1/8 scale transom design

[Chris Lina]

I've got a couple of questions for the scale unlimited experts. I'm planning on building a scratch built 1/8 scale cmb powered Peters & May U-11. I have already scratch built the U-8 LLumar from Newton plans so I am not a total novice. I am an exact scale freak so I want to duplicate the full size boat as much as possible. I have been very impressed with the Joe Moceri, Doug Shepard, and Mike Luszcz hulls.

One area that seems to be neglected in all available hulls is the rear swimdeck design of the modern hydroplanes mainly Dale Van Weiringen designed hulls.To me none of the available hulls; RC boat, ML Boatworks, or even Roger Newtons plans of the T-6 have the rear swimdeck inset designed deep enough according to my documentation. The area in question is the distance from the ends of the rear ride pads to the inset transom.

My second question is; On the full size hydros does the left rear ride pad extend back a touch further than the right rear ride pad? In alot of pictures it appears that it does, but I can"t be sure, and I realize on the model this would be reversed.

On this model I am going to scratch build a scale rudder bracket and rudder using tubular stainless steel silver soldered together. What I would really like to do is purchase one of Mike Luszcz T-6 kits and modify it accordingly.

Your thoughts please, Thank You.

Chris Lina

 

[Samuel Hagan JR]

Me and Harvey (Harvnox) had the same conversation about one rear ski sticking out farther then the other. I know in the bud T-6 from looking at pictures on does stick out farther.

 

[Hydro Junkie]

I can say the same thing about the Oberto's rear shoes, one is cut back and recessed but don't remember which one. I've got most of the dimensions for the Oberto at home from measuring the boat so I'll see what I can dig up either tonight or tomorrow

 

[Douglas P Shepherd]

Good topic

 

[harvknox]

Look at the second photo that Doug posted.Note that the deck break down at the rear of the vertical fins appears at the same point left and right.Since the swim deck side of the boat has a single slanted plane at the rear ,it would be longer than the opposite side which is cut back.I made my gas scale T-6 rear to look like Doug's photo.

If you are building an MLB wood hull,you will have to cut the transom down lower at the swim deck to make everything line up.

You are right Roger's drawings and the MLB kit do not detail this area.

Harvey

 

[P THOMAS]

Yes best to get good pictures first. get your wood kit or glass hull and scratch build it to your specs.

I thinking it is best the mirror the sponson designs so the boat hull works like the real one keeping those features on the inside of the hull as the model would turn right not left like the real boats.

 

[hgatjens]

When the boat gets back to town I would be happy to take some pics for you. O am sure somethig will be different for this year as they have to replace port sponson.

 

[Mike Luszcz]

It is really tough to get the swim platform exactly as it needs to be. I just put the deck on the T6 extreme Spirit of Qatar build last night, and I will be adding a rear nosing to sharpen out the very tail of the swim platform. It does seem the transom inset could be a touch deeper, but its tough to focus on one hull, as I have not seen 2 that are exactly the same, seems there are always little changes. That is where the frame kit is builder friendly as changes can be made during the build to focus on the exact boat the builder is looking into building. Mike

 

[Greg Hahn]

Actually the "upwind" rear shoe or sponson on the T-6 type boats especially the Qatar boat has been cut off. According to Dave V. the original T-6 rear shoes were the same length and after much wind tunnel testing they ended up cuting the upwind shoe off almost half with a saws all to decrease lift on that side. He said he took a guess at how much to cut off and ended up with the results they needed so they patched up the back and painted it. The rear shoes also have two 40 degree steps.

If you set the vertical stabs in the correct scale position, the upwind shoe transome will directly line up with the trailing edge of the vertical stab

 

[Hydro Junkie]

That is very close to what was done to the Oberto when it was built. The right shoe is cut back and recessed 7.5" from where the left one stops. Here are two pictures taken in Kent WA in front of the Oberto plant, back in 2008 IIRC. Unfortunately, I don't have a clear shot showing the top of the transom over the swim platform to see if it's lowered like T-6, this third shot is the best I've got

 

[Chris Lina]

Thanks to all for your responses, I've got about every picture ever taken of the transom details of these hydroplanes but unfortunatly without actual dimensions or a dead on overhead shot it is very difficult to design an accurate rendition of the rear end of these boats. I need two dimensions of the full size hull if anyone has access to one; 1) distance from the end of the left side rear ride pad to the transom line if drawn through the swimdeck and 2) distance from end of right side rear ride pad to transom on the rudder side. These measurements would be enough to design a proper tail end.Mark it would be great if you could get those dimensions from the Oberto and thanks for your pictures.and Greg thank you for your pictures and explanation on your Qatar build which I enjoyed very much, and Doug thanks for your pictures and your find your hulls to be about the most accurate in the business. Harry, I don't know if you remember but you helped me out about 12 years ago with my LLumar build for which I'll be forever grateful. Mike, I am following your T-6 build very closely, I love it, but I am not crazy about the bottom design though, I know its done for speed and stability but I like the more traditional bottom look with the dropped center section with maybe a change in the bottom- gradual gentle curve all the way up to reduce lift instead of the break in the hull at the rear. I just don't care for the abrupt air breaks you incorporated into your extreme series build. Maintaining a somewhat scale look is more important to me than all out speed. Again thanks to all.

Chris

 

[Greg Hahn]

Chris,

just for your reference here's the scale bottom of the Qatar (I've already started sanding the clear) but you can see the steps and center tub and bottom view of the transom.

gh

 

[Hydro Junkie]

Okay, here's what I have have found so far, measured from the sponson transom to each point:

Transom....................16' 5"

Rear of right shoe......17' 11"

Rear of left shoe........18' 6.5"

I'm still looking for the rough drawings I made at the time so I hope this is enough to get you started. I have swim platform and other dimensions as well, once I find them. The only thing I can't remember is if the measurements I took to the rear of the shoes are along the bottom of the airtrap, that being the case on the left shoe, or to the furthest point aft on the right shoe. I'll keep looking and let you know as soon as I find the rest of the data

 

[Hydro Junkie]

Chris, I dug out my Newton plan set for T-5/6 and Oberto. I have already made the changes to the sponson insides showing the actual dimensions as measured on the Oberto. To make the transom arrangement "correct" for the Oberto, the transom must be moved forward and both sponson insides lengthenned and reshaped on the aft end Two other changes to fix the plans are the bottom needs to be lowered slightly and the bottom break moved slightly aft of where Roger drew them. You would also have to rework the crossframes slightly to fit the changes in the sponson insides as well, no biggie on that one. I can scan the aft end as redrawn and either attempt to post it, send it as an email attachment or copy the sheet and send it to you, you cover the costs on that one.

 

[Mike Luszcz]

Thanks to all for your responses, I've got about every picture ever taken of the transom details of these hydroplanes but unfortunatly without actual dimensions or a dead on overhead shot it is very difficult to design an accurate rendition of the rear end of these boats. I need two dimensions of the full size hull if anyone has access to one; 1) distance from the end of the left side rear ride pad to the transom line if drawn through the swimdeck and 2) distance from end of right side rear ride pad to transom on the rudder side. These measurements would be enough to design a proper tail end.Mark it would be great if you could get those dimensions from the Oberto and thanks for your pictures.and Greg thank you for your pictures and explanation on your Qatar build which I enjoyed very much, and Doug thanks for your pictures and your find your hulls to be about the most accurate in the business. Harry, I don't know if you remember but you helped me out about 12 years ago with my LLumar build for which I'll be forever grateful. Mike, I am following your T-6 build very closely, I love it, but I am not crazy about the bottom design though, I know its done for speed and stability but I like the more traditional bottom look with the dropped center section with maybe a change in the bottom- gradual gentle curve all the way up to reduce lift instead of the break in the hull at the rear. I just don't care for the abrupt air breaks you incorporated into your extreme series build. Maintaining a somewhat scale look is more important to me than all out speed. Again thanks to all.

Chris

Chris, I understand that completely, which is why the T6 kit is still available in the standard design which is close to the newton plans. The break is a little further forward, but other than that, its close. Something for everyone!!! haha

 

[Chris Lina]

I just want to say you guys are something, freely sharing your knowledge and willingness to help. Thank you. Greg- Youe bottom shots of your Qatar are fantastic alot of good info there to work from.

Mark- The dimensions you provided should be extremely helpful, along with any other info you may locate, and if you can't figure out how to scan and send me drawings I would be glad to send something to cover your costs for mailing. Sounds like me, I'm not really fluent on this computer either. Mike- It sounds like your standard design T-6 would be the one I'd be interested in.

Chris

 

[Propeler]

Actually the "upwind" rear shoe or sponson on the T-6 type boats especially the Qatar boat has been cut off. According to Dave V. the original T-6 rear shoes were the same length and after much wind tunnel testing they ended up cuting the upwind shoe off almost half with a saws all to decrease lift on that side. He said he took a guess at how much to cut off and ended up with the results they needed so they patched up the back and painted it. The rear shoes also have two 40 degree steps.

If you set the vertical stabs in the correct scale position, the upwind shoe transome will directly line up with the trailing edge of the vertical stab

View attachment 46381View attachment 46382

another question.

I know that the boats run only on three points.

the two edges of the running surfaces of the sponsons and the half-submerged propeller, right?

But what about when I place the boat without strut installed on a flat underground?

the shorter rear shoe would still be standing in the air and not on the flat surface?

 

[Hydro Junkie]

IF you've placed the boat on a table, sitting on the sponsons and shoes, the short shoe will still be above the table, IF you place the boat on the table, resting on the airtraps, the shoes should both be resting on the table if they are flush with the bottom of the airtraps or in contact at the same point of the shoe if they stop below the airtrap

 

[Propeler]

Thx Man, that helps me a lot

 

[Lennard Cuenco]

ok...

so how did you set the depth of each rear shoe on the setup board?

if the shorter shoe is up in the air, the boat is buck like bronco and never ride flat