24" Wild Thing plug

[kookie_guy]

I'm building a scaled down wild thing that I'll be using as a plug to make a mold. Then I'll be making it out of carbon fiber. Here's where I'm at right now. All glued together, and starting to fill all the seams.

I have 2 quick questions.......

1) on the third picture, you can see the small flat spot where the 2 bottoms meet. Can this spot be flat as is? Or is it better to have them come to a point?

2) the last pic, you can see the front of the deck has a downward bow to it in the middle. Should I fill this until it has a nice uniform hump? Or is this ok?

thanks for the help, here are the pics.

[CornelP]

For the first question: you need either a sharp edge or flatten it more to get a ridepad if you're looking for more lift. This should be a long triangle going from about 20mm at transom to a point somewhere around the front bulkhead.
The small warp is give by the fact you used two pieces of balsa glued on the lenght of the grain. It looks ok, but, to get a flat area you should have used thin ply, one piece. On my first wildthing, I got the same result, and came back with a second layer, crossgrain, to lift it back.

[Simon.O.]

Good build so far.
A small tip for Balsa builders, do not cut lightning holes in your frames. The reduction in weight is not worth the loss of stiffness or rigidity. Just a little bit of experience here.
Considering I ballast most of my small balsa hulls for speed the extra weight is a bonus.

I am keen to see how this one will pan out.

[j.m.]

To avoid having to make a seam in the hull, you would have to join the top and bottom peices with a composite tape (usually fiberglass, cheapest and plenty strong) while the parts in the mold are still wet. I suggest doing this because making one part (deck or hull bottom) the thickness of the layup thinner than the other part around the seam is very difficult.

Doing this on a boat hull however is rediculously hard. You can't use a silicon plug, because it would then be trapped inside the hull.

Inflating a balloon inside the hull would work, but only if you had a hole in the mold where the hatch is.

It's best to join the two hull halves while the layup is still wet, it'll give the strongest bond.

But you'll most likely end up having to join the two parts after they have cured and cut the hatch out of the top.

This'll help:

http://www.rcgroups.com/forums/showthread.php?t=864161

[kookie_guy]

For the first question: you need either a sharp edge or flatten it more to get a ridepad if you're looking for more lift. This should be a long triangle going from about 20mm at transom to a point somewhere around the front bulkhead.
The small warp is give by the fact you used two pieces of balsa glued on the lenght of the grain. It looks ok, but, to get a flat area you should have used thin ply, one piece. On my first wildthing, I got the same result, and came back with a second layer, crossgrain, to lift it back.

I'll sharpen the sucker up. I'll be adding strakes so they should provide plenty of lift. I don't really want a super flat area. I like the little hump you get on the wild thing. Just wondering if it's ok that mine sags to form a slight vee near the front. If it does not affect anything functionally, then I'll leave it, it looks ok.

Good build so far.
A small tip for Balsa builders, do not cut lightning holes in your frames. The reduction in weight is not worth the loss of stiffness or rigidity. Just a little bit of experience here.
Considering I ballast most of my small balsa hulls for speed the extra weight is a bonus.

I am keen to see how this one will pan out.

I did the holes because I never intended on running this boat. Right from the start, this was intended to be used as a master to make the mold. But now as I type this, why the hell did I put the holes if it's just a master, lol!

To avoid having to make a seam in the hull, you would have to join the top and bottom peices with a composite tape (usually fiberglass, cheapest and plenty strong) while the parts in the mold are still wet. I suggest doing this because making one part (deck or hull bottom) the thickness of the layup thinner than the other part around the seam is very difficult.

Doing this on a boat hull however is rediculously hard. You can't use a silicon plug, because it would then be trapped inside the hull.

Inflating a balloon inside the hull would work, but only if you had a hole in the mold where the hatch is.

It's best to join the two hull halves while the layup is still wet, it'll give the strongest bond.

But you'll most likely end up having to join the two parts after they have cured and cut the hatch out of the top.

This'll help:
http://www.rcgroups.com/forums/showthread.php?t=864161

My plan is make a 2 part mold, split along the middle of the hull. As you described, both parts will be molded and clamped together with fiberglass tape to join both halves. The hatch opening will be cut into the mold, so I will be able to join them when all is still nice and moist.

[screwball]

will you be selling these?

will you be making smaller versions of it? 18"???

id love to get an 18 incher and put in a flood chamber......

[bigpapa]

looks great good luck on the build

[kookie_guy]

if the first one I pull from the mold (which will be my personal one made out of CF) comes out looking good, and I get people interested, then yes, I will likely do a limited run. They will all be handlaid fiberglass, made by me personally, so like I said, they will be limited.

[j.m.]

My point is putting the fiberglass tape inside the seam of the hull is very difficult without something pushing the fabric up against the seam.

I would see if you can't use a small weather balloon inserted inside the mold after you have the tape in place, and then inflating the balloon so it will push the tape against the seam.

Doing this by hand is very messy, not uniform, and will not make for a strong hull at all because using fiberglass of adequate strength won't want to stay in place.

[kookie_guy]

My point is putting the fiberglass tape inside the seam of the hull is very difficult without something pushing the fabric up against the seam.

I would see if you can't use a small weather balloon inserted inside the mold after you have the tape in place, and then inflating the balloon so it will push the tape against the seam.

Doing this by hand is very messy, not uniform, and will not make for a strong hull at all because using fiberglass of adequate strength won't want to stay in place.

that's a good point. The balloon is a good idea. I guess the other thing I can do is lay it on it's side and do one side at a time. This will of course have to be done when it's dry tho.

[j.m.]

Yeah, but still.

I would think a glass with a weight of at least 8 oz/sq yd would be necessary, which would not stay in the seam crevice. Even when wetted with epoxy. Anything heavier would certainly need something to hold it in place until the epoxy is dry. I have a hard time getting 10 oz/ sq yd glass to conform to the inside of a v hull in the bottom, and that is a much more open area.

[Quietlee]

I've built a couple WTs and have a couple suggestions. On the hatch area, square it off. It makes it much easier to tape up when you have straight lines instead of trying to curve the tape around the hatch line. I would also suggest not putting strakes in the mold. This gives you the option to change them around to tune the hull. If they are molded in, you won't have that option. The WT really doesn't need strakes, but it will depend on the class you are trying to run in.

[kookie_guy]

I've built a couple WTs and have a couple suggestions. On the hatch area, square it off. It makes it much easier to tape up when you have straight lines instead of trying to curve the tape around the hatch line. I would also suggest not putting strakes in the mold. This gives you the option to change them around to tune the hull. If they are molded in, you won't have that option. The WT really doesn't need strakes, but it will depend on the class you are trying to run in.

both great suggestions. Now that I think about it, the tape makes perfect sense, so that will be done. Same with the strakes, it will be much easier/less time consuming to mold without them. Thanks for the input.

cheers.

[Darin Jordan]

I've built a couple WTs and have a couple suggestions. On the hatch area, square it off. It makes it much easier to tape up when you have straight lines instead of trying to curve the tape around the hatch line. I would also suggest not putting strakes in the mold. This gives you the option to change them around to tune the hull. If they are molded in, you won't have that option. The WT really doesn't need strakes, but it will depend on the class you are trying to run in.

I have to agree with all of this. Having built a 32" WT for P-Mono and using it extensively, taping the rounded hatch is a PITA... especially when you are in a hurry...

As for the strakes... You want to have the spray rails (chine strakes) on there, but I'm still not convinced that adding the mid strakes on mine was necessary... the hull doesn't need the additional lift, though mine does corner with some good speed... I think partially do to them being there...

They are easy enough to add later. My next one will be without them, and I'll add them if it seems necessary after testing...

Keep up the good work!

[kookie_guy]

awesome. thanks for the input Darin. I'll add the spray rails and leave the strakes out. And will deffinitely square off the hatch area