Need input on .12 rigger ideas

[MikeP]

I got the weight of the MikeP motor mount system, It's .5 oz. But it takes the place of a bulkhead that was about .3 oz.

www.ad.kengarff.com/mikep/mpmount.jpg

Sheesh... it's hard to reduce weight when they are already light! Is all this brian damage worth a 1/2 ounce?

-MikeP

 

[Don Templeton]

Mike,

I assume that is the bulkhead mount. Are you just going to run longer screws through the CF into the rear of the engine and brace the CF bulkhead with two strips of wood and tooth pick them? Are the wood strips going top & bottom or side to side? I guess you'r not going to use that blue anodized back plate you found. Can't quite figure out what you've got there. ???

 

[E]

Wow, Mike if that's your first attempt, now I'm real ancious to see the next-generation MikeP special. I sort of got the idea that you where not new to boats...

Eric Perez

 

[MikeP]

Don,

The motor will bolt directly to the plate with longer screws. The plate will be mounted so it's arms extend through the tub sides. Then the 1/4" hardwood square top to bottom in front and in back pinned with dowels( toothpicks).

I think I will get some support from the flex cable and stuffing box during starting.

Here is a drawing of the side view to see how I would use the 1/4" hardwood. This is still only and idea, the truck load of lumber doesn't come until next week.

www.ad.kengarff.com/mikep/sidemount.jpg

-MikeP

 

[Don Templeton]

" Sounds like a plan to me! "

That should be plenty strong and light! Good Design.

 

[MikeP]

I tried some new building techniques with great results.

First is (I can't believe I haven't tried this before) I used the table saw to cut plywood and the spyder foam. got really square parts with perfect fits and nice clean cuts.

Next (I can't believe I haven't done this either) I used orderless CA to sheet the foam. Apply CA to the foam and CA kicker to the wood.

-MikeP

 

[Chris Attebery]

Mike,

I think that rear sponson/hull design you have in your drawing will have too much lift in the rear. The rear sponsons should only have about 1 degree AOA. Also the width of the surface will cause the rear end to hop or even worse cause the nose to stuff. I've seen that happen on my 45SG with 3 shoes. Andy changed the rears on the SGx to reduce the lift because of this problem. Also the sloping top on the back of the boat will cause aerodynamic lift as the boat gets up to speed. This is going to make the boat even more prone to stuff. If it were my decision I would try building the hull like the drawing Don posted.

I'm really tempted to try the V sponson on my 45 but I just finished two new hulls (SGx21, SG 45) this winter. I'd like to spend some more time running and less time building for a while.

Good luck and keep us up to date,

Chris

PS: Have you run your 84 rigger yet?

 

[MikeP]

Hey Chris,

I haven't run the .84 yet. About 3 or 4 weeks the weather should good. It's ready to go. ( little nervous about running it)

I was wondering if you think a 26-28 deg. vee on a 2" wide hull would still give too much lift? I did reduce the AOA to 1.8.

As for the top, Do you know of a way to reduce lift without changing the design. I was thinking of a small wicker bill across the back to break the air foil but laid back enough not to cause drag.

-MikeP

 

[Chris Attebery]

Mike,

I think the ride surface should be as narrow as possible. Maybe 1/2" to 3/4". I think 26- 28 degree sides should be fine. I think the AOA should be a little shallower. Just for reference, the SGx rears are right around 1 degree and the total width is about 1". The rears should only be touching in rough water, and then only to settle the rear, not to lift it.

I think the sloped back is a problem no matter what you do. You could try a wicker type spoiler, but a flat back is easy to make and guaranteed not to lift.

Chris

 

[Ian Inverarity]

Mike,

I dont think the aerodynamic lift you may generate from the sloped rear of the hull will be significant compared to the lift generated from the rear sponson design. The aspect ratio of the rear of the hull is very low, as an airfoil section it would be very inefficient. If you round off the top edges of the hull in that area it should enable air to flow up over the sides to fill any low pressure area being created above the back of the hull.

My personal thoughts on a 12 rigger: Make a geared mount so that the engine is mounted with the carb forward and exhaust back. The mount would have the shaft going down the right hand side insted of under the motor to keep the CG low. The boat would have two fairly conventional rear sponsons mounted under the tub. No rear strut, with the flex running inside the right rear sponson and exiting the back of the sponson. But those are just my thoughts! ;D

Cant wait to hear how that 84 boat goes! 8)

Nitrocrazed racing: Bring on the new technology...

 

[MikeP]

That a cool idea with the gear mount, it would be nice to have the exhaust come out the rear.

It looks like my strutless desire is perfect for a vee hull. I think I am going to give it a try. 26deg. vee fits nicely on 2.25" wide hull.

I never considered too much lift only too much drag from the back of the hull.

-MikeP

 

[MikeP]

Ok,

With 1deg. AOA and 26deg. vee. I can run the stuffing box straight down the middle of the hull on the inside. From the motor to the transom with no bends. Is having a straight stuffing box good? Any ideas on the prop height and angle.

www.ad.kengarff.com/mikep/12/veehull.jpg

-MikeP

 

[TomMoorehouse]

i would say the prop should exit at the bottom of the V. If you have it up too high the prop will loose efficiency cause it wont get enough water.

the verdict is still out on stuffing boxes if you ask me. ive seen world records both ways. some will say straight will have les drag. others say you need an S bend of the cable will "chatter".

for a 12 boat 1-2 degrees is about right for the prop shaft angle

 

[Don Templeton]

Hey Mike!

How are you able to get the engine low enough to run a straight tube at 1 or 2 degrees? Are you planning on a well for the flywheel?

When you finish this one and are looking for something radical for your next boat, here is something to think about! :

 

[Don Templeton]

Mike,

The first thing I tried when I got my foam was the table saw and you'r right it works great!

Also I bought this small hot wire from Micro Mark and boy does it ever work great for sponsons and hulls. (29.95) Cuts up to 8" wide. I really like the trigger on the handle. It heats up immediately and cools down the same.

 

[MikeP]

Well Don,

I finally got around to finding out about the stuffing box. It looks like 3-4 deg is needed to get it there straight. Then I will need to bend one end or the other a few degrees to flatten out the prop angle.

www.ad.kengarff.com/mikep/cf90/tube.jpg

Thanks for the info on how the hot wire works, I think you posted those before but I didn't know you had one. I will get one coming.

Could some of you .12 rigger owners post your measurements from the rear of the front sponsons to the drive dog.

-MikeP

 

[TomMoorehouse]

about 15.75"

 

[Don Templeton]

Not sure these will help but it will be interesting to see how they fit into the other designs.

Old 12- 14 5/8" to drive dog, Hull length 23 1/4", Depth of TE 5/8"

New 12- 14 1/16" to drive dog, Hull lingth 22 5/8", Depth of TE 5/8"

(Just remember neither one has yet to run!) :

 

[Don Templeton]

Mike,

I have a question for you! Would the .064 graphite flex plate work ok for my .12 radio box and tank lid? ( From ACP) I really don't know much about graphite. Would I be better off using wood?

Thanks Don

 

[Ron Olson]

Don, you're in luck, kind of. I just came up from the basement to take a break while I've got some glue drying. I did some cutting on some Carbon Fiber sheet while I was there. You can use thinner with no trouble and it does cut easily using a Dremel re-enforced cutting wheel. Doesn't cut worth a crap in a laser cutter though, we found that out last week. : Check in eBay, there is a guy in there, Graphite_Elegance, that has some nice CF sheet. It's in the R/C boat section and is .030" thick.