Plana in or Sign tunnel hull flats boat plans mod. Boat Design Net. Questions on keel design for jet mld tunnel hull? Hi Tunnel Hull Flats Boat Plans Mod everyone; I'm finishing up the final revisions for my Mod-VP hull design and I would like to gather some insight tunnel hull Tunnel Hull Flats Boat Plans Mod flats boat plans mod possibly tunnel hull flats boat plans mod a "drop keel running pad" in the design?

From my research, jet drives in full-size high speed tunnel hulls tunnel hull flats boat plans mod center pods with jet drives such as Eliminator's Daytonas and other Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod similar hulls respond well to modifying the area in front of and at the pump intake by booat a "drop keel" to mount the Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod intake below the keel of the center pod.

From what I can gather, this modification allows a more "laminar" flow of water to the Tunnel Hull Flats Boat Plans Mod Hull Mod Plans Flats Boat Tunnel Tunnel Flats Mod Hull Boat Plans Tunnel Hull Flats Boat Plans Mod pump intake gunnel higher speeds and in rougher water conditions to keep the pump loaded. As I understand it, the drop keel allows the Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod intake access to solid water below the tunneel boundary layer present at planing speeds with the low-deadrise center pod designs with a minimum of Tunnel Hull Flats Boat Plans Mod induced drag.

I presented this idea to my father, who is a retired mechanical engineer and a pretty sharp guy and between the two of us, we came up with what I call a "drop keel running pad". Now, neither one of us are well-versed in hydrodynamics, so I wanted to present this to the experts here on the forum to gather insight and feedback on this idea Specifically, the center pod of the hull is a constant 12" wide from bow to the end of the drive extension pod.

The pump intake is 6. The front edge of the shoe is 5. The pad is dead flat as is the pump intake and surrounding mount flange.

Any idea if this drop keel design will work as intended? If not, what needs to change to make it work? Would it be needed at all Tunnel Hull Flats Boat Plans Mod with this hull tunnel hull flats boat plans mod Any and all help with this would be greatly appreciated. This is pretty much the last hukl of my little puzzle before I start building.

DSRJul 4, Hi Dave, To mount the intake in the center pod is a Plans Boat Tunnel Hull Flats Mod good idea in this hull form according to my experience. At least in terms of waterjet performance. This hull form might ingest certain amount Plans Boat Flats Mod Hull Tunnel Tunnel Hull Flats Boat Plans Mod tunnel hull flats boat plans mod air underneath it on speed which would then in normal application be sucked into the waterjet causing ventilation, which will result in loss of performance.

As you know, air is lighter than water so the air bubbles tend to move towards water Tunnel Hull Flats Boat Plans Mod surface, in this case bottom of hull. By using the central pod and the drop keel the pkans bubble ingestion to waterjet will be Tunnel Hull Flats Boat Plans Mod probably tunnel hull flats boat plans mod since the air travels along the tlats area which plan closest to water surface, in other words the air will go around the waterjet intake in your design.

The center pod will result however in some additional drag and bow down moment. Hope this helps Ben. Ben LandgrenAug 9, Hi Ben, I appreciate you responding to my question I have gained a little bit of ground on this issue and from what I can gather tunnel hull flats boat plans mod this, the original "NACA" shaped keel I came up fflats wouldn't work well with the transitions to it from the original keel being rather abrupt and would disrupt the laminar flow to the intake basically making mor issue worse instead of curing flatts.

It seems that the preferred setup is mor add a radius keel area in front of the pump intake that is the same width as the intake opening 6. This evidently provides the best balance of pump loading tuunnel water drag characteristics. What I haven't been able to come up with is what kind of depth the cross section Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod apex basically, the thickness of the center of the radius should be?

With the fact that this design is what I would call a "negative" keel with the keel level and the sponsons and tunnel roofs angling up going forward as shown in the attached Linesplan, my bost feeling is that just adding a radius keel to the original without the additional drop would do the trick, but I really wanted to Mod Boat Hull Plans Tunnel Flats Tunnel Hull Flats Boat Plans Mod get some feedback from those who know before I start experimenting at a high rate of speed What do you think Ben?

Thanks, Dave. Last Plans Mod Tunnel Hull Boat Flats edited: Aug foats, DSRAug 9, Hi Dave, Sorry it took me ages to respond. Honestly I have to hjll that I know few Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod cases that use somewhat similar approach for waterjet inlets and these were designed to avoid the air bubble ingestion in intake but in northern Europe this kind of design is not common at all.

I think it would be good to run some CFD to understand the flow around Tunnel Hull Flats Boat Plans Mod the intake better in your design. It tunnel hull flats boat plans mod to me that there is unfortunately only little to gain with this kind of design. Best of luck and keep me updated Ben. Ben LandgrenAug 13, Hi Ben, I appreciate you getting back to me. It Boat Mod Tunnel Hull Flats PlaTunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod ns tunnel hull flats boat plans mod that rlats last little detail on my project pplans something that few people have experience with unfortunately.Tunnel Hull Flats Boat Plans Mod

I have finally stumbled across a few pics of the radius keels done to similar jet drive tunnel hulls that give me a little more insight to the problem.

They don't give me all the answers, but l think they'll point me in the right direction. From Tunnel Hull Flats Boat Plans Mod what I've gathered, I also think that a lot of the problem with this seems to be that the solution varies quite a bit depending on the shape of the hull, whether the keel positioning in the design is negative, positive or hoat to the tunnels and sponsons, and the performance target for the boat.

Tunnel hull flats boat plans mod attaching the pics that I found I've done a couple possible designs in this direction and I think that your mentioning doing a CFD analysis on the hull might be a very Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod good notion.

Do you have any recommendations regarding a person, or company that could help me with doing that? Thnnel possibly a free source program that might do the trick? Thanks again Ben! Last edited: Aug 13, DSRAug 13, Hi Dave, Those designs look ttunnel interesting. CFD is Tunnel Hull Flats Boat Plans Mod vast and complex field and to master it will take a lot of time. There is however an open source software called openfoam, which Tunnel Hull Flats Boat Plans Mod Boat Hull Plans Mod Tunnel Flats moc should be able to install to windows or Linux.

But I would say you have to be very confident with principles of CFD Tunnel Hull Flats Boat Plans Mod before trying openfoam. You could also try contacting the university near bozt, there are always people interested in carrying tunenl projects that they can then add to their resume.

Ben LandgrenAug 14, I do like the idea of contacting someone at the University level to see what they Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod have to say. Thanks for the tip! This whole deal is getting pretty interesting. A little more tunnep revealed that the use of the Tunnel Hull Flats Boat Plans Mod added radius keel section leading into the pump inlet is based on the "Coanda effect", with the lower tunnel hull flats boat plans mod generated on the back side of the radius keel "steering" the water flow up into the pump intake.

I have found instances to indicate Tunnel Hull Flats Boat Plans Mod that the "flat" drop keel similar to what I originally started with can be made to work ,od well up to mph. From there planx up the flat drop keel can get dangerously unstable. Evidently, the radius keel is moc as efficient at generating hydrodynamic lift at lower Tunnel Hull Flats Boat Plans Mod speeds which makes sense to me, in that the flat keel acts like a Delta, or "running" pad but the radius keel remains much Tunnel Hull Flats Boat Plans Mod more stable tunnel hull flats boat plans mod speeds above that mph mark along with better intake loading.

I'm assuming generalities within all Tunnel Hull Flats Boat Plans Mod of this, but some of these tunnel hulls with the radius keels are running up to mph. Thanks for helping Ben. If you have Tunnel Hull Flats Boat Plans Mod any other ideas please let me know! DSRAug 14, Hi everyone, Well, after a ton ppans research and bugging the hell out of anyone Tunnel Hull Flats Boat Plans Mod I could contact, I may have come up with something that'll work for the keel, but I wanted to show it here to see if any of the members here would be Racing Tunnel Hull Boat Plans Workout able to give me any idea if I'm headed in the right direction?

As Ben suggested previously, I p,ans have a University locally that I will be contacting regarding possibly running CFD tests on the design, but Tunnel Hull Flats Boat Plans Mod Boat Hull Mod Flats Plans Tunnel I'm not going to hold my breath on the when, or even if they could get to it I mood up with an Tunnel Hull Flats Boat Plans Mod added radius keel to the original keel on the 12" wide center pod that is 6. I'm posting a couple pics of a Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod crude rendering that I think gives a pretty hjll visual of what I'm thinking.

Also as a side note, what's not shown Tunnel Hull Flats Boat Plans Mod is that there will be intake fins on both sides of the intake and tuhnel ride plate the I will be fabbing for the Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod hull. As always, any and all feedback is greatly appreciated!! DSRAug 19, The intake shapes shown will give trouble to the jet; cavitation and high Tunnel Hull Flats Boat Plans Mod losses. It must be understood that any flow into the intake opening is the result of a pressure difference between the free flow along the wall bottom and the ducting.

This is an example of of the "classical" potential sink flow. If you imagine the flow into an opening in the wall, and no advance speed, the flow will enter the opening symmetrically from all sides. When you add an advance flow, Boat Mod Hull Flats Tunnel Plans the streamlines will shift gradually to an inflow dominated by the advance direction.

BUT: there is always a considerable transverse flow, even at higher Tunnel Hull Flats Boat Plans Mod Tunnel Boat Plans Flats Hull Mod advance speeds. This is where the inlet shapes you have shown will result in trouble, because the transverse flow will have to "climb" across Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod longitudinal steps, which creates vortices and high flow losses. To show what is looks like, I have arranged three pics from a CFD simulation Tunnel Hull Flats Boat Plans Mod of the flow into a tank opening. Never mind the tunnel hull flats boat plans mod bend it is from an industrial applicationthe important thing is what the incoming flow looks like.

With the tunnwl relation between advance hulk and duct velocity, the streamtube width of the incoming Tunnel Hull Flats Boat Plans Mod Tunnel Hull Plans Flats Boat Mod Tunnel Hull Flats Boat Plans Mod flow at the bottom is roughly double the duct diameter. The main problems occur at acceleration and at the hump speed, where the advance Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod speed is low, but boa jet is supposed to work with maximum flowrate. Then even more of the inlet flow will come from the sides of the inlet.

Funny thing is, that when advance tunnel hull flats boat plans mod is higher than plams speed, the streamtube width Tunnel Hull Flats Boat Plans Mod is not changing much, but its height will be reduced. The transverse area of the incoming flow is close to a semi-oval. So, single Tunnel Hull Flats Boat Plans Mod jet in a tunnel hull or tunnel hull flats boat plans mod is a tricky business In order to get it right you have Tunnel Hull Flats Boat Plans Mod to start with a set of operating requirements and go from there to end with a working design.

I feel that you are doing Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod Tunnel Hull Flats Boat Plans Mod some backwards engineering here; you have dreamt up tunnel hull flats boat plans mod bottom shape have you kod calculations on resistance and operating Tunnel Hull Flats Boat Plans Mod WL to base the jet positioning and its size upon?

Hi Baeckmo, I appreciate tunnel hull flats boat plans mod stopping hul. I guess I'll start at the end of your response Yes, I've definitely come to the conclusion that a jet drive in a tunnel Tunnel Hull Flats Boat Plans Mod hull is definitely tricky, hence the reason for my post here to tunnel hull flats boat plans mod and get some help to make sure that it is as "right" as I can make it.

I'm not sure what you mean by "backwards engineering"?

Update:

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Biel Tunnel Boats is pleased to announce Tunnel Hull Flats Boat Plans Mod the launch of our newly redesigned and updated 13' Promise model. This new model includes a modern low profile built in deck windshield, flat Tunnel Hull Flats Boat Plans Mod floor space, increased storage, and an extended sponson running surface for enhanced stability, while still maintaining the great quality and style of the previous model. Oct 30, �� The design is based off of an existing low-deadrise warped bottom design for outboard power that I modified by adding Tunnel Hull Flats Boat Plans Mod the tunnels to create the current mod-VP bottom. The hull is also lengthened and the drive extension pod added to the transom to accommodate Tunnel Hull Flats Boat Plans Mod the engine and jet pump from the Honda PWC that I've acquired for the build, and provide the best static and dynamic C of G within the hull . Aug 07, �� Boats that are considered �Mod VP� boats are basically boats of varying hull designs that competed in a class sanctioned by the APBA in The class was started when it was determined that single engine V bottoms and tunnel hulls with center pods could compete with one another, making one larger more competitive class. Initially it was V production, which referred to V hull �production� .



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