| Author: | Hounddog [ February 4th, 2025, 1:28 pm ] |
| Post subject: | Ideas in designing TBOAT MOD VP Bottom?? |
The early efforts from 30 years ago were achieved by using the lower portion of a V hull that had a pad as the center pod to.make a Mod VP out of a 13 foot tunnel. Easy process but it really didn’t perform as well as expected. In later years the the larger 18 to 20 foot Mod VP’s had more of a square or rectangle shaped center pod. The pod wasn’t as big and didn’t extend as far in the tunnel. Those hulls don’t balance on the center pod and rock side to side with the sponsons touching the water. The center pod and sponsons are all in contact at the same time. There is more setback on these hulls as well so as the boat lifts the center pod looses contact with the water and the sponsons stay in contact. That keeps air pressure trapped under the hull and it no longer spills out the sides. The hull is far more efficient. Oddly enough the Stoker hull was a early simple design. That works! Their Mod VP just had rectangular shaped tunnels formed into the hull with small trim tabs where the tunnels exit the transom. The center pod was square shaped. https://www.wavetowave.com/home/2018/8/ ... ld-buy-one So the questions are do you want a round shape bow or a pickle fork style? What type of center pod and what hull to use? Just to get the thought process started. Here is a video of an AE21 Hydrostream bottom. There was a lot of creative thinking in the design of that bottom. Many say it was over done, too extreme and would work better if simpler. https://www.youtube.com/watch?v=LgROfH5rQAA&t=23s |
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| Author: | Hounddog [ February 5th, 2025, 11:49 am ] |
| Post subject: | Re: Ideas in designing TBOAT MOD VP Bottom?? |
I was asked if the STV Mini on marketplace was an STV or a Mod VP Speedcat? https://www.facebook.com/marketplace/it ... d30e12d6d7 This is the small STV https://boats-from-usa.com/not-specifie ... stv-181546 Speedcat without the Mod VP option https://www.youtube.com/watch?v=1zgL4y3-wT8 |
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| Author: | Hounddog [ February 5th, 2025, 7:22 pm ] |
| Post subject: | Re: Ideas in designing TBOAT MOD VP Bottom?? |
Here is an interesting boat. Likely an original 45SS raceboat. 45SS class was prior to SST 45. These boats had no safety cells. When Sport C class started many of these boats were converted to a Sport C. The original Sport C boats were smaller. In later years the Sport C boats were different sizes. This boat is a production fiberglass not wood boat The boat already has a small center pod. Too small a pod to be called a Mod VP , but it could be enlarged to become a Mod VP. Mirage did offer a center pod Mod VP option on their 14 footer cheetah model. Certainly be a nice T750 Mod VP .....could be too small for a T850 Mod VP. https://www.youtube.com/watch?v=StHLlTpT8Fo |
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| Author: | David [ February 5th, 2025, 7:41 pm ] |
| Post subject: | Re: Ideas in designing TBOAT MOD VP Bottom?? |
If someone wanted to design a T boat sized MVP, it would be good to start with Jim Russel's software, or even consulting him. https://www.aeromarineresearch.com/index.html I have never owned one, but the 19 foot pickle fork STV seems like as good as it gets for that size of boat. But scaling down to T boat size changes a lot. There will be more weight for the size of the boat in a T boat, and relatively less power. Mr Russel's software should be able to calculate the effects. Of course what is the purpose of the center sponson? it will make the boat slower than a true tunnel, but it would likely be faster than a pad V hull. The center sponson has advantages for a recreational boat, but I'm not sure there is a recreational market for 13' MVP hulls. So if race only, why not just go regular tunnel? |
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| Author: | Hounddog [ February 5th, 2025, 10:30 pm ] |
| Post subject: | Re: Ideas in designing TBOAT MOD VP Bottom?? |
David wrote: Of course what is the purpose of the center sponson? it will make the boat slower than a true tunnel, but it would likely be faster than a pad V hull. The center sponson has advantages for a recreational boat, but I'm not sure there is a recreational market for 13' MVP hulls. So if race only, why not just go regular tunnel? David, thank you for your post. The T Boat group has far more recreational users than racers. They enjoy their boats . Many have expressed the need for a better designed T Boat. Mike Hooper years ago was looking into doing a scan of his critchfield and putting it into a cad program so he could see what different design changes could be done to improve and modernize the boat. He may get back looking at that again. The letter “T” in the name means V hull. A tunnel is an “S”. So a regular tunnel would be a totally different class. We want to keep the class V hull. Mod VP was an improvement in V hull design. When Mod VP became its own class Allison raced a V hull not a Mod VP. So we would be entering the same beginning stages . If a Mod VP does appear at the races the class members will decide if they want it to race. In the class past history the group has allowed the Smaller Mod VP’s to race and even one S750 Tunnel. There was a larger one that they allowed to race for 1 day and then disallowed it the second day, not because it was too fast, but, because it made the waves extremely rough in the corners and the other boats couldn’t turn. The T race group wants the class to grow. I have promoted a separate small tunnel class for years on this site. I get some interest, but it hasn’t happened...yet! . Maybe seeing a Mod VP race will help promote a tunnel class. “Would there be a commercial market for a 13 foot Mod VP??” The last High Performance 13 footer was the VooDoo. You owned one. Think back....at that time ...you’re younger...different life style...different interests. I think the younger people and parents with teenagers would take notice of a modern 13 foot Mod VP boat...especially if they saw it at the boat show and at the boat races. If the same old boats still get interest at the races....something new should draw more interest. BUT, I could be wrong! |
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| Author: | Hounddog [ February 5th, 2025, 10:43 pm ] |
| Post subject: | Re: Ideas in designing TBOAT MOD VP Bottom?? |
I was asking if anyone knew of a 13 footer with a similar shape to a stoker. It could be a good platform for a Mod VP. Tim sent me this one. https://www.youtube.com/watch?v=r8UozSNZCmI |
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| Author: | Hounddog [ February 6th, 2025, 11:22 am ] |
| Post subject: | Re: Ideas in designing TBOAT MOD VP Bottom?? |
Most people don’t realize that the only difference between the raceboat version and the recreational version of many of these Mod VP’s is the deck. The hull can be the same on both. The original Mod VP boats were open style recreational production boats. The change in the race rules for safety cells made manufacturers change the raceboats. Production recreational boats improve thru boat racing. The small 45SS mirage would have been a low 70 mph boat on the racecourse and an 80 mph boat in a kilo run. The Canadian engine spec rules for that OMC in T750 allows you to race that motor as you see it with two changes...you run the stock gearcase with or without a nose cone and you run the stock 15 inch midsection. You can run that powerhead, base plate and tuner. With the center pod and gearcase it still should be a 70 mph boat on the lake. With SST 60 power? Has to be over 80 mph. This mirage is a Brad Collins designed boat. Brad improved his boats continuously with small but noticeable changes. Look at the bottom of this mirage. https://www.facebook.com/groups/351515736473372/ Putting those changes and adding a similar center pod in the small tunnel is a weekend project. |
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| Author: | Hounddog [ February 6th, 2025, 6:13 pm ] |
| Post subject: | Re: Ideas in designing TBOAT MOD VP Bottom?? |
Simple modification to the critchfield that could improve the boat. If you look at a critchfield hull from the front you will notice two rails several inches apart running the length of the boat. Between the rails is a bump protruding outward. If you reversed that bump so in extends inward inside the boat you have created a trough to force air down the sides. Make the outside lip larger to hold the air in. That mod should reduce chine walk and make the boat run flatter. In my opinion. |
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| Author: | David [ February 7th, 2025, 4:28 pm ] |
| Post subject: | Re: Ideas in designing TBOAT MOD VP Bottom?? |
You remember my old Voo Doo. That was a fun little boat. The Voo Doo was less of a thrill when I got my SS2000, and I wanted a better water ski boat, so the Voo Doo was replaced with a 16' Baja. I still like to watch T boat races at Gravenhurst. And I had fun helping the Spaeth's make two VooDoos last winter. The trouble with that size of boat, is that it's expensive to make. Sure everything is expensive now, but the cost to build a 13' boat seems crazy for those of us with old days pricing in our heads. For a recreational boat without a lot of power, I think a V bottom is superior to a tunnel or MVP bottom. I had a Hydrostream Virage, and it did not like weight, ie passengers. It ran well enough with just me in it. By contrast, you could put people in my brother's Charger DL and it still performed. I think a 13 foot Voodoo with a new Merc 60 4 stroke would run better with 2 people than a 13 foot MVP boat. So for a guy at a cottage like me, the V bottom would be better. I found this bit from Ron Hill Boat Racing Facts, about the origins of MVP racing" https://www.boatracingfacts.com/forums/ ... /t-43.html "Dick and I wrote the rules, for MOD VP..... SIMPLE: 1. Production parts in WARRANTEEABLE CONDITION.... 2. Nose cones 3. V-6 PRODUCTION PARTS ONLY 4. MOD VP bottom, center pod to be equal or lower than the outside runners.. we both knw outboard blew over...easily, mod vp bottom seemed to be the best of both worlds... This would become Divison IV at Parker... Then, someone built and tunnel boat and put a pod in it...It looked like a tunnel boat...but was much slower...but it was faster than our Sleek Crafts, our Laveies, our Hydrostreams..." Thinking about 'Mod T', a couple of things stand out. First, the boats designed for the original rules would have had the center pad even or lower than the outer sponsons. I have no idea if that is the best way to do it if you were just designing a boat. Second, the tunnel boats with pad added were faster than the V bottom designs with sponsons added. I think this shows the direction to take with a new hull It would be a lot of fun to consult with Mr Russel and build a killer 13 foot MVP hull. But it would have to be a labour of love, vs a successful business venture. I can recommend Mr Russel's books on tunnel boat and propeller design |
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| Author: | Hounddog [ February 7th, 2025, 9:31 pm ] |
| Post subject: | Re: Ideas in designing TBOAT MOD VP Bottom?? |
Another good post, thank you David. You have made several excellent observations and the Ron Hill thread was a very interesting read. “Sure everything is expensive now, but the cost to build a 13' boat seems crazy for those of us with old days pricing in our heads.” Agree 100%....but that’s the way things are and new prices are not going to decrease. It’s one reason why the T Boat group is mostly DIY types and most work on restoring older used boats. It’s also the reason I show the small tunnel as a project to make into a mod vp. More cost effective. “For a recreational boat without a lot of power, I think a V bottom is superior to a tunnel or MVP bottom. So for a guy at a cottage like me, the V bottom would be better.” At this point in time, I agree. But we haven’t seen the new Mod VP version yet. It could be a total surprise. I think it will. A better feature of the Mod VP is it will be smoother and easier to drive than the V hull with the same horsepower. “SOME” people just can’t drive a V bottom performance boat...but they can a tunnel.....those people will like the tunnel. “4. MOD VP bottom, center pod to be equal or lower than the outside runners Then, someone built and tunnel boat and put a pod in it...It looked like a tunnel boat. Thinking about 'Mod T', a couple of things stand out. First, the boats designed for the original rules would have had the center pad even or lower than the outer sponsons. I think this shows the direction to take with a new hull” Agree!.....that’s the direction I am suggesting. The later tunnel Mod VP center pods are much better....by the rules the center pod can be equal to the sponsons, there is no mention in the rules as to the width or length of the center pod...so the center pod is narrow likely about 8 inches wide at the last section. The pod doesn’t go the complete length of the hull likely 2 feet shorter. The pod doesn’t need to be the same depth as the sponsons it’s complete length. Now look at the picture of the larger mirage mod vp. You can see the narrow pad and the step in the pod at the rear. The pods doesn’t touch the water in that rear section. https://www.facebook.com/groups/351515736473372/ Result is the boat is like a true tunnel and the pod actually makes the boat a very good recreational boat. “It would be a lot of fun to consult with Mr Russel and build a killer 13 foot MVP hull. But it would have to be a labour of love, vs a successful business venture.I can recommend Mr Russel's books on tunnel boat and propeller design” Certainly a good idea. |
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